Water Quality and Trend Analysis of Colorado-Big Thompson System

Home , Big Thompson River, Granby Dam, Shadow Mountain Lake

Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances, 1969 Through 2000

By Michael R. Stevens

Prepared in cooperation with the NORTHERN COLORADO WATER CONSERVANCY DISTRICT, BUREAU OF RECLAMATION, and the CITY OF FORT COLLINS

Water-Resources Investigations Report 03–4044

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary

U.S. Geological Survey Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2003

For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. iii

Contents

Abstract...... 1 Introduction ...... 2 Purpose and Scope ...... 2 Previous Studies and Acknowledgments...... 3 Description of Study Area ...... 4 Hydrology ...... 6 Water Quality...... 8 Chemical Characteristics ...... 9 Field Measurements and Major-Ion Concentrations...... 13 Nutrients...... 13 Trace Elements...... 17 Colorado Water-Quality Standards...... 22 Limnology ...... 22 Reservoir Profile Characteristics...... 22 Hypolimnetic Oxygen Dynamics...... 23 Trophic Indicators and Nutrient Limitation...... 23 Trend Analysis...... 26 Time-Series Data ...... 26 Statistical Testing...... 28 Summary and Conclusions...... 31 References Cited ...... 33 Hydrologic and Water-Quality Data...... 35

Figures

1. Map showing location of study area and sampling sites ...... 3 2. Schematic diagram of CBT Project facilities...... 4 3. Graph showing percentage of Colorado–Big Thompson water supplied for municipal use ...... 5 4–6. Maps showing: 4. Land uses in watershed upstream from Lake Granby...... 6 5. Land uses in watershed upstream from the mouth of Big Thompson Canyon ...... 7 6. Land uses in watershed draining directly to Horsetooth Reservoir ...... 8 7–11. Graphs showing: 7. Maximum, mean, and minimum daily streamflows for the period of record (1953 to 2000) at Colorado River below Baker Gulch (09010500) ...... 9 8. Time-series plots of operation of selected Colorado–Big Thompson conveyances ...... 10 9. Time-series plots of operation of selected Colorado–Big Thompson reservoirs...... 11 10. Monthly average discharge characteristics of selected Colorado– Big Thompson conveyances ...... 12 11. Monthly average reservoir contents of selected Colorado–Big Thompson reservoirs...... 12 iv

12. Boxplots of selected water-quality constituents ...... 14 13. Piper diagram showing major-ion composition of samples at selected sites...... 17 14–17. Graphs showing: 14. May and October field-measurement profiles at Lake Granby (dam)...... 18 15. May and October field-measurement profiles at Shadow Mountain Lake ...... 19 16. May and October field-measurement profiles at Carter Lake ...... 20 17. May and October field-measurement profiles at Horsetooth Reservoir (Soldier Canyon Dam) ...... 21 18. Time-series plots of annual areal hypolimnetic oxygen deficit in reservoirs...... 24 19. Annual trophic status index (TSI) computations for Secchi depth, total phosphorus, and chlorophyll-a by the Carlson (1977) method...... 25 20. Nonmonotonic distribution and seasonal Kendall test results for pre-1983 and post-1983 of ammonia plus organic nitrogen (total) at Adams Tunnel east portal ...... 27 21. Monotonic distribution and seasonal Kendall test results for all samples of dissolved iron at Adams Tunnel east portal...... 27 22. Time-series plots of reservoir reciprocal hydraulic residence time in terms of the proportion of water entering or leaving the water body...... 31 23–37. Graphs showing temporal variations in periodic measurements and concentrations at: 23. Lake Granby near spillway, sampled near the surface...... 38 24. Lake Granby near spillway, sampled near the bottom ...... 44 25. Lake Granby near Rainbow Bay, sampled near the surface...... 49 26. Lake Granby near Rainbow Bay, sampled near the bottom ...... 55 27. Granby Pump Canal...... 60 28. Shadow Mountain Lake, sampled at the surface...... 65 29. Shadow Mountain Lake, sampled near the bottom...... 71 30. Adams Tunnel, east portal, near Estes Park ...... 76 31. Olympus Tunnel...... 81 32. Carter Lake, sampled near the surface...... 86 33. Carter Lake, sampled near the bottom...... 92 34. Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the surface...... 97 35. Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the bottom...... 103 36. Horsetooth Reservoir, near Spring Canyon Dam, sampled near the surface...... 108 37. Horsetooth Reservoir, near Spring Canyon Dam, sampled near the bottom...... 114

Tables

1. Water-quality sampling sites ...... 2 2. Seasonal periods and period of record tested by seasonal Kendall test ...... 29 3. Summary of significant upward and downward temporal trends at Colorado– Big Thompson sampling sites...... 30 4. Summary statistics for site 1, Lake Granby, near spillway, near surface ...... 119 5. Summary statistics for site 1, Lake Granby, near spillway, near bottom...... 120 6. Summary statistics for site 2, Lake Granby (Rainbow Bay), sampled near surface..... 121 7. Summary statistics for site 2, Lake Granby (Rainbow Bay), sampled near bottom...... 122 v

8. Summary statistics for site 3, Granby Pump Canal...... 123 9. Summary statistics for site 4, Shadow Mountain Lake, sampled at the surface...... 124 10. Summary statistics for site 4, Shadow Mountain Lake, sampled near bottom...... 125 11. Summary statistics for site 5, Alva B. Adams Tunnel east portal ...... 126 12. Summary statistics for site 6, Lake Estes, sampled at surface...... 127 13. Summary statistics for site 6, Lake Estes, sampled near bottom ...... 128 14. Summary statistics for site 7, Olympus Tunnel ...... 129 15. Summary statistics for site 8, Carter Lake, sampled near surface...... 130 16. Summary statistics for site 8, Carter Lake, sampled near bottom...... 131 17. Summary statistics for site 9, Horsetooth Reservoir (Soldier Canyon Dam), sampled near surface ...... 132 18. Summary statistics for site 9, Horsetooth Reservoir (Soldier Canyon Dam), sampled near bottom ...... 133 19. Summary statistics for site 10, Horsetooth Reservoir (Spring Canyon Dam), sampled at surface...... 134 20. Summary statistics for site 10, Horsetooth Reservoir (Spring Canyon Dam), sampled near bottom ...... 135 21. Trend analysis results for site 1, Granby Reservoir, near dam, surface samples...... 136 22. Trend analysis results for site 1, Granby Reservoir, near dam, bottom samples ...... 137 23. Trend analysis results for site 2, Granby Reservoir (Rainbow Bay), surface samples ...... 138 24. Trend analysis results for site 2, Granby Reservoir (Rainbow Bay), bottom samples ...... 139 25. Trend analysis results for site 3, Granby Pump Canal, samples ...... 140 26. Trend analysis results for site 4, Shadow Mountain Reservoir, surface samples...... 141 27. Trend analysis results for site 4, Shadow Mountain Reservoir, bottom samples ...... 142 28. Trend analysis results for site 5, Adams Tunnel east portal...... 143 29. Trend analysis results for site 7, Olympus Tunnel, samples ...... 144 30. Trend analysis results for site 8, Carter Reservoir, surface samples...... 145 31. Trend analysis results for site 8, Carter Reservoir bottom samples...... 146 32. Trend analysis results for site 9, Horsetooth Reservoir (Soldier Canyon Dam), surface samples...... 147 33. Trend analysis results for site 9, Horsetooth Reservoir (Soldier Canyon Dam), bottom samples...... 148 34. Trend analysis results for site 10, Horsetooth Reservoir (Spring Canyon Dam), surface samples...... 149 35. Trend analysis results for site 10, Horsetooth Reservoir (Spring Canyon Dam), bottom samples...... 150 vi

Conversion Factors, Vertical Datum, and Abbreviations

Multiply By To obtain

acre 0.00156 square mile acre-foot (acre-ft) 1,233 cubic meter cubic foot per second (ft3/s) 0.02832 cubic meter per second foot (ft) 0.3048 meter inch 2.54 centimeter mile 1.609 kilometer millimeter 0.03937 inch square centimeter (cm2) 0.1550 square inch (in2) square foot (ft2) 0.0929 square meter square mile (mi2) 2.590 square kilometer (km2)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F = 1.8(°C) + 32

Vertical coordinate information is referenced to the National Geodectic Vertical Datum of 1929 (NGVD 29); horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Additional Abbreviations

MRL minimum reporting level mg milligrams mg/L milligrams per liter mm millimeters mL milliliters NTU nephelometric turbidity units ROE residue on evaporation µg/L micrograms per liter µS/cm microsiemens per centimeter at 25 degrees Celsius WY water year, begins on October 1 and ends on September 30 of the following year. Identified by year in which it ends (water year 2000 ended on September 30, 2000). Water Quality and Trend Analysis of Colorado– Big Thompson System Reservoirs and Related Conveyances, 1969 Through 2000

By Michael R. Stevens

Abstract This report summarizes and assesses: 1. Water-quality and field-measurement profile data col- The U.S. Geological Survey, in an ongoing coopera- lected by the U.S. Geological Survey and stored in the tive monitoring program with the Northern Colorado U.S. Geological Survey National Water Information Water Conservancy District, Bureau of Reclamation, System, and City of Fort Collins, has collected water-quality data 2. Time-series trends of chemical constituents and physical in north-central Colorado since 1969 in reservoirs and properties, conveyances, such as canals and tunnels, related to the 3. Trends in oxygen deficits in the hypolimnion of the reser- Colorado–Big Thompson Project, a water-storage, collec- voirs in the late summer season by the seasonal Kendall tion, and distribution system. Ongoing changes in water use trend test method, among agricultural and municipal users on the eastern slope of the Rocky Mountains in Colorado, changing land use in 4. Nutrient limitation and trophic status indicators, and reservoir watersheds, and other water-quality issues among 5. Water-quality data in terms of Colorado water-quality Northern Colorado Water Conservancy District customers standards. necessitated a reexamination of water-quality trends in Water quality was generally acceptable for primary uses the Colorado–Big Thompson system reservoirs and related throughout the Colorado–Big Thompson system over the site conveyances. The sampling sites are on reservoirs, canals, periods of record, which are all within the span of 1969 to and tunnels in the headwaters of the Colorado River (on the 2000. Dissolved solids and nutrient concentrations were low western side of the transcontinental diversion operations) and typical of a forested/mountainous/crystalline bedrock and the headwaters of the Big Thompson River (on the hydrologic setting. Most of the more toxic trace elements eastern side of the transcontinental diversion operations). were rarely detected or were found in low concentrations, due Carter Lake Reservoir and Horsetooth Reservoir are off- at least in part to a relative lack of ore-mineral deposits within channel water-storage facilities, located in the foothills of the drainage areas of the Colorado–Big Thompson Project. the northern Colorado Front Range, for water supplied from Constituent concentrations consistently met water- the Colorado–Big Thompson Project. The length of water- quality standard thresholds set by the State of Colorado. quality record ranges from approximately 3 to 30 years Trophic-State Index Values indicated mesotrophic conditions depending on the site and the type of measurement or con- generally prevailed at reservoirs, based on available Secchi depth, total phosphorus concentrations, and chlorophyll-a stituent. Changes in sampling frequency, analytical meth- concentrations. ods, and minimum reporting limits have occurred repeat- Based on plots of time-series values and concentrations edly over the period of record. and seasonal Kendall nonparametric trends testing, dissolved The objective of this report was to complete a ret- solids and most major ions are decreasing at most sites. Many rospective water-quality and trend analysis of reservoir of the nutrient data did not meet the minimum criteria for profiles, nutrients, major ions, selected trace elements, time-series testing; but for those that did, nutrient concentra- chlorophyll-a, and hypolimnetic oxygen data from 1969 tions were generally stable (no statistical trend) or decreasing through 2000 in Lake Granby, Shadow Mountain Lake, and (ammonia plus organic nitrogen and total phosphorus). Iron the Granby Pump Canal in Grand County, Colorado, and and manganese concentrations were stable or decreasing at Horsetooth Reservoir, Carter Lake, Lake Estes, Alva B. most sites that met testing criteria. Chlorophyll-a data were Adams Tunnel, and Olympus Tunnel in Larimer County, only collected for 11 years but generally indicated quasi-stable Colorado. or downward temporal trends. 2 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

Introduction summarized water-quality data available at the time, analyzed time-series trends, and evaluated the sampling network design The U.S. Geological Survey (USGS), in an ongoing for most of the sampling sites considered in this report and cooperative monitoring program with the Northern other sites on the eastern plains where the water is used for Colorado Water Conservancy District (NCWCD), Bureau agricultural purposes. of Reclamation (BOR), and City of Fort Collins, has collected water-quality data in north-central Colorado since 1969 in Purpose and Scope reservoirs and conveyances such as canals and tunnels related to the Colorado–Big Thompson (CBT) Project, a water- Part of the value of such a long-term monitoring record storage, collection, and distribution system. The sampling is the ability to test for temporal trends in water quality. Tem- sites are on reservoirs, canals, and tunnels in the headwaters poral trends in nutrients, major ions, trophic variables, and of the Colorado River (on the western side of the transcon- oxygen can indicate changes in water quality related to eutro- tinental diversion operations) and the headwaters of the Big phication. Ongoing changes in water use among agricultural Thompson River (on the eastern side of the transcontinental and municipal users on the eastern slope of Colorado, chang- diversion operations). Carter Lake and Horsetooth Reservoir ing land uses in reservoir watersheds, and other water-quality are off-channel water-storage facilities, located in the foothills issues among NCWCD customers necessitated a reexamina- of the northern Colorado Front Range, for water supplied from tion of water-quality trends in CBT system reservoirs and the CBT Project (table 1, fig. 1). The length of water-quality related conveyances. record ranges from approximately 3 to 30 years depending on The overall objective of the project is to complete a the site and the type of measurement or constituent. Sampling retrospective analysis of reservoir profiles, nutrients, major frequency, analytical methods, and minimum reporting limits ions, selected trace elements, chlorophyll-a, and hypolim- have changed repeatedly over the period of record. netic oxygen data from 1969 through 2000 in Lake Granby, The CBT Project was authorized by Congress in 1937 Shadow Mountain Lake, and the Granby Pump Canal in Grand and completed in 1956, resulting in the construction of several County, Colo., and Horsetooth Reservoir, Carter Lake, Lake reservoirs, more than 120 miles of tunnels and canals, and Estes, east portal of the Alva B. Adams Tunnel (hereinafter numerous power-generation facilities. The USGS became “Adams Tunnel”), and Olympus Tunnel in Larimer County, involved in monitoring in the CBT Project area as part of a Colo. Sampling sites in this report are in the headwater areas cooperative water-quality evaluation of the BOR Pick-Sloan of the CBT Project where diversion and storage facilities are Missouri Basin Program. When operation of the CBT Project located. Areas downstream from Lake Granby on the western was assumed by NCWCD, collection of baseline water- slope and water delivery areas downstream from Carter Lake quality information continued. A report by Mueller (1990) and Horsetooth Reservoir are beyond the scope of this report.

Table 1. Water-quality sampling sites.

[15-digit U.S. Geological Survey (USGS) identification numbers are latitude and longitude of site location with a 2-digit code at the end; 8-digit identification numbers are USGS downstream order numbering]

Site U.S. Geological Survey Number Period number Site name identification number of samples of record (fig. 1) 1 09018500 Lake Granby near Granby, Colo. (near spillway) 154 1973–75, 1979–present 2 400844105530800 Lake Granby near Granby, Colo. (near dam in Rainbow Bay) 123 1989–present 3 09018300 Granby Pump Canal near Grand Lake, Colo. 179 1970–present 4 09014500 Shadow Mountain Lake near Grand Lake, Colo. 125 1989–present 5 09013000 Alva B. Adams Tunnel east portal, near Estes Park, Colo. 283 1970–present 6 402231105291900 Lake Estes near dam near Estes Park, Colo. 16 1998–present 7 06734900 Olympus Tunnel at Lake Estes, Colo. 247 1970–present 8 06742500 Carter Lake near Berthoud, Colo. 309 1970–present 9 06737500 Horsetooth Reservoir near Fort Collins, Colo. (Soldier Canyon Dam) 518 1969–present 10 403147105083800 Horsetooth Reservoir near Fort Collins, Colo. (Spring Canyon Dam) 100 1983–present 11 09010500 Colorado River below Baker Gulch near Grand Lake, Colo. -- 1953–present Introduction 3

Study area PLATTE RIVER

R SOUTH DENVER O RAD LO O C Grand Junction

GU NN Pueblo ISO N RIVER COLORADO

106°30' 106° 105°30' 105° 104°30'

41° WYOMING

r COLORADO t h

P l a t t e LARIMER Ri ver COUNTY

Ro ari ng Cache La er Fork Poudre Riv

JACKSON Horsetooth COUNTY Rocky Mountain 9 National Park Rerservoir Fort Collins WELD 40°30' 10 COUNTY

CO NT B Estes Park INE i 7 NTAL g DIVI T DE ho m 6 er 11 ps iver Riv on R OLYMPUS 8 pson hom r ADAMS 5 TUNNEL tle T e Lit v TUNNEL Grand i Creek Lyons R 3 Lake Saint Vrain

Shadow e

t 4 t

Mountain a 2 l Lake Longmont P GRAND 1 BOULDER COUNTY Lake h COUNTY t F Granby Bo u r u o a l S er s de iv e r Creek 40° R r o R d iv a e r r r lo o C ADAMS P DENVER in CLEAR COUNTY ey COUNTY R CREEK JEFFERSON iv er SUMMIT COUNTY COUNTY COUNTY

Base from U.S. Geological Survery Digital Data Transverse Mercator Projection Central Meridian Datum 1983 EXPLANATION 0 20 40 MILES Towns 2 Sites and number 0 20 40 KILOMETERS Roads Streams Counties

Figure 1. Location of study area and sampling sites (modified from Mueller, 1990).

This report summarizes water-quality and field-measurement Previous Studies and Acknowledgments profile data collected by the USGS and stored in the USGS National Water Information System; assesses time-series A report by Mueller (1990) discussed trends determined trends of selected chemical constituents and physical proper- by using the seasonal Kendall method; general water-quality ties, trends in oxygen deficits in the hypolimnion of the reser- analysis and sampling network evaluation were the primary voirs in the late summer season by the seasonal Kendall trend focus of that report. Trend analysis at the Adams Tunnel test method, and nutrient limitation and trophic status indica- east portal that is included in this report also was computed tors; and evaluates water-quality data in terms of Colorado for selected chemical constituents in Middelburg (1993, water-quality standards. p. 204). Jassby and Goldman (1999) studied water-quality 4 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances and biological conditions in Horsetooth Reservoir and Carter include the Willow Creek Canal, which conveys water stored Lake in 1998–99. Greve (1999) designed a water-quality in Willow Creek Reservoir, and water pumped from Windy monitoring network for the Big Thompson watershed in coop- Gap Reservoir (built in 1985 by the Municipal Subdistrict of eration with the Big Thompson Watershed Forum, a watershed the NCWCD to use the unused capacity in CBT facilities), group within the study area. Johnson and Goettl (1999) studied located on the Colorado River downstream from the conflu- food web changes for 14 years following the introduction of ence with the Fraser River. Storage on the western slope is pri- rainbow smelt into Horsetooth Reservoir. marily in Lake Granby (539,800 acre-ft total capacity). Water The author thanks Don Carlson at the NCWCD and is pumped through the Farr Pumping Plant and the Granby Gene Price and Jeff Lucero at the BOR for their assistance Pump Canal into Shadow Mountain Lake. Shadow Mountain in bringing this report to fruition, and Dave Dzurovshin at the Lake and Grand Lake are similar (hydraulically connected) Colorado State Engineers Office for assistance in retrieving and relatively nonfluctuating. Their function is to convey discharge data at some sites. project water into the Adams Tunnel, the largest transcontinental diversion in Colorado (average 230,000 acre-ft diverted annually). Description of Study Area On the eastern side of the Continental Divide, project water is conveyed through tunnels and eventually to Lake The study area involves parts of two mountainous Estes, where it mixes with water from the Big Thompson watersheds. On the western side of the Continental Divide, River, a watershed with headwaters located primarily several major tributaries in the headwaters of the Colorado within Rocky Mountain National Park. The Olympus River (North Fork Colorado River, North Inlet, East Inlet, and Tunnel then conveys water from Lake Estes to a series of Arapaho Creek) are connected to parts of the western slope tunnels and small reservoirs to Carter Lake or the Hansen CBT reservoir system (Lake Granby, Shadow Mountain Lake, Feeder Canal. The Hansen Feeder Canal can convey the water and Grand Lake) and, thus, are the primary sources of water (and accept water diverted at the mouth of Big Thompson diverted by the CBT Project (fig. 2). Other water sources Canyon through the Dille Tunnel) to Horsetooth Reservoir.

Cache La Poudre River

Horsetooth Reservoir Dille Tunnel Diversion Hansen Lake Estes Big Thompson River

Feeder Canal South Platte River

Colorado River Shadow Mountain Big Thompson River and Grand Lakes Olympus Tunnel

Adams Tunnel Mary's Lake

Carter Lake Willow Creek Willow

Lake Granby

Willow Creek DIVIDE CONTINENTAL

Reservoir Granby Pump Canal Little Thompson River

Windy Gap Willow Creek St. Vrain Creek Reservoir Canal

Colorado River Boulder Fraser River Reservoir

Boulder Creek

Figure 2. Schematic diagram of CBT Project facilities (from Mueller, 1990). Introduction 5

100 350,000

90 300,000 80

70 250,000

60 200,000

150,000 40

30 100,000 OF CBT WATER, IN ACRE-FEET TOTAL WATER YEAR DELIVERY 20 50,000 DELIVERED FOR MUNICIPAL USE 10 PERCENTAGE OF CBT PROJECT WATER

0 0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 WATER YEAR

EXPLANATION

TOTAL WATER YEAR DELIVERY OF CBT WATER PERCENTAGE OF CBT WATER TO MUNICIPAL USE

Figure 3. Percentage of Colorado–Big Thompson (CBT) water supplied for municipal use.

Carter Lake (112,230 acre-ft total capacity) and Horsetooth by sedimentary rock (fig. 6). While one of the primary uses of Reservoir (156,735 acre-ft total capacity) are the primary water resources is recreation, there are two developed urban storage facilities on the eastern slope and were constructed areas that could affect the water quality within the study area: by damming valleys of intermittent drainages along the Front Grand Lake and Estes Park. Grand Lake is a town of approxi- Range. Project water is then conveyed to water users by way mately 250 people, on the shores of Grand Lake. Similar, of streams, canals, and pipelines within the NCWCD boundar- though less dense, residential development is present along ies to Boulder Creek, Saint Vrain Creek, Big Thompson River, the shores of Shadow Mountain and Granby Lakes (fig. 4). Cache La Poudre River, and the main-stem South Platte River. Before 1982, individual sewage disposal systems (ISDS) were Drinking water is supplied to 30 Front Range cities and towns, used for sanitation. Due to increasing water-quality concerns, and water for supplemental irrigation is provided to more a municipal sanitation system that pumps waste downstream than 600,000 acres of agricultural land. Project water was from Lake Granby for treatment was completed in 1982. initially used primarily for agriculture, but municipal uses The town of Estes Park is located around Lake Estes and have increased in recent years (fig. 3). has a population of approximately 3,000 (fig. 5). Less dense Primary land uses within the parts of the watersheds development is located along the Big Thompson Canyon from where CBT project water is diverted and stored are unde- Estes Park to the mouth of the canyon west of Loveland. Water veloped forest and rangelands under the management of the quality is potentially affected by treated sewage effluent from U.S. Department of Agriculture Forest Service and National Estes Park discharged into the Big Thompson River upstream Park Service (figs. 4 and 5). The facilities on the western slope from Lake Estes. Smaller sewage-treatment facilities and and those near Estes Park are located in mountainous terrain ISDS’s located along the Big Thompson River downstream (greater than 6,000-ft elevation) covered in coniferous forest, from Lake Estes could affect the quality of water diverted to underlain by mostly crystalline bedrock. Annual precipitation Horsetooth Reservoir through the Dille Tunnel (located just is in the range of 16 to more than 40 inches per year (Colorado upstream from the mouth of Big Thompson Canyon) and Climate Center, 1984). Horsetooth Reservoir and Carter Lake Hansen Feeder Canal. Development around Carter Lake is are located in more arid foothills on the edge of the mountain minimal, but residential development around Horsetooth front, are surrounded by grass/shrublands, and are underlain Reservoir could affect water quality (fig. 6). 6 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

EXPLANATION Land-use type and percentage of basin

Open water, 4 percent

Developed, less than 1 percent

Forest, 71 percent

Grand Lake Grass/shrubland, 24 percent

Agriculture, less than 1 percent Shadow Mountain Lake

Lake Granby

0 5 10 MILES

0 5 10 KILOMETERS

Figure 4. Land uses in watershed upstream from Lake Granby.

Hydrology mid-June when daily streamflow runoff peaks. Daily fluctuations in streamflow, which can substantially affect stream- The study area, because of its location in high mountains, water quality by influencing dilution and particle transport, derives annual streamflow primarily from snowmelt during may be largely due to diurnal variations in air temperatures, May through July as shown in the streamflow statistics for affecting snowmelt. the period of record at the Colorado River below Baker Gulch Operation of reservoirs and conveyances can affect sea- stream gage (fig. 7). The watershed area upstream from Lake sonal water quality, streamflow, and limnological characteris- Granby outlet is about 310 square miles. The watershed area tics of storage reservoirs. Some streamflow and reservoir data upstream from the mouth of Big Thompson Canyon is about were available from USGS sources, but most was obtained 306 square miles. The high-elevation areas of these catch- from either NCWCD or the Colorado State Engineers Office. ments receive large amounts of snow from September to Seasonal and annual operational characteristics of selected May. Maximum snowpack accumulation generally occurs conveyances and reservoirs are shown in figure 8. Release and about the beginning of May and is mostly melted by about storage patterns are relatively similar over the period of record Hydrology 7 Open water, less than 1 percent Developed, not greater than 1 percent Forest, 68 percent Grass/shrubland, 30 percent Agriculture, less than 1 percent EXPLANATION Land-use type and percentage of basin Lake Estes Estes Park N 00 5 5 10 KILOMETERS 10 MILES Land uses in watershed upstream from the mouth of Big Thompson Canyon. Figure 5. 8 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

EXPLANATION

Horsetooth Land-use type and percentage of basin Reservoir Open water, 17 percent

Developed, 1 percent

Forest, 21 percent

Grass/shrubland, 59 percent

Agriculture, 1 percent

0 2 4 MILES

0 2 4 KILOMETERS

Figure 6. Land uses in watershed draining directly to Horsetooth Reservoir. on a year-to-year basis at Shadow Mountain Lake, Horsetooth elevation in July of each year, falling steadily through sum- Reservoir, and Carter Lake (fig. 9). The contents of Shadow mer and winter until April, when storage of the next snowmelt Mountain Lake, and consequently Grand Lake, vary little begins (fig. 11). Storage in Horsetooth Reservoir is some- because the reservoir is controlled to minimize fluctuations what different from Lake Granby in that average storage in in water-surface elevation. Multiyear patterns of storage can Horsetooth increases from November through May or June be seen in plots of contents for Lake Granby. Storage accu- and is then depleted during the summer season. In Carter mulated in wet years can persist for several years. Similarly, Lake, storage increases from about October through April. when depleted, Lake Granby can take several years to refill. The effects of drought years such as 1977 can be seen clearly in plots of reservoir contents for Lake Granby and Horsetooth Water Quality Reservoir. Seasonal flow patterns among the conveyances are evi- In this report, water quality will be described in two dent in the plots. Highest flow rates occur at the Willow Creek general categories: chemical characteristics and limnology. Canal and the Windy Gap pipeline during snowmelt season The discussion of chemical characteristics will present sum- (fig. 10). Flow rates are highest in Granby Pump Canal, Adams mary statistics, boxplots of chemical constituents, and descrip- Tunnel, and Carter Lake inflow during the winter months. tions of general water-quality conditions at the sampling sites. Hansen Feeder Canal conveys flow mostly in winter and The number of samples may differ from boxplot to summary summer and generally maintains lower rates of flow in early statistics because of the automated nature of the summary spring and fall. On average, Lake Granby reaches maximum statistics/database and the use of estimated values in the Water Quality 9

1,000 EXPLANATION

MAXIMUM DAILY

800 DAILY MEAN

MINIMUM DAILY

600

400 PER SECOND

200 STREAMFLOW, IN CUBIC FEET

0 JFMAMJ J ASOND

Figure 7. Maximum, mean, and minimum daily streamflows for the period of record (1953 to 2000) at Colorado River below Baker Gulch (09010500). boxplots. The discussion of limnology will present reservoir collected approximately monthly from May to October. In field-measurement profiles, hypolimnetic oxygen dynamics, 1998, sampling frequency decreased to four times per year trophic indicators, and nutrient limitation at reservoir sites. during the growing season. Sampling at Lake Granby (site 2) in Rainbow Bay was started in 1989 and followed a schedule of one per month during May to September until 2000. Chemical Characteristics Sampling at Granby Pump Canal (site 3) was approximately bimonthly on average from 1970 to 2000. The exact months The types of water-quality data collected at most sites sampled varied because samples were not collected in a that are part of the scope of this report include field measurements (water temperature, specific conductance, pH, and particular month if there was no flow at the time of the visit. dissolved oxygen), major ions (calcium, magnesium, sodium, Sampling at Shadow Mountain Lake (site 4) began consis- potassium, acid-neutralizing capacity or alkalinity, sulfate, tently in 1989 at a frequency of three per year during the chloride, fluoride), nutrients (ammonia plus organic nitro- growing season, increased to six per year from 1991 to 1997, gen, ammonia, nitrite, nitrite plus nitrate, total phosphorus, and decreased to four per year from 1998 to 2000. Sampling dissolved phosphorus, orthophosphorus), and selected trace at the Adams Tunnel East Portal (site 5) began in 1970 at a elements (iron, manganese, barium, strontium, and zinc). Sum- monthly frequency until 1988, when the bimonthly schedule mary statistics were compiled for the 10 sites in this study and that continued through 2000 was implemented. Sampling at are listed in tables 4 to 20 in the “Hydrologic Data” section Lake Estes (site 6) was begun in 1998 at a frequency of two (appendices at back of this report). per year, with samples collected at the surface and near the Surface and near-bottom sampling from each reservoir bottom in May and August. Monthly sampling at Olympus included field-measurement profiles. Some reservoir sites Tunnel (site 7) began in the fall of 1970 until 1986. By 1989, during the 1970’s had only a surface sample collected or an frequency had dropped to three samples per year, one each in additional intermediate depth sample collected in addition to spring, summer, and fall, and continued at the same frequency the surface and near-bottom samples. Sampling frequency has until 2000. Sampling at Carter Lake Reservoir (site 8) began not remained constant throughout the history of the program. in 1970 at a frequency of 9 or 10 per year, April to November The frequency history described here includes only the sites until 1979. By 1983, sampling frequency was reduced to three considered for this report. Other discontinued sampling sites per year during the spring through fall and continued to 2000. on Carter Lake and Horsetooth Reservoir are not described in Sampling at Horsetooth Reservoir (Soldier Canyon Dam) this report but are described in Mueller (1990). (site 9) began in 1969, and samples were collected at surface, Lake Granby (site 1, fig. 1) near the dam was sampled bottom, and an intermediate depth from April to October or quarterly at the surface from 1973 to 1975. During 1979 to November until 1978. By 1982, frequency was down to one 1988, annual samples were collected from the surface and surface and one near-bottom sample in spring, summer, and near bottom. From 1989 to 1990, samples were collected fall. Sample collection began at the Spring Canyon Dam at surface and bottom, three times during the growing sea- (site 10) on Horsetooth in 1983 at a frequency of three per son (May to October). From 1991 to 1997, samples were year, surface and near bottom. 10 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40,000 ADAMS TUNNEL

20,000

0 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

40,000 GRANBY PUMP CANAL

20,000

0 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

40,000

WINDY GAP CANAL

20,000

0 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

40,000

WILLOW CREEK CANAL

20,000

0 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

MONTHLY MEAN STREAMFLOW, IN ACRE-FEET 40,000

HANSEN FEEDER CANAL

20,000

0 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

40,000

CARTER LAKE INFLOW

20,000

0 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

Figure 8. Time-series plots of operation of selected Colorado–Big Thompson conveyances. Water Quality 11 R HORSETOOTH RESERVOI CARTER LAKE SHADOW MOUNTAIN LAKE LAKE GRANBY 1948 1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 19941948 1996 1950 1998 2000 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 1948 1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 19961948 1998 1950 2000 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 0 0 0 plots of operation selected Colorado–Big Thompson reservoirs. Time-series

19,000 18,000 17,000 16,000 50,000

800,000 600,000 400,000 200,000 200,000 100,000 150,000 100,000 RESERVOIR CONTENTS, IN ACRE-FEET IN CONTENTS, RESERVOIR Figure 9. 12 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

30,000 EXPLANATION ADAMS TUNNEL 25,000 GRANBY PUMP CANAL HANSEN FEEDER CANAL CARTER LAKE INFLOW 20,000 WILLOW CREEK CANAL WINDY GAP PIPELINE

15,000 IN ACRE-FEET

10,000 MONTHLY AVERAGE DISCHARGE, 5,000

0 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

Figure 10. Monthly average discharge characteristics of selected Colorado–Big Thompson conveyances.

450,000 EXPLANATION LAKE GRANBY 400,000 SHADOW MOUNTAIN LAKE CARTER LAKE 350,000 HORSETOOTH RESERVOIR

300,000

250,000

200,000 IN ACRE-FEET

150,000

100,000

MONTHLY AVERAGE RESERVOIR CONTENTS, 50,000

0 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

Figure 11. Monthly average reservoir contents of selected Colorado–Big Thompson reservoirs. Water Quality 13

Field Measurements and Major-Ion but calcium is predominant (fig. 13). Anion compositions are Concentrations primarily bicarbonate. Adams and Olympus Tunnel water had the most variability, with some samples containing relatively In snowmelt-dominated mountain streams, one of the less bicarbonate and more sulfate. Horsetooth Reservoir primary processes controlling specific-conductance and major- composition was less variable but is mostly within the range of ion concentrations is dilution; minimum values of specific water sampled from the tunnels. Despite having larger concen- conductance occur during peak snowmelt discharge and maxi- tration of dissolved solids, Horsetooth Reservoir water seemed mum values occur during winter low-flow conditions (Stevens, to be a more concentrated version of the tunnel water. 2001; Clark and others, 2000). Daily fluctuations of specific conductance in streams not affected by reservoirs also reflect dilution by the daily diurnal fluctuation of flow during high Nutrients snowmelt (Stevens, 2001). In reservoirs and conveyances that Compounds of nitrogen and phosphorus are referred to as move water from reservoirs, these fluctuations are tempered “nutrients” because they are the major building blocks of plant by mixing that occurs during storage. Thus, concentrations are growth. In excess quantities, nutrients can promote nuisance smoothed substantially in a reservoir like Lake Granby that algae growth in streams and reservoirs. Natural sources of can potentially store multiple years of runoff. nutrients include precipitation and biochemical processes in Water at CBT sampling sites was dilute and typical of the watershed. Possible anthropogenic sources of nutrients in high-elevation snowmelt runoff (fig. 12). Median concentra- the CBT system include the following: tions of specific conductance at sites on the western slope (such as Lake Granby and Shadow Mountain Lake) and the 1. Urban runoff.—Associated with developed areas and high-elevation sites on the eastern slope (such as Adams roads, storm runoff may have higher nutrient concentra- Tunnel, Lake Estes, and Olympus Tunnel) were generally tions and, as road runoff, may bypass natural removal below 60 microsiemens per centimeter at 25 degrees Celsius processes in soil by rapid delivery to a receiving stream (µS/cm). These sites are indicative of a hydrologic setting that or reservoir; is typical of snowmelt-source water—low rates of evapo- 2. Sewage effluent.—Septic-tank effluent can move with transpiration (ET) and crystalline bedrock geology. Specific ground water into surface-water systems. Rural areas are conductance at sites at Carter Lake and Horsetooth Reservoir often developed beyond the practical extent of municipal were generally greater than 70 µS/cm. These sites possibly sewer lines, necessitating the use of septic leach fields. show the cumulative effects of development and ET from the Although the town of Grand Lake has installed a sewer rest of the storage and conveyance system. These sites are at system (Three Lakes Sanitation District), not all resi- lower elevations (higher ET) in areas of sedimentary rocks dences within the watershed are connected to it. Estes that can increase dissolved-solids content. Even so, all water Park effluent is treated (Estes Park Sanitation District sampled in this system should be considered to be high quality and Upper Thompson Sanitation District) and returned to because of its low dissolved-solids content. the Big Thompson River. Other scattered development in Water temperature varied seasonally, with reservoir sites the Big Thompson watershed is not connected to munici- developing strong stratification patterns. The pH at CBT sites pal sewer systems; and was generally in a neutral range of 7 to 8. Dissolved oxy- 3. Erosion of soil and plant materials exposed near roads gen was generally in the range of 6 to 10 mg/L except in the or streams can cause loading of organic nitrogen and hypolimnetic water of the reservoirs, where seasonal stratifi- particulate phosphorus when transported to a stream. cation sometimes produced dissolved-oxygen concentrations approaching 2 mg/L or less. Nutrient concentrations at CBT sites generally were low Major-ion composition of selected waters was plotted (fig. 12). Data censoring levels changed many times through- on a Piper diagram (fig. 13) to determine if the composition out the study, and data analyses at times were of insufficient of water is changing as it moves from one part of the system precision to fully characterize concentration. Median con- to another. Adams Tunnel east portal was chosen because it centrations of ammonia plus organic nitrogen were less than represents the composition of water that is diverted from the 0.3 mg/L at all sites. Median concentrations of dissolved western slope and reflects any urban influences present on the nitrite plus nitrate concentrations were generally less than west side of the Continental Divide. Olympus Tunnel repre- 0.2 mg/L, and median concentrations of total phosphorus were sents water with urban influences from Estes Park. Horsetooth less than 0.05 mg/L at all sites. Concentrations of nitrite and Reservoir represents water with urban influences around the orthophosphorus were rarely reported. The largest concentra- reservoir and sedimentary substrate, and any influences of tions of nutrients tended to be at Carter Lake and Horsetooth wastewater treatment, septic tanks, and highway runoff in Reservoir. The smallest concentrations were generally mea- water diverted from the Dille Tunnel near the mouth of Big sured at Lake Granby and Shadow Mountain Lake. Bottom Thompson Canyon. Cation compositions in water from all samples tended to have larger concentrations of most nutrients three sites are somewhat mixed calcium-magnesium-sodium, than surface samples at the same site. 14 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances Adams Tunnel Carter Lake top Carter Lake bottom Lake Granby top Lake Granby bottom Granby Pump Canal Lake Granby Rainbow Bay top Lake Granby Rainbow Bay bottom Horsetooth Reservoir Soldier Dam top Horsetooth Reservoir Soldier Dam bottom Horsetooth Reservoir Spring Dam top Horsetooth Reservoir Spring Dam bottom Olympus Tunnel Shadow Mountain Lake top Shadow Mountain Lake bottom Lake Estes top Lake Estes bottom 90th percentile 75th percentile Median 25th percentile 10th percentile Reporting limit Data point plotted when number of observations is less than 10 EXPLANATION 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 (202) Number of observations (8) (8) (8) (8) (8) (8) (8) (8) (50) (58) (34) (58) (34) (58) (49) (58) (50) (65) (35) (58) (35) (58) (49) (65) (51) (181) (52) (173) (158) (244) (146) (241) (60) (58) (58) (59) (69) (59) (59) (72) (78) (61) (60) (57) (60) (57) (80) (60) (35) (37) (34) (37) (125) (124) (133) (129) 1234567891011121314151617 (279) (156) (179) (194) (35) (56) (202) (35) (56) (276) (143) (170) constituents. Boxplots of selected water-quality 0 5 0 3 2 1 0 8 4 0

15 10

200 100

IN MILLIGRAMS PER LITER PER MILLIGRAMS IN

PER CENTIMETER PER IN MILLIGRAMS PER LITER PER MILLIGRAMS IN

CHLORIDE, DISSOLVED, CHLORIDE, SULFATE, DISSOLVED, SULFATE, IN MICROSIEMENS MICROSIEMENS IN OXYGEN, DISSOLVED, OXYGEN, SPECIFIC CONDUCTANCE, SPECIFIC Figure 12. Water Quality 15 Adams Tunnel Carter Lake top Carter Lake bottom Lake Granby top Lake Granby bottom Granby Pump Canal Lake Granby Rainbow Bay top Lake Granby Rainbow Bay bottom Horsetooth Reservoir Soldier Dam top Horsetooth Reservoir Soldier Dam bottom Horsetooth Reservoir Spring Dam top Horsetooth Reservoir Spring Dam bottom Olympus Tunnel Shadow Mountain Lake top Shadow Mountain Lake bottom Lake Estes top Lake Estes bottom Number of observations 90th percentile 75th percentile Median 25th percentile 10th percentile Reporting limit Data point plotted when number of observations is less than 10 EXPLANATION 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 (188) (8) (5) (8) (8) ) (8 (5) (8) (8) (41) (58) (39) (55) (42) (58) (35) (53) (42) (59) (36) (60) (42) (65) (33) (54) (91) (38) (53) (40) (126) (178) (127) (121) (59) (55) (59) (53) (58) (70) (66) (56) (59) (59) (73) (54) (78) (59) (53) (54) (64) (76) (35) (42) (98) (102) (104) (98) 1234567891011121314151617 (70) (66) (53) (188) (35) (139) (179) (131) (134) (122) (108) (48) constituents.—Continued Boxplots of selected water-quality 0 0 1 0 1.0 0.5 0.3 0.5 0.2 0.1 0.2 0.1

0.15 0.10 0.05 0.05 0.02 0.01

0.005 0.002 0.001

MILLIGRAMS PER LITER PER MILLIGRAMS IN MILLIGRAMS PER LITER PER MILLIGRAMS IN MILLIGRAMS PER LITER PER MILLIGRAMS

IN MILLIGRAMS PER LITER PER MILLIGRAMS IN

ORGANIC, TOTAL, IN IN TOTAL, ORGANIC, NITRATE, DISSOLVED, DISSOLVED, NITRATE, DISSOLVED, IN IN DISSOLVED,

PHOSPHORUS, TOTAL, PHOSPHORUS, NITROGEN, AMMONIA PLUS PLUS AMMONIA NITROGEN, NITROGEN, NITRITE PLUS PLUS NITRITE NITROGEN, NITROGEN, AMMONIA, AMMONIA, NITROGEN, Figure 12. 16 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances m Data point plotted when number of observations is less than 10 90th percentile 75th percentile Median 25th percentile 10th percentile Reporting limit Horsetooth Reservoir Spring Dam top Horsetooth Reservoir Spring Dam bottom Olympus Tunnel Shadow Mountain Lake top Shadow Mountain Lake bottom Lake Estes top Lake Estes bottom Adams Tunnel Carter Lake top Carter Lake bottom Lake Granby top Lake Granby bottom Granby Pump Canal Lake Granby Rainbow Bay top Lake Granby Rainbow Bay bottom Horsetooth Reservoir Soldier Dam top Horsetooth Reservoir Soldier Dam botto 1 2 3 4 5 6 7 8 9 EXPLANATION 10 11 12 13 14 15 16 17 note: log scale 1 234 567 891011121314151617 constituents.—Continued Boxplots of selected water-quality 1 0 0 0 1

0.3 0.2 0.1 0.1 IN MILLIGRAMS PER LITER PER MILLIGRAMS IN

0.15 0.10 0.05 0.01

MILLIGRAMS PER LITER PER MILLIGRAMS

NITROGEN, TOTAL, NITROGEN, 0.001

IN MILLIGRAMS PER LITER PER MILLIGRAMS IN

DISSOLVED, IN IN DISSOLVED, AMMONIA PLUS ORGANIC PLUS AMMONIA

AMMONIA, DISSOLVED, AMMONIA,

PHOSPHORUS, TOTAL PHOSPHORUS, NITRITE PLUS NITRATE, NITRATE, PLUS NITRITE Figure 12. Water Quality 17

100

100 CALC 80

IUM PLUS M 80

60 AGNESIUM

SULFATE 20 PLUS CHLORIDE

0 PERCENT

0 0

0 PERCENT 20

0 20 100 40 100 0 20 SODIUM PLUS 40 PO 60 80 80 20

40 60 SULFATE 80 60 60 40

60 TASSIUM MAGNESIUM 80 100 40 40 60

80 CARBONATE PLUS BICARBONATE 100 20 20 80 100

100 80 60 40 20 0 0 0 100

0 20 40 60 80 100 CALCIUM CHLORIDE, FLUORIDE, NITRITE PLUS NITRATE

PERCENT

EXPLANATION Adams Tunnel

Olympus Tunnel

Horsetooth Reservoir

Figure 13. Piper diagram showing major-ion composition of samples at selected sites.

