Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada, Through September 1998

By Timothy G. Rowe1, Dina K. Saleh2, Sharon A. Watkins1, and Charles R. Kratzer3

1 U.S. Geological Survey, Carson City, Nevada. 2 California State University, Sacramento, California. 3 U.S. Geological Survey, Sacramento, California.

U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 02-4030

Prepared in cooperation with the LAHONTAN REGIONAL WATER QUALITY CONTROL BOARD TAHOE REGIONAL PLANNING AGENCY UNIVERSITY OF CALIFORNIA, DAVIS

Carson City, Nevada 2002

Cover photograph: Incline Creek inflow to Lake Tahoe, looking south from mouth near Incline Village, Nev., June 1999. Photograph by Timothy G. Rowe, U.S. Geological Survey. U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY CHARLES G. GROAT, Director

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.

All World Wide Web links that appear in this document were current only at the time of publication and are not maintained.

For additional information contact:

District Chief U.S. Geological Survey 333 West Nye Lane, Room 203 Carson City, NV 89706–0866 email: [email protected] home page: http://nevada.usgs.gov CONTENTS

ABSTRACT...... 1 INTRODUCTION ...... 2 Background ...... 2 Acknowledgements ...... 2 Purpose and Scope ...... 8 ENVIRONMENTAL SETTING ...... 8 Subdivided Areas ...... 8 Climate ...... 12 METHODS...... 18 Streamflow ...... 18 Watershed-Drainage Information...... 18 Water-Quality Data...... 18 Field Measurements...... 18 Nutrients and Suspended Sediment ...... 18 Nutrient and Suspended-Sediment Load Estimation ...... 19 ESTIMATOR Program ...... 19 FLUX Program ...... 19 Trend Calculations ...... 20 RESULTS ...... 20 Streamflow ...... 20 Water-Quality Data...... 29 Field Measurements...... 29 Water Temperature ...... 29 Specific Conductance...... 29 pH...... 29 Dissolved Oxygen ...... 29 Nutrients and Suspended Sediment ...... 41 Dissolved Nitrite Plus Nitrate Nirtogen ...... 41 Dissolved Ammonia Nitrogen...... 41 Total Ammonia and Organic Nitrogen...... 41 Soluble Reactive Phosphorus...... 41 Total Phosphorus...... 41 Biologically Reactive Iron ...... 52 Suspended Sediment ...... 52 ConcentrationVersus Time and Streamflow...... 52 Load Estimations ...... 52 Comparison of Nutrient and Suspended-Sediment Load Estimations...... 52 Monthly Loads from Primary and Secondary Stations...... 52 Dissolved nitrite plus nitrate nitrogen ...... 65 Dissolved ammonia nitrogen ...... 65 Total nitrogen...... 65 Soluble reactive phosphorus...... 65 Total phosphorus...... 65 Biologically reactive iron ...... 65 Suspended sediment ...... 65 Index Station Monthly Loads...... 65 Incline Creek near Crystal Bay...... 75 Upper Truckee River at South Lake Tahoe...... 75 Watershed-Load Comparison...... 75 Within-Watershed Station Load Comparisons...... 75 Yields and Ranks...... 89

CONTENTS III Primary Stations...... 94 Within-Watershed Stations...... 94 Trends in Concentrations...... 94 SUMMARY...... 114 REFERENCES CITED ...... 115

APPENDICES

1. Water-Quality and Streamflow Information on the Internet ...... 117 2. Estimated Nutrient and Suspended-Sediment Monthly Loads ...... 117

FIGURES

1–7. Map showing: 1. Lake Tahoe Basin and selected monitored watersheds...... 3 2. Incline Village area, Nev., and LTIMP sampling stations...... 11 3. Glenbrook area, Nev., and LTIMP sampling stations ...... 12 4. Stateline area, Nev., and LTIMP sampling stations ...... 13 5. South Lake Tahoe area, Calif., and LTIMP sampling stations...... 14 6. Tahoe City to Meeks Bay area, Calif., and LTIMP sampling stations...... 15 7. Geology of selected monitored watersheds in Lake Tahoe Basin...... 16 8. Graphs of: (A) total annual precipitation water years 1915–98, Tahoe City, Calif., and (B) Median monthly precipitation water years 1915–98 and 1988–98 at a national weather station at Tahoe City, Calif...... 17 9. Map showing average annual runoff for 10 primary LTIMP stations for water years 1989–98...... 25 10. Map showing unit runoff and unit-runoff rank for 10 primary LTIMP stations for water years 1988–98 ...... 26 11. Plots for Incline Creek near Crystal Bay, a representative LTIMP gage station, for water years 1988–98: (A) Annual discharge, and (B) Median monthly and seasonal runoff...... 27 12. Plots for Upper Truckee River at South Lake Tahoe, a representative LTIMP gage station: (A) Annual discharge for water years 1984–98, and (B) Median monthly and seasonal runoff for water years 1988–98 ...... 28 13. Time-series plots of nutrient and suspended-sediment concentrations for Incline Creek near Crystal Bay...... 57 14. Time-series plots of nutrient and suspended-sediment concentrations for Upper Truckee River at South Lake Tahoe...... 58 15. Plots of nutrient and suspended-sediment concentrations versus streamflow for Incline Creek near Crystal Bay 59 16. Plots of nutrient and suspended-sediment concentrations versus streamflow for Upper Truckee River at South Lake Tahoe...... 60 17–19. Plots for Incline Creek near Crystal Bay, a representative LTIMP station: (A) monthly loads, and (B) loads by month and season with seasonal medians: 17. Nitrogen nutrients, water years 1988–98 ...... 76 18. Phosphorus nutrients, water years 1988–98...... 77 19. Biologically reactive iron and suspended-sediment concentrations, water years 1991–98 and 1988–98, respectively ...... 78 20–22. Plots for Upper Truckee River at South Lake Tahoe, a representative LTIMP station: (A) Monthly loads, and (B) loads by month and season with seasonal medians: 20. Nitrogen nutrients, water years 1984–98 and 1989–98 ...... 79 21. Phosphorus nutrients, water years 1984–98...... 80 22. Biologically reactive iron and suspended-sediment concentrations, water years 1984–98...... 81

IV Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada 23–29. Map showing median monthly loads for 10 primary LTIMP stations for period of comparison, water years 1988–98: 23. Dissolved nitrite plus nitrate nitrogen...... 82 24. Dissolved ammonia...... 83 25. Total nitrogen ...... 84 26. Soluble reactive phosphorus ...... 85 27. Total phosphorus ...... 86 28. Biologically reactive iron...... 87 29. Suspended sediment...... 88 30–31. Graphs showing within-watershed comparison of streamflow and nutrients and suspended-sediment concentrations at selected stations: 30. Three Incline Creek watershed stations, water years 1991–98...... 90 31. Three Upper Truckee River watershed stations, water years 1991–98...... 92 32–38. Map showing median monthly yields and yield ranks for 10 primary LTIMP stations for period of comparison, water years 1988–98: 32. Dissolved nitrite plus nitrate nitrogen...... 95 33. Dissolved ammonia...... 96 34. Total nitrogen ...... 97 35. Soluble reactive phosphorus ...... 98 36. Total phosphorus ...... 99 37. Biologically reactive iron...... 100 38. Suspended sediment...... 101 39. Map showing overall yield ranks for 10 primary LTIMP stations for period of comparison, water years 1988-98 ...... 102 40–46. Map showing trends in nutrient and suspended-sediment concentrations for 10 primary LTIMP stations for period of records: 40. Dissolved nitrite plus nitrate nitrogen...... 107 41. Dissolved ammonia...... 108 42. Total nitrogen ...... 109 43. Soluble reactive phosphorus ...... 110 44. Total phosphorus ...... 111 45. Biologically reactive iron...... 112 46. Suspended sediment...... 113

TABLES

1. Information for current USGS LTIMP primary and secondary surface-water quality sampling/gage stations and miscellaneous water-quality stations in the Lake Tahoe Basin, California and Nevada...... 4 2. LTIMP surface-water sample analysis; constituents, abbreviations, parameter codes, and reporting levels ...... 7 3. Drainge information for LTIMP monitored watersheds and unmonitored watersheds in the Lake Tahoe Basin.. 9 4. Streamflow summary statistics through water year 1998 for LTIMP gaging stations in the Lake Tahoe Basin... 21 5. Flood frequency information for LTIMP and USGS gaging stations in the monitored watersheds in the Lake Tahoe Basin...... 30 6–16. Data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous water-quality stations, by area, in the Lake Tahoe Basin: 6. Water temperature ...... 32 7. Specific conductance...... 34 8. pH...... 36 9. Dissolved oxygen...... 38 10. Dissolved nitrite plus nitrate nitrogen...... 42

CONTENTS V 11. Dissolved ammonia nitrogen...... 44 12. Total organic plus ammonia nitrogen concentration...... 46 13. Soluble reactive phosphorus concentration...... 48 14. Total phosphorus concentration ...... 50 15. Biologically reactive iron concentration ...... 53 16. Suspended-sediment concentration...... 55 17. Comparison of monthly load summary statistics and percent difference for load-estimation programs for the 10 primary LTIMP sampling stations, through water year 1998 in the Lake Tahoe Basin ...... 61 18. Nutrient and suspended-sediment monthly load summary statistics and median monthly yields for period of comparison and for complete period of record for the 10 primary LTIMP sampling stations in the Lake Tahoe Basin...... 66 19–23. Nutrient and suspended-sediment monthly load and runoff summary statistics, percent change in sums and yields between stations for period of comparison for the LTIMP sampling stations: 19. Incline Creek watershed...... 69 20. Edgewood Creek watershed...... 70 21. Trout Creek watershed ...... 72 22. Upper Truckee River watershed...... 73 23. Ward Creek watershed ...... 74 24. Average percent change in sums among downstream, middle, and upstream stations for nutrients and suspended-sediment monthly loads and runoff, for the periods of comparison in the five multiple- station watersheds in the Lake Tahoe Basin...... 93 25. Trends, P values, and probability plot correlation coefficient values from Seasonal-Kendall and ESTIMATOR results for 10 primary and 10 secondary LTIMP stations...... 103

CONVERSION FACTORS AND VERTICAL DATUM

Multiply By To obtain

acre feet (acre-ft) 0.001233 cubic hectometer cubic foot per second (ft3/s) 0.02832 cubic meter per second foot (ft) 0.3048 meter inch (in.) 25.4 millimeter mile (mi) 1.609 kilometer square mile (mi2) 2.590 square kilometer kilogram (kg) 2.205 pounds kilogram per square kilometer (kg/km2) 5.712 pounds per square mile

Water-Quality Units: microgram per liter (µg/L) microsiemens per centimeter (µS/cm) milligrams per liter (mg/L) kilograms per month (kg/mo) kilograms per square kilometers per month (kg/km2/mo)

Temperature: Degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) by using the formula °F = [1.8(°C)] + 32. Degrees Fahrenheit can be converted to degrees Celsius by using the formula °C = 0.556(°F - 32).

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929, formerly called “Sea-Level Datum of 1929”), which is derived from a general adjustment of the first-order leveling networks of the United States and Canada. NOTE: U.S. Bureau of Reclamation datum for the surface-water elevation of Lake Tahoe is 1.14 feet higher than the National Geodetic Vertical Datum of 1929.

VI Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada, Through September 1998

By Timothy G. Rowe1, Dina K. Saleh2, Sharon A. Watkins1, and Charles R. Kratzer3

ABSTRACT conductance ranged from 13 to 900 microsiemens per centimeter at 25C. pH ranged from 6.7 to The U.S. Geological Survey, in cooperation 10.6. Dissolved-oxygen concentrations ranged with the Tahoe Regional Planning Agency, and the from 5.2 to 12.6 mg/L and from 70 to 157 percent University of California, Davis–Tahoe Research of saturation.1 23 Group, has monitored tributaries in the Lake Tahoe Basin since 1988. This monitoring has character- Loads, yields, and trends of nutrients and ized streamflow and has determined concentra- suspended sediment during water years 1988–98 at tions of nutrients and suspended sediment, which the streamflow gaging stations also are described. may have contributed to loss of clarity in Lake The Upper Truckee River at South Lake Tahoe had Tahoe. The Lake Tahoe Interagency Monitoring the largest median monthly load for five of the six Program was developed to collect water-quality measured nutrients and of suspended sediment, data in the basin. In 1998, the tributary-monitoring while Trout Creek at South Lake Tahoe had the program included 41 water-quality stations in 14 largest median monthly load for the remaining of the 63 watersheds totaling half the area tributary nutrient. Logan House Creek near Glenbrook had to Lake Tahoe. The monitored watershed areas the smallest median monthly loads for all nutrients range from 1.08 square miles for First Creek to and suspended sediment. Seasonal load summaries 56.5 square miles for the Upper Truckee River. at selected stations showed nutrient and sus- Annual and unit runoff for 20 primary and pended-sediment loads were greatest in the spring secondary streamflow gaging stations in 10 months of April, May and June and least in the selected watersheds are described. Water years summer months of July, August, and September. 1988–98 were used to compare runoff data. The Monthly load comparisons also were described for Upper Truckee River at South Lake Tahoe, Calif., five watersheds with multiple stations. had the highest annual runoff and Logan House Incline Creek had the highest combined rank Creek near Glenbrook, Nev., had the lowest. for all nutrients and sediment. Incline Creek had Blackwood Creek near Tahoe City, Calif., had the the largest monthly yields for dissolved nitrite plus highest unit runoff and Logan House Creek had the nitrate nitrogen and soluble reactive phosphorus. lowest. The highest instantaneous peak flow was Third Creek had the second highest combined rank recorded at Upper Truckee River at South Lake and had the largest monthly yields for total nitro- Tahoe during the January 2, 1997, flood event. gen, total phosphorus, biologically reactive iron, Certain water-quality measurements were made in the field. Ranges and median values of 1 U.S. Geological Survey, Carson City, Nevada. those measurements are described for 41 stations. 2 California State University, Sacramento, California. Water temperature ranged from 0 to 23C. Specific 3 U.S. Geological Survey, Sacramento, California.

ABSTRACT 1 and suspended sediment. Edgewood Creek had station types was emphasized during spring snowmelt, the largest monthly yield for dissolved ammonia rain-on-snow events, summer thunderstorms, and fall nitrogen. Logan House Creek had the lowest com- rain events, whether they occurred during day or night. bined rank and the smallest monthly yields for all nutrients and sediment. Background Trends in concentrations are either decreasing or not significant for all nutrients in all sampled Lake Tahoe is within the crest of the Sierra watersheds, with the exception of biologically Nevada Range and lies within the states of California reactive iron. Biologically reactive iron and sus- and Nevada (fig. 1). Lake Tahoe is described as an out- pended sediment show an increasing trend in three standing natural water resource and is famous for its watersheds and decreasing or no significant trend alpine setting and deep, clear waters. Protection of in the other seven watersheds. these clear waters has become very important in the past half century, because water clarity has been decreasing by about 1 ft/yr (Goldman and Byron, INTRODUCTION 1986). This decrease in clarity is mainly due to human activities, which have increased dramatically in the Since the early 1970’s, monitoring stream water quality in the Lake Tahoe Basin has been done by the Lake Tahoe Basin since 1960. Tahoe Regional Planning Agency (TRPA), the U.S. Increased nutrient concentrations within Lake Geological Survey (USGS), the Tahoe Research Group Tahoe are considered the primary cause of algal growth, (TRG) of the University of California at Davis, and and thereby loss of lake water clarity. Suspended sedi- State and local agencies. The Lake Tahoe Interagency ment also is of concern, because nutrients attach to and Monitoring Program (LTIMP) was began in 1978 and are transported by sediment particles. Within the Lake described in Rowe (2000), Boughton and others (1997), and Rowe and Stone (1997). A tributary-monitoring Tahoe Basin, one of the major pathways for nutrient and program, a cooperative effort by TRPA, USGS, and sediment transport to the lake is streamflow. Transport TRG, began in water year 1988 and continues currently of those materials has been accelerated progressively (2002). Fourteen of the 63 watersheds in the Lake by development activities such as urbanization of wet- Tahoe Basin (fig. 1) are monitored in the LTIMP net- lands and steeply sloping terrain around the lake mar- work including a total of 41 tributary stations (table 1). gin. Data collected from the LTIMP network stations Public concern for the clarity of Lake Tahoe has include streamflow, water-quality parameters, nutri- increased over the years. In 1986 and 1996, voters in ents, and sediment (table 2). Schedules for sampling Nevada passed bond acts to fund construction projects were determined by the type of station (primary, sec- to reduce erosion and the transport of nutrients and sed- ondary, or miscellaneous). A primary station has a con- iments to Lake Tahoe in the Nevada portion of the Lake tinuous streamflow gage and 25–40 water-quality Tahoe Basin. The Lake Tahoe Interagency Monitoring samples are collected annually at near mouth locations in 10 watersheds. A secondary station has a continuous Program (LTIMP) was developed to collect water-qual- streamflow gage and 20–30 water-quality samples are ity data in the basin. LTIMP water-quality data collected annually at 10 multiple-station sites in 5 of 10 and streamflow data are available to the public through watersheds. Samples are collected from primary and several USGS internet web sites (app. 1). secondary stations during monthly baseline periods and runoff events. A miscellaneous station is a sampling station, urban-runoff sampling station, or water-tem- Acknowledgements perature network station. The 12 miscellaneous sampling stations are ungaged and 6–10 water-quality Dr. John Reuter, Patty Arneson, and Loren samples are collected annually (mainly during snow- Hatch, all of the University of California at Davis, melt and storm-runoff periods). Sampling at the three contributed long-term nutrient data.

2 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada County (mi) length Channel Channel -quality stations in the the in stations -quality -quality stations in the the in stations -quality (mi) Distance from mouth from Altitude sea level) (feet above (feet above ) 2 area (mi Drainage Drainage Misc. 6.57 6,240 .01 5.52 Douglas Misc. 1.08 6,410 .10 1.70 Douglas Misc. 3.75 6,320 .48 3.44 Douglas Misc. 1.01 6,760 1.76 1.20 Washoe Misc. 4.32 7,350 3.04 4.01 Washoe Misc. 4.48 6,720 1.84 5.21 Washoe Misc. 1.30 6,880 1.71 2.25 Washoe Misc. 1.97 6,250 .02 3.94 Washoe Misc. 1.37 6,250 .02 3.02 Washoe Misc. 1.07 6,280 0.08 2.26 Washoe station Type of Primary 2.09 6,640 .30 3.00 Douglas Primary 6.69 6,240 .17 4.49 Washoe Primary 4.10 6,240 .09 3.83 Douglas Primary 6.02 6,240 .13 6.92 Washoe Secondary 4.54Secondary 6,320 2.85 6,920 .86 1.86 3.80 Washoe 2.80 Washoe r r r r r r r r r r r r r r r r 54 24 04 51 17 20 32 38 46 20 39 44 38 30 35 18 b b b b b b b b b b b b b b b b 56 56 56 55 56 55 56 56 56 56 56 56 57 57 58 59 p p p p p p p p p p p p p p p p 119 119 119 119 119 119 119 119 119 119 119 119 119 119 119 119 r r r r r r r r r r r r r r r r 05 08 00 12 44 32 52 25 47 15 47 46 35 58 00 26 b b b b b b b b b b b b b b b b 58 04 04 05 14 15 15 14 16 05 15 15 14 14 15 14 p p p p p p p p p p p p p p p p Latitude Longitude Glenbrook area (fig. 3) (fig. area Glenbrook Incline 2) Village area (fig. Station number 10336735 39 10336700 39 10336692 39 10336694 39 103366993 39 103366997 39 103366958 39 /s, cubic feetper second; ND, not determined; Misc., miscellaneous] 3 Station name Station , square miles; ft 2 North Logan House Creek at Highway 50 near near 50 Highway at Creek House Logan North Glenbrook, Nev. Incline near Crystal CreekLakeshore (above Dr.) Bay, Nev. Incline Creek above Tyrol Village near Incline Incline near Village Tyrol above Creek Incline Nev. Village, near County atIncline Dr. Club Creek Tributary Nev. Village, Incline Third Creek below unnamed tributary near Incline Incline near tributary unnamed below Creek Third Nev. Village, Wood Creek Jenniferabove St.Wood near Incline Nev. Village, Wood Creek near mouth (atWood near Lakeshore Dr.) Nev. Bay, Crystal . Information for current USGS LTIMP primary and secondary surface-water quality sampling/gage stations and miscellaneous water miscellaneous and stations sampling/gage quality surface-water primary secondary and LTIMP USGS current for . Information . Information for current USGS LTIMP primary and secondary surface-water quality sampling/gage stations and miscellaneous water miscellaneous and stations sampling/gage quality surface-water secondary and primary LTIMP USGS current for Information . 9 Nev. Village, Incline at 28 Highway at Creek Incline 103366995 39 8 7 6 Nev. Village, Incline at Blvd. Village at Creek Third 103366965 39 5 Third Creeknear (atLakeshore Nev. Crystal Dr.) Bay, 10336698 39 4 3 2 Second Creek at Lakeshore near Crystal Dr. Nev. Bay, 10336691 39 1 First Creek(at Highway 28)Nev. near Crystal Bay, 10336688 39 Map 16 near EdgewoodCreek Stateline, at LakeTahoe Nev. 10336765 38 15 14 Logan House Creek near Glenbrook, Nev. 10336740 39 13 Glenbrook Creek atHighway Old nearGlenbrook, Nev. 10336725 39 10 11 12 Glenbrook Creek(near mouth) at Glenbrook, Nev. 10336730 39 number Lake Tahoe Basin, California and Nevada and California Basin, Tahoe Lake Table 1 mi miles; mi, [Abbreviations: Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake Table 1

4 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada El El El El El El El Dorado Dorado Dorado Dorado Dorado Dorado Dorado County (mi) length Channel Channel -quality stations in the the in stations -quality (mi) Distance Distance from mouth Altitude sea level) (feet above (feet above ) 2 ND 6,270 .00 ND Douglas 0.47 6,240 0.23 1.80 Douglas area (mi 41.0 6,230 .10 12.1 36.7 6,240 2.75 9.45 40.4 6,240 1.50 10.7 12.8 6,260 .01 7.95 56.5 6,230 .10 21.3 Drainage Drainage Misc. Misc. Misc. .80 7,000Misc. 1.10 1.40 Douglas Misc. Misc. .73 7,160 3.76 1.77 Douglas Misc. urban urban (gage) station Type of Primary 5.61 6,270 .86 4.67 Douglas Primary Primary Primary Primary (sample) Secondary 3.13Secondary 6,640 .63 6,480 1.63 3.90 .25 Douglas 1.20 Douglas Secondary 23.1Secondary 6,270 7.41 6,850 4.10 8.10 9.20 3.00 temperature temperature temperature ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ 44 11 10 54 36 00 23 06 17 40 37 04 26 57 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 56 56 56 54 55 54 59 58 58 58 53 58 57 59 ° ° ° ° ° ° ° ° ° ° ° ° ° ° 119 119 119 119 119 119 119 119 119 119 119 119 119 119 ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ 58 58 58 00 24 32 12 44 12 56 00 13 48 04 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 57 57 57 58 57 58 56 54 55 55 58 54 51 56 ° ° ° ° ° ° ° ° ° ° ° ° ° ° Latitude Longitude 38 38 Stateline area (fig. 4) South Lake Tahoe area (fig. 5) (fig. area Tahoe South Lake Station Station number 385758- 385758- 10336795 38 10336790 38 10336750 38 10336775 38 10336612 38 119564401 119561101 103367585 38 Station name Edgewood Edgewood Creek above Tributary Clubhouse near Stateline, Nev. near Creek mouth—east Trout near Bellevue/ Ave. El Dorado Culvert—Highway 50 runoff into Edgewood Creek— Edgewood into runoff 50 Culvert—Highway Nev. 50, Highway upstream, bank, left Edgewood Creek at Palisade Dr. nearEdgewood Creek at Palisade Dr. Nev. Kingsbury, Trout CreekTrout (at Highway 50) at SouthLake Tahoe, Calif. Edgewood Creek below South Benjamin Dr. Dr. Benjamin South below Creek Edgewood near Daggett Nev. Pass, Trout Creek at Pioneer Trail near South Lake Tahoe, near at South Creek PioneerLake Tahoe, Trout Trail Calif. Upper Truckee River at mouth near Venice Dr. Dr. at mouth nearVenice River Upper Truckee near Calif. South Lake Tahoe, . Information for current USGS LTIMP primary and secondary surface-water quality sampling/gage stations and miscellaneous water miscellaneous and stations sampling/gage quality surface-water primary secondary and LTIMP USGS current for . Information Map 17 24 18 19 Edgewood Creek (at Highway50) at Stateline,Nev. 20 10336760 21 38 Eagle 22Rock Creek nearStateline, Nev. Edgewood Creek near Tributary Daggett Pass, Nev. 10336756 38 103367592 38 25 23 27 Cold Creek at mouth near Calif. SouthLake Tahoe, 10336779 38 26Calif. Valley, Creek Trout near(at Tahoe Martin Ave.) 10336780 38 28 29 Creek Trout at USFS Rd. 12N01 near Meyers, Calif. 30 10336770 38 number Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake Table 1

INTRODUCTION 5 El El El El El El El Dorado Dorado Dorado Dorado Dorado Dorado Dorado County (mi) length Channel Channel -quality stations in the the in stations -quality (mi) Distance Distance from mouth Altitude sea level) (feet above (feet above ) 2 area (mi 33.2 6,320 10.0 11.4 50.1 6,280 5.40 16.0 Drainage Drainage gage Misc. 6.35 6,480 .05 5.45 Misc. station Type of Primary 9.73 6,230 .25 5.65 Placer Primary 11.1 6,240 .08 6.12 Placer Primary 7.39 6,250 .04 9.13 Primary 54.0 6,230 1.70 19.7 Secondary 14.2 6,490 17.4 4.00 Secondary 4.96 6,600 3.50 2.40 Placer Secondary 8.97 6,440 1.50 4.40 Placer Secondary 39.3 6,310 9.40 12.0 temperature Discontinued Discontinued r r r r r r r r r r r 05 54 40 24 48 34 24 16 40 03 22 b b b b b b b b b b b 01 00 12 01 10 01 09 00 09 07 59 p p p p p p p p p p p 120 120 120 120 120 120 120 120 120 120 119 r r r r r r r r r r r 47 06 27 35 13 55 56 32 27 07 21 b b b b b b b b b b b 47 48 08 50 08 50 07 52 06 03 55 p p p p p p p p p p p Latitude Longitude Stateline area (fig. 4) Tahoe City to Meeks Bay area (fig. 6) (fig. area Bay to Meeks City Tahoe Station Station number 10336580 38 10336593 38 10336675 39 10336660 39 10336610 38 103366092 38 103366098 38 Station name below confluence near Tahoe City, Calif. confluenceCity, below near Tahoe 10336674 39

Upper Truckee River at SouthUpper River Upper Rd. near Truckee Truckee Calif. Meyers, GrassLakeRd.) CreekGrass near (at Lake Meyers, Calif. Ward Creek at Stanford Rock Trail crossing near Tahoe Creek at crossing StanfordRock Trail near Tahoe Ward Calif. City, Upper Truckee River at Highway 50 above Meyers, Meyers, at Highway50 above River Upper Truckee Calif. Blackwood Creek City, (at Highway 89) nearTahoe Calif. Upper Truckee River at Highway50Upper bridge River Truckee below Calif. Meyers, Upper Truckee River (at Highway 50)Upper River at Truckee South Lake Calif. Tahoe, . Information for current USGS LTIMP primary and secondary surface-water quality sampling/gage stations and miscellaneous water miscellaneous and stations sampling/gage quality surface-water primary secondary and LTIMP USGS current for . Information Map 36 35 41 Creek Ward 40 34 near Upper River Meyers, Truckee Calif. 10336600 38 39Pines, Creek Calif.at State Highway 89nearTahoe Ward 10336676 39 33 38 32 31 37 General Creek(at Highway Calif. 89)near MeeksBay, 10336645 39 number Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake Table 1

6 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Table 2. LTIMP surface-water sample analysis; constituents, abbreviations, parameter codes, and reporting levels

[Total nitrogen = total organic plus ammonia nitrogen (TKN) plus dissolved nitrite plus nitrate (NO2 + NO3); soluble reactive phosphorus (SRP) = dissolved orthophosphate phosphorus. Abbreviations: mg/L, milligrams per liter; Ng/L, micrograms per liter; pC, degrees Celsius; ft3/s, cubic feet per second; NS/cm, microsiemens per centimeter]

Constituent Abbreviation Parameter code Reporting level

Nutrients

Dissolved nitrite plus nitrate nitrogen NO2 + NO3 00631 0.002 mg/L

Dissolved ammonia nitrogen NH4 00608 0.003 mg/L Total organic plus ammonia nitrogen (Kehldahl) TKN 00625 0.035 mg/L Soluble reactive phosphorus SRP 00671 0.001 mg/L Total phosphorus TP 00665 0.002 mg/L Biologically reactive iron BFe 46568 3.0 Ng/L