Trace Elements because, in large concentrations, they are toxic to aquatic life; a large proportion of Colorado’s regulated constituents are Trace elements, for the purpose of this report, are metal trace elements (Colorado Department of Public Health and and transition metal elements commonly found in small (less Environment, Water Quality Control Commission, 2001). than 1 milligram per liter) concentrations. Analytes commonly Concentrations of common dissolved trace elements detected at most sites in this study included barium, iron, man- (such as iron and manganese) were commonly above ganese, strontium, and zinc. Most samples also were analyzed Minimum Reporting Limits (MRL’s) but usually less than for barium, beryllium, boron, cadmium, chromium, cobalt, 1 milligram per liter (fig. 12). Others, such as beryllium, copper, lead, lithium, molybdenum, nickel, silver, and vana- chromium, cobalt, lithium, molybdenum, nickel, silver, and dium. Trace elements are important indicators of water quality vanadium, were almost never reported. Zinc, lead, cadmium, 18 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances 89 MAY OCTOBER pH, IN STANDARD UNITS 67 0 0 20 40 60 80 20 40 60 80 180 100 120 140 160 100 120 140 160 180 15 MAY OCTOBER IN DEGREES CELSIUS WATER TEMPERATURE, 0510 0 0 20 40 60 80 20 40 60 80 100 120 140 160 180 100 120 140 160 180 10 5 OCTOBER OCTOBER MAY DISSOLVED OXYGEN, 0 IN MILLIGRAMS PER LITER 0 0 20 40 60 80 20 40 60 80 100 120 140 160 180 100 120 140 160 180 100 50 CELSIUS AT 25 DEGREES MAY OCTOBER May and October field-measurement profiles at Lake Granby (dam). SPECIFIC CONDUCTANCE, 0 0 0

20 40 60 80 20 40 60 80

100 120 140 160 180 100 120 140 160 180 DEPTH BELOW WATER SURFACE, IN FEET IN SURFACE, WATER BELOW DEPTH Figure 14. Water Quality 19 OCTOBER MAY pH, IN STANDARD UNITS 678 9 0 5 0 5 10 15 20 25 30 10 15 20 25 30 14 OCTOBER MAY 2 IN DEGREES CELSIUS WATER TEMPERATURE, 0 4 6 8 10 12 0 5 0 5 10 15 20 25 30 35 10 15 20 25 30 OCTOBER MAY DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER 0246810 0 5 0 5 10 15 20 25 30 35 10 15 20 25 30 80 OCTOBER CELSIUS 20 AT 25 DEGREES MAY May and October field-measurement profiles at Shadow Mountain Lake. SPECIFIC CONDUCTANCE, 46 12 04060

0 5 0 5

10 15 20 25 30 35 10 15 20 25 30 35 DEPTH BELOW WATER SURFACE, IN FEET IN SURFACE, WATER BELOW DEPTH Figure 15. 20 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances MAY OCTOBER pH, IN STANDARD UNITS 20 MAY IN DEGREES CELSIUS OCTOBER WATER TEMPERATURE, 1167 8 9 510156 15 MAY DISSOLVED OXYGEN, OCTOBER IN MILLIGRAMS PER LITER 0510 50 CELSIUS AT 25 DEGREES OCTOBER MAY 0 100 SPECIFIC CONDUCTANCE, May and October field-measurement profiles at Carter Lake. 0 0

20 40 60 80 20 40 60 80

100 120 140 160 180 100 120 140 DEPTH BELOW WATER SURFACE, IN FEET IN SURFACE, WATER BELOW DEPTH Figure 16. Water Quality 21 MAY OCTOBER pH, IN STANDARD UNITS 689 5 OCTOBER MAY IN DEGREES CELSIUS WATER TEMPERATURE, 010157 2 MAY DISSOLVED OXYGEN, OCTOBER 0 4 6 8 10 20 IN MILLIGRAMS PER LITER 50 12 CELSIUS AT 25 DEGREES OCTOBER MAY May and October field-measurement profiles at Horsetooth Reservoir (Soldier Canyon Dam). 0 100 SPECIFIC CONDUCTANCE, 0 0

20 40 60 80 20 40 60 80

100 120 140 160 180 100 120 140 160 DEPTH BELOW WATER SURFACE, IN FEET IN SURFACE, WATER BELOW DEPTH Figure 17. 22 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances boron, and copper concentrations were reported infrequently, Environment, Water Quality Control Commission, 2001). and when reported, ranged from a few micrograms per liter to Estimates of the Colorado water-quality standards for samples a few tens of micrograms per liter (zinc). Sources of the more collected at the 10 sampling sites were calculated on the toxic trace elements (such as copper, cadmium, lead, and zinc) basis of numeric fixed standards or equations (Table of Value are generally associated with ore deposits or urban runoff. The Standards [TVS]) for each element (Colorado Department relative lack of such ore deposits and the relatively low density of Public Health and Environment, Water Quality Control of development in the drainage areas of the CBT project will Commission, 2001). Laboratory MRL’s for trace elements tend to limit concentrations of these toxic trace elements to such as cadmium, mercury, silver, and lead were commonly relatively low levels. too high to determine concentrations at the level of the standard. These constituents might be present in the sample at Colorado Water-Quality Standards concentrations lower than the laboratory MRL but higher than the standard. Samples were not analyzed for some constituents In Colorado, water-quality standards are determined by listed in the Colorado water-quality standards (for example, the Colorado Water Quality Control Commission and consist arsenic, chlorine, cyanide, selenium, and sulfide). of a narrative or numeric restriction established to protect the Based on all samples collected over the period of record, beneficial uses of water. Water-quality standards for streams in standards for chloride, sulfate, un-ionized ammonia, nitrate, Colorado are based on use classifications such as aquatic life, dissolved chromium, and dissolved nickel were not exceeded recreation, water supply, and agriculture. Some water-quality at any of the sampling sites in the study area. Dissolved standards for streams are set to specific values or concentra- oxygen exceeded minimum concentrations, and pH was not tions (such as dissolved oxygen, pH, nitrite, nitrate, chloride, below or above standards. Silver, lead, and cadmium concen- sulfate, iron, and manganese). Others, such as un-ionized trations occasionally exceeded computed standard values. The ammonia and some trace elements, are usually site specific fixed standard for dissolved iron (300 µg/L) was exceeded at and use hardness data and equations for each element to cal- Lake Granby (two samples), Adams Tunnel (one sample), and culate standards (Colorado Department of Public Health and Shadow Mountain Lake (one sample). The fixed standard for Environment, Water Quality Control Commission, 2001). In dissolved manganese (50 µg/L) was exceeded at Lake Granby certain cases, fixed numeric standards have been established (10 samples), Horsetooth Reservoir (17 samples), and Shadow that reflect site-specific conditions and may specify trace- Mountain Lake (17 samples). Many of the manganese exceed- element phases and analytical techniques (such as dissolved ances were in the early 1990’s, mainly in near-bottom samples. or total recoverable methods). The fixed standard for manganese was not exceeded at Carter Trace-element concentrations are assumed to be Lake. The presence of manganese is a common problem in the dissolved unless designated otherwise by the numeric standards (Colorado Department of Public Health and bottom water of lakes and reservoirs and can adversely affect Environment, Water Quality Control Commission, 2001). drinking-water treatment, cause staining of laundry when used Acute standards are values or concentrations not to be for washing, and when it precipitates in excessive quantities, exceeded for 1 day. Chronic standards are not to be exceeded can smother aquatic life (Niyogi and others, 1999). by the 85th percentile of sample concentrations in a represen- tative period. Extraordinary ephemeral or seasonal conditions Limnology do not constitute violations. Stream-standard concentrations and values are not to be exceeded more than once every The following sections of the report will discuss issues 3 years on average (Colorado Department of Public Health of water quality that pertain to the reservoir sites. Conditions and Environment, Water Quality Control Commission, 2001). in the reservoirs affect not only that particular water body but Thus, continued systematic monitoring is needed to determine the conveyances and streams into which that water is released, compliance or noncompliance with a standard. diverted, or pumped. The State of Colorado specifies that hardness concentrations used to calculate the trace-element standards be computed from the lower 95-percent confidence limit of the mean Reservoir Profile Characteristics hardness at the periodic low-flow criteria determined from regression analysis of site-specific or regional data. In this Reservoir profile data are routinely measured when study, however, hardness concentrations were determined from water-quality samples are collected. These measurements are analysis of water samples collected at the time of sampling. typically made with an instrument that contains sensors for The comparison of standards in this report, therefore, is a water temperature, specific conductance, pH, and dissolved general indicator. oxygen. The instrument is lowered beneath the surface from The use classifications for CBT sampling sites for this a boat that is held as stationary as possible over the sampling report are Aquatic life cold 1, Recreation 1, Water supply, location. Successive readings are taken throughout the depth and Agriculture (Colorado Department of Public Health and profile when the instrument stabilizes at a particular depth. Water Quality 23

Plots of profiles measured in May and October at the oxygen concentration begins to decrease steadily through- Lake Granby, Shadow Mountain Lake, Carter Lake, and out the stratification season as a result of decay processes Horsetooth Reservoir are shown in figures 14 to 17. The pro- that steadily consume oxygen. The rate at which oxygen is files are intended to show how these measurements vary with consumed is indicative of the rate of biological activity, which depth at the beginning of the ice-free season (May) and the is indicative of the level of eutrophication (Green, 1996). end of the ice-free season (October). May and October The hypolimnion does not remix and reoxygenate until fall also were the two months commonly measured at all sites overturn in lakes that are stratified in summer. These lakes a number of times during the study period. restratify in winter and remix again in spring. By May, water-temperature stratification had already The technique of computing and using areal hypolimnetic begun at most of the reservoirs, particularly at the lower oxygen deficits for analysis of eutrophication is described in elevations of Carter Lake and Horsetooth Reservoir, where detail in Green (1996) and will be described briefly in this conditions may be ice-free a couple of months earlier. Specific report. Through the use of one of the PROFILE routines in the conductance, pH, and dissolved oxygen have not yet become U.S. Army Corps of Engineers BATHTUB model (Walker, strongly stratified with depth in May, and dissolved-oxygen 1996), areal hypolimnetic oxygen deficit (AHOD) was com- concentrations are relatively high throughout the profiles. puted for each growing season in each of four reservoirs (Lake In the fall (October), conditions at the deeper reservoirs Granby, Shadow Mountain Lake, Carter Lake, and Horsetooth usually remained strongly stratified from summer heating Reservoir) when sufficient profile data were available. The except at Shadow Mountain Lake, where shallow depths model can be used with data inputs of bathymetry, profile (mean depth approximately 15 ft) interfere with the full data, estimates of the elevation of the hypolimnion for each development of a thermocline. In the other reservoirs, the top profile, and time series of reservoir water levels to make com- of the thermocline was at approximately 30 to 60 ft of depth putations of AHOD, which is defined as the change in oxygen most years in October (figs. 14–17). During stratification, per square meter of hypolimnetic surface per day through specific conductance sometimes increased slightly with depth the stratification season (approximately May to September or in Lake Granby and Horsetooth Reservoir. Dissolved oxygen October). To ensure that fall overturn reoxygenation has not was sometimes hypoxic in October profiles in the hypolim- begun, Walker (1996) recommends that the profile period of nion of the deeper reservoirs, and pH generally decreased computation for AHOD begin with a spring profile in which with depth in May and October profiles at Lake Granby, stratification has already been established (usually May in this Horsetooth Reservoir, and Carter Lake. The lowest hypolim- study) and end with a profile that is not beyond the peak of netic dissolved-oxygen concentrations in October were from near-bottom oxygen depletion (usually July or August in this Lake Granby and Horsetooth Reservoir, where near-bottom study). AHOD is computed as the rate of change (slope) of the concentrations in some years were less than 2 mg/L. areal hypolimnetic oxygen content (AHOC) computed by the model through the stratification season. Time-series plots of computed annual AHOD are shown Hypolimnetic Oxygen Dynamics in figure 18 for Shadow Mountain Lake, Lake Granby, Carter Dissolved-oxygen profiles show the distribution of Lake, and Horsetooth Reservoir. There may be patterns present oxygen concentrations with depth, but the shape of the pro- in the AHOD data, and the cycles are not necessarily the same files, their seasonal characteristics, reservoir water level, and for each reservoir. These patterns suggest that climatic, biologi- hydraulic residence time (flushing rate) can be highly vari- cal, or operational cycles may influence the rates of oxygen able. This variation makes it difficult to compare from year consumption in these reservoirs. The AHODs for each reservoir to year or site to site. One approach to using the dissolved- should not be directly compared to one another because they oxygen profile data involves making computations that take include the influences of water temperature and morphological into account reservoir bathymetry, reservoir contents, and the characteristics, which may vary in each reservoir. development of the oxygen profile during the growing season. In this way, there is the potential to compare dissolved-oxygen Trophic Indicators and Nutrient Limitation dynamics from year to year. Because low concentrations of dissolved oxygen can be cited as a consequence of eutrophic The relative fertility of a lake or reservoir can be evalu- conditions, a comprehensive measure of those concentrations ated by assessing the trophic status. Oligotrophic (nutrient- can contribute to the understanding of trends in eutrophication. poor) lakes have characteristics such as high transparency, The zone in a reservoir where oxygen depletion is small organic-matter content, relatively large dissolved- generally greatest is in the hypolimnion. The hypolimnion is oxygen concentrations, small nutrient concentrations, and the deep portion of the water-temperature profile, below the small algal biomass. Eutrophic (nutrient-rich) lakes have the thermocline, that becomes isolated from the epilimnion and opposite characteristics (Woods, 1992). On the basis of data metalimnion during temperature stratification. After becom- collected over the period of record at each site, CBT reservoirs ing isolated from the atmosphere and other sources of oxygen, were assessed using the method developed by Carlson (1977). 24 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

100

80 SHADOW MOUNTAIN LAKE

0 1,000

800 LAKE GRANBY

600

400

200

0 2,000

CARTER LAKE 1,500

1,000

500

0 1,500

HORSETOOTH RESERVOIR

1,000

500 AREAL HYPOLIMNETIC OXYGEN DEFICIT, IN MILLIGRAMS PER SQUARE METER DAY

0 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

Figure 18. Time-series plots of annual areal hypolimnetic oxygen deficit in reservoirs.

Trophic-state index (TSI) values were calculated from the Secchi-disk depth, total phosphorus (surface only), and following equations: chlorophyll-a values were averaged for each year to compute TSI(SD) = 60 – 14.41(ln SD) (1) mean values. The annual mean values were then used to com- TSI(TP) = 14.42(ln TP) + 4.15 (2) pute annual TSI values plotted in figure 19. Censored values of TSI(CHLA) = 9.81(ln CHLA) + 30.6 (3) total phosphorus were common in the 1990’s, and not all TSI’s where could be computed. The Carlson (1977) TSI index assumes SD is Secchi-disk depth, in meters; phosphorus limitation. The boundary between oligotrophic (nutrient-poor) and mesotrophic (moderate nutrients) is a TSI TP is total phosphorus concentration, in micrograms per liter; value of 30. The boundary between mesotrophic and eutrophic (nutrient-rich) is a TSI value of 50. Most of the TSI values CHLA is chlorophyll-a concentration (high-performance liquid chromatography was used), in for the reservoirs in this study are in the mesotrophic range. micrograms per liter; A tendency toward decreasing trophic status in the 1990’s at Lake Granby and Shadow Mountain Lake is based primarily and on Secchi depth, and chlorophyll-a concentrations and can be ln is the natural logarithm of the indicated variable. seen in the plots. Water Quality 25

The indices are meant to normalize the three indicators not affect or might even decrease the chlorophyll-a index so that any of the three could describe the conditions in the due to reduced light penetration. Other cyclic factors such as water body. At Lake Granby and Shadow Mountain Lake, the grazing of phytoplankton by zooplankton can make interpreta- three indices agree fairly well. At Carter Lake and Horsetooth tion of chlorophyll-a indices problematic. The use of TSI can Reservoir, the index for phosphorus does not compare well give a qualitative indication of relative status of water bodies with the indices for Secchi depth and chlorophyll-a. Turbid but should not be used exclusively to evaluate whether lakes conditions caused by suspended sediment could raise both the and reservoirs are meeting the criteria of their water-quality total phosphorus and Secchi-depth TSI’s relatively but might classifications.

100

LAKE GRANBY NEAR DAM LAKE GRANBY RAINBOW BAY 80

60 EUTROPHIC EUTROPHIC

40 MESOTROPHIC MESOTROPHIC

20 OLIGOTROPHIC OLIGOTROPHIC

0 100 SHADOW MOUNTAIN LAKE CARTER LAKE

EUTROPHIC EUTROPHIC 60

40 MESOTROPHIC MESOTROPHIC

20 OLIGOTROPHIC OLIGOTROPHIC

0 100

TROPHIC STATUS INDEX, DIMENSIONLESS HORSETOOTH RESERVOIR SOLDIER HORSETOOTH RESERVOIR SPRING CANYON DAM CANYON DAM 80

EUTROPHIC EUTROPHIC 60

40 MESOTROPHIC MESOTROPHIC

OLIGOTROPHIC 20 OLIGOTROPHIC

0 1970 1980 1990 2000 19701980 1990 2000

EXPLANATION TSI, Secchi depth TSI, Total phosphorus TSI, Chlorophyll-a

Figure 19. Annual trophic status index (TSI) computations for Secchi depth, total phosphorus, and chlorophyll-a by the Carlson (1977) method. 26 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

Nitrogen (N) to phosphorus (P) mass ratios have been 1. Many time-series data are not exclusively monotonic, used to characterize the limiting nutrient for algal growth a condition that could obscure small-scale trends in the present in water (Britton and Gaggiani, 1987; Woods, 1992). trend testing. For example, a normal distribution curve If a nutrient is limiting, the hypothesis is that the addition of would represent strong trends if it were a time series, that nutrient would then cause an increase in algal produc- but the symmetrical qualities would cancel out the tion (in the absence of other limiting factors) (Britton and monotonic properties and no significant trends would Gaggiani, 1987; Woods, 1992). Due to the large number of be computed. This problem is particularly evident in censored nitrogen and phosphorus concentrations, the N/P the nutrient data at some of the sites that have long ratios were not analyzed. An analysis of N/P ratios would periods of record. Sites such as Granby Pump Canal, indicate only certain conditions when nutrient concentrations Olympus Tunnel, Adams Tunnel east portal, Horsetooth were high (greater than minimum reporting limits) and not the Reservoir at Soldier Canyon Dam, and Lake Granby full range of ratios for different concentration conditions in the Dam show clearly some peaking of nutrient concentra- reservoirs. tions in the early 1980’s (despite the problematic changes in minimum reporting limits) that might not be assessed adequately by monotonic trend testing of the full period of record (fig. 20). Other constituents are well character- Trend Analysis ized as monotonic distributions (fig. 21). 2. In general, specific conductance, dissolved solids, Time-series trend analysis is a common approach to and most of the major ions at most sites have similar evaluating the temporal changes in long-term data sets. The LOWESS curve shapes, indicating that some of the data method chosen for the CBT data is the seasonal Kendall for constituents and properties may be providing redun- nonparametric test. The test is robust in that it does not require dant trend information. normality, can be used with censored data, and seasonal effects that can obscure the detection of a trend can be removed. The 3. Because the data at most sites are collected in a very test is computed on the ranks of the data and will indicate limited number of seasons, some of the variability and the significance of monotonic trends (generally increasing or representativeness of the annual water-quality changes decreasing with time) and provide an estimate of the slope of at the sites are potentially lost. Trend results apply to the change in the median of the data. Further details on the seasons represented in the data set. method and applications can be found in publications such as 4. Apparent decreases in nutrient concentrations through- Helsel and Hirsch (1995), Middelburg (1993), Clark and oth- out the system are accompanied by decreases in iron ers (2000), and Mueller (1990). (Fe) and manganese (Mn) concentrations. This pattern could indicate a relation between fertility and bottom- water hypoxia (which can cause reducing conditions that Time-Series Data release Fe and Mn). 5. The degree of variability is high in the chlorophyll-a Time-series data were compiled from the USGS database data, indicating that sampling frequency may not be suf- for the period of record at each site. To help with visual assimi- ficient to adequately describe algal population dynamics lation of these large data sets, scatterplots of each constituent of that occur in short time scales. interest were made and a trace of a LOWESS smooth regression was drawn unless periods of data were missing or a series of Some qualitative temporal trend information based on values were less than MRL (see figs. 23–37 in “Hydrologic and visual inspection of the time-series plots is summarized here: Water-Quality Data” section at back of report). The LOWESS 1. Field measurements of dissolved oxygen and pH are smooth curve was estimated using the MRL in cases where data relatively stable through time at most sites. Small fluc- were censored. Total ammonia and total nitrate were considered tuations are probably related to factors such as changes similar to dissolved ammonia and dissolved nitrite plus nitrate in water temperature, water depth, collection date, and for plotting and trend-testing purposes. Mueller (1990) made a reservoir contents. Slight decreases in dissolved oxygen comparison of the total and dissolved data for these constituents are shown by the LOWESS curves in the near-bottom and found no statistical difference. If a field specific conduc- samples at Lake Granby (Rainbow Bay) (fig. 26), Carter tance or pH value was missing or erroneous, the laboratory Lake (fig. 33), and Horsetooth Reservoir (fig. 35). value was substituted. 2. Specific conductance, dissolved solids, and most major Certain characteristics of the data are visible in the plots ions show decreases in concentrations at most sites that are not evident in the application of the statistical trend over time. Since 1998, however, downward trends have test. Variability, nonmonotonic trends, and nonseasonal cycles flattened at sites on the western slope (Lake Granby, are important information that are not conveyed by a p-value Shadow Mountain Lake, Granby Pump Canal), and since or slope. 1998, upward trends are evident at Horsetooth Reservoir. A few general observations about the data from the time- Some decreases might be related to high runoff years series plots (see figs. 23–37 in “Hydrologic and Water-Quality when large volumes of water containing low dissolved Data” section at back of report) are listed here: solids are stored, influencing concentrations for many Trend Analysis 27

2.0 All data 1978 to 2000 EXPLANATION Downward trend LOWESS CURVE 1.8 Slope = –0.006888 mg/L per year ALL DATA p-value = less than 0.0001 LOWESS CURVE 1.6 SEASONAL UNCENSORED CENSORED 1.4

1.2

1.0 Post-1982 data Pre-1983 data Downward trend Upward trend Slope = –0.00857 mg/L per year 0.8 Slope = 0.1008 mg/L per year p-value = less than 0.0001 p-value = less than 0.0001 0.6 IN MILLIGRAMS PER LITER

0.4

0.2 NITROGEN, AMMONIA PLUS ORGANIC,TOTAL,

0 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

Figure 20. Nonmonotonic distribution and seasonal Kendall test results for pre-1983 and post-1983 of ammonia plus organic nitrogen (total) at Adams Tunnel east portal.

300 EXPLANATION LOWESS CURVE ALL DATA All data 1978 to 2000 LOWESS CURVE 250 Downward trend SEASONAL Slope = –1.791 micrograms per year p-value = less than 0.0001 UNCENSORED CENSORED

200

150

100

50 IRON, DISSOLVED, IN MICROGRAMS PER LITER

0 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

Figure 21. Monotonic distribution and seasonal Kendall test results for all samples of dissolved iron at Adams Tunnel east portal. 28 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

years afterward, as that dilute water is pumped through- Constituents chosen for analysis included field measurements, out the system from the Lake Granby storage. The dilu- major ions, nutrients, chlorophyll-a and -b, fecal and total coli- tional effects of high runoff in 1995 can be seen in many form bacteria, and trace elements that were routinely reported plots (figs. 23–37). above censoring levels. 3. At sites with 20 years or more years of record, nutrient Trend for a particular constituent was only computed concentrations have decreased (sometimes substantially) when less than 50 percent of the data was below the MRL and from early 1980’s levels. Multiple MRL’s and large more than 5 years of data was available. Lake Estes had less amounts of data below the MRL in recent years have than 5 years of data and was therefore excluded. If more than made it difficult to characterize the most recent trends. 5 percent of the data was censored, the slope of the median It is clear, however, that nutrient concentrations seem was not reported. Small breaks in the time series were accept- to have peaked sometime in the 1970’s and early 1980’s able if they occurred in the middle one-third of the data. Many and have stayed at relatively low levels during the 1990’s. of the nutrient species at particular sites were mostly censored Good examples of this pattern can be seen in some plots data and were not tested. Top- and bottom-sample constitu- of ammonia plus organic nitrogen, ammonia, nitrite plus ents were tested separately. No flow adjustments were made nitrate, and total phosphorus for Adams Tunnel (fig. 30), because all sites were reservoirs or conveyances receiving Olympus Tunnel (fig. 31), Granby Pump Canal (fig. 27), water from reservoirs. Because multiple MRL’s were common, Horsetooth Reservoir (Soldier Canyon Dam) (figs. 34 all censored data were recensored to the highest MRL. Or, in a and 35), and Carter Lake (figs. 32 and 33). This pattern few cases, the highest MRL data in a series were ignored if the is much less definitive in Lake Granby (figs. 23 and 24). data could be eliminated by minor shortening of the beginning 4. Trace elements such as iron (Fe) and manganese (Mn) or ending of the period of record for the analysis. Estimated have a high degree of variability that is probably caused data were treated as legitimate. Most outliers were allowed to by seasonal reducing conditions. Reducing conditions remain, as the data sets commonly were very large, and the can cause the release of Fe and Mn from bottom sedi- seasonal Kendall method is relatively unaffected by outliers. ments and are proportional to the degree of hypolimnetic The choice of available seasons was limited as sampling oxygen depletion in a given growing season and the prox- frequency at most sites was down to three samples per year imity to which the near-bottom sample can be collected near the end of the period of record. Seasons were chosen to close to the reservoir bottom sediment (a variable and maximize the length of record for testing. The seasons and uncertain exercise). Similar to nutrients, concentrations of periods of record used for testing each site are listed in table 2. Fe and Mn in the long records at Adams Tunnel (fig. 30), The period of record tested may differ slightly depending on Olympus Tunnel (fig. 31), and Horsetooth Reservoir the particular constituent or property and the sampling history. (figs. 33 and 35, iron only) peak in the early 1980’s When multiple samples were available for a particular season, and generally decline through 2000. the most complete set of sample constituents was first criterion, 5. Miscellaneous measurements such as transparency, and the sample closest to the beginning of the target month was chlorophyll-a, and bacteria also show patterns that the next criterion for choosing among multiple samples. can be observed on time-series plots. Records of transpar- Summary results of trend testing are summarized in ency generally show increasing clarity in CBT system table 3. Detailed summaries by site that include p-values and reservoirs from 1970 to 2000, although seasonal variability any trend slopes that were computed are listed in Hydrologic is fairly high (often 50 to 100 inches or more over a few and Water-Quality Data tables 21 to 35 at back of report. months). The record for chlorophyll-a is relatively short Three alpha-significance levels were used in the summaries: (about 11 years). Two peaks of concentration can be seen greater than 90 percent was considered significant; greater at Lake Granby (spillway) (fig. 23), Shadow Mountain than 95 percent was moderately significant; and greater than Reservoir (fig. 28), and Horsetooth Reservoir (figs. 34 99 percent was highly significant. The slope is the median of and 36) corresponding to approximately 1990–91 and all slopes between data pairs in the same season and is reported 1995–96. Concentrations of bacteria are generally very in the tables in units of change per year for the median. Posi- low (less than 10 colonies per 100 milliliters) for all sites. tive slopes indicate upward trends (increasing concentrations Some large spikes in concentrations of fecal and total coli- or values with time); negative slopes indicate downward trends form bacteria (more than 100 colonies per 100 milliliters) (decreasing concentrations or values) with time. fecal coliform and more than 1,000 colonies per 100 mil- Among field measurements, a downward (decreasing) liliters total coliform were reported in the early 1980’s at trend in specific conductance was common at all sites except Olympus Tunnel (fig. 31). surface samples in Shadow Mountain Lake (site 4S). An upward (increasing) temporal trend for pH was noted at all the conveyances and the surface samples of Carter Lake (site 8S) Statistical Testing and Horsetooth Reservoirs (sites 9S only). A negative trend in pH was computed for the near-bottom samples from Lake Seasonal Kendall test (Helsel and Hirsch, 1995) was Granby Rainbow Bay (site 2B). Trends for dissolved-oxygen used to determine the significance of monotonic temporal concentrations decreased in the near-bottom samples at Lake trends over the period of record for selected constituents. Granby Rainbow Bay (site 2B), Carter Lake (site 8B), and Trend Analysis 29

Table 2. Seasonal periods and period of record tested by seasonal Kendall test.

[Seasons are shown as ranges in months of the year; the hyphens connect months that represent ranges of the seasonal periods]

Site Period number Site name Seasons of record (fig. 1) 1 Lake Granby near Granby, Colo. (near spillway) May–June, July–Aug, Sept, Oct 1973–present 2 Lake Granby near Granby, Colo. (near dam in Rainbow Bay) May–June, July–Aug, Sept, Oct 1989–present 3 Granby Pump Canal near Grand Lake, Colo. No seasonal partition 1970–present 4 Shadow Mountain Lake near Grand Lake, Colo. May, July–Aug, Sept 1989–present 5 Alva B. Adams Tunnel east portal, near Estes Park, Colo. Bimonthly 1970–present 6 Lake Estes near dam near Estes Park, Colo. Insufficient record (less than 5 years) 1998–present 7 Olympus Tunnel at Lake Estes, Colo. Mar–Apr, July, Nov 1970–present 8 Carter Lake near Berthoud, Colo. Apr–May, July–Aug, Sept–Oct 1970–present 9 Horsetooth Reservoir near Fort Collins, Colo. (Soldier Canyon Dam) May–June, July–Aug, Sept–Oct 1970–present 10 Horsetooth Reservoir near Fort Collins, Colo. (Spring Canyon Dam) May–June, July–Aug, Sept–Oct 1983–present

Horsetooth Reservoir (sites 9B and 10B), and increased in the Carter Lake (site 8S and 8B). The trend in manganese was near-bottom samples of Lake Granby spillway (site 1B) and downward at Olympus Tunnel (site 7). Strontium, a minor Shadow Mountain Lake (site 4B). ion with similar chemistry to the major ions, showed a In general, major ions and hardness at all sites showed downward trend at all sites. Zinc was a downward trend significant downward trends. The exceptions were silica, at Olympus Tunnel (site 7), the only significant trend for which indicated upward trends at Shadow Mountain (site 4), zinc. The trend in barium was downward at Carter Lake Adams Tunnel (site 5), and all eastern slope sites (sites 6–10), (site 8S and 8B) and upward in the near-bottom samples at and chloride, which indicated upward trends at Carter Lake Horsetooth Reservoir (site 9B). (site 8) and Horsetooth Reservoir (sites 9 and 10). Trends for The AHOD data computed for Lake Granby, Shadow fluoride and sodium adsorption ratio were not significant. Mountain Lake, Carter Lake, and Horsetooth Reservoir at When significant, dissolved-solids trends were downward. the dam locations (related to hypolimnetic oxygen dynam- Among nutrients, a small number of significant trends ics described earlier) also were tested for temporal trends. were mostly stable (no trend) or downward. Downward trends First, the annual AHOD data were correlated with year were computed for total phosphorus at the Granby Pump Canal (temporal variable) by using a parametric Pearson correla- (site 3), Olympus Tunnel (site 7), Carter Lake (site 8), and tion. R-squared values ranged from less than 0.1 (Carter the surface samples at Horsetooth Reservoir (site 9S). Down- Lake Reservoir) to 0.14 (Granby Reservoir), indicating ward trends also are noted for ammonia plus organic nitrogen no linear correlation. Green (1996) established a correla- (total) at Granby Pump Canal (site 3), Shadow Mountain Lake tion between AHOD and reciprocal hydraulic residence (site 4S), and Adams Tunnel east portal (site 5). Nitrite plus time (RHRT) that explained additional variance in the nitrate had a significant downward trend at the Granby Pump temporal correlation. Plots of time-series RHRT (May to Canal (site 3) and an upward trend at Horsetooth Reservoir August each year) at four CBT reservoirs were computed (site 10B) in the near-bottom sample. using annual inflow or outflow data and average reservoir Transparency and chlorophyll-a variables, which are contents for each year (fig. 22). With CBT reservoir data, directly related to perceptions of eutrophication, showed some a correlation of log(AHOD) with log(RHRT) yielded improvement with time in Lake Granby (sites 1S and 2S). r-squared values ranging from 0.11 to 0.65. Encouraged Transparency showed an upward trend and chlorophyll-a a by the potential of the residence time to improve the downward trend at both of the surface sites in Lake Granby. temporal correlation, a regression model for log(AHOD) The only other significant trend in transparency was an that included log(RHRT) and the year was computed and upward trend at Horsetooth Reservoir (site 9S). No significant yielded r-squared values ranging from 0.12 to 0.65. Resid- trends in fecal coliform bacteria were detected. uals from a logAHOD/logRHRT regression (effects of Among trace elements, only barium, iron, manganese, RHRT removed) were then regressed with year. The largest strontium, and zinc had sufficient uncensored data for trend r-squared obtained was 0.13, indicating little evidence of testing. Downward trends in iron and manganese were notable AHOD changes with time (temporal trend). The AHOD at Lake Granby (sites 1 and 2, Fe-Mn), Granby Pump Canal data and RHRT data were then tested for trend using (site 3, Fe-Mn), and Shadow Mountain Lake (site 4S and Kendall’s tau and testing correlation with time. None of 4B, Mn only). On the eastern slope, iron showed downward the AHOD, RHRT, or residuals from the log(AHOD) and trends at Adams Tunnel (site 5), Olympus Tunnel (site 7), and log(RHRT) relation data had significant temporal trends. 30 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances Site 10(B) Site 10(S) 9(B) Site 9(S) Site 8(B) Site 8(S) Site 7 Site 5 Site per liter] urface sample; B, near-bottom sample; site names listed in table 1; mg/L, milli- sample; B, near-bottom urface nt; **, greater than 95 percent; ***, 99 A, no trend computation 4(B) Site Significant trends by study site 4(S) Site 3 Site 2(B) Site 2(S) Site 1(B) Site A -- A -- -- A ------A -- A -- 1(S) Site (–)*** -- (–)*** -- -- 0 ------0 -- 0 -- 0 -- ) (–)*** (–)*** (–)*** (–)*** (–)*** (–)* (–)*** 0 0 (–)*** (–)*** (–)*** (–)*** (–)* (–)*** 3 g/L) A (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** -- (–)** A 0 0 A 0 0 S/cm) (–)*** (–)*** (–)*** (–)*** (–)*** 0 (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** g/L) (–)*** (–)*** (–)*** (–)*** (–)*** (–)** (–)*** (–)*** (–)** (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** µ µ µ g/L) 0 0 0 0 0 0 (0)** 0 0 (–)* (–)* 0 (+)* 0 0 Property or constituent µ g/L) A 0 A A 0 A 0 0 (–)** 0 0 0 0 A A g/L) (–)*** (–)*** (–)*** (–)*** (–)*** 0 (–)*** (–)*** (–)*** (–)** 0 0 0 0 g/L) g/L) µ µ µ µ ( ( a b Summary of significant upward and downward temporal trends at Colorado-Big Thompson sampling sites. Chloride, dissolved (mg/L)Chloride, dissolved (mg/L)Fluoride, dissolved (mg/L)Silica, dissolved (mg/L) dissolved Sulfate, total (mg/L as N)Nitrogen, ammonia plus organic, (mg/L as N)Nitrogen, ammonia, dissolved 0 (mg/L as N)Nitrogen, nitrite plus nitrate, dissolved (mg/L as N)Nitrogen, nitrite, dissolved A (mg/L as P)Phosphorus, dissolved 0 A A (mg/L as P)Phosphorus, ortho, dissolved 0Phosphorus, total (mg/L as P) A 0 (–)*** 0 0 at 180°C (mg/L)Residue, dissolved A A 0 solids, sum of constituents Dissolved (–)*** A Secchi disk (inches)Transparency, (–)*** 0 0 A 0 AColiform, fecal (colonies per 100 mL) (–)*** A A 0 A (–)*** (–)***Chlorophyll- 0 (–)*** (–)*** A A 0 (–)*** (–)** (–)*** A 0 A (–)*** 0 (–)*** (–)** A A (–)*** (–)*** A A 0 (–)*** 0 (–)*** (–)*** A A 0 0 (–)*** A A (–)*** 0 0 *** A -- A 0 (–)*** 0 A A 0 0 -- 0 (+)*** -- 0 0 0 (+)** 0 A (–)* A A 0 0 -- (–)** 0 0 A A (–)* A A 0 0 A A (+)*** 0 0 0 -- A (+)*** 0 -- (–)*** 0 A (+)*** 0 (–)* (+)*** A (–)** A 0 (+)*** (+)*** 0 0 (–)* (–)*** A (–)*** -- 0 0 (+)*** (+)** (–)*** A A 0 0 0 (+)*** -- 0 (–)** (+)* A A A (–)*** 0 (+)*** A (–)*** 0 0 -- A 0 (+)* A (+)*** -- A 0 A 0 0 (–)*** (–)*** (+)*** -- (–)*** (–)*** A A 0 -- A (–)*** (–)*** A A (–)* 0 (–)*** 0 (–)*** -- A 0 A (+)* A 0 0 -- A A A A 0 (+)*** A A -- 0 0 A -- A 0 A 0 A A 0 A -- -- 0 -- Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance ( Specific temperature (°C)Water Hardness, total (mg/L)Calcium (mg/L)Magnesium (mg/L)Potassium (mg/L) (–)**Sodium adsorption ratio (mg/L)Sodium, dissolved (–)*** 0Sodium (percent) 0Acid-neuralizing capacity (mg/L as CaCO 0 0 (–)*** (–)* (–)*** (–)*** 0 0 (–)*** (–)*** (–)*** 0 (–)*** (–)*** (–)** (–)*** (–)*** (–)*** (–)*** 0 0 (–)*** (+)*** (–)*** (–)*** (–)* (–)*** (–)*** (+)*** (–)*** (+)* (–)*** (–)*** (–)*** 0 (–)*** (–)*** (–)*** 0 (–)*** 0 (–)*** (–)*** -- (–)** 0 (–)*** (–)*** 0 0 (–)*** (–)*** (+)** (–)*** (–)** 0 (–)*** (–)*** -- 0 (+)*** 0 (–)*** (–)*** 0 0 (–)*** (+)* (+)*** (–)*** (–)*** (–)** 0 0 0 (–)*** (–)*** (–)*** (–)*** (+)** 0 (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** (–)*** 0 0 0 (–)*** (–)*** 0 (–)*** (–)** 0 0 (–)** (–)*** (–)*** (+)*** (–)* (–)*** 0 (+)** 0 (–)** 0 (–)** (–)*** 0 0 0 0 (–)** (–)*** 0 0(–)*** 0 (–)* (–)* (+)* 0 0 0 (–)*** 0 (–)* 0 0 (+)** 0 0 0 0 0 0 0 0 (+)** 0 0 0 Chlorophyll- Manganese, dissolved ( Manganese, dissolved Barium, dissolved ( Barium, dissolved ( Iron, dissolved ( Strontium, dissolved ( Zinc, dissolved Table 3. Table *, greater than 90 perce significance: trend; 0, trend not significant; trend; (–, downward data; (+), upward [--, insufficient less than 5 years; S, s not tested because period of record was 50 percent of data; site 6 was exceeded because censored values Celsius; mL, milliliter; µg/L, micrograms Celsius; °, degree grams per liter; µS/cm, microsiemens centimeter at 25 degrees Summary and Conclusions 31

0.015

SHADOW MOUNTAIN LAKE

0.010

0.005 VOLUME PUMPED INTO RESERVOIR BY GRANBY PUMP CANAL PER DAY, MAY PROPORTION OF RESERVOIR THROUGH AUGUST EACH YEAR 0 0.08

LAKE GRANBY 0.06

0.04 GRANBY PUMP CANAL, MAY DAY THROUGH OUTLET AND PROPORTION OF RESERVOIR THROUGH AUGUST EACH YEAR

VOLUME LEAVING RESERVOIR PER 0.02

10 5

2 CARTER LAKE 1 0.5

0.2 0.1 0.05

0.02 0.01

0.06

HORSETOOTH RESERVOIR RESERVOIR PER DAY, 0.04 MAY THROUGH AUGUST EACH YEAR

0.02 PROPORTION OF RESERVOIR VOLUME ENTERING

0 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

Figure 22. Time-series plots of reservoir reciprocal hydraulic residence time in terms of the proportion of water entering or leaving the water body.

Summary and Conclusions This report assessed and summarized (1) water- quality and field-measurement profile data collected The U.S. Geological Survey (USGS), in an on- by USGS and stored in the USGS National Water going cooperative monitoring program with the Northern Information System, (2) time-series trends of chemical Colorado Water Conservancy District (NCWCD), Bureau constituents and physical properties by using the seasonal of Reclamation (BOR), and City of Fort Collins, has col- Kendall trend test method, (3) oxygen deficits in the hypo- lected water-quality data in reservoirs and conveyances such limnion (reservoirs only), (4) trophic status indicators, and as canals and tunnels related to the Colorado–Big Thompson (5) water-quality data in terms of Colorado water-quality (CBT) Project in north-central Colorado since 1969. standards. 32 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

Water at CBT sites is dilute and typical of high-elevation concentrations occasionally exceeded computed standard snowmelt runoff. Median concentrations of specific conduc- values. The fixed standard for dissolved iron (300 micro- tance at sites on the western slope (Lake Granby and Shadow grams per liter) was exceeded in two samples at Lake Granby, Mountain Lake) and the high-elevation sites on the eastern one sample at Adams Tunnel east portal, and one sample at slope (Adams Tunnel east portal, Lake Estes, and Olympus Shadow Mountain Lake. The fixed standard for dissolved Tunnel) were generally below 60 microsiemens per centimeter manganese (50 micrograms per liter) was exceeded at Lake at 25 degrees Celsius. These sites are indicative of a hydro- Granby (10 samples), Horsetooth Reservoir (17 samples), and logic setting that is typical of snowmelt source water—low Shadow Mountain Lake (17 samples). Many of the exceed- rates of evapotranspiration (ET) and crystalline bedrock ances of manganese were in the early 1990’s in mainly near- geology. Sites with large specific conductances (generally bottom samples. The fixed standard for manganese was not greater than 70 microsiemens per centimeter at 25 degrees exceeded at Carter Lake. Celsius) and concentrations of major ions are Carter Lake and Time-series of computed annual areal hypolimnetic oxy- Horsetooth Reservoir. These sites show the cumulative effects gen deficit (AHOD) were plotted for Shadow Mountain Lake, of urban development and ET from the rest of the storage and Lake Granby, Carter Lake, and Horsetooth Reservoir. Multi- conveyance system. These sites are in lower elevations (higher year patterns are evident in the AHOD data, and the cycles ET) in areas of sedimentary rocks that can increase dissolved- are not necessarily the same for each reservoir. This pattern solids content. Even so, all water sampled in this system suggests that climatic, biological, or operational cycles may should be considered to be of high quality in terms of low influence the rates of oxygen consumption in these reservoirs. dissolved-solids content. On the basis of data collected over the period of record Water temperature varied seasonally, with reservoir sites at each site, CBT reservoirs were assessed for trophic status developing strong stratification patterns. The pH at CBT sites using the Trophic-State Index (TSI) method developed by was generally in a neutral range of 7 to 8. Dissolved oxygen Carlson (1977). Most of the index values for the reservoirs was generally in the range of 6 to 10 milligrams per liter, are in the mesotrophic range most years. A tendency toward except in the hypolimnetic water of the reservoirs, where decreasing trophic status in the 1990’s at all reservoirs based seasonal stratification sometimes produced dissolved-oxygen mostly on Secchi depth and chlorophyll-a can be seen in time- concentrations approaching 2 milligrams per liter or less. series plots of index values. The use of TSI can give a qualita- Cation compositions at Adams Tunnel, Olympus tive indication of relative status of water bodies but should not Tunnel, and Horsetooth Reservoir are somewhat mixed be used exclusively to evaluate whether lakes and reservoirs calcium-magnesium-sodium, but calcium is predominant. are meeting the criteria of their water-quality classifications. Anion compositions are primarily bicarbonate. Despite having Time-series data were compiled from the USGS database larger concentrations of dissolved solids, Horsetooth Reservoir for the period of record at each site. To help with visual assim- water seems to be simply a more concentrated version of the ilation of these large data sets, scatterplots of each constitu- tunnel waters. ent of interest were made and a trace of a LOWESS smooth Nutrient concentrations at CBT sites generally were regression was drawn when sufficient data over the minimum low. Data censoring levels changed many times throughout reporting limit were present. the study and at times had insufficiently high reporting levels A few general observations and interpretations from the to fully characterize concentration. Largest nutrient con- time-series plots were made: centrations tended to occur at Carter Lake and Horsetooth Reservoirs. The smallest nutrient concentrations were gener- 1. Many time-series data are not exclusively monotonic, ally measured at Lake Granby and Shadow Mountain Lake. a condition that could obscure small-scale trends in the Bottom samples tended to have larger concentrations of most trend testing. Other constituents are well characterized nutrients than did surface samples at the same site. as monotonic distributions. Concentrations of common dissolved trace elements 2. Specific conductance, dissolved solids, and most of the such as iron and manganese commonly exceeded MRL’s, but major ions have similar LOWESS curve shapes, indicat- concentrations were usually less than 1 milligram per liter. ing that some of the constituent concentrations may be Beryllium, chromium, cobalt, lithium, molybdenum, nickel, providing redundant trend information. silver, and vanadium were almost never detected. Zinc, lead, 3. Because the data at most sites are collected in a very lim- cadmium, boron, and copper concentrations were reported infrequently, and concentrations ranged from a few micro- ited number of seasons, some of the variability and rep- grams per liter to a few tens of micrograms per liter (zinc). resentativeness of the annual water-quality changes at the Based on all samples collected over the period of sites are potentially lost. Trend results should be applied record, standards for dissolved oxygen, pH, chloride, sulfate, cautiously to seasons not represented in the sampling. un-ionized ammonia, nitrate, dissolved chromium, and dis- 4. Apparent decreases in nutrient concentrations through- solved nickel were not exceeded at any of the sampling sites out the system are accompanied by decreases in iron in the study area. Silver, lead, copper, cadmium, and zinc (Fe) and manganese (Mn) concentrations. This pattern References Cited 33

could indicate a relation between fertility and bottom- of the AHOD, RHRT, or residuals from the log(AHOD) and water hypoxia (which can cause reducing conditions that log(RHRT) relation data had significant temporal trends. release Fe and Mn). Major conclusions of the study were as follows: 5. The degree of variability in the chlorophyll-a data is 1. Water quality was generally good throughout the high, indicating that sampling frequency is not dense CBT system over the period of record, which ranged enough to adequately describe algal population dynamics from 1969 to 2000. Dissolved solids and nutrient that occur on short time scales. concentrations were low and typical of a forested/ mountainous/crystalline bedrock hydrologic setting. Seasonal Kendall test was used to determine the signifi- Most of the more toxic trace elements were rarely cance of monotonic temporal trends over the period of record detected or were found in low concentrations, for field measurements, major ions, nutrients, chlorophyll-a which was due at least in part to a relative lack of ore- and -b, fecal and total coliform bacteria, and trace elements mineral deposits within the drainage areas of the CBT that were routinely reported above censoring levels. project. Among field measurements, a downward trend in specific conductance was common to all sites except surface samples 2. Constituent concentrations consistently met water-quality in Shadow Mountain Lake. In general, major ions and hard- standard thresholds set by the State of Colorado. ness at all sites showed significant downward trends. The 3. Trophic-state index values indicated mesotrophic condi- exceptions were (1) silica, which had an upward trend at tions generally prevail at reservoirs based on available Shadow Mountain Lake, Adams Tunnel east portal, and all Secchi depth, total phosphorus concentrations, and eastern slope sites, and (2) chloride, which indicated upward chlorophyll-a concentrations. trends at Carter Lake and Horsetooth Reservoir. Fluoride and 4. Based on plots of time-series values and concentrations sodium adsorption ratio had no significant trends. When sig- and seasonal Kendall nonparametric trend testing, nificant, dissolved-solids trends were downward. concentrations of dissolved solids and most major ions Among nutrients that met testing criteria, most either had were decreasing at most sites. Many of the nutrient time- no evidence of trend or a downward trend. Transparency and series data did not meet the minimum criteria for testing. chlorophyll-a, variables that are directly related to percep- But for those that did, nutrient concentrations had insuf- tions of eutrophication, showed some improvement with time ficient evidence of trends or downward temporal trends in Lake Granby. The trend for transparency was upward and (ammonia plus organic nitrogen and total phosphorus). chlorophyll-a was downward at both of the surface sites in Iron and manganese data either had insufficient evidence Lake Granby. The only other significant trend in these vari- of trend or indicated downward trends. Chlorophyll-a ables was an upward trend in transparency at the Horsetooth data were collected for only 11 years but generally indi- Reservoir (Soldier Canyon Dam). No significant trends in cated insufficient evidence of trend or downward tempo- fecal coliform bacteria were detected. Among trace elements, ral trends. only barium, iron, manganese, strontium, and zinc had sufficient uncensored data for trend testing. Downward trends in iron and manganese were notable at Lake Granby (Fe-Mn), Granby Pump Canal (Fe-Mn), and Shadow Mountain Lake References Cited (Mn only). On the eastern slope, the trend in iron was upward at Adams Tunnel, Olympus Tunnel, and Carter Lake. Manga- Britton, L.J., and Gaggiani, N.G., 1987, Water-quality assess- nese trend was downward at Adams and Olympus Tunnels. ment of Arvada Reservoir, Denver Metropolitan area, Colo- The zinc trend was downward at Olympus Tunnel, the only rado: U.S. Geological Survey Water-Resources Investiga- significant trend for zinc. tions Report 87–4107, 66 p. The AHOD data (computed for Lake Granby, Shadow Mountain Lake, Carter Lake, and Horsetooth Reservoir, at Carlson, R.E., 1977, A trophic state index for lakes: Limnol- the dam locations) related to hypolimnetic oxygen dynamics ogy and Oceanography, v. 22, no. 2, p. 361–369. also were tested for temporal trend. A regression model that Clark, M.L., Eddy-Miller, C.A., and Mast, M.A., 2000, included log(AHOD), log(RHRT), and the year, was com- Environmental characteristics and water quality of Hydro- puted. The model yielded r-squared values that ranged from logic Benchmark Network stations in West-Central United 0.12 to 0.65. Residuals from a logAHOD/logRHRT regres- States, 1963–95: U.S. Geological Survey Circular 1173–C, sion (effects of RHRT removed) were then regressed with 115 p. year. The largest r-squared obtained was 0.13, indicating little evidence of AHOD changes with time (temporal trend). The Colorado Climate Center, 1984, Colorado average annual pre- AHOD data and RHRT data were then tested for trend by cipitation map 1951–1980: Fort Collins, Colorado Climate using Kendall’s tau and testing correlation with time. None Center map, scale 1:500,000. 34 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

Colorado Department of Public Health and Environment, Middelburg, R.F., 1993, Colorado stream water quality, Water Quality Control Commission, 2001, Classifications in Paulson, R.W., and others, National water summary, and numeric standards for South Platte River Basin; Lara- Hydrologic events and stream water quality: U.S. mie River Basin; Republican River Basin; Smoky Hill River Geological Survey Water-Supply Paper 2400, Basin: Denver, Colorado Department of Public Health and p. 204. Environment, Water Quality Control Commission Report, 3.8.0 (5 CCR 1002–8), variously paginated. Mueller, D.K., 1990, Analysis of water-quality data and sam- Green, W.R., 1996, Eutrophication trends inferred from hypo- pling programs at selected sites in north-central Colorado: limnetic dissolved-oxygen dynamics within selected White U.S. Geological Survey Water-Resources Investigations River reservoirs, northern Arkansas-southern Missouri, Report 90–4005, 79 p. 1974–94: U.S. Geological Survey Water-Resources Investi- gations Report 96–4096, 22 p. Niyogi, D.K., McKnight, D.M., and Lewis, W.M., 1999, Influences of water and substrate quality for periphy- Greve, A.I., 2002, Data-quality measures of stakeholder- ton in a montane stream affected by acid mine drain- implemented watershed-monitoring programs: U.S. Geo- age: Limnology and Oceanography v. 44, no. 3, logical Survey Open-File Report 02–141, 19 p. p. 804–814. Helsel, D.R., and Cohn, T.A., 1988, Estimation of descriptive Stevens, M.R., 2001, Assessment of water quality, road runoff, statistics for multiply censored water-quality data: Water Resources Research, v. 24, p. 1997–2004. and bulk atmospheric deposition, Guanella Pass area, Clear Creek and Park counties, Colorado, water years 1995–97: Helsel, D.R., and Hirsch, R.M., 1995, Statistical methods U.S. Geological Survey Water-Resources Investigations in water resources, studies in environmental science 49, Report 00–4186, 183 p. 3d ed.: New York, Elsevier, 529 p. Walker, W.W., 1996, Simplified procedures for eutrophication Jassby, A.D., and Goldman, C.R., 1999, Horsetooth and Carter assessment and prediction, user manual: U.S. Army Corps Lake Reservoirs, water quality comparisons: Davis, Calif., of Engineers, Waterways Experiment Station, Instruction Report of Ecological Research Associates, 49 p. Report W–96–2, 227 p. Johnson, B.M., and Goettl, J.P., 1999, Food web changes over fourteen years following introduction of rainbow smelt into Woods, P.F., 1992, Limnology of Big Lake, south-central a Colorado reservoir: North American Journal of Fisheries Alaska, 1983–84: U.S. Geological Survey Water-Supply Management, v. 19, p. 629–642. Paper 2382, 108 p. Hydrologic and Water-Quality Data Hydrologic and Water-Quality Data 37

Abbreviations

CaCO3 Calcium carbonate Ca Calcium Mg Magnesium K Potassium Na Sodium Cl Chloride F Fluoride

SiO2 Silicon dioxide

SO4 Sulfate N Nitrogen P Phosphorus As Arsenic Ba Barium Be Beryllium B Boron Cd Cadmium Cr Chromium Co Cobalt Cu Copper Fe Iron Pb Lead Li Lithium Mn Manganese Mo Molybdenum Ni Nickel Ag Silver Sr Strontium V Vanadium Zn Zinc 38 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

20 9

15 8

10 7

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5 100

80 20

40 10

CENTIMETER AT 20 IN DEGREES CELSIUS MICROSIEMENS PER 25 DEGREES CELSIUS WATER TEMPERATURE,

SPECIFIC CONDUCTANCE, IN 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 23. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the surface. Hydrologic and Water-Quality Data 39

40 10

8 30

3 6 20

CACO 4

HARDNESS, TOTAL, 2 CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER AS 0 0

4 2

2 1

1 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE ALL DATA 20 LOWESS CURVE SEASONAL UNCENSORED 10 CENSORED SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 23. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the surface.—Continued 40 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

80 80

60 60

40 40 PER LITER 20 20 OF CONSTITUENTS, DEGREES CELSIUS, SOLIDS, DISSOLVED, SUM IN MILLIGRAMS PER LITER SOLIDS, RESIDUE AT 180 DISSOLVED, IN MILLIGRAMS 0 0 250 5

200 4

150 3

100 2 IN INCHES

1 50 COLIFORM, FECAL, IN TRANSPARENCY, SECCHI,

0 COLONIES PER 100 MILLILITERS 0 15 0.4

, 0.3 a 10

0.2 , PHYTOPLANKTON, b 5 0.1 CHLOROPHYLL- PHYTOPLANKTON, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

1970 1975 1980 1985 1990 1995 2000CHLOROPHYLL- 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 23. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the surface.—Continued Hydrologic and Water-Quality Data 41

4 0.10

0.08 3

0.06 2 0.04 DISSOLVED, 1 ORGANIC, TOTAL, 0.02 NITROGEN, AMMONIA, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS 0 0

0.20 0.10

0.08 0.15

0.06 0.10 0.04 DISSOLVED, 0.05

NITROGEN, NITRITE, 0.02 NITRATE, DISSOLVED, IN MILLIGRAMS PER LITER NITROGEN, NITRITE PLUS IN MILLIGRAMS PER LITER 0 0 0.10 0.10

0.08 0.08

0.06 0.06

0.04 0.04 DISSOLVED, 0.02 0.02 IN MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, PHOSPHORUS, DISSOLVED, 0 IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000 0.10

0.08 EXPLANATION LOWESS CURVE 0.06 ALL DATA LOWESS CURVE 0.04 SEASONAL UNCENSORED 0.02 CENSORED PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 23. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the surface.—Continued 42 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 2

3 30

20 1

LITER AS CACO 10 IN MILLIGRAMS PER CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0 0.4 10

8 0.3

6 0.2 4

0.1 2 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 10

8 EXPLANATION LOWESS CURVE 6 ALL DATA LOWESS CURVE 4 SEASONAL UNCENSORED 2 CENSORED SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 23. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the surface.—Continued Hydrologic and Water-Quality Data 43

20 100

80 15

60 10 40

5 IRON, DISSOLVED, 20 BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 20 80

15 60

10 40

5 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE 20 ALL DATA LOWESS CURVE SEASONAL 10 UNCENSORED ZINC, DISSOLVED, CENSORED IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 23. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the surface.—Continued 44 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

10 9

8 8

6 7 4

6 2 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5 100 20

80 15

60 10 40

5 PER CENTIMETER

IN MICROSIEMENS 20 IN DEGREES CELSIUS WATER TEMPERATURE, SPECIFIC CONDUCTANCE, 0 0 100 100

80 80

60 60

40 40

20 SOLIDS, DISSOLVED, 20 SUM OF CONSTITUENTS, SOLIDS, RESIDUE AT 180 IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

DEGREES CELSIUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 24. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the bottom. Hydrologic and Water-Quality Data 45

40 20

30 15 3

20 10 AS CACO 10 5 HARDNESS, TOTAL, CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

4 2

2 1

1 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0 0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE ALL DATA 20 LOWESS CURVE SEASONAL UNCENSORED 10 CENSORED SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 24. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the bottom.—Continued 46 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 0.4

0.3 30

0.2

20 0.1 FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 10 0

15 6

10 4

5 2 SILICA, DISSOLVED, SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000

1.5 EXPLANATION LOWESS CURVE 1.0 ALL DATA LOWESS CURVE SEASONAL UNCENSORED 0.5 CENSORED CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 24. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 47

1.0 0.10 0.9 0.8 0.08 0.7 0.6 0.06 0.5 0.4 0.04

0.3 DISSOLVED, IN

0.2 NITROGEN, AMMONIA, 0.02 MILLIGRAMS PER LITER ORGANIC, TOTAL, IN

MILLIGRAMS PER LITER 0.1 NITROGEN, AMMONIA PLUS 0 0 0.4 0.10

0.08 0.3

0.06 0.2 0.04 DISSOLVED, IN 0.1 NITROGEN, NITRITE, 0.02 MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.10 0.4

0.08 0.3

0.06 0.2 0.04

0.1 0.02 PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 24. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the bottom.—Continued 48 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

20 100

80 15

60 10 40

5 IRON, DISSOLVED, 20 BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

200 80

150 60

100 40

50 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 60

EXPLANATION 40 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 20 UNCENSORED

ZINC, DISSOLVED, CENSORED

IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 24. Temporal variations in periodic measurements and concentrations at Lake Granby near spillway, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 49

15 9 14 13 8 12 11 10 7 9 8 6 7 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS

IN MILLIGRAMS PER LITER 6 5 5

100

80 20

CELSIUS 40 10

MICROSIEMENS PER 20 IN DEGREES CELSIUS WATER TEMPERATURE, SPECIFIC CONDUCTANCE, IN CENTIMETER AT 25 DEGREES 0 0 100 100

80 80

60 60

40 40 PER LITER

SOLIDS, DISSOLVED, 20 20 SOLIDS, DISSOLVED, CELSIUS, IN MILLIGRAMS RESIDUE AT 180 DEGREES SUM OF CONSTITUENTS, IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 25. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the surface. 50 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 20

30 15 3

20 10 AS CACO 10 5 HARDNESS, TOTAL, CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

4 2

2 1

1 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0 0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 25 LOWESS CURVE ALL DATA LOWESS CURVE 20 SEASONAL UNCENSORED CENSORED 15 SODIUM, IN PERCENT

10 1970 1975 1980 1985 1990 1995 2000

Figure 25. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the surface.—Continued Hydrologic and Water-Quality Data 51

40 2

30 3

20 1 AS CACO 10 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.4 10

8 0.3

6 0.2 4

0.1 2 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 5

4 EXPLANATION 3 LOWESS CURVE ALL DATA 2 LOWESS CURVE SEASONAL 1 UNCENSORED SULFATE, DISSOLVED,

IN MILLIGRAMS PER LITER CENSORED 0 1970 1975 1980 1985 1990 1995 2000

Figure 25. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the surface.—Continued 52 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

1.0 0.10

0.08

0.06 0.5 0.04 DISSOLVED, IN 0.02 ORGANIC, TOTAL, IN NITROGEN, AMMONIA, MILLIGRAMS PER LITER MILLIGRAMS PER LITER

NITROGEN, AMMONIA PLUS 0 0

0.20 0.04

0.15 0.03

0.10 0.02

0.05 DISSOLVED, IN 0.01 NITROGEN, NITRITE, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.20 0.04

0.15 0.03

0.10 0.02

0.05 DISSOLVED, IN 0.01 MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 0.08

0.06 EXPLANATION LOWESS CURVE 0.04 ALL DATA LOWESS CURVE SEASONAL 0.02 UNCENSORED

PHOSPHORUS, TOTAL, CENSORED IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 25. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the surface.—Continued Hydrologic and Water-Quality Data 53

300 80

60 200

IN INCHES 100 20 COLIFORM, FECAL, IN TRANSPARENCY, SECCHI,

0 COLONIES PER 100 MILLILITERS 0

10 0.4

8 , , 0.3 b a

6 0.2 4

0.1 CHLOROPHYLL- PHYTOPLANKTON, CHLOROPHYLL- PHYTOPLANKTON, 2 IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 25. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the surface.—Continued 54 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

20 100

80 15

60 10 40

5 IRON, DISSOLVED, 20 BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

30 80

60 20

10 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 30

20 EXPLANATION LOWESS CURVE ALL DATA 10 LOWESS CURVE SEASONAL

ZINC, DISSOLVED, IN UNCENSORED MICROGRAMS PER LITER CENSORED 0 1970 1975 1980 1985 1990 1995 2000

Figure 25. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the surface.—Continued Hydrologic and Water-Quality Data 55

10 9

8 8

6 7 4

6 2 MILLIGRAMS PER LITER pH, IN STANDARD UNITS OXYGEN, DISSOLVED, IN

0 5

100

80 20

40 10

DEGREES CELSIUS 20 CENTIMETER AT 25 IN DEGREES CELSIUS MICROSIEMENS PER WATER TEMPERATURE,

SPECIFIC CONDUCTANCE, IN 0 0

100 100

80 80

60 60

40 40 DISSOLVED, IN DEPTH, IN FEET

20 DEGREES CELSIUS, 20 MILLIGRAMS PER LITER SOLIDS, RESIDUE AT 180 0 0 1970 1975 1980 1985 1990 1995 2000 80

EXPLANATION 60 LOWESS CURVE ALL DATA 40 LOWESS CURVE SEASONAL UNCENSORED 20 CENSORED OF CONSTITUENTS, IN MILLIGRAMS PER LITER SOLIDS, DISSOLVED, SUM 0 1970 1975 1980 1985 1990 1995 2000

Figure 26. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the bottom. 56 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 20

30 15 3

20 10 AS CACO

10 5 HARDNESS, TOTAL, IN MILLIGRAMS PER LITER MILLIGRAMS PER LITER CALCIUM, DISSOLVED, IN 0 0

3 2.0

1.5 2

1.0

1 0.5 MILLIGRAMS PER LITER MILLIGRAMS PER LITER POTASSIUM, DISSOLVED, IN MAGNESIUM, DISSOLVED, IN 0 0

0.4 4

0.3 3

0.2 2

0.1 1 MILLIGRAMS PER LITER SODIUM, DISSOLVED, IN SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 20 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 10 UNCENSORED

SODIUM, IN PERCENT CENSORED

0 1970 1975 1980 1985 1990 1995 2000

Figure 26. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 57

40 1.0

30 3

20 0.5 AS CACO

10 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.4 20

0.3 15

0.2 10

0.1 5 SILICA, DISSOLVED, IN FLUORIDE, DISSOLVED, MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 5

4 EXPLANATION LOWESS CURVE ALL DATA 3 LOWESS CURVE SEASONAL 2 UNCENSORED CENSORED 1 MILLIGRAMS PER LITER SULFATE, DISSOLVED, IN

0 1970 1975 1980 1985 1990 1995 2000

Figure 26. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the bottom.—Continued 58 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

0.8 0.10

0.08 0.6

0.06 0.4 0.04 DISSOLVED,IN 0.2

ORGANIC, TOTAL, IN 0.02 NITROGEN, AMMONIA, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS 0 0

0.20 0.10

0.08 0.15

0.06 0.10 0.04 DISSOLVED, IN 0.05 NITROGEN, NITRITE, 0.02 MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS

0 0

0.08 0.08

0.06 0.06

0.04 0.04

0.02 DISSOLVED, IN 0.02 MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 0.08

0.06 EXPLANATION LOWESS CURVE ALL DATA 0.04 LOWESS CURVE SEASONAL UNCENSORED 0.02 CENSORED MILLIGRAMS PER LITER PHOSPHORUS, TOTAL, IN

0 1970 1975 1980 1985 1990 1995 2000

Figure 26. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 59

20 100

80 15

60 10 40

5 20 IRON, DISSOLVED, IN BARIUM, DISSOLVED, IN MICROGRAMS PER LITER MICROGRAMS PER LITER 0 0

100 80

80 60

60 40 40

20 20 MICROGRAMS PER LITER MICROGRAMS PER LITER MANGANESE, DISSOLVED, IN STRONTIUM, DISSOLVED, IN 0 0 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 20 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 10 UNCENSORED CENSORED ZINC, DISSOLVED, IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 26. Temporal variations in periodic measurements and concentrations at Lake Granby near Rainbow Bay, sampled near the bottom.—Continued 60 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

1,000 20

800 15

600 10 400

5 200 OXYGEN, DISSOLVED, IN MILLIGRAMS PER LITER IN CUBIC FEET PER SECOND INSTANTANEOUS DISCHARGE, 0 0

9 100

80 8

60 7 40

6 CENTIMETER AT 20 MICROSIEMENS PER 25 DEGREES CELSIUS pH, IN STANDARD UNITS

5 SPECIFIC CONDUCTANCE, IN 0

10 20 DISSOLVED, IN DEGREES CELSIUS, IN DEGREES CELSIUS WATER TEMPERATURE, MILLIGRAMS PER LITER SOLIDS, RESIDUE AT 180 0 0 1970 1975 1980 1985 1990 1995 2000 60

EXPLANATION 40 LOWESS CURVE ALL DATA UNCENSORED 20 CENSORED OF CONSTITUENTS, IN MILLIGRAMS PER LITER SOLIDS, DISSOLVED, SUM 0 1970 1975 1980 1985 1990 1995 2000

Figure 27. Temporal variations in periodic measurements and concentrations at Granby Pump Canal. Hydrologic and Water-Quality Data 61

40 15

30 10 3

AS CACO 5 10 HARDNESS, TOTAL, IN MILLIGRAMS PER LITER MILLIGRAMS PER LITER CALCIUM, DISSOLVED, IN

0 0

2.0 2.0

1.6 1.6

1.2 1.2

0.8 0.8

0.4 0.4 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 MILLIGRAMS PER LITER SODIUM, DISSOLVED, IN SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 20 LOWESS CURVE ALL DATA UNCENSORED CENSORED 10 SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 27. Temporal variations in periodic measurements and concentrations at Granby Pump Canal.—Continued 62 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 2

30 3

20 1 AS CACO 10 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

1 10

SILICA, DISSOLVED, 2 FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 6

EXPLANATION 4 LOWESS CURVE ALL DATA UNCENSORED CENSORED 2 SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 27. Temporal variations in periodic measurements and concentrations at Granby Pump Canal.—Continued Hydrologic and Water-Quality Data 63

1.5 0.10

0.08

1.0 0.06

0.04 0.5 PER LITER

ORGANIC, TOTAL, IN 0.02 MILLIGRAMS PER LITER NITROGEN, AMMONIA, NITROGEN, AMMONIA PLUS DISSOLVED, IN MILLIGRAMS 0 0

0.4 0.10

0.08 0.3

0.06 0.2 0.04

0.1 DISSOLVED, IN 0.02 NITROGEN, NITRITE, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.10 0.04

0.08 0.03

0.06 0.02 0.04

DISSOLVED, IN 0.01 0.02 MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 0.10

0.08 EXPLANATION LOWESS CURVE 0.06 ALL DATA UNCENSORED 0.04 CENSORED

0.02 PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER

0 1970 1975 1980 1985 1990 1995 2000

Figure 27. Temporal variations in periodic measurements and concentrations at Granby Pump Canal.—Continued 64 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

20 100

80 15

60 10 40

5 IRON, DISSOLVED, 20 BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

100 80

80 60

60 40 40

20 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE ALL DATA 20 UNCENSORED CENSORED 10 ZINC, DISSOLVED, IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 27. Temporal variations in periodic measurements and concentrations at Granby Pump Canal.—Continued Hydrologic and Water-Quality Data 65

20 9

15 8

10 7

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5 1970 1975 1980 1985 1990 1995 2000 100

80 EXPLANATION LOWESS CURVE 60 ALL DATA LOWESS CURVE SEASONAL 40 UNCENSORED CENTIMETER CENSORED 20 IN MICROSIEMENS PER AT 25 DEGREES CLESIUS SPECIFIC CONDUCTANCE, 0 1970 1975 1980 1985 1990 1995 2000

Figure 28. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled at the surface. 66 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 15

30 10 3

AS CACO 5 10 HARDNESS, TOTAL, CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

2 2

1 1 POTASSIUM, DISSOLVED, MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 20 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 10 UNCENSORED CENSORED SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 28. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled at the surface.—Continued Hydrologic and Water-Quality Data 67

40 2

20 1

10 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.4 10

8 0.3

6 0.2 4

0.1

SILICA, DISSOLVED, 2 FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 6

4 EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE 2 SEASONAL UNCENSORED

SULFATE, DISSOLVED, CENSORED IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 28. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled at the surface.—Continued 68 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

1.0 0.15

0.10

0.5

0.05 DISSOLVED, IN ORGANIC, TOTAL, IN NITROGEN, AMMONIA, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS 0 0

0.20 0.10

0.08 0.15

0.06 0.10 0.04

0.05 DISSOLVED, IN 0.02 NITROGEN, NITRITE, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.10 0.04

0.08 0.03

0.06 0.02 0.04 PER LITER 0.01 0.02 PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, DISSOLVED, IN MILLIGRAMS 0 0 1970 1975 1980 1985 1990 1995 2000 0.06

EXPLANATION 0.04 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 0.02 UNCENSORED CENSORED PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 28. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled at the surface.—Continued Hydrologic and Water-Quality Data 69

80 80

60 60

40 40 PER LITER 20 20 CONSTITUENTS, IN SOLIDS, DISSOLVED, MILLIGRAMS PER LITER CELSIUS, IN MILLIGRAMS RESIDUE AT 180 DEGREES 0 SOLIDS, DISSOLVED, SUM OF 0

200 20

150 15

100 10 IN INCHES 50 5 COLIFORM, FECAL, IN TRANSPARENCY, SECCHI,

0 COLONIES PER 100 MILLILITERS 0

30 1.0

0.8 , , b a 20 0.6

0.4 10

CHLOROPHYLL- 0.2 CHLOROPHYLL- PHYTOPLANKTON, PHYTOPLANKTON, IN MICROGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 28. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled at the surface.—Continued 70 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

15 200

150 10

100

5 50 IRON, DISSOLVED, BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

100 80

80 60

60 40 40

20 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION LOWESS CURVE 20 ALL DATA LOWESS CURVE SEASONAL UNCENSORED 10 CENSORED ZINC, DISSOLVED, IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 28. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled at the surface.—Continued Hydrologic and Water-Quality Data 71

40 15

30 10

5 10 OXYGEN, DISSOLVED, IN MILLIGRAMS PER LITER SAMPLING DEPTH BELOW WATER SURFACE, IN FEET 0 0

9 100

80 8

60 7 40

6 20 AT 25 DEGREE CELSIUS pH, IN STANDARD UNITS SPECIFIC CONDUCTANCE, 5 0 IN MICROSIEMENS PER CENTIMETER 80 80

60 60

40 40

20 20 SOLIDS, DISSOLVED, SUM OF CONSTITUENTS, MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 180 DEGREES CELSIUS, IN 0 0