Sediment Suspended-sediment concentration SS 80154 1 mg/L Suspended-sediment discharge SSQ 80155 0.01 tons/day Sand break (higher suspended-sediment 70331 1 percent finer concentrations only)

Field Measurements Water temperature WT 00010 0.5pC Air temperature AT 00020 0.5pC Gage height GH 00065 0.01 ft Instantaneous discharge Q 00061 0.01 ft3/s Specific conductance SC 00095 1 NS/cm pH 00400 0.1 units Dissolved oxygen DO 00300 0.1 mg/L Barometric pressure BP 00025 1 mm Dissolved oxygen (saturation, percent) DO% 00301 1 percent Weather (clear, cloudy, rain, snow, thunderstorm) 00041 Hydrologic event (routine, storm, snowmelt) Stage conditions (stable, rising, falling) Sample method (equal width increment, dip) 82398 Sampler type (depth-integrated, handheld 48/81/59; 84164 depth-integrated 74) Sample collecting agency 00027 Sample analyzing agency 00028

INTRODUCTION 7 Purpose and Scope Creek to 56.5 mi2 for the Upper Truckee River. Drain- age perimeters range from 5.60 mi for North Logan This report presents summaries of the streamflow, House Creek to 53.9 mi for Upper Truckee River. The water-quality, and nutrient and suspended-sediment mainstream channel lengths range from 2.34 mi for concentrations data for 41 selected tributary stations in First Creek to 21.4 mi for the Upper Truckee River; 14 watersheds. Estimated monthly loads, yields, and channel elevations range from 6,229.1 ft (maximum trends for nutrients and suspended sediment also are lake level) to 9,170 ft for Third Creek. The maximum presented for 20 sampling stations in 10 watersheds in basin elevation (10,890 ft) occurs in the Trout Creek the Lake Tahoe Basin. These estimates were derived watershed. General Creek and North Logan House using concentration and daily streamflow data com- Creek have the largest areas in the lower elevation bined from the LTIMP study (water years 1988–98; groups from 6,229 to 8,000 ft (Jeton, 1999, fig. 5). from October 1, 1987, to September 30, 1998) and from Third Creek watershed has the largest area in the high- previous monitoring data. All annual data used in this est elevation groups from about 9,000 to 11,000 ft. report are based on water years. Estimations of load are reported here only when daily streamflow records exist. Comparisons between the 10 watersheds and within Subdivided areas watershed comparisons in 5 multiple-site watersheds The 14 watersheds monitored in the LTIMP study also are presented. were subdivided into 5 areas: Incline Village, Nev. (northeast), Glenbrook, Nev. (east), Stateline, Nev. ENVIRONMENTAL SETTING (southeast), South Lake Tahoe, Calif. (south), and Tahoe City to Meeks Bay, Calif. (west). Monitoring The elevation of Lake Tahoe, averaging about stations in each of the areas are shown in figures 2–6. 6,224 ft above sea level, is greater than any other lake The Incline Village (northeast) area has 11 sam- of its size in the United States. The maximum length pling stations (2 primary, 2 secondary, and 7 miscella- and width of the lake is about 22 mi by 12 mi. The level neous; fig. 2). Features in the Incline Village area that of Lake Tahoe is controlled by a 6-ft high dam at the might affect stream water quality include Highways 28 Truckee River outlet. A Federal Court Decree limits the and 431 (Mt. Rose Highway), concentrated develop- maximum permissible elevation of Lake Tahoe to ment in the lower elevations, two golf courses, and one 6,229.1 ft, U.S. Bureau of Reclamation (BOR) datum, ski resort. Incline Lake in the Third Creek watershed is which equals 6,227.96 ft above sea level. The USGS the largest impoundment in the area and some diver- water-level gage at Tahoe City, Calif., records lake- sions from upper Third Creek to Ophir Creek can occur surface elevation; the maximum recorded level was at times. Geology in this area consists mainly of intru- 6,231.26 (BOR datum) in July 1907 and the minimum sive igneous rocks and unconsolidated sediments with recorded level was 6,220.26 ft (BOR datum) on some volcanic rocks (fig. 7; Cartier and others, 1994). November 30, 1992. The average depth of the lake is The Glenbrook (east) area has four sampling sta- 1,000 ft and the greatest depth is about 1,636 ft (Smith tions (two primary and two miscellaneous; fig. 3). Fea- and others, 1999). The total Lake Tahoe Basin area is tures in the Glenbrook area that might affect stream 506 mi2, consisting of 192 mi2 in lake-surface area and water quality include U.S. Highway 50, an old highway 314 mi2 in surrounding watershed area, and has a drain- route, previous logging activities, and unpaved logging age perimeter of 138 mi (Cartier and others, 1995, roads. Within the Glenbrook area, Logan House Creek plate). watershed is largely undeveloped, except for historic The 14 watersheds monitored in this study repre- logging. Geology in this area consists mainly of intru- sent half of the Lake Tahoe Basin watershed land area sive igneous rocks with some volcanic rocks, metamor- at 157 mi2, with an average area per watershed of phic rocks, and unconsolidated sediments (fig. 7). 11.2 mi2. The remaining 49 unmonitored watersheds The Stateline area (southeast) area has eight sam- also cover 157 mi2 with an average area per watershed pling stations (one primary; two secondary; five miscel- of 3.2 mi2. Specific watershed information for the 14 laneous which include two urban-runoff stations; fig. monitored watersheds derived from Cartier and others 4). Features in the Stateline area that might affect (1995) is listed in table 3. The drainage area of the stream water quality include U.S. Highway 50, Nevada selected watersheds ranges from 1.08 mi2 for First State Route 207 (Kingsbury Grade), concentrated

8 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada 0 0 0 0 0 0 0 0 0 0 (0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (<1) 0.41 0.06 (1.0) (1.0) <0.01 Between 10,ft 001–11,000 (percent of total) 0 0 0 0 0 (0) (0) (0) (0) (0) (16) (24) (14) (18) 6.59 2.83 0.33 2.06 0.07 0.28 0.25 0.08 (5.0) (5.0) (1.0) (7.0) Between 9,001–10,000 ft (percent of total)

) 2 (13) (29) (31) (15) (33) (13) (36) (36) (35) (30) (40) 1.46 12.0 17.5 0.30 1.00 0.71 0.04 0.53 2.18 2.41 0.69 0.41 0.43 (4.0) (4.0) Between 8,001–9,000 ft 8,001–9,000 (percent of total) Drainage area (miDrainage area (50) (19) (29) (55) (45) (60) (86) (65) (13) (45) (33) (38) (36) 5.60 7.83 16.4 4.20 2.99 1.29 0.94 2.67 0.78 3.01 0.65 0.52 0.39 Between 7,001–8,000 ft 7,001–8,000 (percent of total) (37) (35) (35) (41) (35) (10) (22) (16) (18) (18) (14) (17) 4.14 14.4 19.8 3.13 2.32 0.15 0.11 0.90 0.97 1.21 0.35 0.19 0.18 (7.0) Between 6,228–7,000 ft 6,228–7,000 (percent of total) altitude (ft above (ft above sea level) Maximum Maximum range range altitude Channel Channel (ft above sea level) length (miles) Channel Channel (miles) Drainage Drainage perimeter , square, Symbol: miles. <, less than. Note:Data from Jorgensonothers and (1978), and Cartierothers and (1995)] 2 ) 2 1.09 5.60 2.53 6,229–7,880 8,560 area (mi 56.5 53.9 21.4 6,229–7,920 10,060 Drainage Drainage . Drainage basin information for LTIMP monitored and unmonitored watersheds in the Lake Tahoe Basin, California and Nevada Nevada and California Basin, Tahoe Lake the in watersheds unmonitored and monitored LTIMP for information basin Drainage .

Watershed Blackwood Creek 11.2 16.1 6.20 6,229–7,140 8,880 Trout CreekTrout Upper Truckee River 41.2 CreekGeneral 34.8 12.2 7.63 6,229–7,760 17.8 10,890 9.17 6,229–7,680 8,720 Edgewood CreekEdgewood 6.64 13.3 5.53 6,229–7,830 9,590 Logan House Creek House Logan 2.15 7.23 3.30 6,229–8,240 8,820 North LoganHouse Creek Glenbrook Creek 4.10 10.6 3.92 6,229–7,710 8,810 Third Creek CreekIncline 6.05 15.7 6.70 11.8 7.05 6,229–9,170 4.66 10,340 6,229–8,400 9,220 Wood Creek Creek Wood 1.97 9.27 3.94 6,229–8,080 9,610 Second Creek 1.37 7.23 3.04 6,229–8,840 9,610 First Creek Creek First 1.08 5.63 2.34 6,229–8,500 9,270 Table 3 mi miles; mi, feet; ft, [Abbreviations:

ENVIRONMENTAL SETTING 9 0 (0) (<1) 0.47 0.03 Between 10,ft 001–11,000 (percent of total) inued 0 (0) 12.5 (8.0) 0.89 Between 9,001–10,000 ft (percent of total)

) 2 (26) (12) 40.8 1.17 2.91 Between 8,001–9,000 ft 8,001–9,000 (percent of total) Drainage area (miDrainage area 52 (33) (48) 4.68 3.71 Between 7,001–8,000 ft 7,001–8,000 (percent of total) (33) (40) 51.7 3.69 3.90 Between 6,228–7,000 ft 6,228–7,000 (percent of total) altitude (ft above (ft above sea level) Maximum Maximum range range altitude Channel Channel (ft above sea level) 6,229–9,170 10,890 (6.18) 86.5 length (miles) Channel Channel (miles) Drainage Drainage perimeter ) 2 area (3.20) (mi (11.2) 157 314192506 75.2 138 10,890 6,228 10,890 157 Drainage Drainage ) ) . Drainage basin information for LTIMP monitored and unmonitored watersheds in the Lake Tahoe Basin, California and Nevada—Cont and California Basin, Tahoe Lake the in watersheds unmonitored and monitored LTIMP for information basin Drainage . Watershed average Lake Tahoe Lake Tahoe watershed area 49 unmonitored unmonitored 49 watersheds (average surface Lake Tahoe area total Tahoe Lake basin 14 monitored monitored 14 watersheds ( Ward CreekWard 9.75 14.6 5.90 6,229–7,040 8,880 Table 3

10 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada 120°00' 119°56'

reek C

° 39 20' Third

Creek Galena NEVADA CO PLACER CO

WASHOE CO WASHOE 431

Wood Ophir Incline Creek First Nevada Second Creek California Lake Incline Creek Creek Creek

Wood reek C Griff 7 Incline Creek

Second T Tributary

ird

F ir s t

C r e 11 e R GE

k Creek 4 o C sewo o u

6 n Creek t o d r RAN C y 10

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b in l c Creek n 267 D I 28 r i

° v 39 15' e 2 Lakes 9 1 hore InclinIncline VilVillagelage SON KiKings 200 3 R Creek BeBeach 8 A

LakeLake 5 Road C 400 Mill 10 0 60 0 0 TTahoeahoe CrCrystatal BayBay

0 3 MILES

0 3 KILOMETERS

EXPLANATION Primary or secondary water-quality station 5 1 Miscellaneous water-quality station

Figure 2. Incline Village area, Nev., and LTIMP sampling stations. development along Route 207, part of one ski resort, temperature network stations; fig. 5). Features in the and one golf course. Numerous small ponds along South Lake Tahoe area that might affect stream water Edgewood Creek, including one just above Edgewood quality include U.S. Highway 50, California State Creek at Stateline, can affect quality of water and Highway 89, Pioneer Trail, many unpaved roads and streamflow. Geology in this area consists mainly of trails, concentrated development in the lower eleva- intrusive igneous rocks and unconsolidated sediments tions, one ski area, two golf courses, and reclamation of (fig. 7). major wetlands. Diversions from the Upper Truckee The South Lake Tahoe (south) area has 13 River watershed are taken from Lower Echo Lake by stations (2 primary, 4 secondary, 1 discontinued gaging the El Dorado Irrigation District and are delivered to station, and 6 miscellaneous which include 5 water- the South Fork American River via tunnel. Geology in

ENVIRONMENTAL SETTING 11 119°57' 119°52'

anyon C

House

SpoonerSpooner hter LakeLake Clear Creek 28 Slaug

° 39 06' 00 14 Glenbrook Creek

GGlleenbnbrookrook 13 k Cr 800 600 Gl o ee 1000 400 enbro k 200 12 1200

Logan Ho th use or C LakeLake N re North Logan 15 e k House Creek TahoeTahoe 14 L og an

ouse H C re ek Logan House Creek

Creek L 39°02' i ncoln

0 3 MILES

0 3 KILOMETERS

EXPLANATION

12 Primary or secondary water-quality station

15 Miscellaneous water-quality station

Figure 3. Glenbrook area, Nev., and LTIMP sampling stations. this area consists mainly of intrusive igneous rocks and Climate unconsolidated sediments with some volcanic rocks For the 1915–98 period of record at the National (fig. 7). Weather Service (NWS) station at Tahoe City, Calif., The Tahoe City to Meeks Bay (west) area has five the average maximum air temperature was 13.5C. sampling stations (three primary and two secondary; The warmest months were June–September, which fig. 6). Features in the west shore area that might affect averaged greater than 20.0C. The average minimum stream water quality include California Highway 89, air temperature was -1.0C. The coldest months were concentrated shoreline development, and part of one December–March which were recorded as less than ski resort. Geology in this area consists mainly of intru- -4.0C. NWS data is available from Western Region sive igneous rocks and unconsolidated sediments with Climate Center internet website at .

12 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada 119°58' 119°52'

ZephyrZephyr CoveCove 1000 39°00' 800

600

400 200

Daggett eek r rib Pass C 22 T k e e k e r r u C B od 16 Edgewo 18 20 19 ek 23 Dagge Creek 17 od Cre t ewo dg E StatelinStateline

LakeLake E a g 21 le

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0 3 MILES

0 3 KILOMETERS

EXPLANATION

19 Primary or secondary water-quality station

22 Miscellaneous water-quality station

Figure 4. Stateline area, Nev., and LTIMP sampling stations.