SOLIDS, DISSOLVED, RESIDUE AT 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 29. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled near the bottom. 72 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 10

8 30 3 6 20

AS CACO 4

10 HARDNESS, TOTAL,IN

MILLIGRAMS PER LITER 2 CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

3 2

1 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 20 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 10 UNCENSORED CENSORED SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 29. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 73

40 1.5

30 1.0

0.5 10 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.4 10

8 0.3

6 0.2 4

0.1

SILICA, DISSOLVED, 2 FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 6

EXPLANATION LOWESS CURVE 4 ALL DATA LOWESS CURVE SEASONAL 2 UNCENSORED CENSORED SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 29. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled near the bottom.—Continued 74 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

1.0 0.20

0.15

0.5 0.10 DISSOLVED, IN

ORGANIC, TOTAL, IN 0.05 MILLIGRAMS PER LITER NITROGEN, AMMONIA, MILLIGRAMS PER LITER

NITROGEN, AMMONIA PLUS 1.0 0 0

0.20 0.04

0.15 0.03

0.10 0.02 PER LITER 0.05 0.01 NITROGEN, NITRITE, MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS

0 DISSOLVED, IN MILLIGRAMS 0

0.08 0.08

0.06 0.06

0.04 0.04

0.02 DISSOLVED, IN 0.02 IN MILLIGRAMS PER LITER MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 0.08

0.06 EXPLANATION LOWESS CURVE ALL DATA 0.04 LOWESS CURVE SEASONAL UNCENSORED 0.02 CENSORED MILLIGRAMS PER LITER PHOSPHORUS, TOTAL, IN 0 1970 1975 1980 1985 1990 1995 2000

Figure 29. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 75

20 300

15 200

100 5 IRON, DISSOLVED, BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

600 100

400 60

40 200 20 STRONTIUM, DISSOLVED, MANGANESE,DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 40

EXPLANATION 30 LOWESS CURVE ALL DATA LOWESS CURVE 20 SEASONAL UNCENSORED 10 CENSORED ZINC, DISSOLVED, IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 29. Temporal variations in periodic measurements and concentrations at Shadow Mountain Lake, sampled near the bottom.—Continued 76 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

15 9 14 13 8 12 12 10 7 9 8 6 7 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS

IN MILLIGRAMS PER LITER 6 5 5

100 20

80 15

60 10 40

5 20 IN DEGREES CELSIUS WATER TEMPERATURE, SPECIFIC CONDUCTANCE, 0 0 IN MICROSIEMENS PER CENTIMETER 80 80

60 60

40 40

20 20 SOLIDS, DISSOLVED, SUM OF CONSTITUENTS AT 180 DEGREES CELSIUS

SOLIDS, RESIDUE, DISSOLVED 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 30. Temporal variations in periodic measurements and concentrations at Adams Tunnel, east portal, near Estes Park. Hydrologic and Water-Quality Data 77

40 10

8 30

6 20 4

HARDNESS, TOTAL, 2 CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

2 2

1 1 POTASSIUM, DISSOLVED, MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

1.0 8

0.5 4

2 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE 20 ALL DATA LOWESS CURVE SEASONAL 10

SODIUM, PERCENT UNCENSORED CENSORED

0 1970 1975 1980 1985 1990 1995 2000

Figure 30. Temporal variations in periodic measurements and concentrations at Adams Tunnel, east portal, near Estes Park.—Continued 78 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 2

20 1

10 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID NEUTRALIZING CAPACITY, 0 0

1.0 10

6 0.5 4

SILICA, DISSOLVED, 2 FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 10

8 EXPLANATION LOWESS CURVE 6 ALL DATA LOWESS CURVE SEASONAL 4 UNCENSORED CENSORED 2 SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 30. Temporal variations in periodic measurements and concentrations at Adams Tunnel, east portal, near Estes Park.—Continued Hydrologic and Water-Quality Data 79

2 0.10

0.08

0.06 1 0.04 DISSOLVED, IN

ORGANIC, TOTAL, IN 0.02 MILLIGRAMS PER LITER NITROGEN, AMMONIA, MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS 0 0

0.4 0.10

0.08 0.3

0.06 0.2 0.04

0.1 DISSOLVED, IN 0.02 NITROGEN, NITRITE, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.10 0.10

0.08 0.08

0.06 0.06

0.04 0.04

0.02 DISSOLVED, IN 0.02 IN MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 0.20

0.15 EXPLANATION LOWESS CURVE ALL DATA 0.10 LOWESS CURVE SEASONAL UNCENSORED 0.05 CENSORED PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 30. Temporal variations in periodic measurements and concentrations at Adams Tunnel, east portal, near Estes Park.—Continued 80 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

300 20

15 200

100 5 IRON, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

80 40

60 30

40 20

20 10 ZINC, DISSOLVED, STRONTIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 30. Temporal variations in periodic measurements and concentrations at Adams Tunnel, east portal, near Estes Park.—Continued Hydrologic and Water-Quality Data 81

20 9

15 8

10 7

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5

100

80 20

40 10

CENTIMETER AT 20 IN DEGREES CELSIUS WATER TEMPERATURE, MICROSIEMENS PER 25 DEGREES CELSIUS

SPECIFIC CONDUCTANCE, IN 0 0

80 80

60 60

40 40

20 20 SOLIDS, DISSOLVED, MILLIGRAMS PER LITER SUM OF CONSTITUENTS, IN MILLIGRAMS PER LITER AT 180 DEGREES CELSIUS, IN SOLIDS, DISSOLVED, RESIDUE 0 0

3,000 1,500

2,000 1,000

1,000 500 COLIFORM, TOTAL, IN COLIFORM, FECAL, IN

COLONIES PER 100 MILLILITERS 0 0 1970 1975 1980 1985 1990 1995 2000 COLONIES PER 100 MILLILITERS 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 31. Temporal variations in periodic measurements and concentrations at Olympus Tunnel. 82 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 10

8 30

3 6 20 4 AS CACO 10 2 CALCIUM, DISSOLVED, HARDNESS, TOTAL, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

4 2.2.0 1.8 1.6 3 1.4 1.2 2 1.0 0.8 0.6 1 0.4 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED,

IN MILLIGRAMS PER LITER 0.2 0 0

0.5 6

0.4

4 0.3

0.2 2

0.1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE ALL DATA 20 LOWESS CURVE SEASONAL UNCENSORED 10 CENSORED SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 31. Temporal variations in periodic measurements and concentrations at Olympus Tunnel.—Continued Hydrologic and Water-Quality Data 83

40 5

4 30 3 3 20 2 AS CACO

10 1 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.5 8

0.4 6

0.3 4 0.2

0.1 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 15

EXPLANATION LOWESS CURVE 10 ALL DATA LOWESS CURVE SEASONAL UNCENSORED 5 CENSORED SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 31. Temporal variations in periodic measurements and concentrations at Olympus Tunnel.—Continued 84 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

0.8 0.3

0.6 0.2

0.4 PER LITER PER LITER 0.1 0.2 NITROGEN, AMMONIA, ORGANIC, IN MILLIGRAMS NITROGEN, AMMONIA PLUS DISSOLVED, IN MILLIGRAMS 0 0

0.4 0.04

0.3 0.03

0.2 0.02

0.1 DISSOLVED, IN 0.01 NITROGEN, NITRITE, MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN MILLIGRAMS PER LITER NITROGEN, NITRITE PLUS 0 0

0.10 0.10

0.08 0.08

0.06 0.06

0.04 0.04 DISSOLVED, IN 0.02 0.02 MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 0.6

EXPLANATION LOWESS CURVE 0.4 ALL DATA LOWESS CURVE SEASONAL 0.2 UNCENSORED CENSORED PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 31. Temporal variations in periodic measurements and concentrations at Olympus Tunnel.—Continued Hydrologic and Water-Quality Data 85

15 300

10 200

5 100 IRON, DISSOLVED, BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

40 80

30 60

20 40

10 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 40

EXPLANATION 30 LOWESS CURVE ALL DATA LOWESS CURVE 20 SEASONAL UNCENSORED 10 CENSORED ZINC, DISSOLVED, IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 31. Temporal variations in periodic measurements and concentrations at Olympus Tunnel.—Continued 86 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

20 9

15 8

10 7

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5

150 30

100 20

50 10 CENTIMETER MICROSIEMENS PER IN DEGREES CELSIUS WATER TEMPERATURE, SPECIFIC CONDUCTANCE, IN 0 0

90 90

80 80

70 70

60 60

50 50 DISSOLVED, IN

40 SOLIDS, DISSOLVED, 40 SOLIDS, RESIDUE AT SUM OF CONSTITUENTS, MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 180 DEGREES CELSIUS, 30 30 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 32. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the surface. Hydrologic and Water-Quality Data 87

60 20

3 40

AS CACO 20 5 HARDNESS, TOTAL, IN MILLIGRAMS PER LITER CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

3 2.0

1.5 2

1.0

1 0.5 POTASSIUM, DISSOLVED, MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 20

15 EXPLANATION LOWESS CURVE ALL DATA 10 LOWESS CURVE SEASONAL UNCENSORED 5 CENSORED SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 32. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the surface. —Continued 88 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

60 2 3

20 ACID-NEUTRALIZING PER LITER AS CACO CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER CAPACITY, IN MILLIGRAMS 0 0

0.6 8

6 0.4

0.2 2 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 8

6 EXPLANATION LOWESS CURVE ALL DATA 4 LOWESS CURVE SEASONAL UNCENSORED 2 CENSORED SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 32. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the surface. —Continued Hydrologic and Water-Quality Data 89

1.0 0.5 0.9 0.8 0.4 0.7 0.6 0.3 0.5 0.4 0.2

0.3 DISSOLVED, IN 0.2 0.1 NITROGEN, AMMONIA, ORGANIC, TOTAL, IN MILLIGRAMS PER LITER

MILLIGRAMS PER LITER 0.1 NITROGEN, AMMONIA PLUS 0 0

0.3 0.08

0.06 0.2

0.04

0.1 DISSOLVED, IN 0.02 NITROGEN, NITRITE, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.08 0.08

0.06 0.06

0.04 0.04

0.02 DISSOLVED, IN 0.02 MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, PHOSPHORUS, DISSOLVED 0 0 1970 1975 1980 1985 1990 1995 2000 0.7

0.6 EXPLANATION 0.5 LOWESS CURVE ALL DATA 0.4 LOWESS CURVE 0.3 SEASONAL UNCENSORED 0.2 CENSORED

PHOSPHORUS, TOTAL, 0.1 IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 32. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the surface. —Continued 90 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

200 10

8 150

6 100 4 IN INCHES

PER 100 MILLILITER 2

TRANSPARENCY, SECCHI DISC, 0

0 COLIFORM, FECAL, IN COLONIES

8 0.4 , , 6 0.3 b -a

4 0.2

2 0.1 CHLOROPHYLL- CHLOROPHYLL PHYTOPLANKTON, IN PHYTOPLANKTON, IN MICROGRAMS PER LITER MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 32. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the surface. —Continued Hydrologic and Water-Quality Data 91

40 30

30 20

10 10 IRON, DISSOLVED, BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

15 80

60 10

5 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE ALL DATA 20 LOWESS CURVE SEASONAL UNCENSORED 10 ZINC, DISSOLVED, CENSORED IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 32. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the surface. —Continued 92 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

20 9

15 8

10 7

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5

200

20 150

100 10

CENTIMETER AT 50 IN DEGREES CELSIUS 25 DEGREES CELSIUS WATER TEMPERATURE, IN MICROSIEMENS PER SPECIFIC CONDUCTANCE, 0 0

100 100

80 80

60 60

40 40 DISSOLVED, IN

20 SOLIDS, DISSOLVED, 20 SOLIDS, RESIDUE AT SUM OF CONSTITUENTS, MILLIGRAMS PER LITER 180 DEGREES CELSIUS, IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 33. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the bottom. Hydrologic and Water-Quality Data 93

40 15

30 10 3

AS CACO 5 10 CALCIUM, DISSOLVED, HARDNESS, TOTAL, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

2 1.0

1 0.5 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 20

15 EXPLANATION LOWESS CURVE 10 ALL DATA LOWESS CURVE SEASONAL 5 UNCENSORED

SODIUM, IN PERCENT CENSORED

0 1970 1975 1980 1985 1990 1995 2000

Figure 33. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the bottom. —Continued 94 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

60 2 3 40

20 LITER AS CACO IN MILLIGRAMS PER CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.4 8

0.3 6

0.2 4

0.1 2 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 6

EXPLANATION 4 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 2 UNCENSORED CENSORED SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 33. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the bottom. —Continued Hydrologic and Water-Quality Data 95

1.0 0.3

0.2

0.5

PER LITER 0.1 ORGANIC, TOTAL, IN NITROGEN, AMMONIA, MILLIGRAMS PER LITER DISSOLVED, IN MILLIGRAMS NITROGEN, AMMONIA PLUS 0 0

0.4 0.08

0.3 0.06

0.2 0.04 PER LITER

0.1 0.02 NITROGEN, NITRITE, DISSOLVED, IN MILLIGRAMS MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.10 0.10

0.08 0.08

0.06 0.06

0.04 0.04 PER LITER

0.02 0.02 PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, DISSOLVED, IN MILLIGRAMS 0 0 1970 1975 1980 1985 1990 1995 2000 0.4

EXPLANATION 0.3 LOWESS CURVE ALL DATA 0.2 LOWESS CURVE SEASONAL UNCENSORED 0.1 CENSORED PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 33. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the bottom. —Continued 96 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 40

30 30

20 20

10 10 IRON, DISSOLVED, BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

40 80

30 60

20 40

10 20 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 40

30 EXPLANATION LOWESS CURVE ALL DATA 20 LOWESS CURVE SEASONAL UNCENSORED 10 CENSORED ZINC, DISSOLVED, IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 33. Temporal variations in periodic measurements and concentrations at Carter Lake, sampled near the bottom. —Continued Hydrologic and Water-Quality Data 97

15 9

8 10

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5 1965 1970 1975 1980 1985 1990 1995 2000 1965 1970 1975 1980 1985 1990 1995 2000

140 30

120

20 100

80 CELSIUS 10

60 IN DEGREES CELSIUS WATER TEMPERATURE, IN MICROSIEMENS PER SPECIFIC CONDUCTANCE,

CENTIMETER AT 25 DEGREES 40 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED

Figure 34. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the surface. 98 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 12

3 30 10

AS CACO 20 8 HARDNESS, TOTAL, IN CALCIUM, DISSOLVED, MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 10 6

2.5 1.1.4

1.2 2.0

1.0 1.5 0.8

1.0 0.6 POTASSIUM, DISSOLVED, MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0.5 0.4

0.4 4

0.3 3

0.2 2 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0.1 1 1965 1970 1975 1980 1985 1990 1995 2000

18 EXPLANATION LOWESS CURVE 16 ALL DATA LOWESS CURVE 14 SEASONAL UNCENSORED 12 SODIUM, IN PERCENT

10 1965 1970 1975 1980 1985 1990 1995 2000

Figure 34. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the surface.—Continued Hydrologic and Water-Quality Data 99

50 3

3 2

AS CACO 1 20 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 10 0

0.8 6

0.6 4

0.4

2 0.2 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1965 1970 1975 1980 1985 1990 1995 2000 12

10 EXPLANATION 8 LOWESS CURVE ALL DATA 6 LOWESS CURVE SEASONAL 4 UNCENSORED CENSORED

SULFATE, DISSOLVED, 2 IN MILLIGRAMS PER LITER 0 1965 1970 1975 1980 1985 1990 1995 2000

Figure 34. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the surface.—Continued 100 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

2 0.4

0.3

1 0.2

DISSOLVED, IN 0.1 ORGANIC, TOTAL, IN NITROGEN, AMMONIA, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS 0 0

0.3 0.10

0.08

0.2 0.06

0.04 0.1 DISSOLVED, IN

NITROGEN, NITRITE, 0.02 MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS 0 0

0.10 0.10

0.08 0.08

0.06 0.06

0.04 0.04 DISSOLVED, IN 0.02 0.02 MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 2.5

2.0 EXPLANATION 1.5 LOWESS CURVE ALL DATA 1.0 LOWESS CURVE SEASONAL UNCENSORED 0.5

PHOSPHORUS, TOTAL, CENSORED IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 34. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the surface.—Continued Hydrologic and Water-Quality Data 101

100 100

80 80

60 60

40 40

20 20 OF CONSTITUENTS, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER SOLIDS, DISSOLVED, SUM AT 180 DEGREES CELSIUS,

SOLIDS, DISSOLVED, RESIDUE 0 0

200 10

150 6

4 IN INCHES 100 MILLILITERS COLONIES PER 100

COLIFORM, FECAL, IN 2 TRANSPARENCY, SECCHI, 50 0

8 1.0

, 6 a , b

4 0.5

2 CHLOROPHYLL- CHLOROPHYLL- PHYTOPLANKTON, IN PHYTOPLANKTON,IN MICROGRAMS PER LITER MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 34. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the surface.—Continued 102 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 120

100 30 80

20 60

40 10 IRON, DISSOLVED,

BARIUM, DISSOLVED, 20 IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

25 80

20 60

15 40 10

20 5 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 30

20 EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE 10 SEASONAL UNCENSORED ZINC, DISSOLVED, CENSORED IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

20 10

9 15

8 10 7

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5

120 20

100 15

80 10 60

CENTIMETER AT 5 40 IN DEGREES CELSIUS 25 DEGREES CELSIUS WATER TEMPERATURE, IN MICROSIEMENS PER SPECIFIC CONDUCTANCE, 20 0 1970 1975 1980 1985 1990 1995 2000 100

80 EXPLANATION LOWESS CURVE ALL DATA 60 LOWESS CURVE SEASONAL UNCENSORED 40 CENSORED MILLIGRAMS PER LITER AT 180 DEGREES CELSIUS, IN SOLIDS, DISSOLVED, RESIDUE 20 1970 1975 1980 1985 1990 1995 2000

Figure 35. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the bottom. 104 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 15

3 30 10

AS CACO 20 5 HARDNESS, TOTAL, IN CALCIUM, DISSOLVED, MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 10 0

3 1.5

2 1.0

1 0.5 POTASSIUM, DISSOLVED, MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

0.6 4

3 0.4

0.2 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1965 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 20 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 10 UNCENSORED CENSORED SODIUM, IN PERCENT

0 1965 1970 1975 1980 1985 1990 1995 2000

Figure 35. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 105

40 2.0

30 1.5 3

20 1.0 AS CACO

10 0.5 CHLORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.4 6

0.3 4

0.2

2 0.1 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 6

EXPLANATION 4 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 2 UNCENSORED CENSORED SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 35. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the bottom.—Continued 106 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

1.0 0.4

0.3

0.5 0.2

DISSOLVED,IN 0.1 ORGANIC, TOTAL, IN MILLIGRAMS PER LITER NITROGEN, AMMONIA, MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS 0 0

0.5 0.10

0.4 0.08

0.3 0.06

0.2 0.04 DISSOLVED, IN

0.1 NITROGEN, NITRITE, 0.02 MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN NITROGEN, NITRITE PLUS

0 0

0.10 0.04

0.08 0.03

0.06 0.02 0.04

DISSOLVED, IN 0.01 0.02 MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000 1.61. 1.4 1.2 EXPLANATION 1.0 LOWESS CURVE ALL DATA 0.8 LOWESS CURVE 0.6 SEASONAL UNCENSORED 0.4 CENSORED PHOSPHORUS, TOTAL, 0.2 IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 35. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 107

30 100

20 60

40 10

IRON, DISSOLVED, 20 BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

250 60

200 50

150 40 100

30 50 STRONTIUM, DISSOLVED, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 20 1970 1975 1980 1985 1990 1995 2000 30

EXPLANATION 20 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 10 UNCENSORED ZINC, DISSOLVED, CENSORED IN MICROGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 35. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Soldier Canyon Dam, sampled near the bottom.—Continued 108 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

20 9

15 8

10 7

5 6 OXYGEN, DISSOLVED, pH, IN STANDARD UNITS IN MILLIGRAMS PER LITER 0 5

100 30

80 20 60

40 10

CENTIMETER AT 20 IN DEGREES CELSIUS MICROSIEMENS PER 25 DEGREES CELSIUS WATER TEMPERATURE,

SPECIFIC CONDUCTANCE, IN 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 36. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the surface. Hydrologic and Water-Quality Data 109

40 15

30 10 3

AS CACO 5 10 CALCIUM, DISSOLVED, HARDNESS, TOTAL, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0

3 1.0

0.8

2 0.6

0.4 1 0.2 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 20

15 EXPLANATION LOWESS CURVE 10 ALL DATA LOWESS CURVE SEASONAL 5 UNCENSORED SODIUM, IN PERCENT CENSORED 0 1970 1975 1980 1985 1990 1995 2000

Figure 36. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the surface.—Continued 110 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

50 3

3 40

2 30

20 1 ACID-NEUTRALIZING PER LITER AS CACO 10 CHLORIDE, DISSOLVED, CAPACITY, IN MILLIGRAMS IN MILLIGRAMS PER LITER 0 0

0.4 6

0.3 4

0.2

2 0.1 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 15

EXPLANATION 10 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 5 UNCENSORED CENSORED SULFATE, DISSOLVED, IN MIILIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 36. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the surface.—Continued Hydrologic and Water-Quality Data 111

1.2 0.10

1.0 0.08

0.8 0.06 0.6 0.04 0.4 DISSOLVED, IN

ORGANIC, TOTAL, IN 0.02 0.2 NITROGEN, AMMONIA, MILLIGRAMS PER LITER MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS 0 0

0.20 0.10

0.08 0.15

0.06 0.10 0.04

0.05 DISSOLVED, IN 0.02 NITROGEN, NITRITE, MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN MILLIGRAMS PER LITER NITROGEN, NITRITE PLUS

0 0

0.10 0.03

0.08

0.02 0.06

0.04 0.01 DISSOLVED, IN 0.02 MILLIGRAMS PER LITER PHOSPHORUS, ORTHO, IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, 0 0 1970 1975 1980 1985 1990 1995 2000

0.10

0.08 EXPLANATION LOWESS CURVE 0.06 ALL DATA LOWESS CURVE 0.04 SEASONAL UNCENSORED 0.02 CENSORED PHOSPHORUS, TOTAL, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 36. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the surface.—Continued 112 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

80 80

60 60

40 40

20 20 SOLIDS, DISSOLVED, SUM OF CONSTITUENTS, IN MILLIGRAMS PER LITER AT 180 DEGREE CELSIUS, IN MILLIGRAMS PER LITER

SOLIDS, DISSOLVED, RESIDUE 0 0

150 15

100 10

IN INCHES 50 5 IN COLONIES COLIFORM, FECAL, PER 100 MILLILITERS TRANSPARENCY, SECCHI, 0 0

8 0.8 , 6 , 0.6 a b

4 0.4

2 0.2 CHLOROPHYLL- CHLOROPHYLL- PHYTOPLANKTON, IN PHYTOPLANKTON, IN MICROGRAMS PER LITER MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 36. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the surface.—Continued Hydrologic and Water-Quality Data 113

40 100

80 30

60 20 40

10 IRON, DISSOLVED, 20 BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

10 80

8 60

6 40 4

20 RECOVERABLE, IN

2 MANGANESE, TOTAL MICROGRAMS PER LITER MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER 0 0

80 40

60 30

40 20

20 10 ZINC, DISSOLVED, STRONTIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 36. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the surface.—Continued 114 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

200 15

150 10

100

5 50 SURFACE, IN FEET OXYGEN, DISSOLVED, SAMPLE DEPTH BELOW IN MILLIGRAMS PER LITER 0 0

9 150

8 100

50 6 CENTIMETER AT pH, IN STANDARD UNITS MICROSIEMENS PER 25 DEGREES CELSIUS

5 SPECIFIC CONDUCTANCE, IN 0

15 80

60 10

5 PER LITER 20 SOLIDS, DISSOLVED, IN DEGREES CELSIUS WATER TEMPERATURE, CELSIUS, IN MILLIGRAMS RESIDUE AT 180 DEGREES 0 0 1970 1975 1980 1985 1990 1995 2000 60

EXPLANATION 40 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 20 UNCENSORED CENSORED CONSTITUENTS, IN MILLIGRAMS PER LITER

SOLIDS, DISSOLVED, SUM OF 0 1970 1975 1980 1985 1990 1995 2000

Figure 37. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the bottom. Hydrologic and Water-Quality Data 115

50 15

3 10 30

20 AS CACO 5

10 HARDNESS, TOTAL, IN MILLIGRAMS PER LITER CALCIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

3 1.5

2 1.0

1 0.5 POTASSIUM, DISSOLVED, IN MILLIGRAMS PER LITER MAGNESIUM, DISSOLVED, IN MILLIGRAMS PER LITER 0 0

0.4 4

0.3 3

0.2 2

0.1 1 SODIUM, DISSOLVED, IN MILLIGRAMS PER LITER SODIUM ADSORPTION RATIO 0 0 1970 1975 1980 1985 1990 1995 2000 20

15 EXPLANATION LOWESS CURVE ALL DATA 10 LOWESS CURVE SEASONAL UNCENSORED 5 CENSORED SODIUM, IN PERCENT

0 1970 1975 1980 1985 1990 1995 2000

Figure 37. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the bottom.—Continued 116 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 2

20 1

10 CHLORIDE, DISSOLVED, IN MILLGRAMS PER LITER IN MILLIGRAMS PER LITER

ACID-NEUTRALIZING CAPACITY, 0 0

0.4 8

0.3 6

0.2 4

0.1 2 SILICA, DISSOLVED, FLUORIDE, DISSOLVED, IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 6

EXPLANATION 4 LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL 2 UNCENSORED CENSORED SULFATE, DISSOLVED, IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 37. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 117

0.8 0.20

0.6 0.15

0.4 0.10 PER LITER 0.2 0.05 ORGANIC, TOTAL, IN NITROGEN, AMMONIA, MILLIGRAMS PER LITER NITROGEN, AMMONIA PLUS DISSOLVED, IN MILLIGRAMS 0 0

0.3 0.08

0.06 0.2

0.04

0.1

DISSOLVED, IN 0.02 NITROGEN, NITRITE, MILLIGRAMS PER LITER NITRATE, DISSOLVED, IN MILLIGRAMS PER LITER NITROGEN, NITRITE PLUS 0 0

0.10 0.08

0.08 0.06

0.06 0.04 0.04

PER LITER 0.02 0.02 IN MILLIGRAMS PER LITER PHOSPHORUS, DISSOLVED, PHOSPHORUS, ORTHO,

0 DISSOLVED, IN MILLIGRAMS 0 1970 1975 1980 1985 1990 1995 2000 0.20

0.15 EXPLANATION LOWESS CURVE 0.10 ALL DATA LOWESS CURVE SEASONAL 0.05 UNCENSORED

PHOSPHORUS, TOTAL, CENSORED IN MILLIGRAMS PER LITER 0 1970 1975 1980 1985 1990 1995 2000

Figure 37. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the bottom.—Continued 118 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances

40 150

30 100

50 10 IRON, DISSOLVED, BARIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

800 150

600 100

400

50 200 MANGANESE, TOTAL, MANGANESE, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0

80 50

40 60

30 40 20

20 ZINC, DISSOLVED, 10 STRONTIUM, DISSOLVED, IN MICROGRAMS PER LITER IN MICROGRAMS PER LITER 0 0 1970 1975 1980 1985 1990 1995 2000 1970 1975 1980 1985 1990 1995 2000