Precipitation in the Lake Tahoe Basin ranges total annual precipitation for the 1915–98 period of from 30 to 40 in/yr on the eastern side to from 70 to record was 29.77 in. and for the period 1988–98 was 90 in/yr on the western side (Crippen and Pavelka, 37.37 in. Total annual precipitation for 1988, 1990–92, 1970, fig. 9). Precipitation occurs mostly as snow, and 1994 was below the median; for 1989, 1993, and mainly from November through March. Precipitation 1997 was near the median; and for 1995–96 and 1998 also occurs during rain events, rain-on-snow events, was above the median. Years with below median total and summer thunderstorms. annual precipitation may be considered drought years. Total annual precipitation for the Tahoe City, Calif., station is plotted in figure 8A for the period of The years of drought conditions affect the nutrient record 1915–98. Total annual precipitation for the and suspended-sediment loads in the watersheds as less period 1988–98 is highlighted in figure 8A. Median runoff is generated creating decreased loads. In general,

ENVIRONMENTAL SETTING 13 A

50 Median 1988-98 Median 40 1915-98

PRECIPITATION, IN INCHES 20

1915 1918 1921 1924 1927 1930 1933 1936 1939 1942 1945 1948 1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 WATER YEAR

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5 PRECIPITATION, IN INCHES

1.0

0.5

0 Oct Nov Dec Jan Feb Mar April May Jun Jul Aug Sep FALL WINTER SPRING SUMMER (median = 2.38) (median = 4.18) (median = 0.98) (median = 0.16) MONTH/SEASON

Figure 8. Graphs of: (A) total annual precipitation for water years 1915–98, Tahoe City, Calif., and (B) Median monthly precipitation for water years 1915–98 and 1988–98 at a national weather station at Tahoe City, Calif.

ENVIRONMENTAL SETTING 17 drought years produce less runoff and loads and above Watershed-Drainage Information average precipitation years produce more runoff and loads. For this report, drainage areas for sampling The greatest total annual precipitation at Tahoe stations (table 1) and watershed areas (table 3) were City, Calif. for the period of record was 69.21 in. in obtained from either the Tahoe Environmental Geo- 1982 and the least was 8.82 in. in 1977. For the study graphical Information System (TEGIS) project as period, precipitation ranged from a high of 60.87 in. in reported in Cartier and others (1995) or LaRue Smith 1995 to a low of 16.59 in. in 1994. Median monthly pre- (U.S. Geological Survey, written commun., 2001). cipitation for the 1915–98 period of record and the Because of improved geographic technology, these 1988–98 study period are plotted in figure 8B. Precipi- drainage areas supersede previously published values tation was highest from November through March and in Water Resources Data Reports (U.S. Geological lowest from July through September. Also during the Survey, 1989–99,published annually). Drainage-basin study period, precipitation associated with intense con- perimeters and station elevations are in Cartier and vective summer thunderstorms was less than normal or others (1995); and channel elevation ranges, maximum nearly absent as observed by sampling personnel. watershed elevations, and channel lengths are in Jorgensen and others (1978). Distance from mouth and channel length above station (table 1) were deter- METHODS mined from USGS topographic maps.

Streamflow Water-Quality Data

Streamflow was measured and continuous Field Measurements streamflow gaging stations were operated according to USGS methods (Buchanan and Somers, 1969; Water-quality measurements of water tempera- Kennedy, 1983). Periods of missing data for stream- ture, specific conductance, pH, dissolved oxygen, and flow gaging stations were estimated by comparing dissolved-oxygen saturation were made in the field at records with other gaging stations on the same or the time of sampling. All measurements were made in nearby watersheds and with temperature and precipita- accordance with USGS methods (U.S. Geological tion records. Survey, 1998). Air temperatures were measured at Streamflow rates at the time of sampling were the same time as water-quality parameters. determined either by making a current-meter measurement or by using a rating-curve estimate; the latter was Nutrients and Suspended Sediments used if the stage-streamflow relation was available and stable for the particular primary and secondary stations. Samples of nutrient and suspended sediment were When samples were collected during periods of chang- collected using USGS methods (Edwards and Glysson, ing stage, an average stage was calculated using the 1988; U.S. Geological Survey, 1998). Discharge- gage heights observed or recorded at the beginning and weighted samples were integrated by depth and used end of the sampling period. The average streamflow the equal-width increment (EWI) method (Edwards then was obtained by looking up the corresponding and Glysson, 1988) for most of the study. Nutrient sam- value on the rating curve. ples, collected first, were composited and mixed in a Annual unit values of runoff were derived from churn splitter. The nutrient samples were then pre- the average annual runoff (acre-feet) divided by the sta- served and shipped overnight to TRG laboratories in tion drainage area (square miles) and reported as acre- Tahoe City and Davis, Calif., for analysis using LTIMP feet per square mile. Flood-frequency values were cal- procedures described in Hunter and others (1993). culated from annual peak streamflow for periods of Suspended-sediment samples were collected sepa- record for each gaging station using methods described rately, after the nutrient samples, and shipped to the in Thomas and others (1997) and U.S. Interagency USGS Sediment Laboratory in Salinas, Calif., for Advisory Committee on Water Data (1982). analysis using USGS standard guidelines (Guy, 1969).

18 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Nutrient and Suspended-Sediment were reviewed and included in the data set if found Load Estimation acceptable after data verification, and greater than 50 percent were not accepted. Monthly load-estimate Two load calculation computer programs, ESTI- results are reported in kilograms per month from the MATOR (Cohn and others, 1989) and FLUX (Walker, ESTIMATOR program. During extreme streamflow 1996), were investigated for estimating nutrient and events, the program may over-estimate load values suspended-sediment loads for this study. The use of a (Doug Glysson, U.S. Geological Survey, oral com- third computer program, LOADEST2 (Crawford, mun., 2000). Estimated nutrient daily and monthly 1986), was contemplated, but problems encountered in loads used in this report are listed in appendix 2, with running this program with the large LTIMP data set pre- estimated SE, estimated SE PRED, and 95-percent cluded its use. confidence intervals. Loads for the 12 miscellaneous stations were not During lower streamflow events FLUX estimates calculated because the samples were collected mainly of nutrient loads for small watersheds exhibited some during high flow (spring snowmelt and storm) events. unusual fluctuations that were not present in the ESTI- Daily streamflow measurements also do not exist for MATOR results. Thus, estimated values for nutrient these ungaged stations. For load calculations, total loads in this report were taken from ESTIMATOR. nitrogen was obtained by combining total ammonia and organic nitrogen and dissolved nitrite plus nitrate nitrogen. Soluble reactive phosphorus is equivalent dis- FLUX Program solved orthophosphate. FLUX, an interactive computer program used to estimate the loadings of nutrients or other water-quality ESTIMATOR Program constituents such as suspended sediment, is described in Walker (1996). Data requirements for FLUX ESTIMATOR, a log-linear, multiple regression include: constituent concentrations, collected on a model, relates constituent concentrations to as many as weekly to monthly frequency for at least a year; date 16 environmental variables or parameters. The pro- collected; corresponding flow measurements (instanta- gram was developed in 1988 to assist USGS personnel neous or daily mean values); and a complete flow in estimating stream-nutrient loads. ESTIMATOR record (daily mean streamflow) for the period of inter- implements the Minimum Variance Unbiased Estima- est. tor (MVUE) for the use of estimating fluvial transport of nutrients and sediment (Cohn and others, 1989) and Six estimation algorithms are available within the Adjusted Maximum Likelihood Estimator (AMLE) FLUX. For calculations in this report the following for the use of data sets containing censored (less than) were used: (1) flow-weighted concentrations (ratio esti- values (Cohn, 1988 and Cohn and others, 1992). The mate), (2) modified ratio estimate, (3) first order regres- LTIMP data set contains censored values, particularly sion, (4) second order regression, and (5) regression those associated with dissolved ammonia. applied to individual daily streamflow. FLUX maps the ESTIMATOR represents concentrations as a flow versus concentration relation developed from the function of three factors; flow, time, and a seasonal fac- sample record onto the entire flow record to calculate tor. Outputs include daily and monthly load rates and total mass, streamflow, and associated error statistics. annual loads for each calendar and water year. To deter- An option included to stratify the data into groups mine a constituent’s total load for a given month, the based upon flow was used to improve the fit of the indi- estimated daily mean load rate was multiplied by the vidual models. number of days in that month. The 95-percent confi- FLUX was used for monthly suspended-sediment dence interval was calculated in the program by multi- load estimations, which are listed in appendix 2. Esti- plying the standard error of prediction (SE PRED) by mates of suspended sediment from FLUX and ESTI- 1.96, which is the value for a 95 percent confidence MATOR were similar except for overestimates by the interval (G. Baier and others, USGS, Reston, Va., writ- latter program for months that included extreme peak ten commun., 1993). Load estimates with standard events, like the January 1997 flood. Because those errors (SE) less than 30 percent were accepted, between ESTIMATOR flood-load results were well above 30 and 50 percent were marked as questionable and expected reasonable limits for three stations (Black-

METHODS 19 wood, Ward, and Logan House Creeks), estimated val- tions, air and soil temperature, amount of snow on the ues for suspended-sediment loads in this report were ground (if present), soil moisture conditions, types of taken from the FLUX program (app. 2). soil and geology, slope and aspect (Jeton, 1999, figs. 6 and 7), type and amount of vegetation coverage (Jeton, 1999, fig. 8) and other natural conditions across the Trend Calculations basin. Calculations for estimating trends in nutrient and Streams in the same general area can differ widely suspended-sediment concentrations were made using in flow, for example, Third and Incline Creeks in the the Seasonal Kendall test (Helsel and Hirsch, 1992). Incline Village area. During the January 1997 flood, the This is a non-parametric test for a monotonic linear streamflow at Incline Creek near Crystal Bay was 179 3 trend that is resistant to outliers and is not dependent on ft /s, establishing a new record peak, markedly greater 3 the normality of the data. This test reduces seasonal than the previous peak of 87 ft /s in 1970. The storm 3 effects on concentrations when testing trends by com- peak at Third Creek was only 108 ft /s in 1997, well 3 paring the data by season. A Locally Weighted Scatter below the previous record peak of 150 ft /s set in 1982 Plot Smoothing (LOWESS; Helsel and Hirsch, 1992) (Rowe and others, 1998). Previous studies in the Incline was used to flow adjust the data by removing the effect area (Rowe, 1993; Glancy, 1988) also noted that these of streamflow variations on the concentrations. The two creeks are similar in size, in close proximity to each Seasonal Kendall test was performed on the flow- other, but exhibit markedly different runoff characteris- adjusted data. Trends detected by the test were consid- tics. ered significant if they had a p-value less than or equal The highest mean annual daily mean streamflow 3 to 0.05; slightly significant with a p-value greater than was 106 ft /s at Upper Truckee River at South Lake 3 0.05 but less than 0.10. Trends were not considered sig- Tahoe and the lowest was 0.56 ft /s at Logan House nificant with a p-value greater than or equal to 0.10. Creek near Glenbrook. The highest daily mean streamflow was 3,150 ft3/s on January 2, 1997, at Upper Truc- kee River at South Lake Tahoe. The lowest daily mean RESULTS streamflow of 0 ft3/s occurred during summer months throughout the period of record at five stations. Streamflow Average annual runoff, and unit runoff and unit- runoff ranks for the 10 primary stations for the period Streamflow summary statistics (period of record, of comparison (1988–98) are shown in figures 9 and 10, average annual mean flows, highest and lowest annual respectively. Upper Truckee River at South Lake Tahoe mean flows, annual runoff, unit runoff, highest and had the highest average annual runoff (65,100 acre-ft) lowest daily mean flow, instantaneous peaks, range and and Logan House Creek near Glenbrook had the lowest median of sampled flow, and number of samples) for (340 acre-ft). Blackwood Creek near Tahoe City had the periods of record 1961–98 for the 21 streamflow the highest unit runoff (2,280 acre-ft/mi2, rank of 1) and (20 active and 1 discontinued) gaging stations at the Logan House Creek near Glenbrook had the lowest unit primary and secondary stations are listed in table 4. runoff (163 acre-ft/mi2, rank of 10). Unit runoff on the Periods of record for the 21 streamflow gaging California or western half of the Lake Tahoe Basin stations ranged from 4 years (1995–98) at Edgewood (627–2,280 acre-ft/mi2) was greater than on the Nevada Creek at Stateline to 38 years (1961–98) at Trout Creek or eastern half of the basin (163–929 acre-ft mi2). at Tahoe Valley and Blackwood Creek near Tahoe City. Daily mean streamflow for the periods of record Instantaneous streamflow during the study period for for two index stations, Incline Creek near Crystal Bay these stations ranged from 0 ft3/s at five stations during and Upper Truckee River at South Lake Tahoe, are base-flow periods to 5,480 ft3/s at Upper Truckee River shown in figures 11A and 12A. These stations were used at South Lake Tahoe during a rain-on-snow flood event to compare a large watershed and a medium-small in January 1997. watershed, a northern and southern watershed, a water- Variations in streamflow in the Lake Tahoe Basin shed with greater precipitation and one with less, and are largely due to differences in weather patterns and one watershed from Nevada and one from California. variations of precipitation amounts and intensity. The annual seasonal pattern is typical of streams in the Smaller variations are due to area and altitude distribu- Lake Tahoe Basin, with most runoff occurring during

20 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada /s) 4 3 52 57 27 12 525 136 535 150 179 143 144 peak peak (ft [date] [1/2/97] [1/2/97] [1/2/97] [1/2/97] [1/2/97] [1/1/97] [8/14/91] [6/18/82] Instantaneous [2/1/63; 1/2/97] [2/1/63; [6/26/95; 1/2/97] [1/2/97; 6/12/98] [3/4/91; 10/26/91] a—Continued a /s) 2 0 0 0 3 .18 .86 .56 1.1 2.5 .08 .19 0 0.66 0 0 (ft [date] Lowest Lowest [9/7/88] [9/28/93 [8/10/92 [6/22/90] [8/11/92] [8/20/92] [9/16/91] [8/12/94] [7/13/88] [8//19/92] [12/20/90] [10/13/77] daily mean daily /s) 3 85 36 16 37 99 85 3.6 8.7 457 102 501 112 (ft [date] [1/2/97] [1/2/97] [1/2/97] [1/2/97] [1/2/97] [1/2/97] [1/2/97] [1/2/97] [1/2/97] Highest [8/27/90] [6/19/82] daily mean daily [6/26/95; 1/2/97] [6/26/95; /s) 3 .41 .31 .36 .05 0 7.71 1.54 1.02 0 1.07 10.2 2.17 2.51 2.92 0 0 (ft [1992] [1992] [1992] [1992] [1992] [1977] [1994] [1992] [1988] [1992] [1992] [1992] Lowest Lowest daily flow [water year] annual mean annual /s) 3 2.59 46.9 10.7 7.56 1.37 1.89 85.3 7.15 15.4 14.1 3.97 1.36 (ft [1997] [1995] [1995] [1983] [1997] [1990] [1983] [1998] [1995] [1983] [1998] [1998] Highest daily flow [water year] annual mean annual Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline Village area (fig. 2) Incline (fig. Village area /s), 3 South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe 8.02 8.38 1.75 (ft period of record daily flow Annual mean 1975 years) (water record record 1970–73 1988–98 1970–73 1977–98 1972–75 1988–98 Period of of Period 38 1961–98 37.4 15 1984–98 .56 Number Number of years of years of record 1 Station name /s, cubic feet per second. Symbol: —, not applicable] 3 Logan House Creek near Glenbrook . Streamflow summary statisticsthrough gaging water year 1998stations LTIMP Basin, for inthe California Lake Tahoe and Nevad . Streamflow summary statistics through water year 1998 for LTIMP gaging stations in the Lake Tahoe Basin, California and Nevad and California Basin, Tahoe Lake the in stations gaging LTIMP for 1998 year water through summary statistics . Streamflow 9 Incline CreekHighway at 28 9 1990–98 6.52 8Bay Crystal near Creek Incline 11 5 ThirdCreek Crystal Bay 27 20Dr. Palisade at Creek Edgewood 9 1990–98 1.3 28 Trail Pioneer at Creek Trout 9 1990–98 26.8 10 Village Incline Creek Tyrol above 9 1990–98 4.65 21 Stateline near Creek Rock Eagle 9 1990–98 .73 12 Glenbrook at Creek Glenbrook 15 16 Tahoe Lake at Creek Edgewood 4 1989–92 1.43 26 Valley near Creek Tahoe Trout 19 Statelineat Creek Edgewood 6 1993–98 4.81 14 Map number Table 4 Table 4 [Abbreviation: ft

RESULTS 21 /s) 3 797 166 peak peak 2,370 1,220 2,940 2,530 2,010 5,120 2,550 5,480 (ft [date] [11/97] [1/1/97] [1/1/97] [1/1/97] [1/2/97] [1/1/97] [1/2/97] [2/1/63] [1/2/97] [6/27/95] Instantaneous a—Continued /s) 0 0 3 .3 .5 .7 .76 1.5 .29 1.2 1.9 (ft [date] Lowest Lowest [8/4/77] [9/1/90] [9/22/94] [8/21/92] [9/24/68] [7/28/94] [8/22/94] [12/22/90] [12/21/90] daily mean [8/31/77–9/7/77] /s) 3 720 600 130 1,300 2,000 1,840 1,390 1,130 2,000 3,150 (ft [date] [1/1/97] [1/2/97] [1/1/97] [1/1/97] [1/2/97] [1/1/97] [1/2/97] [1/2/97] Highest [6/28/95] [12/23/64] daily mean daily /s) 3 7.69 5.56 8.71 5.29 15.7 14.1 4.96 4.48 26.1 29.2 (ft [1994] [1992] [1977] [1977] [1977] [1994] [1988] [1992] [1994] [1988] Lowest Lowest daily flow [water year] annual mean annual /s) 3 29 59 128 169 203 47.5 73.4 72.3 34.7 19.8 (ft [1995] [1995] [1982] [1983] [1983] [1995] [1982] [1995] [1995] [1983] Highest daily flow [water year] annual mean annual /s), 3 South Lake Tahoe area (fig. 5) area South Lake Tahoe Tahoe CityMeeks to Bay 6) (fig. Tahoe (ft period of record daily flow 106 Annual mean years) (water record record 1972–75 1980–98 Period of of Period 7 1992–98 28.9 9 1990–98 40.4 9 1990–98 12 9 1990–98 90.3 26 1973–98 26.9 23 Number Number of years of years of record Station name Ward Creek at Highway 89 nearWard Pines Tahoe RockCreek at Stanford Ward Crossing Upper Truckee River at South Upper Rd. Truckee Trout Creek at U.S. Forest Service Service Forest U.S. at Creek Trout 12N01Rd. Upper Truckee RiverSouth at Lake Tahoe Upper Truckee River at Highway Highway at River Truckee Upper 50 aboveMeyers . Streamflow summary statisticsthrough gaging water yearstations 1998 LTIMP Basin, for inthe California Lake Tahoe and Nevad 41Creek below Ward Confluence 7 1992–98 18.3 39 40 38 CityTahoe near Creek Blackwood 38 1961–98 37.5 34Meyers near River Truckee Upper 36 26 1961–86 68.2 29 37 General Creek nearMeeks Bay 19 1980–98 17.6 31 33 Map number Table 4

22 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada size Sample a—Continued Minimum Maximum Median years Water 1992–98 463463 — 620 .01 1.1 95 133 2.4 5.6 194 216 3 3 years Water 1991–98 474 474 2 2 years Water 1988–98 record Period of Stateline area(fig. 4) Glenbrook area(fig. 3) years Water Incline Village area (fig. 2) (fig. area Village Incline 1992–98 South Lake Tahoe area (fig. 5) area South Lake Tahoe 2,600 158 2,600 3,480 620 years Water 3 1991–98 3 2,660 2,660 years years Water 2 1988–98 2 403 403 340 381 193 163 182 — .01 12 .3 367 Annual runoff, acre-feet per yearper acre-feet runoff, Annual per mile square acre-feet runoff, Unit second feet per cubic Sampledflow, 3,370 — 3,370 1,180 — 1,180 — .24 46 3.2 314 8,690 — 8,690 — 1,170 — 1,170 — 2.8 160 8.8 196 1,040 record 76,500 65,100 74,20065,400 — — 65,400 1,420 — 1,210 1,370 1,660 — — 1,660 .7 5,400 — 180 2 203 1,300 81 264 27,100 23,000 27,300 — 738 627 744 — 3.2 526 56.5 176 Period of 1 1 Station name Station Upper Truckee River at South Lake Tahoe Upper River Truckee at Highway 50 aboveMeyers Logan House Creek near Glenbrook Incline Creek above Tyrol Incline Creek above Tyrol Village Trout Creek at U.S. Forest Forest U.S. at Creek Trout 12N01 Rd. Service . Streamflow summary statisticsthrough gaging water yearstations 1998 LTIMP Basin, for inthe California Lake Tahoe and Nevad 5 ThirdCreek Crystal Bay8 Incline Creek near CrystalBay 9 Incline CreekHighway at 5,810 28 6,070 5,910 5,590 4,730 6,220 6,120 — 4,730 1,010 868 929 883 1,040 1,020 930 — — 1,040 — 0.93 — .56 118 161 .55 7 91 6.6 520 496 4.7 295 31 33 12 Glenbrook at Creek Glenbrook 14 1,270 1,27016 1,290 EdgewoodCreek at LakeTahoe 1,370 310 31526 334 Valley near Creek Tahoe Trout — .01 140 1.3 407 19 Stateline at Creek Edgewood 20 Dr. Palisade at Creek Edgewood 21 3,480 942 Stateline near Creek Rock Eagle 526 — — 942 1,080 526 565 301 835 — 301 — 345 835 897 .1 .04 35 4 1.2 282 .65 230 10 28 Trail Pioneer at Creek Trout 29 19,400 — 19,400 — 840 — 840 — 4 215 19 274 Map number Table 4

RESULTS 23 size Sample a—Continued Minimum Maximum Median years Water 1992–98 years Water 1991–98 years Water 1988–98 record Period of years Water 1992–98 South Lake Tahoe area (fig. 5) area South Lake Tahoe Tahoe CityMeeks to Bay 6) (fig. Tahoe years Water 1991–98 years years Water 1988–98 Annual runoff, acre-feet per yearper acre-feet runoff, Annual per mile square acre-feet runoff, Unit second feet per cubic Sampledflow, record 49,40029,200 — 29,20027,200 — 25,30019,500 2,060 — 18,000 1,490 21,000 — — — 2,060 22,100 — 2,450 — 2,000 2,280 1,850 21,000 1.1 — — 2,340 520 2,270 — — 45 — .22 1.1 289 1,990 2,340 2,720 67 88 .38 235 235 441 48 157 Period of Station name Station Upper River Truckee near Meyers Blackwood Creek nearTahoe City Upper Truckee River at South Upper Rd. Truckee Creek at Highway 89 nearWard Pines Tahoe RockCreek at Stanford Ward Crossing . Streamflow summary statisticsthrough gaging water yearstations 1998 LTIMP Basin, for inthe California Lake Tahoe and Nevad Gaging station location for Trout Creek at South Lake Tahoe sampling station. 1989–98 combined runoffs used as estimate for 1988–98 period. Runoffcombined from Edgewood CreekLake at Tahoe andat Stateline for1991–98 comparison period. 1 2 3 34 37 General Creek nearMeeks Bay38 12,800 11,400 — 1,730 1,540 — — .41 716 40 212 36 39 40 41Creek below Ward Confluence 13,200 — — 13,200 2,660 — — 2,660 .01 288 31 145 Map number Table 4

24 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada A

150

100

50 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW,

0 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR

700

600

500

400

300

200

MEDIAN MONTHLY RUNOFF, IN ACRE FT IN ACRE RUNOFF, MEDIAN MONTHLY 100

0 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep FALL WINTER SPRING SUMMER (median = 193) (median = 255) (median = 518) (median = 179)

MONTH/SEASON

Figure 11. Plots for Incline Creek near Crystal Bay, a representative LTIMP gage station, for water years 1988–98: (A) Annual discharge, and (B) Median monthly and seasonal runoff.

RESULTS 27 A

4,000

3,000

2,000

1,000 STREAMFLOW, IN CUBIC FEET PER SECOND

0 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR B

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

MEDIAN MONTHLY RUNOFF, IN ACRE FEET 2,000

0 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep FALL WINTER SPRING SUMMER (median = 812) (median = 3,270) (median = 12,200) (median = 970)

MONTH/SEASON

Figure 12. Plots for Upper Truckee River at South Lake Tahoe, a representative LTIMP gage station: (A) Annual discharge for water years 1984–98, and (B) Median monthly and seasonal runoff for water years 1988–98.

28 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada the spring snowmelt period (April, May, and June). Glenbrook Creek at old highway and the lowest was Other events include rainstorms in the fall period 21 mS/cm at General Creek near Meeks Bay. For pri- (October, November, and December), rain-on-snow mary and secondary stations, the highest median spe- storms in the winter period (January, February, and cific conductance was 455 mS/cm at Glenbrook Creek March), and convective thunderstorms in the summer at Glenbrook and the lowest was 21 mS/cm at General period (July, August, and September). Median monthly Creek near Meeks Bay. Specific conductance typically runoff values are plotted in figures 11B and 12B. These increases downstream, as noted for Incline Creek in plots show that more streamflow occurs in the spring Rowe (1999). In general, specific conductance is higher period and less in the summer and fall periods. on the eastern side of the basin. A flood-frequency summary for 20 streamflow gaging stations and 6 historical (discontinued) streamflow gaging stations in the monitored watersheds is pH listed in table 5. The 50-year and 100-year peak stream- pH (table 8) ranged from 6.6 during spring snow- flows and maximum recorded peak streamflows melt at Trout Creek at Pioneer Trail to 10.6 during sum- through water year 1998 (Glen W. Hess, U.S. Geologi- mer low-flow periods at Edgewood Creek at Lake cal Survey, written commun., 2000) also are listed in Tahoe. For all stations, the highest median pH was 8.8 table 5. at Edgewood Creek at Lake Tahoe and the lowest was 7.2 at General Creek near Meeks Bay. For primary and Water-Quality Data secondary stations, the highest median pH was 8.2 at Logan House Creek near Glenbrook and the lowest was Field Measurements 7.2 at General Creek near Meeks Bay. In general, pH Field measurements were made during sample appears to be higher on the eastern side of the basin and collection. Summary statistics (minimums, maximums, does not seem to vary in a downstream direction. medians, and number of samples) are listed in tables 6, 7, 8 and 9 for 10 primary, 10 secondary, and 14 miscel- Dissolved Oxygen laneous water-quality stations. Dissolved oxygen (DO; table 9) ranged from Water Temperature 5.2 milligrams per liter (mg/L) at Edgewood Creek at Water temperatures (table 6) ranged from 0C Lake Tahoe to 12.6 mg/L at Logan House Creek near during winter periods at many locations to 23.0C dur- Glenbrook and Incline Creek near Crystal Bay. For all ing summer periods at two lower elevation stations, stations, the highest median DO was 10.2 mg/L at Ward Edgewood Creek at Lake Tahoe and Ward Creek at Creek at Highway 89 near Tahoe City and the lowest Highway 89 near Tahoe City. For all stations, the high- was 8.3 mg/L at Edgewood Creek Tributary near Dag- est median temperature was 14.0C at Tributary to gett Pass. For primary and secondary stations, the high- Edgewood Creek and the lowest was 2.5C at Ward est median DO was 10.2 mg/L at Ward Creek at Creek below confluence. For primary and secondary Highway 89 and the lowest was 9.2 mg/L at Glenbrook stations, the highest median temperature was 6.0C at Creek at Glenbrook. many locations and the lowest was 2.5 C at Ward Creek Dissolved-oxygen concentration was near satura- below confluence. Water temperatures typically tion (100 percent) for most stations. Dissolved-oxygen increased slightly downstream. saturation ranged from 70 to 157 percent; both occurred at Edgewood Creek at Lake Tahoe. For all stations, the Specific Conductance highest median saturation was 106 percent at Edge- Specific conductance (table 7) ranged from 8 wood Creek at Lake Tahoe and the lowest was 92 per- microsiemens per centimeter (mS/cm) at General Creek cent at Edgewood Creek Tributary near Daggett Pass. near Meeks Bay during snowmelt in the spring to 900 For primary and secondary stations, the highest median mS/cm at Glenbrook Creek at Glenbrook during low saturation was 103 percent at Upper Truckee River at summer streamflow. For all stations, the highest South Lake Tahoe and the lowest was 96 percent at median specific conductance was 466 mS/cm at Glenbrook Creek at Glenbrook.