EXPLANATION LOWESS CURVE ALL DATA LOWESS CURVE SEASONAL UNCENSORED CENSORED

Figure 37. Temporal variations in periodic measurements and concentrations at Horsetooth Reservoir, near Spring Canyon Dam, sampled near the bottom.—Continued Hydrologic and Water-Quality Data 119 ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM AUG 1973 TO NOV 2000 near surface. near spillway, Summary statistics for site 1, Lake Granby, WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 4. Table ------70300 RESIDUE70301 DIS DISSOLVED00077 180C SOLIDS TRANSPARENCY MG/L00300 MG/L (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C) 59 6700925 59 DISSOLVE MAGNESIUM00935 (MG/L 75 57 DISSOL (MG/L 59 POTASSIUM AS00931 (MG/L AS 79 DISSOL CA) 236.000 SODIUM AS CAO3)00930 (MG/L 73.000 ADSORPTIO MG) SODIUM AS00932 (RATIO) 77 8.700 DISSOLVED K) 78 SODIUM, 56.00090410 (MG/L 43.800 9.100 PERCENT 60 ANC, 10.400 AS00940 67.000 TIT. NA) 60 46.000 CHLORIDE PERCENT00950 4.5, DISSOLV 60 68.000 FLUORIDE L 19.50000955 (MG/L 16.000 DISSOLV 6.800 MG/L 27.800 SILICA AS 129.881 28.00000945 (MG/L 60 DISSOLVED CL) 5.700 SULFATE AS AS 5.00000608 (MG/L 56.915 DISSOLVE F) CACO3 60 8.700 NITROGEN AS00625 (MG/L 41.000 AMMONIA SIO2) 60 37.158 1.600 NITROGEN AS 34.62000610 (MG/L 0.000 217.400 AMM+ORG 18.000 SO4) 7.664 NITROGEN AS00631 (MG/L 59 1.000 AMMONIA N) 60 7.931 NO2 AS 7.79400630 (MG/L 60 64.000 60 + N) 54.805 2.900 NO2 AS 5.500 158.00000613 NO3 60 + N) 13.887 NITROGEN,NITRITE 0.300 50.100 DISSOL 0.972 22.617 6000666 40.800 NO3 MG/L (MG/L 31.000 PHOSPHORUS TOTAL00671 AS AS 8.400 DISS. 0.550 62.000 1.100 PHOSPHORUS 24.000 118.000 N N)00665 (MG/L (MG/L 59 7.200 8.920 ORTHO 67.100 PHOSPHORUS 9.300 AS 1.600 AS 6.96131625 (MG/L 41.500 78 0.300 TOTAL P) 37.000 N) 19.005 COLIFORM AS 0.159 1.255 27.095 5.00070953 (MG/L 20.000 24 FECAL P) CHL-A AS70954 57.000 0 14.600 94.000 PHY 7.900 P) 0.681 CHLOROPHYLL-B, COLS./100 0.10001005 61.000 CHROMA 0.050 P 2.300 ML 8.300 37.000 60 BARIUM UG/L -- 8.600 2.160 35.00001010 17.125 UG/L 3.900 24.600 DISSOLVED 24.814 8.490 BERYLLIUM 59 0.19801020 (UG/L 1.700 57 30 0.060 DISSOL 53.000 16.660 69.600 1.500 BORON AS01025 (UG/L 60 DISSOLVED BA) 53.000 7.600 CADMIUM AS -- 0.447 33.50001030 78 31.700 0.800 DISSOLVE BE) 15.150 5.047 58 7.900 CHROMIUM 0.089 (UG/L -- 22.200 7.50001035 (UG/L -- DISSOLV AS 29.000 2.700 COBALT AS -- 7.600 47.000 01040 (UG/L B) 2.945 0.053 DISSOLVED 0.100 CD) 18.100 COPPER 0.238 AS 1.400 48.50001046 (UG/L 0.020 DISSOLVED CR) 20.600 59 0.111* 7.500 IRON AS 28.900 11.17501049 (UG/L -- 20.825 0.170 DISSOLVED CO) 0.700 59 2.000 0.800 LEAD 7.600 AS01130 27.000 7.200 6.690 DISSOLVED CU) LITHIUM -- 2.475 -- 6.87001056 17.475 60 DISSOLVE 43.000 (UG/L 69 0.012* 58 MANGANESE -- 0.214 1.200 59 4.09501060 *0.200 (UG/L AS DISSOL (UG/L -- 59 0.344* 9.000 MOLYBDENUM 18.130 AS -- FE) 7.100 --01065 (UG/L 5.500 -- AS DISSO LI) 24.000 59 0.700 0.023* NICKEL AS 0.500 PB) 7.080 01075 (UG/L 6.500 DISSOLVED 5.700 MN) 16.450 69 SILVER AS 13.000 2.20001080 6.430 *0.030 (UG/L 40.000 DISSOLVED MO) *0.100 2.000 STRONTIUM AS 0.300 0.199 -- 0.015* 1.15001085 *0.758 (UG/L 3.300 DISSOL NI) VANADIUM AS 2.000 23.000 60 --01090 *0.060 (UG/L DISSOLV AG) 59 0.005* 0.100* 0.600 ZINC AS 0.400 75 15.725 14.022------(UG/L DISSOLVED SR) *0.020 4.850 60 0.002* -- AS -- 0.400 *0.100 2100.000 1.800 ------5.621 *0.072 V) *0.300 59 0.013* 0.765** 0.176 1.005 2.950 21.000 (UG/L *0.040 73 - 7.932 *0.020 *0.100 AS 13.700 VALUE -- 14.805 58 5.000 ZN) 0.571 *0.010 30.000 0.325 *0.011 IS -- *0.100 -- 59 4.400 ESTIMATED *0.016 *0.200 -- 2.947 *0.040 -- 1.605 *1.000 BY *0.015 10.000 USING 59 0.162 2.425 *0.006 *0.100 -- A ------*0.005 -- *0.002 LOG-PROBABILITY -- 4.569* 9.000 *0.064 71 0.516* 57.000 0.084* REGRESSION 0.105 *0.006 *0.156 *0.020 *0.909 3.905 TO *0.007 -- PREDICT -- 8.360 *0.003 *0.100 2.418* -- *15.000 2.000 51.669* *0.003 *0.001 -- -- 40.000 *2.000 32.900 *0.300 *0.002 8.100 *0.081 *0.009 *0.731 *0.003 -- *59.000 *0.001 *0.100 2.597* *8.718 -- *5.586 3.600 1.468* -- 2.120* *0.000 -- *0.649 42.766 *0.100 *0.001 *0.005 *0.607 -- 8.000 *30.000 1.196* *10.000 *0.001 *0.100 *3.013 -- *2.682 -- *4.000 *9.950 *0.000 2.050 -- *0.380 *0.056 *10.000 *0.002 52.000 *0.460 -- *4.987 *3.307 -- 7.800 -- *1.608 *1.345 *1.902 *2.000 5.077* *0.214 *0.031 -- 1.300 *4.245 47.000 *1.300 *1.734 -- *0.759 *0.504 -- 7.000 *1.212 -- *12.400 *0.878 *0.099 *0.013 *1.165 42.000 -- -- 0.900 -- *0.581 *0.919 *0.295 *0.800 *8.000 *0.325 -- 38.000 -- *0.257 *0.447 -- -- *0.424 *3.000 *0.088 ------33.500 *0.087 *1.834 ------*0.819 ------120 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM AUG 1973 TO NOV 2000 near bottom. near spillway, Summary statistics for site 1, Lake Granby, WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 5. Table ------70300 RESIDUE70301 DIS DISSOLVED00300 180C SOLIDS OXYGEN MG/L00400 MG/L DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C) 5800925 58 DISSOLVE MAGNESIUM00935 (MG/L 67 DISSOL (MG/L POTASSIUM AS00931 (MG/L AS 72 57 DISSOL CA) 58 SODIUM AS CAO3)00930 (MG/L 80.000 ADSORPTIO MG) SODIUM AS00932 (RATIO) 69 8.000 DISSOLVED K) 73 SODIUM,90410 (MG/L 8.300 PERCENT 59 ANC, AS 60.00000940 50.500 TIT. 8.600 NA) 59 50.000 CHLORIDE PERCENT00950 4.5, DISSOLV 59 80.000 FLUORIDE L 18.00000955 (MG/L DISSOLV 6.600 MG/L SILICA AS 30.60000945 (MG/L 24.000 59 DISSOLVED CL) 6.500 29.800 SULFATE AS AS00608 (MG/L 60.328 DISSOLVE F) CACO3 0.000 59 9.600 NITROGEN AS00625 (MG/L 43.000 AMMONIA SIO2) 59 1.600 NITROGEN AS00610 (MG/L 4.000 AMM+ORG 20.300 SO4) 7.166 40.088 NITROGEN AS 37.45900631 (MG/L 58 1.400 AMMONIA N) 59 7.166 NO2 AS00630 (MG/L 59 70.050 59 + N) 56.942 4.571 4.100 NO2 AS 6.29000613 NO3 59 + N) NITROGEN,NITRITE 0.400 DISSOL 1.090 23.937 5900666 NO3 6.658 MG/L (MG/L 35.000 PHOSPHORUS 58.000 TOTAL00671 44.335 AS AS 7.710 DISS. 0.560 63.000 1.000 PHOSPHORUS 26.000 N N)00665 (MG/L (MG/L 58 8.600 7.760 ORTHO 70.500 PHOSPHORUS AS 1.700 AS 7.37631625 (MG/L 70 0.300 TOTAL 7.875 P) N) COLIFORM AS 0.162 1.323 28.200 4.00070954 (MG/L 19.000 44.000 18 FECAL P) 40.875 CHLOROPHYLL-B, AS 8.79001005 61.000 0 14.300 P 7.325 P) 0.730 BARIUM COLS./100 0.10001010 65.000 UG/L 0.070 DISSOLVED 4.800 ML 7.300 59 BERYLLIUM -- 2.29801020 (UG/L 1.300 25.500 DISSOL 25.672 6.175 40.000 8.800 BORON AS 37.850 58 0.20501025 (UG/L 2.000 56 23 0.040 DISSOLVED BA) 55.750 16.695 1.500 CADMIUM AS01030 7.400 59 DISSOLVE BE) 55.000 7.100 CHROMIUM (UG/L -- 0.44401035 (UG/L 70 0.900 DISSOLV AS 6.305 7.100 COBALT 0.200 AS -- 23.900 36.00001040 (UG/L B) 2 33.550 -- DISSOLVED CD) 29.100 4.800 2.900 COPPER AS -- 7.800 53.000 01046 (UG/L 2.963 0.030 DISSOLVED 0.200 CR) 58 18.500 IRON 0.252 AS 1.400 49.50001049 (UG/L 6.500 0.030 DISSOLVED CO) 58 0.108* 6.975 LEAD AS01130 -- 21.700 0.290 DISSOLVED CU) 0.800 26.900 -- 0.800 7.000 LITHIUM 31.975 01056 27.000 8.100 DISSOLVE (UG/L 69 MANGANESE 3.050 -- 2.600 -- 7.300 58 11.00001060 (UG/L 17.400 AS 1 DISSOL 44.500 (UG/L 58 0.017* MOLYBDENUM AS -- FE) 0.217 1.300 -- 3.70001065 *0.200 (UG/L AS 5.550 DISSO LI) -- 58 0.232* NICKEL 20.700 AS -- PB) 6.795 01075 (UG/L DISSOLVED MN) 26.000 68 0.700 0.019* SILVER AS 0.500 6.700 01080 (UG/L 10.000 DISSOLVED 7.200 MO) 16.500 5.000 STRONTIUM AS -- 2.300 1.230 -- 6.70001085 *0.060 (UG/L 2.000 DISSOL NI) *0.100 VANADIUM AS -- 59 0.202 -- 0.091*01090 1.200 *0.745 (UG/L 3.300 DISSOLV AG) 4.410 58 ZINC AS 23.000 68 12.832------*0.040 (UG/L DISSOLVED SR) 57 0.008* 0.107* 0.660 AS -- 0.400 15.900 2500.000 -- -- V) *0.030 5.900 58 0.006* -- *0.100* 1.900 6.330 7.545 *0.180 (UG/L *0.221 68 0.019* - -- 0.183 AS 1.160 3.000 560.000 10.000 VALUE 22.000 -- *0.030 58 ZN) -- *0.028 IS *0.200 -- -- 14.600 58 ESTIMATED 0.580 *0.010 -- -- 0.300 *0.020 -- *0.100 BY 5.500 *0.110 *0.179 -- *0.064 USING 1.800 58 -- -- A *0.020 -- 9.000 0.165 -- 2.600 *0.010 LOG-PROBABILITY *0.100 4.679* 69 0.358* 59.000 REGRESSION *0.006 *0.008 -- *0.061 TO -- 0.200 *0.087 *0.135 *0.020 PREDICT -- 5.000 -- 2.858* -- *0.009 *10.000 60.812* *0.005 *0.100 8.000 -- -- 40.000 *1.000 37.900 2.300 *0.003 -- *0.004 -- *0.059 *0.064 28.046* *0.010 -- *50.000 2.008* *8.746 *5.761 *0.004 -- *0.003 *0.072 -- -- *0.376 45.545 *131.000 7.900 -- *0.002 -- *20.000 *0.032 *0.005 *10.000 -- *3.570 -- *3.997 -- *19.500 *0.001 *0.051 -- -- *0.159 -- *20.000 *0.001 55.050 -- 7.000 *2.194 *0.002 -- *2.000 *2.894 -- *6.000 *10.000 6.627* *0.064 -- -- 49.000 -- *1.153 -- 4.950 *1.171 *1.790 ------*19.000 *1.000 *3.139 *0.018 -- 46.500 -- -- *0.545 -- *10.000 *0.525 *0.141 -- -- 40.950 -- -- *0.226 ------*4.000 ------37.995 -- *2.340 ------*1.102 ------Hydrologic and Water-Quality Data 121 ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM MAY 1989 TO NOV 2000 Summary statistics for site 2, Lake Granby (Rainbow Bay), sampled near surface. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 6. Table ------70300 RESIDUE70301 DIS DISSOLVED00077 180C SOLIDS TRANSPARENCY MG/L00300 MG/L (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C) 59 5600925 59 DISSOLVE MAGNESIUM00935 (MG/L 60 58 DISSOL (MG/L 57 POTASSIUM AS00931 (MG/L AS 59 DISSOL CA) 206.000 SODIUM AS CAO3)00930 (MG/L 87.000 ADSORPTIO MG) SODIUM AS00932 (RATIO) 60 8.500 DISSOLVED K) 60 SODIUM, 71.00090410 (MG/L 54.600 9.000 PERCENT 59 ANC, AS00940 TIT. 9.400 NA) 59 47.000 CHLORIDE PERCENT 9.50000950 4.5, DISSOLV 59 87.000 FLUORIDE L 19.70000955 (MG/L 14.000 DISSOLV 7.000 MG/L 28.100 SILICA AS 35.80000945 (MG/L 59 DISSOLVED CL) 7.100 109.812 SULFATE AS AS 11.00000608 (MG/L 59.508 DISSOLVE F) CACO3 4.900 59 NITROGEN AS00625 (MG/L 41.000 AMMONIA SIO2) 59 38.569 2.000 NITROGEN AS 36.44000610 (MG/L 4.800 AMM+ORG 18.200 SO4) 7.649 NITROGEN AS 187.65000631 (MG/L 59 1.000 AMMONIA N) 58 7.982 NO2 AS00613 (MG/L 5.660 59 79.000 59 + N) 56.367 7.519 3.900 NITROGEN,NITRITE AS00666 NO3 58 MG/L N) 14.158 145.250 PHOSPHORUS 0.284 54.100 DISSOL 0.981 23.732 5800671 47.570 AS DISS. (MG/L 38.000 PHOSPHORUS N00665 (MG/L AS 8.300 ORTHO 0.550 63.000 1.300 PHOSPHORUS 19.900 AS N)00680 (MG/L 7.327 59 9.600 8.890 TOTAL 102.500 P) 75.850 CARBON AS 1.60031625 (MG/L 44.000 59 0.300 ORGANIC 8.900 P) 37.800 19.300 COLIFORM AS 0.160 1.305 31.600 4.50070953 T 20.000 18 FECAL P) CHL-A (MG/L70954 59.000 0 14.400 PHY 7.800 AS 0.687 CHLOROPHYLL-B, COLS./100 0.100 75.50001005 61.000 CHROMA C) 10.000 0.075 P 2.400 ML 8.375 38.000 59 BARIUM UG/L -- 2.263 36.200 5901010 17.475 UG/L 56 0.600 25.400 DISSOLVED 25.881 8.200 BERYLLIUM 0.20101020 (UG/L 1.700 59 0.040 DISSOL 53.000 16.595 1.700 BORON AS01025 (UG/L 60 42.250 DISSOLVED BA) 55.000 7.600 CADMIUM AS -- 0.438 34.00001030 32.050 -- 0.800 DISSOLVE 7.900 BE) 14.550 5.551 53 7.950 CHROMIUM 0.070 (UG/L -- 23.200 1101035 (UG/L 0.118 DISSOLV AS 33.000 7.400 3.300 COBALT AS -- 48.000 01040 (UG/L B) 3.012 0.020 DISSOLVED CD) 18.800 COPPER 0.265 AS 1.400 49.25001046 (UG/L 0.045 DISSOLVED CR) 14.950 59 0.112* 7.500 IRON AS 28.890 11.125 70.00001049 (UG/L -- 21.200 DISSOLVED CO) 0.700 7.100 59 1.005 LEAD 7.700 AS --01130 9.000 28.000 8.900 DISSOLVED CU) LITHIUM 7.000 -- 2.50001056 17.400 59 DISSOLVE 44.000 (UG/L -- 59 0.014* 58 MANGANESE -- 0.215 1.300 59 11.000 4.02001060 *0.200 (UG/L AS DISSOL -- (UG/L 59 0.215* MOLYBDENUM 19.300 AS FE) 7.200 --01065 (UG/L 7.320 AS DISSO LI) 25.000 59 0.700 0.016* 6.540 NICKEL AS 0.500 PB) 7.300 01075 (UG/L 3.300 DISSOLVED 6.300 MN) 16.500 59 SILVER AS 12.000 2.300 6.500 --01080 *0.050 (UG/L 20.000 DISSOLVED MO) *0.100 STRONTIUM AS 0.300 0.203 -- 0.018* 1.18001085 *0.300 (UG/L 2.000 3.325 DISSOL NI) 0.008* VANADIUM AS 23.000 59 --01090 *0.040 (UG/L DISSOLV AG) 59 0.003* -- 0.600 ZINC AS 5.880 0.400 58 15.800 ------(UG/L 4.318 DISSOLVED SR) *0.020 5.200 59 0.014* AS -- 0.500 *0.100 1.900 -- -- 2.077* *0.068 V) *0.250 59 130.000* *0.022 0.175 1.090 8.110 3.000 21.000 (UG/L *0.022 59 - *0.012 AS -- 20.000 VALUE 14.800 59 4.000 ZN) 0.580 *0.009 23.000 0.300 *0.040 IS -- *0.100 59 4.600 *5.300 ESTIMATED *0.020 *0.200 -- 2.822 9.000 -- -- 1.600 BY *0.008 *0.010 -- USING -- 59 0.165 10.000 2.500 *0.002 -- -- A ------*0.004 -- *0.020 LOG-PROBABILITY 4.549* *0.065 58 73.000 0.080* *1.000 REGRESSION 0.100 *0.011 *0.170 4.100 TO *0.004 4.300 -- *0.007 PREDICT -- 7.900 *0.001 -- *10.000 9.000 1.995 106.000 *0.002 *0.010 -- 22.002* -- 33.200 *0.300 *0.301 *0.006 *0.127 -- -- *0.002 -- *0.003 -- 3.600 *0.000 3.599* *5.958 3.700 1.690* *70.000 -- -- 2.531* *0.007 8.000 45.022 *0.100 *0.091 *0.002 *0.001 -- -- *10.060 *30.000 *0.000 *14.000 -- *3.672 -- *3.208 3.500 *0.004 2.000 -- -- *0.053 *0.016 7.500 -- 65.000 -- -- *10.000 *4.509 -- *3.000 *2.405 *2.158 5.562* 3.300 *0.028 -- 1.200 -- 48.000 7.000 *5.379 *2.546 -- *14.100 *1.000 *1.324 -- *1.559 ------*0.011 -- 44.000 -- 0.500 *1.895 -- *1.444 *5.556 *0.400 *1.101 -- -- 38.100 -- *0.628 -- -- *2.442 *0.107 *0.743 ------33.900 *1.093 ------*0.384 ------122 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------37.715 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM MAY 1989 TO SEPT 2000 Summary statistics for site 2, Lake Granby (Rainbow Bay), sampled near bottom. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 7. Table ------70300 ------RESIDUE70301 DIS DISSOLVED00300 180C SOLIDS OXYGEN MG/L00400 MG/L DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C) 5800925 58 DISSOLVE MAGNESIUM00935 (MG/L 60 DISSOL (MG/L POTASSIUM AS00931 (MG/L AS 59 57 DISSOL CA) 56 SODIUM AS CAO3)00930 (MG/L 92.000 ADSORPTIO MG) SODIUM AS00932 (RATIO) 60 8.200 DISSOLVED K) 60 SODIUM,90410 (MG/L 8.100 PERCENT 58 ANC, AS 67.00000940 57.400 TIT. 9.000 NA) 58 51.000 CHLORIDE PERCENT00950 4.5, DISSOLV 58 90.000 FLUORIDE L 15.50000955 (MG/L DISSOLV 6.700 MG/L SILICA AS 35.80000945 (MG/L 18.000 58 DISSOLVED CL) 6.800 30.000 SULFATE AS AS 11.00000608 (MG/L 60.690 DISSOLVE F) CACO3 1.100 58 NITROGEN AS00625 (MG/L 44.000 AMMONIA SIO2) 58 2.000 NITROGEN AS00610 (MG/L 4.700 AMM+ORG 18.600 SO4) 7.252 39.789 NITROGEN AS 37.32900631 (MG/L 58 0.900 AMMONIA N) 57 7.400 NO2 AS00613 (MG/L 5.750 58 83.100 58 + N) 58.017 5.349 4.100 NITROGEN,NITRITE AS00666 NO3 57 MG/L N) PHOSPHORUS 0.299 DISSOL 1.010 24.181 5700671 AS 9.453 DISS. (MG/L 38.000 PHOSPHORUS 60.000 N00665 52.790 (MG/L AS 7.715 ORTHO 0.500 11.000 63.250 1.300 PHOSPHORUS 21.000 AS N)00680 (MG/L 7.460 59 8.000 TOTAL P) 86.850 CARBON AS 1.70031625 (MG/L 59 0.300 ORGANIC 8.800 P) COLIFORM AS 0.160 1.334 34.640 4.50001005 T 20.000 46.000 18 14.685 FECAL P) 39.050 BARIUM (MG/L01010 60.000 0 14.400 DISSOLVED 7.500 AS 0.688 BERYLLIUM 3.300 COLS./100 0.10001020 63.000 (UG/L C) 11.000 0.070 DISSOL ML 7.600 59 BORON AS -- 2.317 5901025 (UG/L 56 0.600 25.800 DISSOLVED BA) 26.103 7.300 39.000 CADMIUM 11.775 AS 36.550 0.20401030 1.900 59 0.070 DISSOLVE BE) 55.000 16.657 1.710 CHROMIUM (UG/L01035 (UG/L 59 DISSOLV AS 55.500 7.200 COBALT AS -- 6.086 0.45301040 (UG/L B) 0.800 DISSOLVED 8.000 CD) 7.400 COPPER 0.110 AS -- 23.450 11 34.00001046 0.030 (UG/L 1 33.100 0.501 DISSOLVED CR) 58 37.000 5.300 3.515 IRON AS -- 8.450 52.950 01049 (UG/L 3.000 0.020 DISSOLVED CO) 58 20.105 LEAD 0.278 AS 1.400 50.00001130 0.040 DISSOLVED CU) 0.106* 7.000 LITHIUM 10.05001056 -- 21.675 DISSOLVE (UG/L -- 0.800 25.700 7.300 58 0.930 7.125 MANGANESE -- 31.155 59 14.00001060 9.300 28.000 (UG/L AS 1.000 DISSOL (UG/L 58 MOLYBDENUM 3.300 AS -- 2.500 FE) 7.600 --01065 (UG/L 17.200 AS DISSO 44.100 LI) 58 0.018* NICKEL AS -- PB) 0.215 1.300 4.21001075 *0.200 (UG/L DISSOLVED MN) 58 0.215* SILVER 20.625 AS 6.800 01080 6.800 (UG/L 10.000 DISSOLVED MO) 25.500 0.700 0.022* 6.682 2.000 STRONTIUM AS -- 0.500 6.900 --01085 (UG/L 7.000 3.200 DISSOL NI) 16.500 VANADIUM AS 2.300 57 1.500 --01090 *0.050 (UG/L 5.800 DISSOLV AG) *0.100 58 ZINC AS 58 0.203 -- 0.036*------1.200 *0.400 (UG/L 3.300 0.002* DISSOLVED SR) 58 0.017* AS -- 23.000 *0.070 -- -- 5.650 V) 58 0.004* 0.608 6.285 0.400 15.875* 8.510 4.018 80.000 (UG/L *0.020 58 0.014* - *0.100 -- 1.900 AS -- VALUE *0.100 *0.300 58 *0.010 ZN) 67.000 *0.030 0.182 IS -- 1.096 3.000 22.950 *0.030 58 -- ESTIMATED -- *0.017 -- 5.075 BY 14.885 -- 0.579 *0.013 -- 0.400 *0.030 USING -- 58 11.000 *0.100 A *0.053 *0.195 -- 9.300 *0.001 1.700 -- -- *0.011 LOG-PROBABILITY 4.358* *0.020 58 0.416* 77.000 REGRESSION 0.168 2.600 *0.005 TO -- *0.008 4.300 *0.020 -- PREDICT -- *0.063 0.190 *0.025 -- *0.156 *10.000 9.000 *0.000 -- *0.005 -- 3.800 -- *0.010 12.000 *1.007 35.100 *0.002 22.992* -- -- 2.190 *0.004 *0.010 -- *0.014 *5.448 *0.108 *0.000 -- 7.927* *0.003 8.000 *71.000 -- *0.522 46.384 *0.005 3.500 -- *0.001 -- -- *0.008 -- *30.850 -- *0.006 *4.000 -- *30.000 *0.000 *0.001 -- *0.323 -- 7.975 *0.000 71.200 -- -- 3.300 *0.004 *20.000 -- *8.000 *2.785 4.181* *0.192 -- -- 49.000 -- 7.295 -- -- 3.200 *8.020 *4.300 *1.811 -- -- *9.050 *0.096 -- -- 45.000 -- -- *3.245 *1.108 -- *5.843 -- -- 40.675 ------*0.403 -- -- *3.279 ------*2.172 ------*1.224 ------Hydrologic and Water-Quality Data 123 ------*0.166 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM NOV 1970 TO NOV 2000 Summary statistics for site 3, Granby Pump Canal. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 8. Table ------70300 ------RESIDUE70301 DIS DISSOLVED00300 180C SOLIDS OXYGEN MG/L00400 MG/L DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00020 MICROSIEMENS/C CONDUCT UNIT AIR (STANDARD00010 US/CM TEMPERATURE UNIT WATER @00900 TEMPERATUR 25C HARDNESS DEGREES 5600915 (DEGREES 56 TOTAL C 171 CALCIUM C)00925 DISSOLVE 170 MAGNESIUM00935 (MG/L 55 DISSOL (MG/L 55 POTASSIUM AS00931 (MG/L AS 70.000 DISSOL CA) 179 SODIUM AS CAO3)00930 (MG/L 8.800 ADSORPTIO MG) 8.900 SODIUM AS 18000932 12.000 (RATIO) DISSOLVED K) SODIUM, 66.00090410 (MG/L 42.500 105.000 PERCENT 56 49.000 ANC, AS00940 8 TIT. NA) 56 CHLORIDE PERCENT00950 4.5, 17.500 DISSOLV 6.600 56 FLUORIDE L 5.30000955 (MG/L 2.000 26.000 DISSOLV MG/L 30.100 SILICA 30.000 AS 28.00000945 (MG/L 60.554 56 DISSOLVED CL) SULFATE 22.100 AS AS00608 (MG/L DISSOLVE F) CACO3 56 8.700 NITROGEN AS00625 (MG/L AMMONIA 1.000 SIO2) 7.489 56 40.691 1.500 NITROGEN AS 7.270 36.74700610 (MG/L 58.827 7.014 AMM+ORG 19.300 SO4) NITROGEN AS00631 (MG/L -6.000 70.000 56 0.900 AMMONIA N) 56 NO2 AS00630 (MG/L 56 56 + N) 2.800 NO2 AS 5.76000613 NO3 57 + N) 5.426 NITROGEN,NITRITE 0.236 54.400 DISSOL 1.120 23.682 5600615 41.780 NO3 70.000 8.030 MG/L (MG/L 64.000 30.000 8.240 NITROGEN,NITRITE TOTAL00666 9.600 AS AS 4.525 MG/L 0.560 1.800 PHOSPHORUS 18.200 N N)00671 AS (MG/L 55 7.700 DISS. 139 PHOSPHORUS N 1.600 AS 7.30570507 (MG/L 44.000 3.000 ORTHO 39.400 N) 12.490 63.000 PHOS AS 0.154 1.306 27.330 5.40000665 62.000 (MG/L 21.000 21 ORTHO 7.775 P) PHOSPHORUS AS 7.60031501 TOT 14.500 8.425 22.100 TOTAL P) 0.726 TOT A 0.10031625 (MG/L 0.080 COLI,MENDO 3.700 MG/L 40.000 55 1.200 COLIFORM AS -- 2.229 37.70031616 M 60.000 25.300 FECAL P) 56.000 25.964 8.515 FECAL 7.500 COLS./100 AS 55 0.19901005 0 1.900 87 0.070 COLI,MFC ML P 7.500 16.452 1.500 BARIUM COLS./100 12.400 7.300 1401010 M 55 7.550 DISSOLVED ML BERYLLIUM COLS./100 -- 0.507 36.00001025 (UG/L -- 55 33.200 0.900 DISSOL ML 5.636 53.000 CADMIUM 0.180 AS 23.900 52.700 01030 (UG/L DISSOLVE BA) 139 30.000 2.700 CHROMIUM AS -- 7.800 4.100 10401035 0.020 (UG/L 3.068 -- DISSOLV 0.300 BE) 7.200 17.915 COBALT 0.229 AS 1.400 3.250 6.90001040 (UG/L 0.040 5.600 DISSOLVED CD) 29.600 72 0.162* COPPER AS 31.400 1401046 47.000 (UG/L -- 21.700 0.032 DISSOLVED CR) 0.800 38 110.000 1.020 IRON AS01049 28.000 (UG/L 7.400 DISSOLVED CO) -- 56 0.350 LEAD AS 2.500 -- 7.400 3.00001130 17.100 -4.500 DISSOLVED CU) 56 0.013* LITHIUM -- 6.785 0.216 1.300 0.358* 10.000 4.15001056 *0.210 6.400 DISSOLVE (UG/L 99 3.310 MANGANESE 20.110 --01060 -- (UG/L 0.020 AS DISSOL (UG/L 26.000 -- 55 0.700 0.019* 1.000 MOLYBDENUM AS 0.575 FE)01065 (UG/L -- AS DISSO 6.400 LI) 16.500 56 9.000 NICKEL AS PB) -6.000 100 2.300 --01075 6.632 *0.039 (UG/L 2.000 *0.890 DISSOLVED -- MN) *0.100 SILVER AS 0.202 0.078* 1.20001080 (UG/L 3.375 DISSOLVED MO) -- 5.000 STRONTIUM AS 24.000 --01085 *0.066 (UG/L -- 0.002* DISSOL NI) 0.092* 0.665 VANADIUM AS 0.400 56 15.625 --01090 (UG/L 100 11.000 DISSOLV AG) *0.020 5.400 55 0.010* ZINC AS 2.000 *0.500 *0.100 1.900------(UG/L 10.110* 6.160 DISSOLVED *0.156 SR) 54 0.007* -- AS 0.178 -- 1.155 3.000 22.000 V) *0.020 56 *0.020 0.022** *0.200 -- 80.000 (UG/L 15.055 99 37.000 - -- 0.597 *0.010 *43.800 11.000 0.400 *0.020 AS *0.300 0.483* *0.100 VALUE 55 5.025 ZN) *0.100 7.298 81.000 *0.016 IS -- 1.700 0.011* 56 ESTIMATED *0.020 1.000* -- -- *0.002 0.169 2.700 *0.053 BY *0.100 *13.000 -- 15.000 -- USING 56 *0.004 -- *0.010 *0.180 *3.000 A *0.044 0.185 *0.074 -- *0.010 LOG-PROBABILITY -- 2.000 *0.020 3.900 98 0.390* 51.000 REGRESSION -- *0.010 *1.000 *0.001 8.030 *0.030 TO *0.100 *3.000 -- 2.285 PREDICT 2.743* -- *0.002 *0.008 *0.279 *0.099 -- *0.048 *0.005 -- -- *0.020 -- 30.000 *1.000 29.000 *1.000 *0.005 23.657* *0.000 *0.018 *0.065 *0.818 8.000 2.074* *6.716 1.951* *0.005 *0.068 10.307* -- *0.033 *0.004 *0.009 *80.000 -- *0.433 44.086 -- *1.000 *0.000 *0.010 *10.000 -- *0.045 *0.142 1.932* *71.250 *3.939 *4.480 *0.003 7.350 *0.017 -- -- *40.000 *0.002 0.700* *0.006 -- *0.197 *1.000 50.150 *2.000 *0.004 *6.000 *7.250 *2.000 -- *2.461 *20.000 *0.002 7.000 -- *2.000 *0.004 7.703* *0.090 -- *1.000 48.000 *0.842 *2.599 *2.350 *1.311 -- *1.457 *7.787 -- -- *20.000 *0.884 *0.027 5.020 45.000 *0.318 -- *1.134 *1.000 *0.696 *0.933 *3.104 *10.000 -- *0.568 -- 40.000 *0.089 -- *0.649 -- *0.459 -- *5.000 *0.364 -- 34.465 *0.277 -- *2.988 -- *0.189 ------*1.452 ------124 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------*1.439 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM AUG 1973 TO SEPT 2000 Summary statistics for site 4, Shadow Mountain Lake, sampled at the surface. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 9. Table ------70300 RESIDUE70301 DIS DISSOLVED00077 180C SOLIDS TRANSPARENCY MG/L00300 MG/L (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00900 MICROSIEMENS/C CONDUCT UNIT HARDNESS (STANDARD00915 US/CM TOTAL UNIT CALCIUM @00925 DISSOLVE 25C MAGNESIUM 58 6400935 (MG/L 58 DISSOL (MG/L POTASSIUM AS00931 (MG/L AS 64 58 DISSOL CA) 54 SODIUM AS CAO3)00930 (MG/L 65 ADSORPTIO MG) 157.000 SODIUM AS00932 (RATIO) 67.000 DISSOLVED K) SODIUM,90410 (MG/L 65 9.200 PERCENT 59 ANC, AS 54.00000940 41.300 9.500 TIT. NA) 59 CHLORIDE PERCENT00950 4.5, 42.000 DISSOLV 9.900 59 30.000 FLUORIDE L00955 (MG/L DISSOLV MG/L 66.000 SILICA AS 27.40000945 (MG/L 59 DISSOLVED 6.800 CL) 19.600 SULFATE AS AS 8.00000608 (MG/L DISSOLVE F) 5.600 CACO3 86.984 59 8.300 NITROGEN AS00625 (MG/L 52.534 AMMONIA SIO2) 3.500 59 1.600 NITROGEN AS00610 (MG/L 27.000 AMM+ORG 11.900 SO4) NITROGEN AS 33.00900631 (MG/L 58 36.190 1.100 AMMONIA N) 7.469 58 NO2 AS 129.25000630 (MG/L 60 59 + N) 7.625 3.100 NO2 AS 3.60000613 NO3 62.150 58 + N) 50.631 7.340 NITROGEN,NITRITE 0.300 DISSOL 0.710 20.751 5800615 NO3 MG/L (MG/L 30.000 NITROGEN,NITRITE TOTAL00605 40.275 AS AS 97.500 MG/L 50.100 0.400 1.000 NITROGEN 22.000 N N)00600 AS (MG/L 59 7.600 8.815 ORGANIC 59.250 NITROGEN N 1.100 AS 6.29400666 (MG/L 65 0.300 9.150 TOTAL N) 64.400 PHOSPHORUS AS 0.139 1.212 25.600 4.00000671 12.000 24 DISS. 9.070 N) 37.200 PHOSPHORUS 83.500 41.25070507 (MG/L -- 13.500 ORTHO (MG/L 0.696 PHOS AS00665 55.000 (MG/L AS 0.089 ORTHO 3.400 7.650 P) 60 PHOSPHORUS AS N) 1.91931625 57.000 TOT 3.700 23.300 TOTAL P) 0.100 7.800 22.241 8.000 COLIFORM A 33.650 59 0.18370953 (MG/L 1.800 70.000 37.500 18 0.060 FECAL MG/L 8.150 16.181 1.420 CHL-A AS70954 0 30 PHY P) 48.500 9 CHLOROPHYLL-B, COLS./100 -- AS01005 CHROMA 1.000 P ML 51.000 P 5.752 7.400 BARIUM 0.130 UG/L -- 21.90001010 UG/L 57 30.400 -- DISSOLVED 0.140 7.600 18 28.050 2.600 32.750 BERYLLIUM 56.750 -- 7.000 0.385*01020 (UG/L 2.903 60 DISSOL 0.100 7.400 19.500 BORON 0.233 AS 1.340 33.900 01025 -- (UG/L 3.700 DISSOLVED BA) CADMIUM AS 46.00001030 -- 18.800 65 DISSOLVE BE) 0.800 52 7.100 CHROMIUM (UG/L 22.375 01035 25.000 (UG/L 19.800 7.395 0.020 *0.715 DISSOLV AS COBALT 7.300 3.700 AS 2.200 -- 6.51001040 (UG/L 16.900 B) 0.014 0.200 DISSOLVED CD) 0.015* 9 COPPER 6.750 AS 0.199 1.280 3.80501046 (UG/L DISSOLVED 31.600 CR) 0.105 -- 59 0.308* IRON 13.200 AS 17.00001049 (UG/L 0.048 DISSOLVED CO) 23.500 59 0.700 0.017* LEAD AS -- *0.500 6.800 01130 -- DISSOLVED 6.575 CU) 16.000 LITHIUM -- 0.250 6.725 1.900 5.70001056 *0.050 -- 57 DISSOLVE (UG/L 0.200 59 58 MANGANESE 59 4.630 0.175 0.035*71890 1.100 *0.570 (UG/L 3.200 AS DISSOL -- (UG/L 59 0.401 9.000 MERCURY AS -- FE) 20.000 --01060 *0.055 (UG/L AS *0.400 DISSOLVE LI) 59 0.100* 0.600 MOLYBDENUM AS PB) 15.10001065 UG/L DISSO MN) *0.020 5.700 58 -- NICKEL AS 23.000 0.509 --01075 1.700 (UG/L 4.000 20.000 DISSOLVED *0.090 HG *0.300 0.100 SILVER AS 0.500 --01080 0.163 (UG/L 0.770 2.900 -- DISSOLVED 13.950 MO) *0.020 0.005* *0.300 STRONTIUM AS 2.000 60 --01085 (UG/L *0.100 -- 2.100 DISSOL NI) 14.100 59 0.001* VANADIUM AS 0.500 *0.010 64 --01090 (UG/L DISSOLV AG) 60 4.900 ZINC AS -- *0.052 0.200 *0.210 1000.000------(UG/L -- -- 1.200 1.207* DISSOLVED SR) 0.014* 0.100 3.700 AS *0.010 *0.011 *0.140 0.144 2.600 V) *0.100 59 6.541 --* *0.010 -- *0.004 10.000 (UG/L 0.373 -- 62 6 - 87.000 AS -- *0.027 *0.171 VALUE 59 *8.050 ZN) 4.405 3.942 *0.030 IS 0.000 -- -- *0.006 -- *0.006 59 ESTIMATED 0.385 0.100 *0.100 -- -- BY *0.001 2.100 -- *0.002 -- -- USING 59 -- -- 0.261 3.734* 8.000 *0.018 A *0.095 -- 0.117* *1.000 *0.020 LOG-PROBABILITY 78.000 *0.003 *0.004 59 49.000 14.200 -- REGRESSION -- *0.100 -- TO *0.000 0.300 -- *10.000 PREDICT -- *0.010 -- -- *0.405 *0.298 0.182 7.700 *0.010 160.000 ------*0.003 13.000 20.000 *0.100 -- -- 4.950 *0.000 3.681* *4.529 0.268 -- -- 9.194* *0.200 *0.092 -- *0.007 87.500 -- *0.002 36.290 -- 0.130 6.800 -- *0.000 -- *46.950 *7.484 -- *2.836 2.800 -- -- 0.250 -- *0.072 -- *0.017 50.000 *0.004 ------47.000 5.700 -- -- *6.875 *4.706 *1.667 1.350 *0.037 -- -- 30.000 -- 4.114* -- -- 42.000 -- *3.000 *3.229 *0.846 4.000 ------*0.013 -- *10.000 0.390 10.500 ------38.400 -- *1.657 *2.258 ------*6.000 ------31.000 -- *0.302 ------*3.000 ------21.000 -- -- *1.896 ------*0.983 ------Hydrologic and Water-Quality Data 125 ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM AUG 1973 TO SEPT 2000 Summary statistics for site 4, Shadow Mountain Lake, sampled near bottom. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 10. Table ------70300 ------RESIDUE70301 DIS DISSOLVED00300 180C SOLIDS OXYGEN MG/L00400 MG/L DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00900 MICROSIEMENS/C CONDUCT UNIT HARDNESS (STANDARD00915 US/CM TOTAL UNIT CALCIUM @00925 DISSOLVE 25C MAGNESIUM 5800935 (MG/L 58 DISSOL (MG/L POTASSIUM AS00931 (MG/L AS 57 DISSOL CA) SODIUM AS CAO3)00930 (MG/L 58 57 ADSORPTIO MG) 54 SODIUM AS00932 (RATIO) 67.000 DISSOLVED K) SODIUM,90410 (MG/L 58 8.100 PERCENT 59 ANC, AS00940 8.600 TIT. NA) 59 CHLORIDE PERCENT 60.00000950 4.5, 41.800 DISSOLV 8.800 59 35.000 FLUORIDE L00955 (MG/L DISSOLV MG/L 76.000 SILICA AS 27.40000945 (MG/L 59 DISSOLVED 6.500 CL) SULFATE AS AS00608 (MG/L 24.000 DISSOLVE F) 6.800 CACO3 23.100 59 8.300 NITROGEN AS00625 (MG/L 54.224 AMMONIA SIO2) 0.700 59 1.600 NITROGEN AS00610 (MG/L 30.000 AMM+ORG 13.700 SO4) NITROGEN AS00631 (MG/L 58 1.500 AMMONIA N) 7.203 58 38.211 NO2 AS 34.23900630 (MG/L 59 59 + N) 7.318 2.800 NO2 AS 4.10000613 NO3 65.000 58 + N) 51.448 5.455 NITROGEN,NITRITE 0.300 DISSOL 0.840 21.522 5800615 NO3 MG/L (MG/L 29.000 NITROGEN,NITRITE TOTAL00605 AS AS MG/L 0.500 1.000 NITROGEN 21.000 54.200 N N)00600 40.100 AS (MG/L 58 8.000 7.705 ORGANIC 61.000 NITROGEN N 1.100 AS 6.53700666 (MG/L 58 0.300 7.850 TOTAL N) 67.050 PHOSPHORUS AS 0.127 1.251 26.100 4.00000671 14.000 18 DISS. 8.010 N) PHOSPHORUS70507 (MG/L 13.200 42.000 ORTHO (MG/L 38.050 0.711 PHOS AS 0.10000665 55.500 (MG/L AS 0.150 ORTHO 4.800 7.400 P) 59 PHOSPHORUS AS N) 1.96801005 57.500 TOT 0.700 24.100 TOTAL P) 0.100 7.400 22.741 8.100 BARIUM A 58 0.18501010 (MG/L 2.200 12 0.140 DISSOLVED MG/L 6.725 15.995 38.000 1.500 BERYLLIUM AS 34.75001020 (UG/L 26 DISSOL P) 50.000 9 BORON AS -- AS 0.38601025 (UG/L 0.900 DISSOLVED BA) 52.500 P 6.227 7.200 CADMIUM 0.130 AS -- 22.00001030 56 -- DISSOLVE BE) 0.138 7.300 11 28.050 2.700 CHROMIUM (UG/L -- 7.400 32.50001035 (UG/L 2.940 59 31.850 DISSOLV 0.100 AS 5.600 18.400 COBALT 0.233 AS 1.370 37.850 01040 -- (UG/L B) 0.600 DISSOLVED CD) COPPER AS 46.75001046 (UG/L -- 19.600 58 DISSOLVED CR) 0.800 58 7.000 0.905 IRON AS01049 26.000 (UG/L 7.600 0.050 DISSOLVED CO) 26.000 58 7.100 LEAD 0.461 AS 2.200 -- 23.850 6.80001130 16.900 0.040 0.200 DISSOLVED CU) 0.021* 9 LITHIUM 4.200 0.203 1.300 3.61001056 DISSOLVE 32.950 (UG/L 0.103 -- 58 0.250* MANGANESE 14.100 58 10.00001060 (UG/L AS 0.060 DISSOL (UG/L 24.000 58 0.700 0.043* MOLYBDENUM AS -- 0.400 FE) 6.695 01065 (UG/L AS -- DISSO 7.000 LI) 15.900 58 1.170 NICKEL AS -- PB) 0.200 6.990 2.000 5.90001075 *0.090 (UG/L -- DISSOLVED MN) 0.200 58 SILVER AS 1.940 0.185 0.039* 1.20001077 *0.505 (UG/L 3.300 -- DISSOLVED MO) 0.273 3.000 SILVER AS -- 20.750 --01080 *0.140 (UG/L 2.000 TOTAL NI) 0.100* STRONTIUM 0.600 AS 0.400 59 14.900 --01085 -- DISSOL AG) *0.021 6.200 58 -- VANADIUM 58 0.346 -- 1.70001090 (UG/L 4.170 DISSOLV *0.093 *0.300 59 0.100 ZINC AS------0.164 (UG/L -- 0.880 2.900 -- DISSOLVED 14.000 SR) *0.065 58 0.007* 260.000 AS (UG/L *0.100 7.138 -- 0.590 V) 13.600 AS 58 0.003* 0.500 *0.010 0.300* AG) 610.000 -- (UG/L -- 57 5.500 5.000 - *0.060 *0.200 AS -- 1.200 VALUE 0.017* 0.100 0.461 ZN) *0.030 -- *0.022 IS -- 0.141 2.600 *0.100 58 ESTIMATED 0.000 0.221* -- *0.020 -- *0.004 BY 0.307 ------9.000 -- USING 0.100 58 *0.028 *0.170 A 4.900 0.513* 2 *0.041 -- *0.020 -- *0.008 LOG-PROBABILITY 0.452 0.100 58 *0.100 52.000 REGRESSION 72.373 *0.800 *0.002 2.200 -- -- *0.002 TO -- PREDICT 0.270 -- *0.017 *0.114 8.000 -- -- *2.000 -- *0.020 *0.007 *0.004 -- -- 29.000 *0.100 20.000 210.000 -- *0.274 56.163* *0.000 0.364 -- 1.548* *0.008 -- 0.180 *0.624 *0.013 *340.000 7.000 -- *0.002 110.000 -- -- 38.105 *0.100 *0.157 *0.000 -- -- 0.280 -- -- *3.596 -- *57.000 -- *0.310 -- *0.008 50.000 *0.001 -- 0.119 -- -- 6.700 *0.090 *0.000 47.100 *10.100 -- *1.989 0.200 -- *0.151 *0.004 20.000 -- 5.199* -- -- *0.040 -- 44.250 5.475 -- *3.000 -- *1.298 -- -- *0.057 -- -- *15.150 10.000 -- -- 39.150 *0.898 -- *0.890 -- *7.000 ------33.000 ------*0.486 ------*3.218 -- -- 22.000 ------*1.734 ------*0.739 ------126 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------(MEDIAN) PERCENTAGE OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM SEPT 1970 TO DEC 2000 Summary statistics for site 5, Alva B. Adams Tunnel east portal. Summary statistics for site 5, Alva B. Adams Tunnel WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 11. Table ------00061 DISCHARGE,70300 INST. RESIDUE70301 CFS DIS DISSOLVED00300 180C SOLIDS OXYGEN MG/L00301 MG/L DISSOLVED OXYGEN00400 (MG/L) DIS. PH,00403 PERC WH, PH, %90095 FIELD WH, OF SPECIFIC00095 LABORATO SATURATIO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM 136 TEMPERATUR UNIT HARDNESS @00915 (DEGREES 157 TOTAL 25C 161 228 CALCIUM C)00925 DISSOLVE 270 276 MAGNESIUM 130.000 18600935 (MG/L 69 DISSOL (MG/L POTASSIUM AS00931 (MG/L AS DISSOL 619.000 CA) 89.000 SODIUM AS CAO3)00930 (MG/L ADSORPTIO MG) 279 9.300 SODIUM AS 27900932 13.400 (RATIO) DISSOLVED 50.000 K) 8.700 SODIUM, 60.000 20790410 8.000 (MG/L PERCENT ANC, AS 207 17.00000421 TIT. NA) 0.400 ALKALINITY,DIS,F PERCENT 207 90.00000410 4.5, 23.800 (MG/L ANC, 6.800 L 10.00000940 AS 5.700 30.000 FET, MG/L 91.776 203 CHLORIDE CACO3 6.200 4.00000950 FIELD 402.434 DISSOLV 48.089 FLUORIDE AS 207 9.20000955 (MG/L DISSOLV -- (MG/L CACO3 SILICA AS 207 1.80000945 (MG/L AS 30.263 DISSOLVED 1.000 CL) SULFATE AS CACO3 7.619 114.00000608 (MG/L 3 8.320 33.333 DISSOLVE 5.000 F) 156 2.700 555.000 NITROGEN AS 7.47200625 (MG/L AMMONIA SIO2) 68.000 203 NITROGEN AS 5.30000610 (MG/L 1.800 AMM+ORG SO4) 45 102.000 NITROGEN AS 20500631 0.500 (MG/L 0.100 40.000 AMMONIA 532.500 N) 203 7.280 21.000 NO2 AS 18.227 36.00000613 (MG/L + 49.000 N) 203 47.088* 8.400 NITROGEN,NITRITE AS 0.200 57.00000666 39.000 9.600 NO3 203 MG/L N) 8.400 PHOSPHORUS DISSOL 27.00000671 92.000 AS 0.800 459.000 5.552 DISS. (MG/L PHOSPHORUS N 35.000 14.000 2.70000665 13.000 (MG/L AS 0.130 1.054 *66.000 ORTHO 16.500 PHOSPHORUS AS N) 40.000 26.00001000 (MG/L 6.000 73 50.000 TOTAL P) 13.000 189 10.000 0.500 ARSENIC 7.850 AS 0.671 360.25001005 (MG/L 8.795 DISSOLVE P) 86.400 BARIUM AS 7.80001010 *55.000 (UG/L 4.000 1.949 30.000 25 DISSOLVED P) BERYLLIUM AS 7.96001020 2.300 12.000 (UG/L 0.100 -- 0.201 34.000 22.000 DISSOL AS) 19.726 BORON AS 39.500 18.995 205 1.50001025 (UG/L -- 0.040 DISSOLVED BA) 183 5.400 CADMIUM 0.300 AS *48.000 7.600 68 75.950 01030 9.100 8.300 DISSOLVE BE) 17.778 28.750 0.980 CHROMIUM (UG/L 7.50001035 (UG/L 96 0.060 DISSOLV AS 192 COBALT 27.500 AS 20.000 2.96001040 (UG/L 6.700 B) 4.532 5.000 0.451 23.000 DISSOLVED CD) *38.077 29.000 COPPER AS -- 28.60001046 0.210 0.300 (UG/L -- 1.300 3 DISSOLVED CR) 67 0.200 IRON AS 3.924 7.37501049 0.030 (UG/L 20.000 -- 7.800 DISSOLVED CO) 67 26.400 LEAD AS -- 0.800 7.10001130 13.000 15.000 *23.000 0.100 DISSOLVED CU) 0.100 LITHIUM 109 0.132*01056 24.000 2.200 5.900 3.000 DISSOLVE 20.000 (UG/L -- -- MANGANESE 67 6.380 0.90001060 (UG/L -- AS 0.200 1.100 DISSOL (UG/L -- 67 8.000 MOLYBDENUM AS FE) --01065 21.000 (UG/L AS 7.100 DISSO LI) 67 7.285 6.860 NICKEL AS -- PB) 110 0.70001075 (UG/L -- 6.600 *0.200 DISSOLVED 8.000 MN) 21.000 0.014* SILVER AS 18.000 0.400* 3.00001080 (UG/L 1.900 4.400 30.000 DISSOLVED MO) 1.900 -- STRONTIUM AS --01085 5.000 (UG/L 0.500 207 0.200 0.860 DISSOL NI) 19.000 0.020* VANADIUM AS 3.000 --01090 (UG/L 111 20.000 DISSOLV AG) 67 ZINC 5.000 AS *0.200 -- 207 16.000------0.500 *0.040 (UG/L 17.000 0.061* *0.885 DISSOLVED -- SR) AS -- 0.014* 360.000 -- 0.004* 1.600 V) 2.500 67 109 14.500* *0.057 4.300 0.400 0.180 (UG/L 0.500 0.007* 19.000 - -- 5.672 0.018* -- AS *0.100 20.000 VALUE *0.020 69 -- *0.140 15.000 *0.500 ZN) 4.000 IS 9.000 -- 0.300 *0.030 67 *0.020 ESTIMATED -- 7.000 -- 12.000 BY *0.030 1.000 -- *0.030 -- 6.300 USING 67 3.700 0.300 *0.050 0.150 *0.100 -- A *0.010 *0.084 *0.300 108 0.498* -- LOG-PROBABILITY 3.791* 4.000 8.000 *0.020 2.500 60.000 *0.004 REGRESSION 47.425 -- TO *0.020 -- *0.010 PREDICT 2.039* -- *0.020 -- *0.064 -- *0.006 *16.000 3.000 0.200 *0.053 *0.200 35.000 *2.000 -- -- *0.010 -- 10.000 *0.002 7.000 116.000 1.300 *0.010 -- *0.003 1.799* *7.000 *0.010 2.487* *4.379 *0.003 *0.030 -- *0.614 *0.083 -- *0.005 33.552 *0.001 -- 58.000 1.211* *0.005 -- 6.000 -- *0.001 *6.728 *2.352 *0.008 *6.640 -- *2.084 -- *0.015 *0.340 0.647* *0.002 -- *0.000 33.000 49.600 *4.459 -- *2.000 *0.000 *1.120 5.000 *0.004 -- *3.000 *0.981 6.430* *0.187 *2.000 -- -- 20.000 41.000 *1.278 *0.847 *0.784 -- *18.550 *2.000 *0.377 -- 3.000 -- *0.083 *0.790 -- 12.400 35.000 *0.638 -- *0.363 *0.294 *9.000 *1.000 *0.453 -- -- 26.000 *0.294 -- *0.127 -- -- *4.398 *0.474 -- *0.257 -- 12.800 *0.100 *2.549 -- -- *0.120 ------*1.146 ------Hydrologic and Water-Quality Data 127 ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM MAY 1998 TO SEPT 2000 Summary statistics for site 6, Lake Estes, sampled at surface. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 12. Table ------00077 TRANSPARENCY00300 (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C)00925 DISSOLVE 8 8 MAGNESIUM 800935 (MG/L DISSOL (MG/L POTASSIUM AS 800931 (MG/L AS DISSOL CA) SODIUM AS CAO3) 800930 (MG/L 119.000 ADSORPTIO MG) SODIUM AS 56.00000932 (RATIO) DISSOLVED K) SODIUM, 8 8.10090410 (MG/L 8 PERCENT ANC, AS00940 7.800 8 TIT. NA) CHLORIDE PERCENT 60.00000950 4.5, 9.300 8 26.000 DISSOLV FLUORIDE L00955 (MG/L 8 46.000 DISSOLV MG/L 17.800 SILICA AS00945 (MG/L 7.200 DISSOLVED CL) 19.400 SULFATE AS AS 870300 (MG/L 7.200 81.750 DISSOLVE F) CACO3 RESIDUE AS 41.50070301 (MG/L 6.400 8 5.720 DIS SIO2) DISSOLVED AS 16.00000608 180C 8 1.330 SOLIDS SO4) NITROGEN MG/L 6.60000625 MG/L 7.475 AMMONIA 119.000 NITROGEN 9.010 800631 0.720 (MG/L 8 7.550 AMM+ORG NO2 AS 8 56.000 800613 (MG/L 33.500 7.838 2.600 + N) 2.640 NITROGEN,NITRITE AS 800666 NO3 12.650 MG/L 0.259 N) 0.582 8 PHOSPHORUS DISSOL00671 92.250 AS 15.089 21.000 DISS. (MG/L PHOSPHORUS N 8.10000665 (MG/L AS 0.350 49.000 1.900 ORTHO 22.700 PHOSPHORUS AS N) 7.00031625 7.800 (MG/L 46.000 TOTAL P) 1.100 4.474 COLIFORM AS70953 0.200 (MG/L 9.300 17.800 FECAL P) 79.000 0.156 0.950 3.600 CHL-A AS 10.000 870954 0 19.400 PHY P) CHLOROPHYLL-B, 44.500 COLS./100 -- 16.300 801005 CHROMA 7.650 0.504 P ML BARIUM 43.750 UG/L01010 8 UG/L 4.000 7.675 7 DISSOLVED -- 1.787 BERYLLIUM 16.625 67.50001020 (UG/L 16.125 8.925 8 5.720 DISSOL 8 0.200 BORON 18.650 AS 1.400 801025 0.052 (UG/L 31.250 19.913 1.330 DISSOLVED BA) CADMIUM AS 801030 0.310 36.000 7.400 DISSOLVE BE) 42.000 CHROMIUM (UG/L 30.700 801035 0.720 (UG/L 12.900 5.038 8 7.550 DISSOLV 60.000 AS COBALT AS01040 -- (UG/L B) 16.150 21.000 7.700 -- 2.600 DISSOLVED 0.091 CD) -- 5.552 0.830* 26.000 COPPER AS 2.17501046 (UG/L -- 22.700 DISSOLVED 0.259 CR) 1.135 22.250 IRON AS 22.00001049 (UG/L 0.160 17.200 8 0.114* 7.225 -- DISSOLVED CO) 84.000 LEAD AS01130 0.585 8 8.825 7.500 DISSOLVED CU) 11.400 LITHIUM 19.750 -- 7.00001056 *1.900 DISSOLVE (UG/L 6.725 2.250 4.700 MANGANESE 22.07501060 8 (UG/L 16.000 AS 8 31.875 8 DISSOL (UG/L 0.242 1.011 8 24.700 3.600 MOLYBDENUM *0.200 AS FE)01065 (UG/L -- AS -- 8 0.240 6.200 DISSO LI) 7.200 -- -- NICKEL AS PB)01075 (UG/L 16.500 8 0.490 0.019* DISSOLVED MN) 6.600 *1.575 -- 7.200 SILVER AS 9.010 01080 (UG/L 6.100 20.300 8 DISSOLVED MO) 13.200 -- 1.800 6.400 -- 3.420 STRONTIUM AS --01085 -- (UG/L *0.175 DISSOL 42.000 NI) 0.183 -- 0.698 VANADIUM 30.700 AS 2.57501090 (UG/L DISSOLV AG) 4.100 12.500 8 -- 0.035* ZINC *0.052 AS *0.450------0.310 (UG/L 8 DISSOLVED 0.405 SR) 8 17.800 -- AS 4.650 8 22.584* -- V) 0.900 *0.100 -- 1.250 -- 41.000 2.640 * 29.800 8 (UG/L -- - 0.167 0.582 2.050 90.000 10.000 *0.091 AS *0.032 8 *0.400 VALUE 5.162 -- -- ZN) -- -- *84.000 -- IS 16.300 0.257 -- 8 0.350 -- ESTIMATED -- *0.072 7 30.500 4.250 BY 25.800 -- 5.900 -- 1.100 USING 30.000 *0.063 *0.012 -- *37.500 A *0.136 -- 8 0.156 1.650 LOG-PROBABILITY -- -- REGRESSION -- 0.245 6.200 *0.051 -- 8 34.600 23.500 TO 20.400 *13.500 4.000 -- PREDICT 13.200 -- 53.750 *0.022 -- *0.003 ------1.400 ------14.500 22.000 0.222 6.025 17.200 -- *1.626 -- 10.675 *0.008 *0.002 -- 90.000 ------23.686 ------*0.504 -- 0.160 5.350 -- -- *0.006 ------3.200 70.000 ------34.600 ------4.200 50.000 -- -- 3.000 ------29.300 ------32.500 -- -- 4.100 -- 0.900 -- -- 23.400 ------30.000 ------17.600 ------14.500 ------128 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM MAY 1998 TO SEPT 2000 Summary statistics for site 6, Lake Estes, sampled near bottom. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 13. Table ------00300 OXYGEN00400 DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C)00925 DISSOLVE 8 MAGNESIUM 800935 (MG/L DISSOL (MG/L POTASSIUM AS 800931 (MG/L AS DISSOL CA) SODIUM AS CAO3) 800930 (MG/L ADSORPTIO MG) SODIUM AS 54.00000932 (RATIO) DISSOLVED K) SODIUM, 8 7.60090410 (MG/L 8 PERCENT ANC, AS00940 8.100 8 TIT. 38.400 NA) CHLORIDE PERCENT00950 4.5, 8 24.000 DISSOLV FLUORIDE L00955 (MG/L 8 44.000 DISSOLV MG/L 15.000 SILICA AS00945 (MG/L 7.000 DISSOLVED CL) 18.900 SULFATE AS AS 870300 (MG/L 6.800 DISSOLVE F) CACO3 2.700 RESIDUE AS 40.12570301 (MG/L 8 5.700 DIS SIO2) DISSOLVED AS 18.00000608 180C 8 1.220 SOLIDS SO4) NITROGEN MG/L 6.40000625 MG/L 7.312 AMMONIA NITROGEN 8.140 8 10.08800631 0.620 (MG/L 8 7.375 AMM+ORG NO2 AS 8 54.000 800613 (MG/L 34.500 2.400 + N) 2.370 NITROGEN,NITRITE AS 800666 NO3 10.387 MG/L 0.251 N) 0.538 8 PHOSPHORUS DISSOL00671 AS 14.381 21.000 DISS. (MG/L PHOSPHORUS N 7.60000665 38.400 (MG/L AS 0.340 48.000 2.200 ORTHO 23.800 PHOSPHORUS AS N) 6.60001005 8.100 (MG/L 44.000 TOTAL P) 1.000 4.244 BARIUM AS01010 0.200 (MG/L 15.000 DISSOLVED P) 0.157 0.911 3.300 BERYLLIUM AS 801020 (UG/L 18.900 DISSOL P) 8.000 BORON 44.500 AS 16.800 801025 (UG/L 7.500 8.500 0.502 DISSOLVED BA) 0.300 CADMIUM 42.750 AS01030 8 4.100 7.475 8 DISSOLVE BE) -- 1.750 CHROMIUM 14.300 (UG/L01035 (UG/L 8 5.700 DISSOLV AS 8 0.200 COBALT 18.275 AS 1.300 15.125 801040 0.074 (UG/L B) 28.500 20.375 1.220 DISSOLVED CD) COPPER AS 801046 0.300 (UG/L 38.500 7.300 7.000 DISSOLVED CR) 52.000 0.938 IRON AS 34.100 801049 0.620 (UG/L 5.037 8 7.350 DISSOLVED CO) LEAD AS 9.95001130 -- 16.000 8 -- 2.400 DISSOLVED 0.081 CU) -- 5.378 24.000 LITHIUM 2.075 21.00001056 -- 23.800 DISSOLVE 0.251 (UG/L 1.125 25.000 MANGANESE 21.00001060 (UG/L AS 0.240 15.600 8 0.104* 7.075 -- 3.700 DISSOL (UG/L 8 MOLYBDENUM AS FE)01065 (UG/L AS 0.587 8 6.600 2.200 DISSO 7.225 LI) -- NICKEL AS PB) 6.900 6.60001075 (UG/L 8 9.932 DISSOLVED 19.750 MN) 2.275 0.014 4.650 SILVER AS 21.60001080 (UG/L 18.000 8 32.500 DISSOLVED MO) 0.241 1.003 25.162 -- 3.300 STRONTIUM *0.200 AS01085 -- (UG/L -- 0.264 DISSOL NI) 7.000 -- 2.700 -- VANADIUM AS01090 (UG/L 0.495 0.045* DISSOLV AG) 4.000 1.675 -- 6.800 8 -- ZINC AS 15.500------(UG/L 6.175 6.400 20.850 8 DISSOLVED SR) 8.140 -- 1.800 8 0.057 -- 2.898 AS *0.100 8 52.000 V) 0.183 0.632 34.100 2.575 --* 8 150.000 (UG/L - *0.074 0.300 AS 8 11.000 0.440 VALUE 5.350 0.500 18.175 -- ZN) -- -- IS -- 4.750 8 -- *0.100 -- 1.225 ESTIMATED -- 39.500 2.370 30.150 8 9.800 0.081 BY -- -- 0.170 40.000 -- 0.538 2.100 USING *0.066 -- -- A -- 8 16.800 0.280 8.000 LOG-PROBABILITY 0.340 -- 0.425 -- *0.078 REGRESSION 32.500 4.200 6.600 27.150 8 34.300 -- TO 1.000 92.500 0.072 PREDICT *0.042 -- 0.157 -- 1.425 ------0.260 *0.061 -- 22.000 -- 0.300 -- 18.575 -- 12.800 6.175 4.100 -- 150.000 -- -- *0.026 -- 0.067 -- 1.300 -- 21.000 122.500 0.242 23.000 15.600 5.854* -- -- *0.019 -- 5.500 ------0.036 ------90.000 -- -- *9.800 0.240 34.300 ------4.375 -- 0.014 70.000 *8.800 ------28.075 ------4.000 -- 40.000 -- -- *6.000 -- 24.750 ------*2.900 ------15.475 ------*1.829 -- -- 12.800 ------Hydrologic and Water-Quality Data 129 ------*5.629 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM SEPT 1970 TO DEC 2000 Summary statistics for site 7, Olympus Tunnel. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 14. Table ------70300 RESIDUE70301 DIS DISSOLVED00300 180C SOLIDS OXYGEN MG/L00400 MG/L DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES 121 TOTAL 25C 123 CALCIUM C)00925 DISSOLVE 236 MAGNESIUM00935 (MG/L DISSOL (MG/L 240 POTASSIUM AS 17200931 (MG/L AS 95 DISSOL CA) 76.000 SODIUM AS CAO3)00930 (MG/L ADSORPTIO MG) 243 8.500 SODIUM AS 24200932 (RATIO) DISSOLVED K) 8.800 SODIUM, 18490410 14.800 (MG/L PERCENT 57.000 ANC, AS 67.000 184 19.00000410 TIT. NA) ANC, PERCENT 184 95.00000940 4.5, 21.000 FET, CHLORIDE 6.900 L00950 FIELD 39.000 DISSOLV MG/L 180 FLUORIDE 6.300 13.50000955 (MG/L 6.400 10.000 DISSOLV 46.017 (MG/L SILICA AS AS 184 9.60000945 (MG/L AS DISSOLVED -- CL) CACO3 SULFATE AS CACO3 184 3.70000608 (MG/L DISSOLVE 0.000 F) NITROGEN AS 7.59000625 (MG/L 30.098 AMMONIA 5.000 SIO2) 121 33.547 1.800 NITROGEN AS 7.44600610 (MG/L 8.925 AMM+ORG SO4) 66.000 61 179 NITROGEN AS 184 4.70000631 (MG/L 1.500 AMMONIA N) 181 NO2 AS00613 0.400 (MG/L 0.100 + N) 7.332 179 NITROGEN,NITRITE AS 17.769 31.00000666 NO3 184 43.105 MG/L N) 47.294* 8.200 PHOSPHORUS 48.400 DISSOL 0.100 56.000 30.00000671 34.000 AS 11.195 DISS. (MG/L 8.200 PHOSPHORUS N 10.000 4.10000665 (MG/L 0.900 AS 5.331 ORTHO PHOSPHORUS AS N)31501 (MG/L 0.153 1.074 39 *70.000 TOTAL P) 14.000 16.000 0.400 TOT AS 35.300 25.60031625 (MG/L 6.000 41.000 40 47.000 COLI,MENDO P) 13.000 156 COLIFORM 7.800 AS 0.67731616 M 4.000 FECAL P) 9.800 FECAL COLS./100 7.70001000 2.400 *58.000 0 0.100 2.006 COLI,MFC ML ARSENIC COLS./100 186 7.87501005 -- 12.000 M -- 31.000 179 0.207 0.080 22.000 DISSOLVE ML 18.207 149 35.000 BARIUM COLS./100 36.500 19.658 1.60001010 (UG/L 0.600 DISSOLVED ML 18.230 0.230 BERYLLIUM AS *50.000 7.60001020 (UG/L 82 DISSOL AS) 184 8.800 1.000 BORON AS 149 7.40001025 (UG/L 4.580 0.726 DISSOLVED BA) 24.350 CADMIUM AS -- 19.000 2.900 25.00001030 2.300 6.600 6.250 13000.000 22.100 0.220 DISSOLVE BE) *36.565 78 28.900 0.090 CHROMIUM (UG/L -- 27.00001035 0.300 (UG/L -- 1.300 DISSOLV AS 70 26.900 COBALT AS 7.40001040 (UG/L B) 0.070 DISSOLVED CD) 1200.000 5.000 8.000 COPPER AS 0.800 4.113* 0.141* 7.20001046 (UG/L 16.130 13.625 3 *22.430 DISSOLVED CR) -- 16.000 34 IRON AS -- 6.600 1.67501049 23.000 (UG/L -- 2.300 5.700 2.000 210.000 0.000 DISSOLVED 21.000 CO) 34 LEAD AS01130 23.000 0.206 1.100 DISSOLVED CU) LITHIUM --01056 -- -- 7.100 *7.650 *0.200 DISSOLVE (UG/L 34 0.026* -- MANGANESE 7.200 0.700 3401055 (UG/L 370.711 AS 6.800 DISSOL 7.450 (UG/L 18.000 34 0.263* 8.000 MANGANESE -- AS FE) 19.000 0.048* --71890 5.200 (UG/L 0.800 AS 2.000 4.000 TOTAL LI) 1.000 20.000 34 MERCURY AS PB)01060 0.200 0.850 DISSOLVE MN) 37 MOLYBDENUM *5.175 (UG/L *0.200 1500.000 --01065 *0.066 UG/L 0.089* -- DISSO AS 0.008* NICKEL AS 13.500 0.015* -- 0.58201075 *0.495 (UG/L MN) 184 17.500 *0.150 DISSOLVED HG SILVER AS 3.000 13.500 --01080 (UG/L 4.500 78.076* 0.600 1.600 DISSOLVED MO) 2.300 34 300.000 0.008* STRONTIUM AS -- 184 37 0.057* --01085 (UG/L *4.100 *0.100 0.197 DISSOL NI) *0.035 0.417 VANADIUM *0.176 AS 10.613* 280.00001090 *0.015 (UG/L -- *523.000 *0.040 DISSOLV AG) *0.300 ZINC AS 15.000 *0.070------(UG/L 8.100 0.300 12 DISSOLVED SR) AS 5.409 -- 53.000 *0.038 6.000 -- 3.800 39.000 0.500 -- *0.060 V) -- 1.125 34 *2.700 *47.850 *0.100 *0.020 *60.000* -- *0.100 10.000 (UG/L *0.009 37 0.167 3 - *0.020 *0.240 AS -- *0.030 VALUE 37 27.000 ZN) -- IS -- 12.000 *0.010 34 -- *14.000 ESTIMATED *0.030 -- *9.000 *1.325 *0.071 -- *0.011 BY 3.100 0.300 *0.063 8.000 82.717 *0.006 -- -- USING *0.010 34 *0.185 *0.010 A ------LOG-PROBABILITY -- 2.000 -- *0.004 34 51.000 *1.500 REGRESSION *0.020 -- *1.000 1.000 *0.006 TO *0.037 180.000 -- *0.004 PREDICT *0.006 -- 6.000 *0.128 *0.005 ------*0.002 18.000 10.000 5.569* *0.018 *0.178 *0.288 100.000 ------*0.016 *0.002 *0.003 13.245* -- -- 5.600 -- *20.000 -- -- *0.001 28.915 *0.006 -- *0.031 70.000 -- *27.000 ------*6.152 0.698* 4.375 ------*19.000 50.000 48.000 ------*3.626 -- *2.000 *11.000 5.623* -- 3.000 -- 20.000 37.750 ------*15.000 -- *2.000 *0.912 *8.066 -- -- 28.500 ------*8.500 *0.732 *0.547 -- -- 19.550 ------*3.409 -- -- *0.323 -- -- 10.750 ------*1.880 -- -- *0.169 ------*0.755 ------130 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------*0.072 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM FEB 1970 TO OCT 2000 Summary statistics for site 8, Carter Lake, sampled near surface. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 15. Table ------70300 ------RESIDUE70301 DIS DISSOLVED00077 180C SOLIDS TRANSPARENCY MG/L00300 MG/L (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES 116 TOTAL 25C CALCIUM C) 5400925 54 DISSOLVE 149 145 MAGNESIUM00935 (MG/L DISSOL (MG/L 143 34 POTASSIUM AS 258.00000931 (MG/L AS DISSOL CA) SODIUM AS CAO3)00930 (MG/L 90.000 ADSORPTIO 116.000 MG) 156 SODIUM AS 15700932 (RATIO) 8.400 DISSOLVED K) 8.900 SODIUM,90410 11.800 (MG/L 50.000 PERCENT 37 ANC, AS00940 8.000 145.000 TIT. NA) 37 60.000 CHLORIDE PERCENT 31.00000950 4.5, 24.000 DISSOLV 37 FLUORIDE L00955 (MG/L DISSOLV 7.100 MG/L 34.600 SILICA AS 5.800 100.941 41.00000945 (MG/L 6.000 37 DISSOLVED CL) SULFATE 56.000 AS AS 14.00000608 (MG/L 74.889 49.966 DISSOLVE F) CACO3 37 NITROGEN AS00625 (MG/L AMMONIA 2.000 SIO2) 37 1.800 NITROGEN AS 40.37900610 (MG/L 162.300 AMM+ORG 25.100 SO4) 7.852 NITROGEN AS 7.69100618 (MG/L 83.577 36 8.347 0.900 AMMONIA N) 35 NITROGEN AS00631 (MG/L 8.090 37 86.750 37 69.700 NITRATE N) 2.800 NO2 AS 14.378 123.50000613 (MG/L 35 + N) NITROGEN,NITRITE 0.220 AS 1.180 30.803 3500666 48.125 NO3 MG/L N) 102.000 39.000 PHOSPHORUS DISSOL00671 AS 8.225 11.200 DISS. (MG/L 0.510 10.110 80.000 1.500 8.400 PHOSPHORUS 16.100 N 54.00000665 (MG/L AS 66 4.300 ORTHO 95.000 PHOSPHORUS AS 1.900 N) 22.50000680 (MG/L 35 0.300 TOTAL P) 42.600 CARBON AS 0.151 1.333 36.680 4.700 90.00031625 (MG/L 26.000 87 ORGANIC P) COLIFORM AS70953 74.500 T 11.000 48.000 93 FECAL 8.100 P) 9.400 0.693 12.200 CHL-A (MG/L 0.100 8.100 79.00070954 0 0.270 20.000 PHY 0.500 AS CHLOROPHYLL-B, COLS./100 -- 2.224 39.500 13801005 CHROMA C) 146 0.500 33.300 P 82.000 ML 32.472 BARIUM UG/L 0.17601010 UG/L 1.000 33 0.400 DISSOLVED 70.750 13.330 44.000 1.530 BERYLLIUM01020 11.000 (UG/L 36 49.170 2.300 DISSOL 7.900 135 7.800 BORON AS -- 15.200 0.634 7.80001025 (UG/L 37.475 0.810 DISSOLVED BA) 2.659 CADMIUM AS -- 30.100 75.00001030 2.300 0.040 DISSOLVE BE) 78 39.000 -- 2.620 CHROMIUM (UG/L -- 62.750 01035 (UG/L 37.000 2.880 DISSOLV AS 9 14.750 COBALT 0.202 AS 1.40001040 (UG/L B) 9.800 10.250 0.023 DISSOLVED CD) 0.000 0.121* 7.675 2.000 7.300 COPPER AS 34.750 01046 7.400 (UG/L 27.950 64.000 DISSOLVED CR) -- 0.800 36 1.180 IRON AS --01049 34.750 (UG/L 4.120 DISSOLVED CO) 36 6.000 LEAD AS 2.40001130 13.800 DISSOLVED CU) 0.033* LITHIUM 5.000 -- 0.183 1.300 4.54001056 *0.220 -- 9.050 35 DISSOLVE 3.000 (UG/L 36 0.071 0.219* 35 MANGANESE 25.190 7.300 -- 6.720 36 32.00001055 (UG/L AS 6.650 DISSOL (UG/L 32.000 36 0.700 0.036* MANGANESE AS 0.800 FE) --01060 (UG/L -- AS TOTAL 3.400 LI) 13.300 36 MOLYBDENUM AS PB) 2.20001065 *0.156 DISSO MN) *0.100 36 NICKEL (UG/L 3.400 0.175 1.26501075 *0.420 (UG/L 3.200 0.062* 20.000 DISSOLVED 13.000 AS 4.200 8.108 0.005* 2.000 SILVER AS 0.200 30.250 --01080 *0.132 (UG/L MN) 0.203 DISSOLVED MO) 0.615 STRONTIUM AS 0.700 37 12.950 --01085 (UG/L DISSOL NI) *0.033 2.500 36 0.005* VANADIUM AS *0.100 36 0.139* -- -- 2.10001090 (UG/L DISSOLV AG) *0.300 37 ZINC *0.161 AS -- 22.892 3.878------*0.016 (UG/L 0.169 -- -- 1.189 -- 2.800 DISSOLVED 26.850 SR) *0.040 0.300 AS 0.634* 12 -- V) 11.180 0.075 36 0.573 *0.011 -- 0.400* *0.020 *0.100 -- *1.300 (UG/L 36 2.050 - *0.200 10.000 AS -- *0.060 1.900 VALUE *0.006 36 ZN) *0.020 30.300 IS -- 0.154 2.600 *2.050 36 13.000 1.411 5.000 ESTIMATED -- -- *0.005 BY *0.005 0.030 *0.070 *0.059 -- -- USING 0.180 36 -- *0.158 -- *0.030 6.106* A 0.950 *0.003 0.497* -- 0.053* *0.008 25.750 LOG-PROBABILITY -- *1.000 36 64.000 -- -- REGRESSION 1.480 -- *0.002 4.100 TO *0.003 *0.020 -- *11.500 3.160 PREDICT -- 0.010 *0.109 *0.012 -- *0.002 *2.000 *0.200 23.150 *0.002 -- *0.387 -- 33.000 31.700 -- -- *0.001 *0.007 *7.275 3.800 -- -- 1.032* *0.005 1.900 -- *0.639 *0.001 0.000 *0.066 18.850 -- *0.197 -- -- 41.422 3.720* -- *0.000 *0.001 -- *5.425 *5.500 3.450 -- *0.351 -- *0.035 *13.000 1.200 15.550 *0.075 ------52.100 -- -- *4.000 *0.952 -- *0.196 *0.018 *4.730 -- 3.400 -- 5.952* 0.800 -- -- 44.750 *2.773 -- *0.467 *0.088 -- *0.007 -- -- *21.950 *2.702 -- -- 41.000 0.380 -- -- *0.242 -- -- *7.750 *1.922 -- -- 37.475 ------*3.185 -- *1.294 -- -- 32.975 ------*1.710 ------*0.731 ------Hydrologic and Water-Quality Data 131 ------*3.000 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM FEB 1970 TO OCT 2000 Summary statistics for site 8, Carter Lake, sampled near bottom. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 16. Table ------00003 SAMPLING70300 DEPTH RESIDUE70301 ( DIS DISSOLVED FEET00300 180C SOLIDS OXYGEN MG/L00301 MG/L DISSOLVED OXYGEN00400 (MG/L) DIS. PH,00403 PERC WH, PH, %90095 FIELD WH, OF SPECIFIC00095 LABORATO SATURATIO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @ 1000915 (DEGREES TOTAL 25C 147 CALCIUM C) 4200925 42 DISSOLVE 117 133 113 MAGNESIUM00935 (MG/L DISSOL (MG/L 34 POTASSIUM AS00931 (MG/L AS 96.000 DISSOL 160.000 CA) SODIUM AS CAO3)00930 (MG/L 81.000 ADSORPTIO MG) 125 SODIUM AS 15100932 12.700 (RATIO) 94.000 8.000 DISSOLVED K) 8.700 SODIUM,90410 (MG/L 50.000 PERCENT 37 ANC, 41.200 AS 25.00000940 149.000 TIT. NA) 37 52.000 CHLORIDE PERCENT00950 4.5, 15.500 DISSOLV 18.000 37 FLUORIDE L00955 (MG/L 2.400 DISSOLV 6.900 MG/L 29.900 105.143 SILICA AS 5.600 38.00000945 (MG/L 71.680 37 DISSOLVED CL) SULFATE 48.000 AS AS 13.00000608 (MG/L 67.452 DISSOLVE F) CACO3 37 NITROGEN AS 48.23000625 (MG/L AMMONIA 2.000 SIO2) 37 1.500 NITROGEN AS 38.697 146.00000610 (MG/L 7.530 AMM+ORG 20.700 SO4) 7.417 NITROGEN AS 7.31500618 (MG/L 76.872 36 96.000 0.900 AMMONIA N) 35 NITROGEN AS00631 (MG/L 6.570 37 75.850 37 NITRATE N) 2.600 NO2 120.000 AS00613 70.300 (MG/L 35 + N) 6.599 NITROGEN,NITRITE 0.204 AS 1.040 28.014 3400666 45.425 NO3 10.760 MG/L N) 35.000 83.725 PHOSPHORUS DISSOL00671 AS 92.700 7.900 DISS. (MG/L 0.570 100.000 72.000 1.300 8.000 PHOSPHORUS 15.300 N00665 (MG/L AS 9.058 65 4.900 ORTHO 53.000 PHOSPHORUS AS 1.600 N)00680 (MG/L 35 0.200 TOTAL P) 41.200 12.140 CARBON AS 0.152 1.297 33.770 4.70031625 (MG/L 22.000 76.800 60 ORGANIC P) 9.150 85.000 COLIFORM AS 90.00001005 67.500 T 11.000 73 FECAL 7.600 P) 0.662 BARIUM (MG/L 0.100 7.600 47.00001010 0 11.200 0.210 DISSOLVED 2.100 AS BERYLLIUM COLS./100 -- 2.154 38.300 10701020 (UG/L C) 115 0.600 30.700 DISSOL ML 29.417 56.900 BORON 7.500 AS 0.17801025 (UG/L 1.600 78.000 33 0.270 DISSOLVED 60.000 BA) 63.000 14.041 7.800 1.437 CADMIUM AS01030 36 41.000 0.240 DISSOLVE BE) 7.450 107 CHROMIUM 10.000 (UG/L -- 0.617 7.30001035 (UG/L 35.900 0.900 DISSOLV AS 3.673 COBALT AS -- 27.60001040 0.979 41.200 (UG/L B) 0.030 DISSOLVED CD) 68.000 15 34.150 2.510 COPPER AS -- 6.000 59.000 01046 (UG/L 2.891 0.012 DISSOLVED CR) 36 9 15.210 6.000 IRON 0.200 AS 1.400 33.700 01049 (UG/L 0.011 DISSOLVED CO) 0.000 36 0.121* 7.200 1.500 LEAD AS 33.200 8.800 7.00001130 24.950 DISSOLVED CU) -- 0.700 1.140 LITHIUM -- --01056 55.300 32.000 4.900 DISSOLVE (UG/L 36 MANGANESE -- 2.300 36 5.000 26.00001055 (UG/L 14.650 AS DISSOL (UG/L 36 0.034* MANGANESE 4.100 AS -- FE) 0.187 3.710 1.300 -- 4.62501060 *0.200 (UG/L -- AS TOTAL LI) 36 0.060 0.230* MOLYBDENUM 23.040 AS PB) 6.900 8.01501065 6.590 DISSO MN) 30.000 36 0.630 0.031* NICKEL (UG/L 0.80001075 (UG/L 10.000 DISSOLVED 12.000 4.450 AS 14.300 2.000 SILVER AS 2.200 --01080 *0.103 (UG/L MN) 3.000 DISSOLVED MO) *0.200 STRONTIUM AS 3.200 37 0.178 -- 1.20001085 *0.440 (UG/L 3.100 -- 0.071* DISSOL NI) 36 0.005* VANADIUM AS 27.000 36 --01090 *0.090 (UG/L 7.362 0.213 DISSOLV AG) 37 0.004* ZINC 0.600 AS -- 18.000 0.600 13.500------(UG/L -- -- DISSOLVED SR) *0.050 3.800 0.004* AS *0.100 0.061* 2.000 12 20.000 V) *0.246 36 *0.212 3.556* *0.011 0.171 1.121 2.900 -- 24.550 (UG/L *0.040 36 4.000 - 35.000 *0.011 AS -- VALUE 11.810 0.080 36 ZN) 0.570 *0.020 24.300 0.400 *0.010 IS -- -- *0.100 *0.306 36 2.850 33.000 ESTIMATED -- *0.200 -- -- *0.082 1.780 BY *0.006 *0.020 -- -- USING 36 0.155 -- 2.575 -- *0.005 4.987* 4.100 A 0.293* -- *0.010 19.000 *0.004 LOG-PROBABILITY 0.040 *0.030 *0.062 36 47.000 -- REGRESSION 0.100 *0.174 -- *0.045 2.280 TO *0.004 -- *0.010 PREDICT -- *0.003 *8.640 -- *1.227 1.825 17.450 *0.005 3.850 *0.003 -- -- *0.020 -- 23.000 29.600 7.732* 0.020 *0.122 *0.029 -- *0.002 *0.004 1.615* -- -- 4.753* *0.002 *6.078 *0.344 16.075 *0.002 *20.000 *0.006 -- -- 39.283 9.522* 3.400 *0.010 *0.001 -- 0.000 *32.300 -- *3.564 *0.001 *4.618 *10.000 -- *0.145 -- -- *33.000 13.445 *0.001 *0.002 -- -- 47.000 3.350 -- -- *5.050 *2.033 *3.606 *11.750 *6.691 *0.065 -- 5.884* -- -- 43.750 *2.000 *1.391 3.200 -- -- *2.598 *7.520 *4.641 *0.021 -- -- *17.900 -- -- 39.500 -- *0.964 *0.979 *3.668 *2.986 -- *7.798 -- -- 35.100 -- -- *0.242 *0.561 -- -- *4.000 ------31.300 -- *2.037 ------*0.931 ------132 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------*0.303 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM OCT 1969 TO AUG 1999 Summary statistics for site 9, Horsetooth Reservoir (Soldier Canyon Dam), sampled near surface. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 17. Table ------70300 RESIDUE70301 DIS DISSOLVED00077 180C SOLIDS TRANSPARENCY MG/L00300 MG/L (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES 103 TOTAL 25C CALCIUM C) 5500925 55 DISSOLVE 144 137 MAGNESIUM00935 (MG/L DISSOL (MG/L 142 46 POTASSIUM AS 177.00000931 (MG/L AS DISSOL CA) 163.000 SODIUM AS CAO3)00930 (MG/L ADSORPTIO MG) 154 SODIUM AS 15400932 (RATIO) 78.000 8.400 DISSOLVED K) 8.800 SODIUM,90410 12.200 (MG/L 53.000 PERCENT 50 ANC, AS 49.00000940 8.000 125.000 TIT. NA) 50 CHLORIDE PERCENT00950 4.5, 25.000 DISSOLV 16.000 50 FLUORIDE L00955 (MG/L DISSOLV 7.100 MG/L 28.400 SILICA AS 6.000 35.00000945 (MG/L 0.000 50 DISSOLVED 70.836 CL) 79.871 SULFATE 48.000 AS AS 11.00000608 (MG/L DISSOLVE F) CACO3 50 NITROGEN AS 50.41600625 (MG/L AMMONIA 2.000 SIO2) 50 1.900 NITROGEN AS 39.17400610 (MG/L AMM+ORG 19.400 SO4) 7.764 NITROGEN AS 7.473 142.60000618 (MG/L 75.994 49 8.208 1.000 AMMONIA N) 81.200 48 NITROGEN AS71851 (MG/L 6.100 50 50 NITRATE N) 5.800 NITR. AS 14.76900631 72.100 (MG/L 48 NO3 N) NO2 0.500 AS 1.000 28.474 4800613 49.470 AS 98.000 + N) 105.000 40.000 NITROGEN,NITRITE NO3 76.000 32.00000666 NO3 8.220 10.700 MG/L MG/L 0.500 8.300 PHOSPHORUS 30.000 DISSOL00671 AS AS 8.963 87 4.900 DISS. (MG/L 56.500 PHOSPHORUS N 1.800 NO3 22.50000665 (MG/L AS 49 10.000 0.500 ORTHO 42.525 PHOSPHORUS AS 76.000 N) 0.166 1.472 33.340 80.00031625 (MG/L 81 70.000 TOTAL P) COLIFORM AS 7.00070953 (MG/L 0.200 12.400 94 FECAL 7.900 P) 9.125 0.716 CHL-A AS 7.800 50.00070954 0 10.890 0.190 20.700 PHY 0.700 P) CHLOROPHYLL-B, COLS./100 -- 2.456 39.000 10301005 CHROMA 57.000 1.300 31.000 P 0.700 75.500 ML BARIUM UG/L 64.000 138 0.19901010 UG/L 29.286 147 3.600 DISSOLVED 15.354 1.800 BERYLLIUM01020 (UG/L 1.410 47 44.000 2.300 DISSOL 7.800 7.800 BORON AS -- 15.500 7.60001025 (UG/L 33 35.300 10.000 0.945 DISSOLVED 9.725 BA) 2.778 126 CADMIUM 38.000 AS -- 28.700 70.00001030 51.800 DISSOLVE BE) 3.737 71 3.190 CHROMIUM (UG/L --01035 2.300 (UG/L 36.500 0.060 DISSOLV AS 17.135 COBALT 0.217 AS 1.600 34.000 01040 (UG/L B) 10.000 0.140 DISSOLVED CD) 0.000 0.136* 7.600 7.200 COPPER AS 29.275 1.85001046 7.100 (UG/L 26.800 0.030 55.000 DISSOLVED CR) 0.000 0.800 9.150 32 2.300 IRON AS 14.00001049 (UG/L 4.645 DISSOLVED CO) -- 32 LEAD 33.000 AS -- 2.60001130 16.000 7.275 DISSOLVED CU) 0.036* LITHIUM -- 0.200 1.50001056 *0.200 31 DISSOLVE 3.500 (UG/L 32 0.135 0.347* 31 MANGANESE 20.760 -- 7.280 6.500 33 28.40001055 (UG/L -- 0.900 AS 6.400 DISSOL -- (UG/L 32 0.566 0.700 0.079* 8.375 MANGANESE AS FE) --01060 (UG/L AS 29.000 TOTAL 3.825 LI) 15.150 32 MOLYBDENUM AS PB) 2.40001065 *0.128 DISSO 4.825 MN) *0.200 32 360.000 NICKEL (UG/L 0.197 -- 1.33701075 *0.890 (UG/L DISSOLVED 14.800 AS 6.500 SILVER AS 0.400 --01080 *0.159 (UG/L MN) 0.700 0.111* 0.273 DISSOLVED MO) 27.000 0.007* 0.600 STRONTIUM AS 6.516 50 14.075 --01085 (UG/L 1.200 DISSOL NI) *0.050 2.750 32 0.013* VANADIUM AS *0.100 32 -- 2.17501090 (UG/L -- DISSOLV AG) *0.450 3.300 50 0.005* ZINC AS 18.444 0.139*------(UG/L 0.180 -- 1.073 -- 0.889* DISSOLVED SR) *0.055 0.200 110.000 *0.261 AS *0.020 20.500 19 0.600 V) 13.110 0.153 32 0.533 *0.020 --* *0.060 -- *0.100 -- (UG/L 0.660 32 1.900 - *0.280 20.000 *0.020 AS -- 1.855 *0.747 VALUE 32 2.500 *2.400 ZN) *0.020 25.540 IS -- -- *0.132 0.170 *0.010 32 20.000 2.242 ESTIMATED -- -- 13.657* *0.009 BY *0.011 0.245 0.100 *0.060 -- USING 32 -- *0.147 -- *0.007 0.400 *0.082 A 0.800 -- 0.056* *1.000 *122.000 *0.006 19.750 LOG-PROBABILITY *0.080 1.090 *0.005 32 53.000 -- -- REGRESSION -- -- *0.004 TO *0.005 -- 5.780 PREDICT -- 0.050 *0.067 *0.003 *0.020 25.214* -- *0.280 *0.353 0.200 *4.581 18.000 *0.002 *0.031 -- -- *0.003 16.000 26.500 -- *0.002 *74.500 -- -- 2.441* *0.001 2.700 *0.009 0.010 *0.063 *0.148 *0.916 16.725 -- *0.010 -- -- *0.001 38.469 0.044 5.305* -- *40.000 -- *0.000 -- *7.900 *0.001 *0.001 -- -- *0.025 *0.042 *0.255 *20.000 1.900 15.385 -- -- *11.812 51.050 -- -- *3.000 *0.010 *0.044 *6.704 ------4.657* 1.100 *7.367 -- -- 43.000 -- *1.852 -- *0.003 -- *14.050 *3.966 -- *2.805 -- 38.500 0.380 -- *0.780 ------*7.500 *2.025 -- -- 32.275 ------*3.000 -- *0.982 -- -- 27.475 ------*1.654 ------*0.672 ------Hydrologic and Water-Quality Data 133 ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM SEPT 1969 TO AUG 1999 Summary statistics for site 9, Horsetooth Reservoir (Soldier Canyon Dam), sampled near bottom. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 18. Table ------70300 ------RESIDUE70301 DIS DISSOLVED00077 180C SOLIDS TRANSPARENCY MG/L00300 MG/L (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C) 4200925 42 DISSOLVE 109 1 111 MAGNESIUM00935 (MG/L DISSOL (MG/L 125 33 POTASSIUM AS00931 (MG/L AS DISSOL CA) SODIUM AS CAO3)00930 (MG/L 80.000 ADSORPTIO MG) 120 SODIUM AS 14700932 48.000 (RATIO) 81.000 8.300 DISSOLVED K) 8.500 SODIUM,90410 12.600 (MG/L 47.100 PERCENT 38 ANC, AS00940 140.000 TIT. NA) 38 57.000 CHLORIDE PERCENT00950 4.5, 25.000 DISSOLV -- 10.000 38 FLUORIDE L00955 (MG/L DISSOLV 6.700 MG/L 32.500 SILICA AS 5.800 34.90000945 (MG/L 0.000 35 DISSOLVED CL) SULFATE 50.000 AS AS 11.00000608 (MG/L 69.405 DISSOLVE F) CACO3 35 NITROGEN AS 48.13500625 (MG/L AMMONIA 2.000 SIO2) 35 4.600 NITROGEN AS 39.15200610 (MG/L AMM+ORG 23.100 SO4) 7.457 NITROGEN AS 7.21300618 (MG/L 72.800 36 7.227 0.900 AMMONIA N) 33 NITROGEN AS71851 (MG/L 6.400 39 79.700 35 -- NITRATE N) 3.400 NITR. AS00631 67.400 (MG/L 37 NO3 N) 7.435 NO2 0.300 AS 1.180 28.550 3300613 46.330 AS + N) 37.000 NITROGEN,NITRITE NO300666 NO3 87.850 8.200 10.700 MG/L MG/L 0.460 74.000 1.300 7.800 PHOSPHORUS 20.000 DISSOL00671 AS AS 8.869 72 4.800 DISS. (MG/L 53.000 PHOSPHORUS N 2.000 NO300665 (MG/L AS 38 0.200 ORTHO 41.450 12.500 PHOSPHORUS AS N) 0.169 1.541 34.140 5.90031625 (MG/L 25.000 57 TOTAL P) -- 78.000 COLIFORM AS01005 70.000 (MG/L 13.500 66 FECAL 7.700 P) 9.150 0.681 BARIUM AS 0.200 7.600 48.00001010 0 10.050 1.200 DISSOLVED 0.600 P) BERYLLIUM COLS./100 -- 2.349 39.20001020 (UG/L 1.000 30.675 DISSOL ML 29.611 76 BORON 9.000 AS 100 0.19301025 (UG/L 1.900 73.000 113 0.160 DISSOLVED BA) 64.750 14.926 1.845 CADMIUM AS01030 36 43.000 0.310 DISSOLVE BE) 7.500 7.500 CHROMIUM (UG/L -- 0.706 7.20001035 (UG/L 33 36.550 0.820 DISSOLV 9.625 AS 3.308 -- COBALT AS -- 28.60001040 (UG/L B) 98 DISSOLVED CD) 69.000 11 35.300 2.840 COPPER 1.400 AS -- 7.000 59.000 01046 0.320 (UG/L 3.388 0.070 DISSOLVED CR) 32 17.040 IRON 0.230 AS 1.600 33.800 01049 (UG/L 0.030 DISSOLVED CO) 0.020 32 0.117* 7.200 5.900 LEAD AS 32.640 01130 6.900 26.550 0.030 DISSOLVED CU) 0.700 8.950 1.300 LITHIUM --01056 54.000 32.000 4.700 1.500 DISSOLVE (UG/L -- 32 MANGANESE -- 2.500 0.089 32 6.000 21.00001055 (UG/L 15.200 AS DISSOL (UG/L 32 0.055* MANGANESE AS -- -- FE) 0.196 1.500 -- 5.55001060 *0.200 (UG/L AS TOTAL LI) 32 0.125 0.244* MOLYBDENUM 23.290 AS -- PB) 6.915 1.600 01065 6.350 DISSO MN) 29.000 32 0.700 0.031* 8.312 NICKEL (UG/L -- 0.900 --01075 (UG/L 20.000 DISSOLVED 4.200 AS 14.700 SILVER AS 2.300 0.525 --01080 *0.154 (UG/L 3.000 MN) 3.000 DISSOLVED MO) *0.100 STRONTIUM AS 39 0.190 -- 1.40001085 *0.810 (UG/L 4.000 -- DISSOL NI) 32 VANADIUM AS 27.250 32 --01090 *0.083 (UG/L 0.117* 0.276 DISSOLV AG) 39 0.004* 0.600 ZINC AS -- 7.169 0.700 14.400 ------(UG/L -- DISSOLVED SR) *0.050 16.556 3.600 0.007* AS *0.100 2.200 14 80.000 V) *0.300 32 0.008* 1.130 --* 0.185 -- 1.209 3.200 210.000 -- 25.000 (UG/L *0.040 32 0.106* - *0.220 *0.010 AS -- VALUE 13.740 0.153 32 ZN) 0.492 *0.030 0.450 *0.022 IS -- -- *0.100 32 19.895 2.600 38.000 ESTIMATED -- *0.194 -- *0.030 -- 2.000 BY -- 0.660 *0.030 -- *0.943 USING *0.155 -- 32 0.170 -- 2.750 *0.004 6.136* A -- *0.010 *0.010 LOG-PROBABILITY 0.120 *0.064 32 50.000 18.000 -- -- REGRESSION 0.200 -- *0.141 *0.010 -- 1.100 TO -- *0.010 *15.202 *0.050 PREDICT *0.110 -- *0.002 0.500 -- 2.040 *0.004 *0.005 22.618* ------17.000 31.600 17.000 0.088 *0.075 21.523* *0.004 -- *7.985 *0.005 *0.030 *0.063 -- -- *0.001 *70.000 *140.000 0.320 -- *0.003 -- -- 40.409 16.000 8.933* -- *0.002 -- 0.040 -- *5.088 *0.010 *30.000 *0.028 *14.000 *0.000 ------*38.000 *0.001 -- 0.172 -- *0.001 48.700 9.500 *20.000 -- -- *3.697 *0.003 *2.000 *10.000 ------5.181* -- -- 45.000 *7.898 *2.143 -- -- *1.000 *6.379 -- -- *13.750 -- -- 40.500 *3.717 -- *0.100 *4.832 ------*6.750 -- -- 35.700 ------*2.694 *4.582 ------31.600 ------*2.471 ------*1.234 ------134 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances ------*0.100 (MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM MAY 1983 TO OCT 2000 Summary statistics for site 10, Horsetooth Reservoir (Spring Canyon Dam), sampled at surface. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 19. Table ------70300 RESIDUE70301 DIS DISSOLVED00077 180C SOLIDS TRANSPARENCY MG/L00300 MG/L (IN OXYGEN00400 (INCHES) DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C) 45 4000925 45 DISSOLVE MAGNESIUM00935 (MG/L 50 37 DISSOL (MG/L 35 POTASSIUM AS00931 (MG/L AS 49 DISSOL CA) 115.000 144.000 SODIUM AS CAO3)00930 (MG/L ADSORPTIO MG) SODIUM AS00932 (RATIO) 50 8.200 DISSOLVED K) 48 SODIUM, 70.00090410 (MG/L 63.000 8.500 PERCENT 40 ANC, 11.000 AS 51.00000940 30.000 TIT. NA) 40 CHLORIDE PERCENT 108.00000950 4.5, DISSOLV 40 FLUORIDE L 24.00000955 (MG/L 20.000 DISSOLV 7.200 MG/L 27.800 SILICA AS 44.60000945 (MG/L 38 DISSOLVED 68.378 CL) 6.700 82.525 SULFATE AS AS 6.000 13.60000608 (MG/L DISSOLVE 49.000 F) CACO3 38 NITROGEN AS00625 (MG/L AMMONIA SIO2) 38 40.243 2.580 NITROGEN AS 37.79100610 (MG/L 6.000 AMM+ORG 19.100 SO4) 7.689 NITROGEN AS 128.70000631 (MG/L 40 0.900 AMMONIA N) 83.700 35 7.710 NO2 AS 66.440 7.88400630 (MG/L 6.000 42 38 + N) 3.100 NO2 AS00613 NO3 40 + N) 16.562 107.500 NITROGEN,NITRITE 0.239 53.800 DISSOL 1.000 27.812 3500666 50.120 NO3 MG/L (MG/L 40.000 PHOSPHORUS TOTAL 73.50000671 AS AS 8.170 DISS. 0.500 2.900 PHOSPHORUS 17.100 N N) 85.25000665 10.150 (MG/L (MG/L 8.778 42 5.800 8.345 ORTHO PHOSPHORUS AS 1.800 AS00680 (MG/L 81.000 45.000 42 12.600 0.200 TOTAL P) 39.900 N) 22.510 CARBON AS 0.165 1.420 31.80031625 (MG/L 21.000 16 68.000 ORGANIC P) COLIFORM AS70953 T 12.300 71.000 FECAL 7.900 P) 0.663 CHL-A (MG/L 0.20070954 0 8.600 10.095 0.090 PHY 0.800 AS 7.925 60.000 40.000 41 CHLOROPHYLL-B, COLS./100 -- 2.326 37.70001005 20.850 CHROMA C) 1.000 29.675 P 2.100 ML 29.025 BARIUM UG/L 63.000 43 0.19301010 UG/L 40 0.050 DISSOLVED 15.200 1.885 BERYLLIUM 66.000 601020 (UG/L 36 DISSOL 7.700 BORON AS -- 0.871 34.00001025 36.150 (UG/L 40 7.600 34.700 0.900 DISSOLVED 9.475 BA) 16.650 2.862 7.650 CADMIUM 0.160 AS -- 28.15001030 52.200 -- DISSOLVE BE) 3.586 34 38.750 2.910 CHROMIUM (UG/L --01035 (UG/L 59.000 0.020 DISSOLV -- AS 9 17.005 COBALT 0.214 AS 1.50001040 (UG/L B) 0.020 DISSOLVED CD) 25.400 0.128* 7.500 COPPER AS 28.680 13.50001046 (UG/L -- 25.700 0.050 7.100 DISSOLVED CR) 0.700 8.960 36 2.020 IRON 7.500 AS 12.00001049 31.000 (UG/L 4.985 DISSOLVED CO) 36 LEAD 49.550 AS -- 2.50001130 16.125 7.000 DISSOLVED CU) 0.021* LITHIUM 5.400 -- 0.203 1.40001056 *0.200 35 DISSOLVE (UG/L -- 36 0.252* 35 MANGANESE 20.270 -- 7.200 36 30.40001055 (UG/L 7.275 AS DISSOL -- (UG/L 29.000 36 6.650 -- 0.650 0.016* 8.150 MANGANESE AS 1.100 FE) 7.255 --01060 (UG/L AS TOTAL 3.825 LI) 15.250 36 MOLYBDENUM AS PB) 2.40001065 *0.083 DISSO 4.000 MN) *0.200 36 NICKEL (UG/L 14.000 2.900 0.192 0.024* 1.30001075 *0.600 (UG/L 14.000 DISSOLVED 14.000 AS 5.000 SILVER AS 0.200 27.000 --01080 *0.050 (UG/L MN) DISSOLVED MO) 0.005* 0.600 STRONTIUM AS 6.371 0.800 42 14.375 --01085 (UG/L DISSOL NI) *0.030 2.750 36 0.004* -- VANADIUM AS *0.100 36 -- 2.10001090 (UG/L DISSOLV *0.110 AG) *0.300 3.200 42 0.010* ZINC -- AS -- 19.011 0.200 4.078------(UG/L 0.183 -- -- 1.043 -- 1.879* DISSOLVED 22.050 SR) *0.020 AS *0.010 18 80.000 V) 13.440 36 0.519 *0.013 -- 0.500* *0.017 209.000 *0.100 -- (UG/L 36 1.750 - *0.022 *0.200 *0.025 AS -- 1.895 VALUE 36 2.800 *9.750 ZN) *0.009 29.125 208.000 2.657 IS -- 0.170 *0.006 36 5.400 ESTIMATED ------*0.007 BY *0.005 -- -- *0.062 -- USING 0.200 36 *0.008 -- *0.138 *0.010 -- 6.290* A 1.030 0.362* -- 0.073* *2.000 *0.004 20.950 -- LOG-PROBABILITY 2.180 *0.004 36 68.500 -- REGRESSION -- 8.160 *0.003 4.800 TO *0.003 -- *11.450 PREDICT -- *0.003 *0.078 *0.008 -- *2.450 *0.200 *1.000 18.400 *0.001 20.820* -- -- *0.002 30.000 26.600 -- -- *0.002 8.089* -- *7.959 3.100 4.000 -- -- *0.001 *0.005 23.233* *70.000 *0.268 *0.100 *0.357 16.175 ------*0.001 38.875 *41.330 *208.000 -- *0.001 -- *5.815 *30.000 *0.003 2.100 3.350 -- *0.072 -- *0.060 *0.102 14.000 ------*14.000 *3.000 -- 52.775 *10.000 -- -- *4.365 *0.018 *0.040 1.500 -- 2.900 -- 5.381* *7.346 -- *1.902 -- 43.000 *5.478 *3.133 -- -- *0.003 -- *0.021 -- *29.200 -- -- *3.776 0.440 -- *0.445 38.000 *2.057 ------*5.000 -- *1.179 -- 33.800 ------*2.208 ------27.790 -- -- *0.897 ------*0.316 ------Hydrologic and Water-Quality Data 135 ------(MEDIAN) PERCENT OF SAMPLES IN WHICH VALUES DESCRIPTIVE STATISTICS WERE LESS THAN OR EQUAL TO THOSE SHOWN SAMPLE STATISTICAL SUMMARY OF SELECTED WATER QUALITY DATA COLLECTED FROM MAY 1983 TO OCT 2000 Summary statistics for site 10, Horsetooth Reservoir (Spring Canyon Dam), sampled near bottom. WATER-QUALITY CONSTITUENT SIZE MAXIMUM MINIMUM MEAN 95 % 75 % 50 % 25 % 5 % THE VALUES OF DATA BELOW THE DETECTION LIMIT (Helsel and Cohn, 1988) Table 20. Table ------70300 RESIDUE70301 DIS DISSOLVED00300 180C SOLIDS OXYGEN MG/L00400 MG/L DISSOLVED PH,00403 (MG/L) WH, PH,90095 FIELD WH, SPECIFIC00095 LABORATO CONDUCT SPECIFIC (STANDARD00010 MICROSIEMENS/C CONDUCT UNIT WATER (STANDARD00900 US/CM TEMPERATUR UNIT HARDNESS @00915 (DEGREES TOTAL 25C CALCIUM C) 4500925 45 DISSOLVE MAGNESIUM00935 (MG/L 50 DISSOL (MG/L POTASSIUM AS00931 (MG/L AS 49 38 DISSOL CA) 103.000 34 SODIUM AS CAO3)00930 (MG/L ADSORPTIO MG) SODIUM AS00932 (RATIO) 50 8.200 DISSOLVED K) 48 SODIUM,90410 (MG/L 7.900 PERCENT 39 ANC, 10.800 AS 66.000 53.00000940 58.000 TIT. NA) 39 CHLORIDE PERCENT 102.00000950 4.5, DISSOLV 39 FLUORIDE L 21.50000955 (MG/L DISSOLV 6.600 MG/L SILICA AS 40.10000945 (MG/L 17.000 36 DISSOLVED 71.733 CL) 6.000 30.700 SULFATE AS AS 0.000 12.30000608 (MG/L DISSOLVE 48.000 F) CACO3 36 NITROGEN AS00625 (MG/L AMMONIA SIO2) 36 2.240 NITROGEN AS00610 (MG/L 5.000 AMM+ORG 20.400 SO4) 7.382 42.237 NITROGEN AS 40.11800631 (MG/L 39 0.800 AMMONIA N) 82.700 34 7.262 NO2 AS 69.400 5.17800630 (MG/L 6.300 42 36 + N) 2.800 NO2 AS00613 NO3 40 + N) NITROGEN,NITRITE 0.216 DISSOL 1.120 29.197 3400666 NO3 7.831 MG/L (MG/L 42.000 PHOSPHORUS 59.350 TOTAL 76.50000671 50.275 AS AS 8.140 DISS. 0.560 1.700 PHOSPHORUS 16.700 N N) 87.45000665 (MG/L (MG/L 9.186 41 5.700 7.700 ORTHO PHOSPHORUS 9.850 AS 1.900 AS00680 (MG/L 42 0.200 TOTAL P) N) CARBON AS 0.170 1.506 34.900 5.10001005 (MG/L 23.000 47.250 17 11.365 72.000 ORGANIC P) 41.800 BARIUM AS01010 T 13.100 76.250 DISSOLVED 7.600 P) 0.681 BERYLLIUM (MG/L 0.20001020 (UG/L 11.000 0.165 DISSOL 0.900 AS 7.500 40 BORON AS -- 7.950 2.35301025 (UG/L C) 0.700 31.600 DISSOLVED BA) 29.974 42.000 CADMIUM AS 67.500 40.200 42 0.19001030 2.500 40 0.060 DISSOLVE 8.375 BE) 14.692 1.800 CHROMIUM (UG/L 70.000 601035 (UG/L 36 DISSOLV AS 7.400 COBALT 10.000 AS -- 0.76201040 (UG/L B) 41 0.800 DISSOLVED CD) 3.624 7.300 COPPER 0.230 AS -- 29.100 5.200 38.00001046 (UG/L 54.500 37.900 DISSOLVED CR) 36 35.000 2.715 IRON AS --01049 0.060 (UG/L 3.285 61.000 0.040 DISSOLVED -- CO) 7.450 36 9 16.615 LEAD 0.210 AS 1.60001130 0.040 DISSOLVED CU) 0.129* 7.100 LITHIUM 9.10001056 -- 27.100 0.096 DISSOLVE (UG/L 0.718 27.450 36 1.625 7.100 MANGANESE 32.350 36 30.10001055 32.000 2.500 (UG/L AS 5.470 DISSOL (UG/L -- 36 MANGANESE 54.000 AS -- 2.500 FE) --01060 (UG/L 15.375 AS TOTAL LI) 36 0.035* 6.925 MOLYBDENUM 5.200 AS -- PB) 0.199 1.500 4.57501065 *0.200 DISSO MN) 36 0.242* NICKEL 22.600 (UG/L -- 6.800 8.500 --01075 (UG/L 20.000 DISSOLVED 13.000 AS 30.000 -- 0.700 0.038* SILVER AS 1.000 6.710 --01080 (UG/L MN) 0.100 DISSOLVED 4.500 MO) 14.700 STRONTIUM AS 2.300 42 --01085 *0.084 (UG/L DISSOL NI) *0.200 36 VANADIUM AS 3.200 5.470 36 0.192 -- 0.113*01090 1.400 *0.500 (UG/L 3.925 DISSOLV AG) 41 ZINC AS -- 17.336 28.000------*0.060 (UG/L 7.090 -- 0.004* DISSOLVED SR) 0.013* 140.000 0.600 AS 0.700 13.800 18 V) *0.050 3.850 36 0.011* *0.100 --* 2.200 -- 685.000 -- *0.216 (UG/L *0.300 36 0.022* - -- 3.956 0.181 AS -- 1.180 3.200 VALUE 24.000 *0.050 36 *0.010 ZN) 23.045 684.000 *0.039 IS -- 13.185 36 ESTIMATED 0.000 0.568 *0.020 -- 0.475 *0.034 -- *0.100 BY 2.775 -- *0.180 *0.200 -- *0.057 USING 1.900 36 -- 6.469* A *0.040 -- *0.004 0.170 2.775 18.000 -- *0.020 LOG-PROBABILITY 5.200 36 59.300 -- REGRESSION 25.548 -- *0.010 *0.019 -- *0.066 TO 0.200 *0.102 -- *0.148 *11.970 *0.030 PREDICT -- -- 1.215 -- *0.028 *0.002 17.400 *0.008 -- -- 42.000 27.300 2.500 *0.006 4.600 80.164* *0.007 -- 78.500 *0.052 *8.000 *0.093 *0.020 -- -- 75.913* *0.020 *590.000 *0.001 16.000 -- *0.004 -- -- 41.342 -- *0.004 *684.000 30.000 -- -- 3.700 -- *0.025 *5.978 *0.008 *72.000 -- -- *0.000 13.850 *0.002 -- -- *40.750 *0.001 52.245 20.000 -- -- *4.130 *0.003 3.350 *7.000 *19.000 ------5.786* ------45.750 10.000 *2.984 -- *2.000 -- 3.200 -- *26.800 *9.500 -- -- 40.500 -- 0.450 *0.172 ------*7.000 *2.214 ------37.000 ------*3.001 ------30.785 ------*1.457 ------*0.520 ------136 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances tects greater than 20 percent; mg/L, milligrams per liter; µS/cm, chromatography; µg/L, micrograms per liter] *, greater than 99 percent; change is percent in median since the -value Slope Median Significance Change p record Period (years) censored Percentage Number Censored ) 45 0 0 11 0.0000–0.5543 22 (–)***–24.1 3 Seasonal Kendall , hplc (µg/L), hplc (µg/L) 46 45 0 33 0 73 11 11 0.0056 A –0.2268 A 2.05 (–)*** A –73.1 A A season-edited data a b near dam, surface samples. analysis results for site 1, Granby Reservoir, Trend Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 46 46 46 0 0 46 0 0 0 0 0 11 11 0 0.0000 11 0.0383 –1.768 0.1719 11 –0.05001 –0.02519 54 0.7760 7.5 –0.02014 7.9 (–)*** (–)** 15.2 –30.1 0 –7.1 0 –3.4 –1.4 Calcium, dissolved (mg/L)Calcium, dissolved (mg/L)Magnesium, dissolved (mg/L)Potassium, dissolved Sodium adsorption (ratio) (mg/L)Sodium, dissolved Sodium (percent)Acid-neutralizing capacity (mg/L) (mg/L)Chloride, dissolved 45 45 (mg/L)Fluoride, dissolved 45 (mg/L)Silica, dissolved (mg/L) dissolved Sulfate, 0 0 45 (mg/L as N)Nitrogen, ammonia plus organic 45 45Nitrogen, ammonia (mg/L as N) 0 Nitrite plus nitrate (mg/L as N) 45 0Nitrogen, nitrite (mg/L as N) 45 0 0 0 0 (mg/L as P)Phosphorus, dissolved 45 45 13 (mg/L as P)Phophorus, ortho, dissolved 0 Phosphorus, total (mg/L as P) 45 0 45 45 11 11 at 180°C (mg/L)Residue, dissolved 0 0 0 9 0 solids, sum of constituents (mg/L)Dissolved 45 11 45 29 Secchi disk (in.)Transparency, 39 0.0000 0.0000 0 32 45Coliform, fecal (colonies per 100 mL) 0 45 11 0 11 0.0000Chlorophyll- 45 11 41 20 –0.1662 –0.03141 0 11 44 34Chlorophyll- 1.0000 41 43 –0.0125 (µg/L)Barium, dissolved 0.0000 0 71 0.0000 0 11 (µg/L)Iron, dissolved 1.2 0.0024 42 0 100 6.85 11 11 0 91 (µg/L)Manganese, dissolved –0.4997 44 25 –0.08776 87 0.7 0 (µg/L)Strontium, dissolved 0.0554 96 11 11 30 0.0374 (µg/L)Zinc, dissolved 0.0000 (–)*** (–)*** 0 0 11 11 24 11 2.2 0 11 0 (–)*** 61 1.7247 –0.2004 0 11 –23.3 –24.9 A 0.0000 0.2 0 11 71 A 45 A 0.3 (–)*** (–)*** –17.7 0.04281 –0.1189 16 39 A 11 11 0 A 0.0000 45 45 0.4 A 11 –35.4 0 –20.4 0 4.85 0.1 A 0.0296 24 2.95 A 0.6643 0 A (–)*** 11 21 34 A 0 A –0.6707 A 0 (–)*** 0 A 35 0.0 0.0002 –12.8 0 0 62 20 A 37 A A 47 B A –35.7 8.037 0 A A 11 10.3 11 0.0 (+)*** A 59 B 11 A 122 (–)** A A 11 0.2263 A 23.6 A 0.0000 A A 11 –18.0 0.0000 A (+)*** 0 A A A –1.219 B A A A A 119.8 A 8 42 26 A A A A (–)*** (–)*** 0 A A –27.2 B 0.0 A A A first year of record; A, no trend computation because nondetects greater than 50 percent; B, slope nonde first Celsius; Celsius; in., inch; mL, milliliter; hplc, high-performance liquid microsiemens per centimeter at 25 degrees °C, degree Table 21. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward Hydrologic and Water-Quality Data 137 tects greater than 20 percent; mg/L, milligrams per liter; µS/cm, *, greater than 99 percent; change is percent in median since the -value Slope Median Significance Change p record Period (years) censored Percentage Number Censored ) 45 0 011 0.0000–0.5513 24 (–)***–22.2 3 Seasonal Kendall season-edited data near dam, bottom samples. analysis results for site 1, Granby Reservoir, Trend Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 45 44 45 0 0 45 0 0 0 0 0 11 11 0 0.0000 11 0.0006 –2.15 0.8224 11 0.2182 55.5 0.0016 0 4.8 (–)*** –0.1245 (+)*** –34.6 7.1 6.5 68.8 (–)*** 0 –18.9 0.0 Calcium, dissolved (mg/L)Calcium, dissolved (mg/L)Magnesium, dissolved (mg/L)Potassium, dissolved Sodium adsorption (ratio)(percent) (mg/L)Sodium, dissolved Sodium Acid-neutralizing capacity (mg/L)(mg/L) 45 (mg/L)Chloride, dissolved dissolved 45Fluoride, 45 (mg/L)Silica, dissolved (mg/L) dissolved Sulfate, 0 0 45 (mg/L as N) 45Nitrogen, ammonia plus organic 45 0Nitrogen, ammonia (mg/L as N) Nitrite plus nitrate (mg/L as N) 45 46 45 0 0 0 45 Nitrogen, nitrite (mg/L as N) 0 0 13 (mg/L as P)Phosphorus, dissolved 0 0 24 (mg/L as P)Phophorus, ortho, dissolved 45 11 0 11 0Phosphorus, total (mg/L as P) 29 45 0 45 0 0 at 180°C (mg/L)Residue, dissolved 11 45 0.0000 solids, sum of constituents (mg/L) 0.0000Dissolved 52 11 45 11 0 39 (µg/L)Barium, dissolved 0.0000(µg/L) 11 29 0.0001 45 00.0730 0–0.2008 –0.1789 –0.0296 11 (µg/L)Iron, dissolved 11dissolved 17 45 25 Manganese, 37 0.4789 –0.01658 11 44 28 7.3 0.0000 1.3 (µg/L)Strontium, dissolved 0.0000 42 42 B 0 64 11 (–)*** (µg/L)Zinc, dissolved 0.7 0 0 –12.1 –0.6636 56 –0.09787 0 (–)*** A (–)*** 820.1 0 0.5170 72 15 (–)*** 93 39 26 11 2.3 11 –23.5 –22.0 11 45 0 11 –22.8 0.2 12 0 0.1085 11 A 0 (–)*** 11 0.0000 36 0 45 (–)*** 11 A 45 –0.08068 0 31 –37.3 A –24.3 11 –0.08859 0 A 0.4 A A B 34 5.9 8 11 11 A 0 3 11 0.0000 A 0.0001 0 0.0 A 0.4151 0.3325 0 17 A –0.9844 A 0 A 18 (–)*** A A –0.377 0 38 B B 11 –27.6 A –13.9 0.0 A 50 4010 A A 11 A 0.1023 (–)*** A 11 0.02 0.0002 A –24.7 (–)*** A 0.0000 8 A 0 0 A A 0 –1.218 B 0.3221 B A –9.8 A 8 A 46.5 A 19.5 B B (–)*** (–)*** 0 8 –24.9 B 0.0 0 B Table 22. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward first year of record; A, no trend computation because nondetects greater than 50 percent; B, slope nonde first Celsius; Celsius; µg/L, micrograms per liter] microsiemens per centimeter at 25 degrees °C, degree 138 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter grams per liter] *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first -value Slope Median Significance Change p record Period (years) censored Percentage Number Censored ) 45 0 011 0.0000 –0.6377 23 (–)***–26.1 3 Seasonal Kendall , hplc (µg/L)hplc (µg/L)hplc , , 45 44 0 34 0 7711 0.0059 11–0.2487 1.8 A (–)***–83.1 A A A A season-edited data a b analysis results for site 2, Granby Reservoir (Rainbow Bay), surface samples. Trend Calcium, dissolved (mg/L)(mg/L) dissolved (mg/L) dissolved Calcium, (ratio) dissolved Magnesium, (mg/L)adsorption Potassium, dissolved Sodium (percent)Sodium, (mg/L) 45 45Sodium dissolved Acid-neutralizing capacity (mg/L)(mg/L) 45 0 0Chloride, (mg/L) dissolved (mg/L)Fluoride, dissolved 45 0 dissolved Silica, 45 0 0 Sulfate, 0 0 (mg/L as N)Nitrogen, ammonia plus organic 01111 45 44 Nitrogen, ammonia (mg/L as N) 00.00000.000011Nitrite plus nitrate (mg/L as N) 46 0 –0.1905–0.02791 0Nitrogen, nitrite (mg/L as N)0.0000 45 4511 0 (mg/L as P)Phosphorus, dissolved –0.01419 1.3 44 7.111 44 0.0586 (mg/L as P)Phophorus, ortho, dissolved 0 0 16 0.7 00.0000Phosphorus, total (mg/L as P) 0 –0.09753 at 180°C (mg/L)Residue, dissolved 45 011 (–)*** 0 (–)*** 0 solids, sum of constituents (mg/L)Dissolved 9 2.3 39 00.1148 35 45 0–20.9 Secchi disk (in.)Transparency, (–)*** –25.4 35 11Coliform, fecal (colonies per 100 mL) (µg/L) 45 3011–19.9 44 0.000011Chlorophyll- (µg/L) 110.7990 20 32 0.2dissolved (–)*** 37–0.2013 Chlorophyll- 0.0000 44 0 28 11 dissolved 0.01451 41Barium, –0.1371–37.2 42 16 67 0 Iron, 0.0000 5 42 82 2.9 (µg/L)Manganese, dissolved 0.0044 82 0.4 11 0 43 0 80 18 (µg/L)Strontium, dissolved –0.6262 93 (µg/L)Zinc, dissolved 11 (–)*** 25 0 0.4901 (–)*** 45 0.0 –12.9 0 0 11 9 0 0 44 0 26 –40.5 9 11 0 35 60 A 11 B 3.2 34 0.0 2 A A 0 0 11 0.2 11 (–)*** A 45 A 0.0000 11 6 11 15 A 0.1052 0.1100 0.10.0036 –23.1 34 –0.8526 11 0 A A 0 9 –0.6271 A A A 440.0000 0.0009 18 36 B A 0 0 0 38.5 A A 7.043 B A B 53 A 8 A 8 (–)*** 0.02 A 11 B 20 113 0 0.0010 A A –22.8 8 A A 0.0000 A 0 0 (–)*** A (+)*** –16.3 B –1.19 A A A 0.0 A A 109.5 A B B 4 44 A A (–)*** (–)*** A –25.6 B A A Oxygen, dissolved (mg/L) dissolved Oxygen, (°C) (standard units)pH, field temperature conductance (µS/cm at 25°C)Specific Water Hardness, total (mg/L as CaCO 45 46 0 46 0 46 0 0 11 00.2757 0 0–0.02509 7.411 00.7486 110.03633 13.45 0 0.0000 11 –3.7 –1.838 0.4714 0 –0.009972 54.75 3.0 7.8 (–)*** –30.7 0 –1.4 Table 23. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; in., inch; mL, milliliter; hplc, high-performance liquid chromatography; µg/L, micro at 25 degrees °C, degree Hydrologic and Water-Quality Data 139 than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter -value Slope Median Significance Change *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first p record Period (years) censored Percentage Number Censored ) 45 0 0 110.0000 –0.5703 23 (–)***–23.7 3 Seasonal Kendall season-edited data analysis results for site 2, Granby Reservoir (Rainbow Bay), bottom samples. Trend Calcium, dissolved (mg/L)Calcium, dissolved (ratio) (mg/L)Magnesium, dissolved adsorption (mg/L)Potassium, dissolved Sodium (mg/L)Sodium, dissolved (percent)(mg/L)Sodium dissolved Acid-neutralizing capacity (mg/L)Chloride, 45 45 45 (mg/L)Fluoride, dissolved 45 (mg/L)Silica, dissolved 0 (mg/L) dissolved Sulfate, 0 0 (mg/L as N)Nitrogen, ammonia plus organic 45 45 44 0 0Nitrogen, ammonia (mg/L as N) Nitrite plus nitrate (mg/L as N) 0 45 0 011 45Nitrogen, nitrite (mg/L as N) 0 00.1164 (mg/L as P)Phosphorus, dissolved 0 44 0 0 18 (mg/L as P)Phophorus, ortho, dissolved 11 45Phosphorus, total (mg/L as P) 11(µg/L)11 44 0 12 45 0 at 80°C (mg/L)Residue, dissolved 0 0 110.1621 dissolved solids, sum of constituents (mg/L)Dissolved 40 40 0.0000 0.0000 45 0 Barium, 35 26 0 11 0.0009 45 0.2 11 27 (µg/L)Iron, dissolved 11 44 –0.1956 –0.03258 28 0.0001 (µg/L)Manganese, dissolved 0 38 11 27 (µg/L)Strontium, dissolved –0.01109 44 0.0000 43 0.0000 0–0.1677 40 58 0 (µg/L)Zinc, dissolved 1.3 11 0 0 0.4 7 0.0067 70 16 45 84 –0.5325 0.7 –0.08457 77 13 0 96 0.0884 11 0 11 0.0 (–)*** 11 (–)*** 0 0 25 11 0 2.3 (–)*** (–)*** 45 11 0.7429 0 33 –24.0 9 0.0000 0 45 11–10.8 A 45 0 –26.3 0.0 –15.9 11 (–)*** 11 12 –0.01608 A (–)*** A 0.2 –0.09972 0.0007 3 46 11 A 11 A 1 0.0000 –33.1 0.100 5.6 –20.8 A 27 2.900 0.6043 26 0.0897 A 0 0 –0.7537 A 7 2 (–)*** 0 A A 0 –0.7479 11 A 8 57 B 36 –31.4 A B 11 A 11 0.0076 39 B A A –3.1 11 0.0002 (–)*** A 0.02 0.0000 0 A B A (–)* –20.5 –1.151 A 0.0 A A B 0 A –18.9 A 7 44 A A A 15 A B (–)*** (–)*** (–)*** A –24.9 B B A A Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 46 45 46 0 0 46 0 0 0 0 0 11 11 0 0.0000 11 0.0878 –2.02 0.0433 11 –0.1285 –0.03346 0.0000 54.5 5.1 –0.6136 7.4 (–)*** (–)* 8.35 (–)** –33.4 –24.1 (–)*** –4.8 –56.1 Table 24. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; µg/L, micrograms per liter] at 25 degrees °C, degree 140 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first -value Slope Median Significance Change p record Period (years) censored Percentage Number Censored ) 56 0 0 110.0000 –0.5282 24 (–)***–21.4 3 Seasonal Kendall season-edited data analysis results for site 3, Granby Pump Canal, samples. Trend Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 179 170 173 0 0 180 0 0 0 0 0 30 30 0 0.0001 30 0.3610 –0.2482 30 0.0004 0.0133 0.0577 60 0.01736 7.55 0.01998 7.3 (–)*** 4.1 0 (+)*** –11.7 (+)* 7.4 5.4 15.8 Calcium, dissolved (mg/L)Calcium, dissolved (mg/L)Magnesium, dissolved (mg/L)Potassium, dissolved Sodium adsorption (ratio) (mg/L)Sodium, dissolved Sodium (percent) Acid-neutralizing capacity (mg/L) 56 56 (mg/L)Chloride, dissolved (mg/L)Fluoride, dissolved 56 (mg/L)Silica, dissolved 0 0 56 (mg/L) dissolved Sulfate, 56 56 (mg/L as N)Nitrogen, ammonia plus organic 0 Nitrogen, ammonia (mg/L as N) 139 0Nitrite plus nitrate (mg/L as N) 0 0 0 56 0Nitrogen, nitrite (mg/L as N) 56 56 0 (mg/L as P)Phosphorus, dissolved 27 (mg/L as P)Phophorus, ortho, dissolved 56 0 1 11 11 Phosphorus, total (mg/L as P) 56 0 0 10 53 0 at 180°C (mg/L)Residue, dissolved 11 128 19 0.0000 solids, sum of constituents (mg/L)Dissolved 0.0000 54 0 54 37 11 0 (µg/L)Barium, dissolved 55 2 0.0000 18 11 0 11 59 55 (µg/L)Iron, dissolved –0.176 –0.02449 40 22 (µg/L) Manganese, dissolved 40 1.0000 55 134 –0.01649 49 0 0.0000 (µg/L)Strontium, dissolved 70 0.0000 11 0 0 11 1.3 (µg/L)Zinc, dissolved 11 46 0.0000 7.4 74 31 –0.6187 0 –0.08641 0.7 74 0 0.0160 89 –0.01652 11 0.1912 11 0.0000 11 56 (–)*** 22 0 (–)*** 26 –0.01837 2.3 46 11 23 (–)*** –0.1822 0.1479 11 0 48 0.38 0.0000 11 0.2 56 –18.6 B A 0.0010 1 –22.9 11 0.4 9 –22.7 0.06661 (–)*** 17 –0.09868 A (–)*** 22 3 (–)*** 47 A 11 0 A 0.0000 B 0 0.1 –33.7 2 A 5.4 –22.9 0.0000 (–)** 3 –63.8 20 19 0.0502 (–)*** –0.745 6 A 0 A A –0.4758 –39.6 0.1 11 0.0 0 –11.1 B 11 A 40 0 (–)*** 38 11 11 0.4783 40 A 0.0000 A (–)*** –30.2 A 11 0.0032 14.7 0.02 B 0.0000 A (–)*** 0 B B (–)* 0.7031 A –1.137 A (–)*** –19.3 B A A –12.2 7 B 45 4 B A A 23 A 5.5 (–)*** (–)*** 0 (–)*** –24.1 B 0 0.0 B B Table 25. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; µg/L, micrograms per liter] at 25 degrees °C, degree Hydrologic and Water-Quality Data 141 -value Slope Median Significance Change than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter p grams per liter] *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first record Period (years) Number Nondetects % nondetect ) 36 0 0 11–0.20030.089885820222 (–)*–9.5 3 Seasonal Kendall , hplc (µg/L), hplc (µg/L) 34 35 1 27 3 77 11 11 0.1967038082 –0.1129 A 2.25 A 0 –42.4 A A A season-edited data a b surface samples. analysis results for site 4, Shadow Mountain Reservoir, Trend Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 36 35 35 0 0 -- 0 0 -- 0 0 11 11 -- 0.119470507 11 0.8687865534 –0.5274 0.6171454802 0.01429 -- 49.6 –0.009913 7.4 7.6 0 -- 0 0 –11.0 -- 2.2 –1.4 ------Calcium, dissolved (mg/L)Calcium, dissolved (mg/L)Magnesium, dissolved (mg/L)Potassium, dissolved Sodium adsorption (ratio) (mg/L)Sodium, dissolved Sodium (percent)Acid-neutralizing capacity (mg/L) (mg/L)Chloride, dissolved (mg/L)Fluoride, dissolved 36 36 (mg/L)Silica, dissolved 36 (mg/L) dissolved Sulfate, (mg/L as N)Nitrogen, ammonia plus organic 0 0 36 36Nitrogen, ammonia (mg/L as N) 36 0Nitrite plus nitrate (mg/L as N) 36 Nitrogen, nitrite (mg/L as N) 0 35 (mg/L as P)Phosphorus, dissolved 0 0 0 0 36 35 (mg/L as P)Phophorus, ortho, dissolved 5Phosphorus, total (mg/L as P) 0 36 at 180°C (mg/L)Residue, dissolved 2 35 36 solids, sum of constituents (mg/L)Dissolved 0 0 1 11 11 0 30 Secchi disk (in.)Transparency, 0 36 27 Coliform, fecal (colonies per 100 mL) 14 11 0 36 23 32 0.0469222566 0.6445834148 0 Chlorophyll- 6 21 11 Chlorophyll- 35 –0.09798 0.1453926983 35 11 0 23 3 11 (µg/L)Barium, dissolved 29 33 0 11 0 (µg/L)Iron, dissolved 6.5 0.8533074921 64 0 0.0690640193 33 (µg/L)Manganese, dissolved 0.0005205513 0 0 11 36 0 70 (µg/L)Strontium, dissolved –0.25 0.0016781137 97 11 –0.05838 11 11 1.3 85 (µg/L)Zinc, dissolved 0 (–)** 92 20 0.9999999996 11 0.7 0 11 1.9 0.0000174818 0.643221044 B 23.5 11 1 –15.2 11 11 –0.2501 0 0.2 38 0 B 11 0.0315551014 0.0018395843 (–)*** 11 36 61 0 0.3 (–)* 0 16 11 0.0991 36 A –0.05731 –28.5 3 0.4 36 36 0 A 11 11 0.0 A 0.1267610508 –11.0 2.8 (–)*** 5.55 A 1 0.1 (–)*** 11 A 0.0 6 –0.25 0.9670087749 27 0.046261307 1 1 0 A 11 (+)** (–)*** 0.0 –15.7 B A 34 0 A 0 11 3 A 0.3826629909 0 –20.1 A 17 22.0 A A 1.415 B 3 3 38 A A 0.0 0 0.02 A 11 41 A 11 83 A A 11 11 0.899098618 A 0.0091607158 0 0 A –7.7 A 11 A 0.2332613662 0.038358664 0 A A B 0 –2.406 –0.6355 0.0453922501 A 0.0 A B A 20.9 56 38.685 A A 4 7 0 (–)** (–)*** 6 0 A –16.5 0 B –37.6 0 0.0 B Table 26. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; in., inch; mL, milliliter; hplc, high-performance liquid chromatography; µg/L, micro at 25 degrees °C, degree 142 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter -value Slope Median Significance Change p *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first record Period (years) censored Percentage Number Censored ) 36 0 0 110.0023115152–0.327822 (–)***–15.0 3 Seasonal Kendall season-edited data bottom samples. analysis results for site 4, Shadow Mountain Reservoir, Trend Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 36 35 35 0 0 -- 0 0 0 -- 0 11 11 -- 0.0003232226 11 0.0044134641 –0.9775 0.254286403 0.2693 -- 52 0.01232 5.6 7.3 (–)*** -- (+)*** –18.6 0 74.4 -- 1.9 -- -- Calcium, dissolved (mg/L)Calcium, dissolved (mg/L)Magnesium, dissolved (mg/L)Potassium, dissolved Sodium adsorption (ratio)(percent) (mg/L)Sodium, dissolved Sodium Acid-neutralizing capacity (mg/L) (mg/L)Chloride, dissolved 36 36 (mg/L)Fluoride, dissolved 36 (mg/L)Silica, dissolved (mg/L) dissolved Sulfate, 36 0 0 (mg/L as N)Nitrogen, ammonia plus organic 36 36Nitrogen, ammonia (mg/L as N) 0 Nitrite plus nitrate (mg/L as N) 36 36 0Nitrogen, nitrite (mg/L as N) 0 35 0 0 0 (mg/L as P)Phosphorus, dissolved 0 35 0 (mg/L as P)Phophorus, ortho, dissolved 6 36Phosphorus, total (mg/L as P) 0 11 0 11 35 1 36 at 180°C (mg/L)Residue, dissolved 0 0 2 11 30 solids, sum of constituents (mg/L)Dissolved 36 0.0009600972 0.2914253772 17 27 (µg/L)Barium, dissolved 11 0 36 11 170.0003709347 0.1815493972 –0.2003 –0.12 0 3 (µg/L)Iron, dissolved 32 11 16 11 20 6 (µg/L)Manganese, dissolved 0 33 35 0.8629658527 11 22 (µg/L) Strontium, dissolved 36 0.004847576 0 0.0000623096 34 0 47 6.8 11 (µg/L)Zinc, dissolved 0 (–)*** 0 0.0300825763 67 –0.06004 11 0 –0.2988 1.3–12.8 92 0 81 0.1113847049 9 94 (–)*** 0.7 11 11 1.9 24 0.9520599211 36 11 0 –0.00999 0 11 0.2 36 11 0 0.6332197237 0.1713121915 –17.6 11 0 36 0.000936414 25 0.4 11 (–)*** 36 B 0 (–)*** –0.01821 0.25 1 11 –0.07128 B 0 3 A –29.2 27 11 6.2 A 0.0 11 1 –12.7 0.1 A 0.028596739 0 1 2.9 A 0.0 0 3 0.0736147125 0.02 0.1247838628 –0.4938 8 15 0.0 0 –0.4997 (–)*** 3 –23.9 A 0 3 A 34 A 11 B B 0 A 39 11 56 –23.6 11 –3.2 0.0465907953 A 11 A B (–)** 0.0000252162 0.02 A A 0.1891830763 (–)* 11 B 0.0002823951 0 –1.917 –14.7 B A –0.993 0 A –13.1 A A 77 7 A 39 15 A B A A A (–)*** (–)*** 0 0 A –24.3 B –23.8 0.0 A A A Table 27. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; µg/L, micrograms per liter] at 25 degrees °C, degree Hydrologic and Water-Quality Data 143 /s, cubic feet per second; mg/L, milligrams liter; µS/cm, 3 than 5 percent; ft *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first -value Slope Median Significance Change p record Period (years) censored Percentage Number Censored )141 0 0 24 0.1679–0.05411 19 0 –6.6 3 /s)175 0 030 0.2191–0.997 455 0–6.4 3 Seasonal Kendall season-edited data east portal. analysis results for site 5, Adams Tunnel Trend Instantaneous discharge (ft Instantaneous discharge Oxygen, dissolved (mg/L) dissolved Oxygen, (°C) (standard units)pH, field temperature conductance (µS/cm at 25°C)Specific Water 176 Hardness, total (mg/L as CaCO 0 165 0179 176 030 0 0 0.3841 0 030 0 0 0.0022 300.02273 8.3 5 30 0.0025 –0.267 0.0000 0 (+)*** 14.7 0.02726 50 0.0 7.5 (–)*** (+)*** –14.8 11.6 Calcium, dissolved (mg/L)(mg/L) dissolved (mg/L) dissolved Calcium, (ratio) dissolved Magnesium, (mg/L)adsorption Potassium, dissolved 141141Sodium (mg/L) (percent)Sodium, 139 0(mg/L) 0capacity Sodium dissolved 0Acid-neutralizing (mg/L)141 0 0(mg/L) 141Chloride, 141dissolved (mg/L) 0 dissolved 0Fluoride, 2424 0 0 dissolved Silica, 024139 Sulfate, 0 0 0.2766 0.0078 (mg/L as N)Nitrogen, ammonia plus organic 124–0.01659–0.005393139 140Nitrogen, ammonia (mg/L as N)24 0.0015 24 139 1.1 133 5.9Nitrite plus nitrate (mg/L as N)–0.005548 0 1138 14 Nitrogen, nitrite (mg/L as N) 0.1300 0.7 0 0.2348 0 0.0006 (mg/L as P)Phosphorus, dissolved 24 0 32 10 (–)***–0.015450.04984 0 (mg/L as P)Phophorus, ortho, dissolved 0 –11.1 0 (–)***2421 1.9Phosphorus, total (mg/L as P) 0 24(µg/L) 67 0.017324 –17.3 at 180°C (mg/L)Residue, dissolved 24 24 –6.5 dissolved 55 solids, sum of constituents (mg/L)Dissolved 0.0066 67 116 0.2 (–)*** 42 0.1741Barium, (µg/L) 0.0000 67 0 131 0–17.7 0.0000 (µg/L)Iron, dissolved dissolved 22(µg/L) 240.05004 –0.1485 51 58Strontium, dissolved 66 63 0 60 4.4 120Zinc, 0 B 0.4 5.9 3.367 0 0.0000 44 76 5017 0 35 0 (+)*** 90 0.0 11 0.1 67 (–)*** 0 0 B 031.8 –69.1 9 0 11 20 29 72 0 11 011 141 A 0.0 0 24 26 0 0.0030 0.0020 0.3 A 20 0.0 0.9159 11 0 36 A 11 0.3101 A (–)*** 0 B 0 0.0057 19 0.7760 –0.04997 0.0000 0 0 A –1.392 A 0.7935 A B 31 0.1 6 0 0.02 0 35 24 A A B 0 A 0 0.0000 0 0.02 34 0 (–)*** A 8 –1.791–35.3 A 0.0 0 –3.8 A B B 0 30 A 0 A B 0.0 (–)*** B –82.1 Table 28. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope microsiemens per centimeter at 25 degrees Celsius; °C, degree Celsius; µg/L, micrograms per liter] Celsius; °C, degree microsiemens per centimeter at 25 degrees 144 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter -value Slope Median Significance Change *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first p record Period (years) censored Percentage Number Censored ) 72 0 0 25 0.0215–0.1313 17.5 (–)**–17.1 3 Seasonal Kendall season-edited data samples. analysis results for site 7, Olympus Tunnel, Trend Potassium, dissolved (mg/L) (mg/L)Calcium, dissolved (ratio) dissolved (mg/L)Magnesium, dissolved adsorption Potassium, Sodium (percent) (mg/L)Sodium, dissolved (mg/L)Sodium dissolved Acid-neutralizing capacity (mg/L) 71Chloride, 72 72 (mg/L)Fluoride, dissolved 71 0 (mg/L)Silica, dissolved 0 (mg/L) dissolved Sulfate, 0 0 0 (mg/L as N)Nitrogen, ammonia plus organic 72 71 72 Nitrogen, ammonia (mg/L as N) 0 Nitrite plus nitrate (mg/L as N) 34 0 25 71Nitrogen, nitrite (mg/L as N) 0 0 0 0 (mg/L as P)Phosphorus, dissolved 70 25 0 0 10 (mg/L as P)Phophorus, ortho, dissolved 0.0154 Phosphorus, total (mg/L as P) 72 25 25 (µg/L) 0 71 69 0 0.4704 at 180°C (mg/L)Residue, dissolved 0 5 dissolved 25 solids, sum of constituents (mg/L)Dissolved 74 29 33 0 0.0271 0.0100Barium, 0 60 15 71 0 25 (µg/L)Iron, dissolved 25 70 25 0 0.4930 27 7 (µg/L)Manganese, dissolved –0.03847 –0.007212 0.6 27 11 31 29 (µg/L)Strontium, dissolved 69 68 0.1399 0 22 0.9084 0.2 0.3087 0 (µg/L)Zinc, dissolved 0 1.1 36 5.15 0 0.3054 25 31 82 0 0 48 10 –0.00499 97 25 25 0 0 0 25 (–)*** (–)** 0 0.6 0.4827 0 0.0 25 B 53 11 2 019 22 0 15 0.0028 0.9754 72 –15.1 25 0.0 –17.0 0.0000 32 18 0.4603 0 25 B 5 0.0000 0.03356 A –0.1287 0.3 11 11 25 0 25 B 0 A 1 0 0.0 0.0137 B 4.6 0 0.1 0.9577 9 0.6943 0.0067 B 3.4 10 0.0 0 –0.1671 0 A –6.0 3 0.04 A (+)*** 0.1778 0.089 (–)*** 0 0.0 18 0 40 B 30 0.01 25 B 0 11 20.2 A –63.4 33 0 6 0.0413 A (–)*** 11 0.0050 (–)** B 0.02 0.0478 B A –1.497 0.0257 B 0 –13.0 B B –0.7347 A (–)*** 0 62.5 0.0 28.5 A B B 6.1 4 A (–)*** (–)** 7 (–)** –45.7 –24.6 B (–)** B Oxygen, dissolved (mg/L) dissolved Oxygen, (°C) (standard units)pH, field temperature conductance (µS/cm at 25°C)Specific Water Hardness, total (mg/L as CaCO 88 81 0 89 88 0 0 0 0 30 0 0 0.0402 0 300.02006 30 9.1 0.3111 30 0.0008 (+)** –0.3754 0.0530 0 6.8 48 0.01051 4.5 7.6 (–)*** 0 –20.9 (+)* 0.0 4.2 Table 29. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; µg/L, micrograms per liter] at 25 degrees °C, degree Hydrologic and Water-Quality Data 145 than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter grams per liter] *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first -value Slope Median Significance Change p record Period (years) censored Percentage Number Censored ) 36 0 0 11 0.0002–0.5723 30 (–)***–18.8 3 , hplc (µg/L) 35 0 0 11 0.1413 0.04964 1.2 0 60.5 Seasonal Kendall season-edited data a surface samples. analysis results for site 8, Carter Reservoir, Trend Potassium, dissolved (mg/L) (mg/L)Calcium, dissolved (ratio) dissolved (mg/L)Magnesium, dissolved adsorption Potassium, Sodium (percent) (mg/L)Sodium, dissolved Sodium 36Acid-neutralizing capacity (mg/L) (mg/L) 36Chloride, dissolved 36 0 36 (mg/L)Fluoride, dissolved (mg/L)Silica, dissolved 0 (mg/L) dissolved Sulfate, 0 0 0 (mg/L as N)Nitrogen, ammonia plus organic 36 36 0Nitrogen, ammonia (mg/L as N) 35Nitrite plus nitrate (mg/L as N) 36 11 0 (mg/L as P)Phosphorus, dissolved 34 0 0 0 (mg/L as P)Phophorus, ortho, dissolved 34 0 11 14 Phosphorus, total (mg/L as P) 0.0370 36 at 180°C (mg/L)Residue, dissolved 0 11 11 34 74 0 1.0000 solids, sum of constituents (mg/L)Dissolved 0 0 5 35 29 77 Secchi disk (in.)Transparency, 40 0 0.0002Coliform, fecal (colonies per 100 mL) 33 0.0001 0 31 1 Chlorophyll- 0 11 31 0 11 79 11 25 51 15 –0.1979 –0.01417 (µg/L)Barium, dissolved 0.7 72 11 (µg/L)Iron, dissolved 0 0.4848 0.2 42 0 56 (µg/L)Manganese, dissolved 0.0009 0.0000 11 3 89 0 1.3 72 (µg/L)Strontium, dissolved 28 9.8 11 86 66 0.0466 –0.499 (µg/L)Zinc, dissolved –0.04227 0 38 0 0.0063 0 30 11 0.3807 11 11 0 0 (–)*** (–)*** 0 11 39 29 0 0.0 2.2 32 0.0331313 36 0.0215 0.0005 68 11 27 0.0004 0.0 –11.3 B –19.8 A 27 36 0 A A 30 29 0.1552 0.7 –0.07395 (–)*** 0.2 0 0.0025 (–)*** 0 19 24 0 27 0.0000 0.0000 8 –0.4891 0.1 0 –19.0 30 2.9 A 2.5 (+)*** –15.7 A A –0.4344 0 0 70 0.0 A 0.03 11 39.5 B 0.3452 30 72.7 (–)*** (+)*** 0 0 47 A 11 A A 0.4081 11 41 0 A B (–)*** –24.3 108.8 11 0.03 11 0.0943 96 (–)*** A B A –12.7 11 0.0030 A A –0.2498 (–)*** 0.0000 A B –24.3 –1.116 0.6150 23 B A 0 A B A A A 41 B 7 A 13.7 (–)* A 7.5 (–)*** –11.2 (–)*** A –25.7 0 B A B Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 88 85 88 0 0 88 0 0 0 0 0 30 30 0 0.0000 30 0.1114 –0.9957 30 0.0121 –0.008112 80 0.01414 0.9071 7.6 8 0 (–)*** 0 –31.3 (+)** 17 –3.2 5.5 0 0.0 Table 30. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; in., inch; mL, milliliter; hplc, high-performance liquid chromatography; µg/L, micro at 25 degrees °C, degree 146 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter -value Slope Median Significance Change p *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first record Period (years) censored Percentage Number Censored ) 36 0 011 <.00001–0.5897 28 (–)***–20.6 3 Seasonal Kendall season-edited data bottom samples. analysis results for site 8, Carter Reservoir, Trend Calcium, dissolved (mg/L)Calcium, dissolved (mg/L)Magnesium, dissolved (mg/L)Potassium, dissolved Sodium adsorption (ratio)(percent) (mg/L)Sodium, dissolved Sodium Acid-neutralizing capacity (mg/L) (mg/L)Chloride, dissolved 36 36 (mg/L)Fluoride, dissolved (mg/L)Silica, dissolved 36 (mg/L) dissolved Sulfate, 0 0 36 (mg/L as N)Nitrogen, ammonia plus organic 36 36Nitrogen, ammonia (mg/L as N) 0 Nitrite plus nitrate (mg/L as N) (mg/L as P)Phosphorus, dissolved 35 36 0 0 0 34 (mg/L as P)Phophorus, ortho, dissolved 0 0 0 34 0Phosphorus, total (mg/L as P) 18 at 180°C (mg/L)Residue, dissolved 36 11 0 11 0 solids, sum of constituents (mg/L)Dissolved 33 64 0 0 0 4 35 (µg/L)Barium, dissolved 11 34 29 <.00001 <.00001 51 (µg/L)Iron, dissolved 11 0 –0.2046 16 11 33 –0.02230.7898 0 (µg/L)Manganese, dissolved 0.0016 0 32 11 11 17 26 (µg/L)Strontium, dissolved 64 12 61 1.0000 11 (µg/L)Zinc, dissolved 8.8 1.3 <.00001 0 0.0001 0 0 0 25 11 0 91 –0.6231 0 11 22 50 9014 –0.04681 (–)*** 0 (–)*** A 0.0004 36 0.6 30 11 30 0.8823 2.2 0 –22.4 11 27 –17.1 11 17 11 0.04391 36 0 27 0.2 0 0.0003 A 0.6375 36 <.00001 0 (–)*** (–)*** B 0 0.6 11 7 A –0.06811 0.1573 0.0 A A 4 27 29 30 0 B –20.8 –20.3 0 A 0.0003 (+)*** 0.1 2.9 0 3.8 0.0 <.00001 <.00001 26 –0.6581 A 10 A A 15 0.03 –0.4577 143.5 0.0 A 0 *** (+)*** B 0 38 11 43 A 8 37 A A 0 60.6 –22.6 8 0.0612 11 0.02 (–)*** A 0.5328 B (–)*** –0.3049 0.0296 A <.00001 8 A A (–)*** –17.3 B –27.4 –1.161 B 9 0.3872 B B A A A 39.5 9.95 (–)* B 4 (–)*** –31.0 0 7 –27.5 (–)** B B 0 B Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 75 79 74 0 0 87 0 0 0 0 0 30 30 0 <.00001 30 <.00001 –0.9488 –0.08366 0.4324 30 71 6.9 0.0385 0 (–)*** 0.02798 (–)*** 7.4 –33.2 6.5 –30.6 (+)** 0 13.8 0.0 Table 31. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; µg/L, micrograms per liter] at 25 degrees °C, degree Hydrologic and Water-Quality Data 147 3.4 -- than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter grams per liter] -value Slope Median Significance Change p *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first record Period (years) censored Percentage Number Censored ) 36 0 011 0.0100–0.3969 28.5 (–)***–14.1 3 Seasonal Kendall , hplc (µg/L)hplc , hplc (µg/L), 35 35 28 80 0 11 0 A 11 A 0.1716 –0.0784 A 1.9 A 0 A –36.4 season-edited data a b analysis results for site 9, Horsetooth Reservoir (Soldier Canyon Dam), surface samples. Trend Potassium, dissolved (mg/L) (mg/L)Calcium, dissolved (ratio) dissolved (mg/L)Magnesium, dissolved adsorption Potassium, Sodium (percent) (mg/L)Sodium, dissolved Sodium Acid-neutralizing capacity (mg/L) 36 (mg/L)Chloride, dissolved (mg/L)Fluoride, dissolved 36 36 36 0 (mg/L)Silica, dissolved (mg/L) dissolved Sulfate, 0 0 0 0 36 36 011 36 34 0 0 011 0 34 0.0432 0 36 1.0000 0 0 0 11 11 5 0 0 011 0 0 0.0097 0.05150.7 15 11 11 0.2 0.2232 –0.1383 –0.01102 0 0.0025 0 11 0.0396 1.5 11 9.05 0 –0.4926 0 –0.01973 0.0001 0.0 1115 0.5380 (–)*** (–)* 29 0.0 2.4 0.0642 0.0417 –15.4 B –7.7 0 (–)*** (–)** 0.7 0.1041 0.1 –17.0 0.0 2.75 (+)*** –8.6 224.3 (+)** 0 53.9 B Nitrogen, ammonia plus organic (mg/L as N)Nitrogen, ammonia plus organic Nitrogen, ammonia (mg/L as N)Nitrite plus nitrate (mg/L as N) 36Nitrogen, nitrite (mg/L as N) (mg/L as P)Phosphorus, dissolved (mg/L as P)Phophorus, ortho, dissolved 14Phosphorus, total (mg/L as P) at 180°C (mg/L)Residue, dissolved 82 solids, sum of constituents (mg/L)Dissolved 81 39 36 Secchi disk (in.) Transparency, 30 39Coliform, fecal (colonies per 100 mL) 77(µg/L) 34 Chlorophyll- 57 dissolved 32 Chlorophyll- 76 28 11 (µg/L) 67 57Barium, 48 0 dissolved (µg/L)Iron, dissolved 70 52 Manganese, 89 0.0338 0 93 68 29 (µg/L)Strontium, dissolved 74 (µg/L)Zinc, dissolved 31 0 31 0 30 36 0 11 0 43 11 0.0348 42 31 0 60 11 A 15 0.3 A 0 0 A 31 29 0 43 36 A 0.0350 36 23 11 0.0000 0.0000 0 27 A –0.4937 A 30 1 0 0.04 A 19 A –0.5625 0.7456 A 39 11 B 0.0065 A 0.4685 2 A 50 0 B 0 A 0 A 1.066 41 A (–)** 0.04 B18.5 (–)*** A 19 A 11 75 B A –12.9 (–)*** A 3 A –29.6 8 0.4434 0.0001 0 (+)*** A A –0.2706 B –1.229 0.5916 A 0.0 A A 0 54.7 13 37.5 B A B (–)*** 0 5.5 –30.1 –32.7 0 B Oxygen, dissolved (mg/L)Oxygen, dissolved (°C) (standard units)pH, field temperature conductance (µS/cm at 25°C)Specific Water Hardness, total (mg/L as CaCO 88 86 88 86 0 0 0 0 0 0 031 0 31 0.8649 30 0.0000 30 0.3364 0 –0.6607 0.0002 15.45 –0.00384 75 0.02104 7.8 0 7.6 (–)*** 0.0 0 (+)*** –23.9 –1.5 8.7 Table 32. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; in., inch; mL, milliliter; hplc, high-performance liquid chromatography; µg/L, micro at 25 degrees °C, degree 148 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter -value Slope Median Significance Change *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first p record Period (years) censored Percentage Number Censored ) 36 0 0 11 0.0001–0.5048 28.5 (–)***–17.6 3 Seasonal Kendall season-edited data analysis results for site 9, Horsetooth Reservoir (Soldier Canyon Dam), bottom samples. Trend Oxygen, dissolved (mg/L)Oxygen, dissolved (°C) (standard units)pH, field temperature conductance (µS/cm at 25°C)Specific Water Hardness, total (mg/L as CaCO 73 78 84 49 0 0 0 0 0 0 0 0 30 30 30 0.0806 17 0.00000.0212 0.0010 –0.4997 7.1 0.6109 –0.07019 73 7.5 0 (+)* 9.4 (–)*** (–)*** 7.2 –18.6 –24.5 0 0.0 Calcium, dissolved (mg/L)Calcium, dissolved (ratio) (mg/L)Magnesium, dissolved adsorption (mg/L)Potassium, dissolved Sodium (percent) (mg/L)Sodium, dissolved Sodium Acid-neutralizing capacity (mg/L) (mg/L)Chloride, dissolved 36 36 (mg/L)Fluoride, dissolved 36 36 (mg/L)Silica, dissolved 0 (mg/L) dissolved Sulfate, 0 0 (mg/L as N)Nitrogen, ammonia plus organic 36 36 0Nitrogen, ammonia (mg/L as N) 0 Nitrite plus nitrate (mg/L as N) 36 36 0 0Nitrogen, nitrite (mg/L as N) 34 0 0 (mg/L as P)Phosphorus, dissolved 34 11 0 0 (mg/L as P)Phophorus, ortho, dissolved 19 Phosphorus, total (mg/L as P) 36 11 11 0 0 34 45 1.0000 0 at 180°C (mg/L)Residue, dissolved 0 5 11 solids, sum of constituents (mg/L)Dissolved 39 53 0.0001 36 0.0033 (µg/L)Barium, dissolved 36 0 20 43 11 0 0 0 (µg/L)Iron, dissolved 11 0.0054 11 34 15 –0.1742 –0.01957 10 (µg/L)Manganese, dissolved 25 11 64 25 (µg/L)Strontium, dissolved –0.009559 0.2 0.0423 37 41 0 0.0001 44 0.0151 11 (µg/L)Zinc, dissolved 1.5 0 8.95 0 11 26 0.7 69 –0.6692 A –0.02498 0 69 12 0 0.0000 95 11 0 (–)*** 17 (–)*** 0.3881 11 36 29 0 (–)*** 2.3 1715 36 11 0.07629 –19.2 17 0.0 0.0876 32 –13.3 0 A 0.3865 33 17 0.0019 36 B –13.9 0.4192 0 (–)** 0.7 11 (–)*** 19 0.1125 A –0.09884 A 0 B 27 17 31 2 A A 0 –11.2 –22.3 0.0006 0.1 B (+)*** 0 3.2 3.65 53 0.0 0.2979 0.0017 11 A –0.4333 0.04 A 6 346.4 0 A A –0.2881 (+)* 0.12 0 11 11 0 38.5 B 41 0 A 11 48 A 11 0.0875 41.6 A 0 A –28.7 (–)*** A B 11 0.03 0.4980 0.1098 0.0000 (–)*** A B –11.6 A 0.8970 A –1.337 B 17 A 0 B –17.0 A 40 B A A 15 (+)* A B (–)*** 6 7.4 0 A –30.6 0 A B B Table 33. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; µg/L, micrograms per liter] at 25 degrees °C, degree Hydrologic and Water-Quality Data 149 than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter grams per liter] -value Slope Median Significance Change *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first p record Period (years) censored Percentage Number Censored ) 36 0 0 11 0.0161 –0.3353 28 (–)**–12.3 3 Seasonal Kendall , hplc (µg/L), hplc (µg/L) 35 35 0 24 0 69 11 11 0.2313 A –0.07486 2.1 A 0 0.1 –32.3 A A season-edited data a b analysis results for site 10, Horsetooth Reservoir (Spring Canyon Dam), surface samples. Trend Magnesium, dissolved (mg/L)(mg/L) dissolved (mg/L)Calcium, dissolved (ratio) dissolved Magnesium, adsorption Potassium, Sodium (mg/L)(percent) (mg/L)Sodium, dissolved (mg/L) 36capacity Sodium dissolved Acid-neutralizing (mg/L) 36 0Chloride, dissolved 36 (mg/L)Fluoride, dissolved 0 36 Silica, 36 0 0 (mg/L) dissolved Sulfate, 0 0 (mg/L as N)Nitrogen, ammonia plus organic 11 0 34 36Nitrogen, ammonia (mg/L as N) 011Nitrite plus nitrate (mg/L as N) 36 0 Nitrogen, nitrite (mg/L as N) 0.3846 36 0 3611 (mg/L as P)Phosphorus, dissolved 0 0 34 0.1143 (mg/L as P)Phophorus, ortho, dissolved 16 0 0 0Phosphorus, total (mg/L as P) 11 1.0000 at 180°C (mg/L)Residue, dissolved 36 0 34 11 11 solids, sum of constituents (mg/L)Dissolved 6 0 0 30 0 36 0 Secchi disk (in.)Transparency, 44 0.0546 30 1.4Coliform, fecal (colonies per 100 mL) 21 36 1.9996 3411 0 0 0.0234 –0.3529 Chlorophyll- 11 26 0.6 34 18 11(µg/L) 0.06687 Chlorophyll- 33 29 29 11 32 dissolved (µg/L)Barium, dissolved 35 –0.1126 0.8 0.2 1.9483 0 58 (µg/L)Iron, 1.1007 0 32 0 0.0243 0.1376 dissolved (µg/L)Manganese, dissolved 87 11 0 0.0567 94 46 0 20 Strontium, 97 8.95 (+)*** 2.75 (–)* 97 (µg/L)Zinc, dissolved 0.0 12 11 –0.03251 0 0184.5 0 11 0.6458 0.0 11–12.5 0 11 0 0 (–)** 63 11 (+)* 2.4 0.0 11 15 A 0.0688 38 36 36 11 36 B 78.7 32 A –12.9 A 0 16 11 11 A 0.3 0 –0.07948 (–)** A 0.1645 0 11 11 A 0 44 1.3793 0.1 27 11 3.2 –13.8 A 0 A –0.2356 A 0.5629 0 A 11 A 0.0 0 34 0.2486 20 11 1.9991 0.03 38 (–)* 0 0.07 1.2370 A 0.02 B 40 0.01 B 0.0000 11 11 0.03 74 0 –23.8 A –1.258 0 B A B A 1.5075 1.8638 0.01 2 A 38 A 0 8 79.5 21.5 A –6.6 0 B A A A (–)*** A 0 A A 7.1 0–30.4 0 18.5 3 A B A 0.0 B 0 0 14 0.0 B A A pH, field (standard units)(mg/L)(standard dissolved field Oxygen, (°C)pH, temperature conductance (µS/cm at 25°C)Specific Water Hardness, total (mg/L as CaCO 50 48 50 0 0 0 48 0 0 1111 0 0 1.8870 1.0620 0 0.01251 11 11 7.65 0 0.0043 0.0597 7.6 0 –0.158 –0.7928 16.65 1.8 0 66 (–)* 0.0 (–)*** –9.9 –12.3 Table 34. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; in., inch; mL, milliliter; hplc, high-performance liquid chromatography; µg/L, micro at 25 degrees °C, degree 150 Water Quality and Trend Analysis of Colorado–Big Thompson System Reservoirs and Related Conveyances than 20 percent; mg/L, milligrams per liter; µS/cm, microsiemens centimeter -value Slope Median Significance Change p *, greater than 99 percent; change is percent change in median since the first year of *, greater than 99 percent; change is percent in median since the first record Period (years) censored Percentage Number Censored ) 36 00 11 0.0002–0.4982 29 (–)***–17.1 3 Seasonal Kendall season-edited data analysis results for site 10, Horsetooth Reservoir (Spring Canyon Dam), bottom samples. Trend Oxygen, dissolved (mg/L)Oxygen, dissolved (standard units)pH, field conductance (µS/cm at 25°C)Specific temperature (°C)Water Hardness, total (mg/L as CaCO 50 48 50 0 0 48 0 0 0 0 0 11 0 11 11 0.0069 0.0709 –0.8994 11 0.1716 –0.09875 –0.00826 70 0.0134 5.2 7.3 0.06656 (–)*** (–)* 7.45 –13.1 0 –18.8 (+)** –1.2 10.4 Calcium, dissolved (mg/L)Calcium, dissolved (mg/L)Magnesium, dissolved (mg/L)Potassium, dissolved Sodium adsorption (ratio) (mg/L)Sodium, dissolved Sodium (percent)Acid-neutralizing capacity (mg/L) (mg/L)Chloride, dissolved 36 36 (mg/L)Fluoride, dissolved 36 (mg/L)Silica, dissolved (mg/L) dissolved Sulfate, 0 0 36 (mg/L as N)Nitrogen, ammonia plus organic 36 36 0Nitrogen, ammonia (mg/L as N) Nitrite plus nitrate (mg/L as N) 0 36 0 0 Nitrogen, nitrite (mg/L as N) 34 0 0 36 0 (mg/L as P)Phosphorus, dissolved 34 (mg/L as P)Phophorus, ortho, dissolved 20 0 36Phosphorus, total (mg/L as P) 11 0 11 0 0 34 36 0 at 180°C (mg/L)Residue, dissolved 4 11 56 31 solids, sum of constituents (mg/L)Dissolved 0.0001 36 0.0070 0 (µg/L)Barium, dissolved 32 0 11 14 36 0 0 12 (µg/L)Iron, dissolved 0.0239 11 11 –0.1634 33 –0.01736 11 (µg/L)Manganese, dissolved 19 11 33 21 1.0000 0 (µg/L)Strontium, dissolved 39 34 34 0 0.0020 0.0759 1.5 (µg/L) 11Zinc, dissolved 0 9.1 35 11 0 11 53 –0.5249 66 –0.01957 A 0 0 94 11 0.0000 11 11 1.9892 (–)*** (–)*** 0.9048 11 36 0.7 0 30 2.3 11 35 0.09665 32 0 11 –11.9 0.133 0.0099 –17.8 11 A 0.2 35 0.1157 11 0.0029 35 B 1 0.0518 0.7 (–)* 0 0.1971 11 (–)*** 3 –0.09941 15 A 25 B A 3 11 11 A A 0 0 –17.4 0.1 B 3 0.0568 (+)*** –8.9 3.2 3.85 9 0.0 1.0000 13 0.2788 A 9 (+)** –0.2659 0.04 A 0 885.2 A 0.0 (+)*** A 0.155 (–)*** 0.4263 0 11 52 B 40 10.3 11 81.3 A –28.8 0 11 42 A 11 (+)* 0.2815 A A 0.1998 B 0.0295 11 0.7407 (–)* 0.0001 0 B B A A B 0 –1.056 A 0 A –7.0 B 17.5 A 40.5 13 11.9 A A 21 B A 0 (–)*** 0 A –24.8 0 0.0 B B A A Table 35. Table *, greater than 90 percent; **, 95 ** trend; significance: trend; (–), downward [0, no trend; (+), upward record; A, no trend computation because nondetects greater than 50 percent; B, slope Celsius; Celsius; µg/L, micrograms per liter] at 25 degrees °C, degree