RESULTS 29 /s) 27 52 12 3 535 (ft Streamflow ter year 1998, 1998, ter year ter year 1998, 1998, year ter of record of record Date Maximum peak streamflow peakMaximum June 12, 1998 January 2, 1997 February 1, 1963 1963 1, February October 26, 1991 June 26,1995 and 26,1995 June March 4, 1991 and and January 2, 1997 2, January and January 2, 1997 and 2, 1997 January 1 94 January 2, 1997 4 /s) 3 ND ND January 2, 1997 136 3 199 August 14, 1991 57 2 2 3 peak peak (ft 100-year 100-year 20 0 0]

streamflow 1 c o m u n. ,

68 /s) 3 ND ND 496 652 January 2, 1997 179 625 907 June 18, 1982 150 149 158 243 January 1, 1997 144 3 2 peak 4,390 5,700 January 2, 1997 5,480 2 3 (ft 50-year 4 streamflow record, record, 1988–98 1978–98 1980–98 1988–98 1970–75, 1972–75, Period of of Period water years 1970–73, 1975, 1972–74, 1978, fr o m G l en W . H e ss , U S g i c al u r v y w t n

N o t e : D a

d e t r m i n ed. USGS station name station USGS / s , c u b i f e et p r co n d ; N D not 3 f t

. Flood-frequency information for LTIMP and USGS gaging stations in the monitored watersheds in the Lake Tahoe Basin through wa through Basin Tahoe Lake the in watersheds monitored the in stations gaging USGS and LTIMP for information Flood-frequency . . Flood-frequency information for LTIMP and USGS gaging stations in the monitored watersheds in the Lake Tahoe Basin through wa through Basin Tahoe Lake the in watersheds monitored the in stations gaging USGS and LTIMP for information Flood-frequency . number 10336700 InclineCreeknear Nev. Lakeshore Crystal (above Dr.) Bay, 10336688 First Creek(at Highway 28) Nev. near Crystal Bay, 10336690 Second Creek at Lakeshore near CrystalDr. Nev. 10336694 Bay, Creek at mouth (at near Wood Nev. Lakeshore Crystal Dr.) Bay, 10336698 Third Creek(atnearNev. Lakeshore Crystal Dr.) Bay, 1970–74 1970–74 1970–74 216 129 164 302 182 225May18, 1970 September 26, 1973 May 18, 1970 22 15 16 10336790 Creek Trout (atHighway Calif. 50) South at Lake Tahoe, 10336780 Calif. Valley, Creek near Trout Tahoe (atMartin Ave.) 1972–74 1961–98 773 716 966 894 May 31, 1973 190 10336775 Creek Trout at PioneerCalif. near Trial South Lake Tahoe, 10336770 Creek Trout at U.S.Forest Service Road12N01 near Meyers, Calif. 10336610(at UpperRiver Highway Truckee 50)at Calif. South LakeTahoe, 1991–98 1991–98 365 505 450 630June 27, 1995 January 2, 1997 166 525 10336760 Edgewood Creek (atHighway 50)Stateline, at Nev. 1993–98 10336740 LoganHouse Creek near Glenbrook,Nev. 1984–98 24 31 10336730 Glenbrook Creek(near mouth) at Glenbrook, Nev. 10336765 near Stateline,Nev. CreekLake atTahoe Edgewood 1989–92 103367585 Nev. Creek near Edgewood Palisade atKingsbury, Dr. 1991–98 103366995 InclineCreek at Highway28 at Incline Nev.Village, 103366993 Nev.Village, Incline near Village Tyrol above Creek Incline 1991–98 1990–98 126 333 157 470 January 2, 1997 143 103367592 Nev. Stateline, near Creek Rock Eagle 1991–98 USGS station station USGS Table 5 California and Nevada—Continued and California California and Nevada and California Table 5 [ A bb r e v i a t o n s:

30 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada /s) 3 (ft Streamflow Streamflow ter year 1998, ter year of record Date Maximum peak streamflow peak streamflow Maximum January 1, 1997 January 2,940 1, 1997 January 2,530 January 2, 1997 January 5,120 rring in any given year. in any given rring 1 /s) 3 mflow is theoretical and statistically has peak (ft 100-year streamflow 1 /s) 3 peak 2-percentoccuchance of 1,4601,230 1,790 1,560 2, 1997 January 1, 1997 January 2,010 797 (ft 50-year 5 streamflow historical flood designation. historical flood record, record, 1961–86 2,900 3,540 February 1, 1963 2,550 where noted. The 100-year peak strea Period of water years retical and statistically has a the monitored watersheds in the Lake Tahoe Basin through wa Tahoe the monitored in thewatersheds Lake guidelines except guidelines ta (1982) guidelines based on Tahoe City, Calif.City, Tahoe 1992–98 2,240 3,030 1, 1997 January 2,370 nes, Calif. 1973–98 2,650 3,620 City, Calif. 1961–98 3,500 4780 yers, Calif. 1991–98 3,310 4,060 ty, Calif.ty, 1992–98 1,390 1,890 1, 1997 January 1,220 50-year peak streamflow is theo r Truckee Road near Meyers, Calif. 1991–98 and a nearby gaging station on the same stream. Committee on Water Data (1982) 89) near Meeks Bay, Calif.near Meeks Bay, 89) 1980–98 USGS station name of Thomas and others (1997). and others of Thomas lue not determined (ND).lue . Flood-frequency information for LTIMP and USGS gagingUSGS and stations in LTIMP . Flood-frequency information for Determined from U.S. Interagency Advisory Affected by regulation; va Estimated by regression methods Determined from U.S. Interagency Advisory Committee on Water Da (1997) and others of Thomas methods by Estimated 1 2 3 4 5 number 10336674 Ward Creek below confluence near Tahoe Ci 10336675 Ward Creek at Stanford Rock Trail Crossing near 10336676 Ward Creek at State Highway 89 near Pi Tahoe 10336645 Creek (at General Highway 10336660 Tahoe near (at Highway 89) Creek Blackwood 10336600 Truckee River Upper near Meyers, Calif. 10336580 Truckee River Upper Uppe at South 103366092 Truckee River Me Upper at Highway 50 above USGS station California and Nevada—Continued Table 5 a 1-percent chance of occurring in any given year. Likewise, the Likewise, year. given in any occurring of chance a 1-percent

RESULTS 31 stations, by by stations, stations, by C Water temperature, Water Minimum Maximum Median 398 0 17.0 6.0 size Sample record 1972–75 1988–98 Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area Station name Station C, degrees Celsius. Symbol:—, not applicable] . Water temperature data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous water-quality water-quality miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data temperature . Water . Water temperature data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous water-quality water-quality miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data temperature Water . 1 Nev. Bay, Crystal near 28) Highway (at Creek First 2 SecondNev. Creeknear at Lakeshore Crystal Bay, Dr. 3Creek near mouth Wood (atnear LakeshoreNev. Crystal Dr.) Bay, 4Nev. Village, Incline near St. Jennifer above Creek Wood 5 Nev. Bay, Crystal near Dr.) Lakeshore (at Creek Third 6 1991–98 Nev. Village, Incline at Blvd. Village at Creek Third 7 1991–98 Nev.Village, Incline near tributary unnamed below Creek Third 8 71 1991–98 73 InclineCreek (aboveLakeshorenear Nev. Crystal 9 Dr.) Bay, 1991–98 69 InclineCreek at Highway 28Incline at Nev. Village, .5 62 1991–98 1988–98 1.0 .5 504 65 14.0 1991–98 13.5 1988–98 .5 70 15.0 478 0 1.5 7.0 12.5 6.5 1990–98 2.0 7.5 14.0 0 22.0 289 7.0 15.5 5.5 6.0 18.5 0 6.5 6.0 14.5 6.0 11 Nev. nearIncline Incline Creek at Village, County Tributary ClubDr. 1991–98 85 1.5 14.5 8.5 13 Nev. Glenbrook, near Highway Old at Creek Glenbrook 14 Logan House Creeknear Glenbrook,15 Nev. North Logan HouseCreek aboveHighway near 50 Glenbrook, Nev. 1991–98 1991–88 71 68 1.0 .5 1984–98 344 16.5 12.0 0 8.0 6.5 12.0 4.0 10 Nev.Village, Incline near Village Tyrol above Creek Incline 1990–98 307 0 18.0 5.0 12 Glenbrook(near Creek mouth) at Glenbrook, Nev. 16 Nev. Stateline, near Tahoe Lake at Creek Edgewood 17 Edgewood CreekTributaryabove Clubhouse 18 near Stateline, Nev. Culvert into Edgewood19 Creek above Highway 50 at Stateline, Nev.Nev. Stateline, at 50) Highway (at Creek Edgewood 20 Nev. Kingsbury, near Dr. Palisade at Creek Edgewood 21 1995–98 Eagle Rocknear Creek Stateline, Nev. 1998 1989–98 9 190 10 5.5 1992–98 .5 1990–98 3.5 210 18.0 273 23.0 18.5 14.0 .5 .5 12.0 9.5 1990–98 14 13.0 220 6.0 5.5 .5 11.0 5.0 Map number area, in the Lake Tahoe Basin, California and Nevada and California Basin, Tahoe Lake the in area, Table 6 [Abbreviation: Table 6 area, in the Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake the in area,

32 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada C Water temperature, Water 0 19.5 6.0 0 12.5 6.0 Minimum Maximum Median size 270 + 191 + Sample recorder recorder record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name Station below confluence near Tahoe City, Calif. City, below confluencenear Tahoe 1992–98 140 0 18.5 2.5

. Water temperature data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous water-quality miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data temperature Water . 22 Nev. Pass, Daggett near Tributary Creek Edgewood 23 Nev.Pass, Daggett near Dr. Benjamin South below Creek Edgewood 24 1990–98 Creek nearmouth Trout Bellevue/El eastoff — Dorado Ave.27 Cold Creekmouth at near South Calif. Lake 77 Tahoe, 28 1990–98 Creek Trout at Pioneer near Trail South Calif. LakeTahoe, 1.5 47 1998 13.5 recorder .5 1990–98 0 7.5 1998 13.0 recorder 17.5 0 6.0 — 37 14.0 GeneralCreek (at Highway Calif. 89) nearMeeks Bay, 38 Calif. City, — Tahoe near 89) Highway (at Creek Blackwood 39 CreekatPines, Highway 89 Calif. near Ward Tahoe 40 Calif. City, Tahoe near crossing Trail Rock Stanford at Creek Ward 41 Creek Ward 1993–98 1993–98 1992–98 214 234 158 1993–98 0 0 0 235 19.0 22.0 22.0 0 3.5 4.0 4.5 23.0 3.5 29 Creek Trout at U.S.Forest Service Rd. 12N01 near Meyers, Calif. 1990–98 30 near Calif. South Lake Dr. Tahoe, Upper River Truckee near mouthVenice off 31 1998 Upper River Truckee (at Highway 50) at South. Calif. LakeTahoe, 32 recorder Upper River Truckee at Highway50 below Meyers, Calif.33 Calif.Meyers, above 50 Highway at River Truckee Upper 035 1993–98 Grass LakeCreek at Grass LakeRd.near Meyers, Calif.36 192Calif. Meyers, near Rd. Truckee Upper South at River Truckee Upper 21.5 0 1998 1990–98 — 1990–98 recorder 280 258 22.0 1998 0 0 recorder 0 6.0 22.0 0 18.0 20.0 — 14.5 4.5 6.0 — Map number stations, by area, in the Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, Table 6

RESULTS 33 S/cm m Specific conductance, Minimum Maximum Median 372 149 900 455 size Sample record 1972–75 1988–98 Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area Station name Station S/cm,microsiemens per centimeter] m . Specific conductance data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data conductance . Specific . Specific conductance data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data conductance Specific . 1 First Creek(at Highway28) Nev. near Crystal Bay, 2 Second CreekNev.nearat Lakeshore Crystal Bay, Dr. 3Creek near mouth (at Wood Nev. Lakeshore near Crystal Dr.) Bay, 4Nev. Village, Incline near St. Jennifer above Creek Wood 1991–98 5 Third Creek(at Nev. Lakeshore near 1991–98 Crystal Dr.) Bay, 6 1991–98 71 Nev. Village, Incline at Blvd. Village at Creek Third 7 73 1991–98 Nev.Village, 69 Incline near tributary unnamed below Creek Third 8 33 InclineCreek (aboveLakeshorenear Nev. Crystal Dr.) Bay, 62 9 1991–98 1988–98 41 28 InclineCreek at Highway 28Incline at Nev. Village, 1991–98 486 94 65 32 104 1988–98 132 69 475 27 54 23 69 66 1990–98 58 26 167 38 57 272 47 76 166 72 39 25 42 77 121 51 11 InclineCreek Tributary at County nearIncline Club Nev.Dr. Village, 1991–98 85 103 210 114 10 Nev.Village, Incline near Village Tyrol above Creek Incline 1990–98 283 19 54 35 13 Glenbrook Creekat Old Highwaynear Glenbrook, Nev.14 Logan House Creeknear Glenbrook, Nev.15 North Logan HouseCreek aboveHighway near 50 Glenbrook, Nev. 1991–98 1991–88 70 68 59 137 1984–98 330 833 111 60 466 86.5 163 128 12 Glenbrook(near Creek mouth) at Glenbrook, Nev. 16 Edgewood near Creek Stateline,at Lake Tahoe Nev. 17 Edgewood CreekTributaryabove Clubhouse near Stateline, Nev. 1995–98 1989–98 9 187 94 80 302 268 167 121 Map number Table 7 Nevada and California Basin, Tahoe Lake the in area, by stations, water-quality [Abbreviation: Table 7 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality

34 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada S/cm m Specific conductance, Minimum Maximum Median size Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name Station below confluence near Tahoe City, Calif.below confluence City, near Tahoe 1992–98 143 22 57 32

. Specific conductance data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data conductance Specific . 18 Culvert into Edgewood Creek above Highway 50 at Stateline,19 Nev. Edgewood Creek(at Highway50) at Stateline,Nev. 20 1995–98 Edgewood Creek at Palisade near Nev. Dr. Kingsbury, 21 10 Eagle Rock Creeknear Stateline, Nev. 22 Edgewood Creek Tributary near Daggett Pass, Nev.23 56 1992–98 Edgewood Creekbelow South near Benjamin DaggettPass, Dr. Nev. 1990–98 1990–9825 198 786 256 Creek Trout (atHighway 50)at South Calif. Lake Tahoe, 28 77 Creek Trout at Pioneer near Trail South Calif. LakeTahoe, 1990–9829 84 280 69 Creek Trout at U.S.Forest Service Rd. 12N01 near Meyers, Calif.31 67 47 1990–98 Calif. Tahoe, Lake South at 50) Highway (at River Truckee 1993–98 Upper 24533 1990–98 1990–98 498 202 1993–98 Upper River Truckee at Highway50 above Meyers, Calif. 49536 172 149 178 245 129 Upper River Truckee at SouthUpper Truckee Rd. nearMeyers, Calif. 188 150 1990–98 28 116 37 335 22 16 1990–98 262 GeneralCreek (at 18 Highway Calif. 89) nearMeeks Bay, 38 17 61 Blackwood Calif. Creek (at Highway City, 89) nearTahoe 199 24539 71 63 Calif.Pines, Tahoe near 89 Highway at Creek 13 Ward 135 6840 Creekat Calif. Stanford crossing City, Rock Ward Trail nearTahoe 52 41 17 1993–98 44 40 1993–98 Creek Ward 1992–98 75 46.5 45 212 120 235 155 1993–98 24 8 233 47 21 27 21 70 92 108 95 21 40 39 40 Map number Table 7 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality

RESULTS 35 pH, standard units pH, standard Minimum Maximum Median 135 6.9 9.1 8.0 size Sample record 1972–75 1988–98 Period of Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline 2) Village area (fig. Station name . pHdata surface-water current for quality USGS LTIMP sampling/gaging stations and miscellaneous water-quality stations, . pH data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous water-quality stations, stations, water-quality miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data . pH 1 First Creek (at Highway 28) nearNev. Crystal Bay, 2 SecondCreek Nev. near at LakeshoreCrystal Bay, Dr. 3 Creek near mouthNev.near (at Wood Crystal Lakeshore Bay, Dr.) 4 Creek Jennifer above St. near Wood Incline Nev. Village, 1991–985 1991–98 ThirdCreek (at near Nev.Crystal Lakeshore Dr.) Bay, 6 1991–98 29 Nev. Village, Incline at Blvd. Village at Creek Third 7 29 29 1991–98 Nev. Village, Incline near tributary unnamed below Creek Third 7.68 7.4 Incline Creek(above near Nev. Lakeshore Crystal Dr.) Bay, 9 27 1991–98 1988–98 7.4 Incline CreekatHighway at 28 Incline Nev. 8.5 Village, 172 1991–98 29 8.5 7.6 1988–98 8.4 31 8.0 7.1 7.2 165 8.1 8.4 8.1 7.1 1990–98 8.7 7.0 8.7 8.0 97 8.4 7.9 8.6 7.9 6.9 7.8 7.9 8.5 7.8 10Nev. nearIncline Village, Village Incline Tyrol above Creek 11 Nev. nearIncline at Village, County Incline ClubDr. Tributary Creek 1991–98 1990–98 34 95 7.5 7.1 8.3 8.6 8.0 7.8 12 Glenbrook Creek (nearmouth) atGlenbrook, Nev. 16near EdgewoodCreek Stateline, at LakeTahoe Nev. 17 Edgewood Clubhouse Creek above Tributary near Stateline,Nev. 18 Culvertinto Edgewood Creek Highway above 50at Stateline, Nev. 1995–98 1995–98 1989–98 1 3 87 — 7.8 7.3 — 8.2 10.6 8.1 8.0 8.8 13 Glenbrook Creek at Old Highway near Glenbrook, Nev. 14 Logan House Creek near Glenbrook, Nev. 15 North LoganHouse CreekHighway above 50 near Glenbrook, Nev. 1991–98 1991–88 32 32 7.5 7.3 1984–98 8.9 124 8.5 7.3 8.2 8.2 8.9 8.2 Map number Table 8 Nevada—Continued and California Basin, Tahoe Lake the in area, by Table 8 Nevada and California Basin, Tahoe Lake the in area, by applicable] not —, [Symbol:

36 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada pH, standard units pH, standard Minimum Maximum Median size Sample record Period of Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Tahoe Lake Tahoe City to Meeks Bay area (fig. 6) (fig. area Bay Meeks to City Tahoe Station name . pHdata surface-water current for quality USGS LTIMP sampling/gaging stations and miscellaneous water-quality stations, 19 Edgewood Creek (at Highway50) at Stateline,Nev. 20Nev. near Edgewood Kingsbury, Creek at Palisade Dr. 21 Eagle Rock Creek near Stateline, Nev. 22 Edgewood Creek near Tributary Daggett Pass, Nev. 23 1992–98 Edgewood Creek South below near Benjamin DaggettPass, Nev. Dr. 1990–98 1990–98 25 47 88 Creek Trout near mouth Bellevue/El — east off Dorado Ave. 33 28 Calif. Tahoe, Lake South at 50) Highway (at 1990–98 Creek 6.7 Trout 29 7.1 7.4Calif. Valley, Creek Trout near(at Tahoe Martin Ave.) 1993–98 31 16 1990–98 8.6 Cold Creek at mouth near Calif. SouthLake Tahoe, 33 8.5 48 1990–98 9.3 Calif. Tahoe, Lake South near 78 Trail Pioneer at Creek Trout 7.2 36 7.9 Creek Trout at U.S. 94 Forest Service Rd. 12N01 near Meyers, Calif. 7.0 1990–98 8.0 7.0 7.9 8.8 37 1990–98 1990–98 6.6 75 (at Upper Highway River Calif. 50) Truckee at South 1993–98 Lake Tahoe, 38 8.4 103 8.7 97 7.7 at Highway50 Upper River below Meyers, Truckee Calif. 39 1993–98 51 6.8 8.4 Calif. Meyers, above 50 Highway at River Truckee Upper 7.0 7.5 40 7.0 7.9 13 GrassLake CreekGrassRd. near at Calif. Meyers, Lake 7.0 41 8.7 7.8 1993–98 at South Upper River Upper Truckee Rd. Truckee nearMeyers, Calif. 8.8 6.7 9.3 1993–98 1992–98 8.4 13 7.9 12 1992–98 7.8 0 7.8 7.7 7.0 7.5 7.3 1 — 7.2 8.0 — 7.9 — 7.4 — 7.5 — 8.1 Map number Table 8 Nevada—Continued and California Basin, Tahoe Lake the in area, by

RESULTS 37 9.6 9.6 9.7 9.7 9.8 9.2 9.6 9.6 9.7 9.4 9.6 9.2 [99] [99] [99] [96] [100] [100] [100] [100] [100] [100] [100] [99.5] 10.8 11.1 12.6 11.8 12.1 10.4 10.7 11.1 11.4 10.9 11.9 12.2 [124] [110] [116] [108] [115] [113] [104] [106] [104] [114] [110] [118] [ s a t u r i on, p e c n ] Dissolved oxygen Dissolved oxygen (mg/L) 7.2 7.9 8.2 8.0 7.3 7.8 8.7 8.0 8.3 8.1 7.2 6.0 [87] [92] [95] [97] [92] [92] [86] [95] [98] [98] [91] [71] Minimum Maximum Median 24 24 67 66 17 17 16 16 71 71 17 17 17 17 17 17 12 12 size 119 119 124 124 107 107 Sample Period of record Glenwood area (fig. 3) Glenwood (fig. area Incline 2) Village area (fig. Station name Station . Dissolved oxygen data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data oxygen Dissolved . . Dissolved oxygen data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous water-quality water-quality miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data oxygen . Dissolved 6 Nev. Village, Incline at Blvd. Village at Creek Third 7 Nev. Village, Incline near tributary unnamed below Creek Third 8 Incline Nev. near Creek Crystal Lakeshore (above Bay, Dr.) 1991–98 9 1991–98 Incline CreekHighway at Nev. 28Incline at Village, 1988–98 1990–98 1 First Creek (at Highway28) Nev. nearCrystal Bay, 1991–98 2 Second Nev. near Creek at Crystal Lakeshore Bay, Dr. 3 Creek nearmouth Wood (atnear Lakeshore Nev. Crystal Dr.) Bay, 4 1991–98 Creek Jennifer above St. near Wood Incline Nev.Village, 1991–98 5 ThirdCreek (at Nev. near Lakeshore Crystal Dr.) Bay, 1991–98 1988–98 11 Nev. near InclineVillage, at County Incline Club Creek Dr. Tributary 1991–98 10 Nev. nearIncline Village, Village Incline Tyrol Creek above 1990–98 12 Nev.Glenbrook, at mouth) (near Creek Glenbrook 1988–98 Map number water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality Table 9 Table 9 Nevada and California Basin, Tahoe Lake the in area, by stations, applicable] not —, Symbol: liter. per milligrams mg/L, [Abbreviation:

38 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada 8.3 8.8 9.8 9.7 9.6 8.1 9.3 9.7 9.8 9.4 9.9 9.5 [92] [96] [98] [98] [83] [99] [99] [99] [100] [100] [106] [100] 11.0 11.5 11.0 11.2 11.5 11.4 11.0 10.2 10.5 12.6 12.1 [114] [114] [119] [114] [112] [116] [103] [106] [108] [157] [106] [saturation percent] Dissolved oxygen Dissolved oxygen (mg/L) —— 7.5 7.9 8.8 7.9 8.2 7.6 6.8 7.9 5.2 8.4 8.7 [79] [88] [88] [93] [92] [87] [91] [94] [70] [92] [94] Minimum Maximum Median 7 7 1 1 14 14 44 44 65 65 34 34 96 96 68 68 21 21 62 61 34 34 14 14 size Sample Period Period of record Stateline area (fig. 4) (fig. area Stateline Glenwood (fig. area 3) South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Station name Station . Dissolved oxygen data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data oxygen Dissolved . 23 Edgewood Creek below South Benjamin near Daggett Dr. Pass, Nev. 1990–98 22 EdgewoodCreek Tributary near DaggettPass, Nev. 1990–98 21 EagleCreek Rock near Stateline, Nev. 1990–98 20 EdgewoodCreek Nev.near at Palisade Kingsbury, Dr. 1990–98 18 Culvert into Edgewood Creek above Highway 50 at Stateline, Nev.19 1995–98 EdgewoodCreek (at Highway 50)Stateline, at Nev. 0 — 1992–98 — — 14 Logan House Creek near Glenbrook, Nev.17 EdgewoodCreek Tributary above Clubhouse nearStateline, Nev. 1984–98 1995–98 28 Calif. Tahoe, Lake South at 50) Highway (at Creek Trout 1990–98 13 GlenbrookCreek at Old Highway near Glenbrook, Nev. 1991–88 16 Edgewood near Creek Stateline,Lake at Tahoe Nev. 1989–98 25 Creek Trout near mouth — east Bellevue/El off DoradoAve. 1993–98 15 North Logan House Creek above Highway50 near Glenbrook,Nev. 1991–98 Map number water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality Table 9

RESULTS 39 — 9.8 9.6 9.7 9.3 9.8 [99] [98] 10.2 10.0 [100] [101] [103] [101] [100] [99] 11.6 11.6 11.3 11.4 11.5 11.2 10.3 12.4 [114] [114] [105] [126] [103] [109] [104] [saturation percent] Dissolved oxygen Dissolved oxygen (mg/L) 8.1 7.3 6.7 7.2 6.8 6.9 8.0 6.6 [95] [86] [86] [88] [91] [93] [90] [88] Minimum Maximum Median 3 3 74 73 73 73 40 40 42 42 41 41 47 47 40 40 size Sample Period Period of record South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name Station below confluence near Tahoe City, Calif. City, Tahoe near confluence below 1992–98 0 — — —

. Dissolved oxygen data for current USGS LTIMP surface-water quality sampling/gaging stations and miscellaneous miscellaneous and stations sampling/gaging quality surface-water LTIMP USGS current for data oxygen Dissolved . 41 Creek Ward 40 Calif.City, CreekStanford at crossing Rock near Trail Tahoe Ward 1992–98 36 Creek Trout at U.S. Forest ServiceRd.12N01 near Meyers, Calif. 1990–98 33 Calif. nearat Creek Pioneer South Trout Lake Trail Tahoe, 1990–98 39 CreekHighway at Pines,Calif. Ward near 89 Tahoe 1993–98 31 Calif. Tahoe, Lake South near mouth at Creek Cold 1993–98 38 Calif.City, Tahoe near 89) Highway (at Creek Blackwood 1993–98 29 Calif. Valley, near Tahoe (at Creek Martin Ave.) Trout 1990–98 37 Calif. Bay, Meeks near 89) Highway (at Creek General 1993–98 Map number water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality Table 9

40 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Nutrients and Suspended Sediment Total ammonia and organic nitrogen

Samples may have higher concentration values Total ammonia and organic nitrogen concentra- than from other studies in the basin, because LTIMP tions (table 12) ranged from less than 0.04 to 24.0 emphasized sampling during storm and snowmelt run- mg/L; both values occurred at Third Creek near Crystal off. Summary statistics (minimums, maximums, Bay, with the higher reading observed during summer medians, and number of samples) for nutrient and thunderstorm runoff. For all stations, the highest suspended-sediment concentrations from 10 primary, median concentration was 4.15 mg/L at Highway 50 10 secondary, and 14 miscellaneous sampling stations Culvert to Edgewood Creek and the lowest was 0.07 are listed in tables 10–16. mg/L at Ward Creek below confluence. For primary and secondary stations, the highest median was 0.21 mg/L at Incline Creek near Crystal Bay and the lowest Dissolved nitrite plus nitrate nitrogen was 0.07 mg/L at Ward Creek below confluence. Total Concentrations of dissolved nitrite plus nitrate ammonia and organic nitrogen concentrations were nitrogen (table 10) ranged from less than 0.002 mg/L at observed to increase only slightly in a downstream three stations to 2.25 mg/L at Highway 50 Culvert to direction. Edgewood Creek during storm runoff. For all stations, the highest median concentration was 0.134 mg/L at Soluble reactive phosphorus Highway 50 Culvert to Edgewood Creek and the lowest was 0.004 mg/L at Second Creek at Lakeshore Drive. Concentrations of soluble reactive phosphorus For primary and secondary stations, the highest median (table 13) ranged from less than 0.001 mg/L at Logan concentration was 0.030 mg/L at Incline Creek near House Creek near Glenbrook to 1.55 mg/L at Edge- Crystal Bay and the lowest was 0.005 mg/L at Trout wood Creek Tributary above Clubhouse during storm Creek at U.S. Forest Service Road 12N01 and General runoff. For all stations, the highest median concentra- Creek near Meeks Bay. Concentrations of dissolved tion was 0.090 mg/L at Highway 50 Culvert to Edge- nitrite plus nitrate nitrogen made-up about 10 percent wood Creek and the lowest was 0.002 mg/L at Logan of the total nitrogen component for all stations. House Creek near Glenbrook. For primary and second- Dissolved nitrite plus nitrate nitrogen concentrations ary stations, the highest median concentration was were observed to increase slightly in a downstream 0.013 mg/L at Glenbrook Creek at Glenbrook and the direction based on median values for the five multiple- lowest was 0.002 mg/L at Logan House Creek near station watersheds. Glenbrook. Soluble reactive phosphorus concentrations made-up about 24 percent of the total phosphorus Dissolved ammonia nitrogen component. Soluble reactive phosphorus concentrations were observed to increase only slightly or not at Concentrations of dissolved ammonia nitrogen all in a downstream direction. (table 11) were low, ranging from less than 0.003 mg/L at many stations to 1.39 mg/L at Edgewood Creek Total phosphorus Tributary above Clubhouse during storm runoff. For all stations, the highest median concentration was 0.166 Total phosphorus concentrations (table 14) mg/L at Highway 50 Culvert to Edgewood Creek and ranged from less than 0.002 mg/L at Logan House the lowest was less than 0.003 mg/L at many stations. Creek near Glenbrook to 11.1 mg/L at Highway 50 For primary and secondary stations, the highest median Culvert to Edgewood Creek during storm runoff. For concentration was 0.003 mg/L at the three Edgewood all stations, the highest median concentration was 4.30 Creek stations and the lowest was less than 0.003 mg/L mg/L at Highway 50 Culvert to Edgewood Creek and at many stations. All stations had medians less than the lowest was 0.0021 mg/L at three stations. For pri- 0.003 mg/L except the eight stations in the Edgewood mary and secondary stations, the highest median con- Creek watershed. In the Edgewood Creek watershed, centration was 0.051 mg/L at Incline Creek near ammonia did not increase in a downstream direction. Crystal Bay and the lowest was 0.021 mg/L at several Dissolved ammonia nitrogen made-up less than 1 per- stations. Total phosphorus concentrations were cent of the total nitrogen component for all stations. observed to increase slightly in a downstream direction

RESULTS 41 Minimum Maximum Median Dissolved nitrite + nitrate nitrogen (mg/L) nitrogen nitrate + nitrite Dissolved size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline 2) Village area (fig. Station name . Dissolved nitrite plus nitrate nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen nitrate plus nitrite Dissolved . . Dissolved nitrite plus nitrate nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen nitrate plus nitrite Dissolved . 1 First Creek(at Highway 28)nearNev. Crystal 2 Bay, Second Creek 3at Lakeshore near Crystal Dr. Nev. Bay, Creek near mouth (at Wood near Nev. Lakeshore Crystal Dr.) Bay, 4 Nev. Village, Incline near St. Jennifer above Creek Wood 5 1991–98 Third Creeknear (atLakeshore Nev. Crystal Dr.) 6 Bay, 1991–98 71 1991–98 Nev. Village, Incline at Blvd. Village at Creek Third 7 72 1991–98 69 Third Creekunnamed below tributary8 near Incline Nev.Village, .002 Incline Nev. Creek nearLakeshore Crystal (above Dr.) Bay, 9 62 0.002 1988–98 1991–98 Nev. Village, Incline at 28 .002 Highway at Creek Incline .101 438 1991–98 0.041 64 .003 1988–98 .021 68 <.002 433 .016 0.006 .002 .093 1990–98 .004 .003 .439 .003 232 .072 .018 .050 .014 .330 .003 .014 .010 .030 .082 .025 10 Nev. Village, Incline near Village Tyrol above Creek Incline 11Nev. Village, Incline near Dr. Club County at Tributary Creek Incline 1991–98 1990–98 84 243 .014 .002 .151 .101 .046 .021 12 Glenbrook Creek(near mouth) at Glenbrook, 13 Nev. Glenbrook CreekatOld Highway near 14 Glenbrook,Nev. Logan House Creek near Glenbrook, 15 Nev. NorthLogan House Creek Highway above 50 near Glenbrook, Nev. 16 1991–98 1991–88 1988–98near EdgewoodCreek Stateline, at LakeTahoe Nev. 17 70 334 67Creek Edgewood Clubhouseabove Tributary nearStateline, 18 Nev. Culvert intoEdgewood Creek Highwayabove 50 at Stateline,Nev. <.002 .002 1995–98 .002 1984–98 1995–98 1.25 292 1989–98 8 .058 10 .068 174 .002 .037 .010 .018 .061 .007 .002 .072 .491 2.25 .184 .013 .095 .134 .016 Map Map number Table 10 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations Table 10 Table Nevada and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations than] less <, Symbol: liter. per milligram mg/L, [Abbreviation:

42 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Minimum Maximum Median Dissolved nitrite + nitrate nitrogen (mg/L) nitrogen nitrate + nitrite Dissolved size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Tahoe Lake Tahoe City to Meeks Bay area (fig. 6) (fig. area Bay Meeks to City Tahoe Station name below confluence near Tahoe City, Calif. City, Tahoe near confluence below 1992–98 143 .002 .107 .014

. Dissolved nitrite plus nitrate nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen nitrate plus nitrite Dissolved . 19 EdgewoodCreek (at Highway 50)Stateline, at 20 Nev. Nev.Creek Edgewoodnear Kingsbury, at Palisade Dr. 21 Eagle Rocknear Creek Stateline, Nev. 22Creek Edgewoodnear Daggett Tributary Nev. Pass, 23 EdgewoodCreek below South nearBenjaminDaggett Dr. Pass, Nev. 1992–98 1990–98 1990–98 25 170 219Creek Trout (at Highway 50)Calif. at South Lake 28 Tahoe, 76Creek Trout at PioneerCalif. nearTrail South Lake 29 Tahoe, 1990–98 .002 0.003 Calif. Meyers, near 12N01 Rd. Service Forest U.S. at Creek Trout 31 .010 47 1990–98 Calif.Tahoe, Lake South at 50) Highway (at River Truckee Upper 33 1993–98 1990–98 .070 0.229 165 1990–98Highway at River Meyers, 50 Upper above Calif. Truckee 36 1993–98 168 152 .101 .003 Calif. Meyers, near Rd. 208 Truckee Upper South at River Truckee Upper 0.016 184 .019 1990–98 .002 37 .002 .002 .027 206 .049 .002 1990–98 General Creek (at Highway89)Calif. 38 near Meeks Bay, .002 .075 Calif. Blackwood Creek City, (atHighway 227 89)near Tahoe 39 .044 .045 .002 .006 Calif. Pines, Tahoe near 89 Highway at Creek .113 Ward 40 .090 Calif.City, Tahoe .011 near crossing Trail Rock Stanford at Creek Ward 41 .002 .005 .009 1993–98 .065 1993–98 1992–98 Creek .006 Ward .012 210 154 233 .079 .012 1993–98 .002 <.002 232 .002 .009 .033 .091 .002 .087 .005 .016 .072 .009 .010 Map Map number Table 10 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations

RESULTS 43 Dissolved ammonia nitrogen (mg/L) Minimum Maximum Median size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area Station name . Dissolved ammonia nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen ammonia Dissolved . . Dissolved ammonia nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen ammonia . Dissolved 1 First Creek(at Highway Nev. 28) near2 Crystal Bay, Second CreeknearLakeshoreNev. at Crystal Dr. 3 Bay, Creek near mouth (at Wood Lakeshore near Nev.Crystal Dr.) Bay, 4 Creek above Jennifer Wood St. nearInclineNev. Village, 5 1991–98 Third Creek Nev.near (atLakeshore Crystal Bay, Dr.) 1991–986 1991–98 71 Nev. Village, Incline at Blvd. Village at Creek Third 7 72 Nev. Village, Incline near tributary unnamed below 69 Creek Third 1991–988 <.003 <0.003 Incline Creek (above Lakeshore near Nev.9 Crystal Dr.) Bay, 62 1991–98 1988–98 <.003 Incline Creek at Highway 28 at Nev. InclineVillage, .043 0.010 437 1991–98 64 <.003 1988–98 .020 <.003 <0.003 68 <.003 <.003 431 .014 <.003 <.003 1990–98 <.003 .063 .013 <.003 229 .009 <.003 <.003 .147 <.003 <.003 <.003 .052 <.003 11 Incline Creek near Tributary at County Nev. Incline ClubVillage, Dr. 1991–98 84 <.003 .015 <.003 10 Nev. Village, Incline near Village Tyrol above Creek Incline 1990–98 244 <.003 .055 <.003 12 Glenbrook Creek(near mouth) at Glenbrook, 13 Nev. Glenbrook Creek at 14 Old Highway near Glenbrook, Nev. Logan House Creek near Glenbrook, 15 Nev. NorthLogan HouseCreek above Highway 50 near Glenbrook, Nev. 16 1991–98 1988–98 1991–88 Edgewoodnear Creek Stateline,atLake Tahoe 17 Nev. 70 333 67 Edgewood CreekTributary above Clubhouse 18 near Stateline,Nev. CulvertintoEdgewood Creek above 19 Highway 50Stateline, at Nev. <.003 <.003 <.003 1995–98 1984–98 Edgewood Creek(at Highway50) at Stateline,Nev. 1995–98 1989–98 291 .029 8 .082 .014 10 173 <.003 <.003 <.003 .007 <.003 .003 <.003 1992–98 .033 1.39 170 .566 .346 <.003 <.003 .144 .166 .006 .178 .003 Map number Table 11 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations Table 11 than] less <, Symbol: liter. per milligram mg/L, [Abbreviation: stations and miscellaneous water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations

44 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Dissolved ammonia nitrogen (mg/L) Minimum Maximum Median size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name belowCalif.confluence City, near Tahoe 1992–98 143 <.003 .016 <.003

. Dissolved ammonia nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen ammonia Dissolved . 20 Edgewood CreekatNev. nearPalisade Kingsbury, 21 Dr. Eagle Rock Creeknear Stateline, 22 Nev. Edgewood CreekTributarynear Daggett 23 Pass, Nev. Edgewood Creekbelow South near Benjamin Daggett Pass, Dr. Nev. 1990–98 1990–98 25 219Creek Trout (at Highway 50)South at Calif. LakeTahoe, 28 76Creek Trout at Pioneer nearTrail Calif. South Lake 29 Tahoe, 1990–98 <0.003 <.003Creek Trout at U.S. Forest Service Rd. 31 12N01near Meyers, Calif. 47 1990–98 Calif. Tahoe, Lake South at 50) Highway (at River Truckee Upper 0.045 33 1993–98 1990–98 1990–98 165 .058 Upper River Truckee at Highway 50 above Meyers, 36 Calif. 1993–98 <.003 169 151 0.003 208 Upper River Truckee at South Upper Rd. near Truckee Meyers, Calif. 184 <.003 1990–98 <.003 37 .007 .014 <.003 <.003 <.003 205 1990–98 General Creek (at Highway Calif. 89) nearMeeks 38 Bay, .139 Calif. City, Tahoe near 89) Highway (at .077 Creek Blackwood 39 225 .003 .026 <.003 .021 .027 CreekatPines,Highway Calif. 89 near Ward Tahoe 40 .003 <.003 <.003 Calif. City, at CreekStanfordcrossing RockTahoe Trail near Ward 41 <.003 <.003 1993–98 .030 <.003 1993–98 Creek Ward 1992–98 209 233 .099 154 <.003 1993–98 <.003 <.003 <.003 <.003 230 .012 .118 <.003 .012 <.003 <.003 <.003 .018 <.003 Map number Table 11 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations

RESULTS 45 Minimum Maximum Median Total organicTotal ammonia+ nitrogen (mg/L) size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area Station name . Total organic plus ammonia nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen ammonia plus organic Total . . Total organic plus ammonia nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen ammonia plus organic . Total 1 First Creek(at Highway Nev. 28) near2 Crystal Bay, Second CreeknearLakeshore at Nev. Crystal Dr. 3 Bay, Creek near mouth (at Wood Lakeshore near Nev.Crystal Dr.) Bay, 4 Creek above Jennifer Wood St. nearInclineNev. Village, 5 1991–98 Third Creek Nev.near (atLakeshore Crystal Bay, Dr.) 1991–986 1991–98 Nev. Village, Incline at Blvd. Village at 71 Creek Third 7 72 Nev. Village, Incline near tributary unnamed below Creek Third 1991–988 69 Incline Creek (above Lakeshore near Nev.9 Crystal Dr.) Bay, .06 1991–98 1988–98 0.05 62 Incline Creek at Highway 28 at Incline Nev.Village, .05 1991–98 455 8.2 64 1988–98 0.83 .05 68 3.0 <.04 426 <.04 .19 0.16 1990–98 1.9 <.04 24.0 <.04 .16 1.8 232 1.9 .18 3.0 .20 <.04 .14 .13 1.7 .21 .17 11 Incline Creek Tributary near at County Nev. Incline ClubVillage, Dr. 1991–98 84 .05 1.3 .17 10 Nev. Village, Incline near Village Tyrol above Creek Incline 1990–98 245 <.04 3.0 .16 12 Glenbrook Creek(near mouth) at Glenbrook, 13 Nev. Glenbrook Creek at 14 Old Highway near Glenbrook, Nev. Logan House Creek near Glenbrook, 15 Nev. NorthLogan HouseCreek above Highway 50 near Glenbrook, Nev. 16 1991–98 1988–98 1991–88 Edgewoodnear Creek Stateline,atLake Tahoe 17 Nev. 70 329 Edgewood CreekTributary above Clubhouse near Stateline,Nev. 66 1995–98 1984–98 .04 .06 .06 1989–98 289 8 1.1 6.0 177 .62 <.04 .39 .22 .20 .07 .15 1.7 5.5 2.0 .20 1.65 .32 18 CulvertintoEdgewood Creek above Highway 50Stateline, at Nev. 1995–98 10 .34 14.0 4.15 Map number Table 12 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations Table 12 than] less <, Symbol: liter. per milligram mg/L, [Abbreviation: stations and miscellaneous water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations

46 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Minimum Maximum Median Total organicTotal ammonia+ nitrogen (mg/L) size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name belowCalif.confluence City, near Tahoe 1992–98 141 <.04 1.4 .07

. Total organic plus ammonia nitrogen concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration nitrogen ammonia plus organic Total . 19 Edgewood Creek(at Highway50) 20 at Stateline,Nev. Edgewood CreekatNev. nearPalisade Kingsbury, Dr. 21 Eagle Rock Creeknear Stateline, 22 Nev. Edgewood CreekTributarynear Daggett 23 Pass, Nev. Edgewood Creekbelow South near Benjamin Daggett Pass, Dr. Nev. 1992–98 1990–98 1990–98 25 170Creek Trout (at Highway 50)South at Calif. 28 LakeTahoe, 219 75 Calif. Tahoe, Lake South near Trail Pioneer at Creek Trout 29 1990–98 0.04Creek Trout at U.S. Forest Service Rd. 12N01 31near Meyers, Calif. .05 1990–98 Calif. .04 Tahoe, Lake South at 4750) Highway (at River Truckee Upper 33 1993–98 1990–98 1990–98 1.1 Upper River Truckee at Highway 50 above Meyers, 36 Calif. 1993–98 167 5.9 167 1.7 154 211 Upper River Truckee at South Upper Rd. near Truckee Meyers, Calif. .12 183 1990–98 0.19 37 .04 <.04 .19 <.04 1990–98 General Creek (at Highway Calif. 89) near 38Meeks Bay, 0.58 .04 207 .25 .05 Blackwood Calif. Creek(at City, Highway89) near 39 Tahoe 16.0 227 2.1 Creek 2.8atPines,Highway Calif. 89 near Ward Tahoe 40 6.6 .26 .04 1.2 Calif. City, at CreekStanfordcrossing RockTahoe Trail near Ward 41 <.04 1993–98 .13 1993–98 Creek Ward 1992–98 .19 .16 .12 .87 209 .16 231 1.0 152 1993–98 .12 .04 <.04 <.04 230 .11 1.7 .57 <.04 .90 1.2 .12 .14 .10 .12 Map number Table 12 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations

RESULTS 47 Soluble reactive phosphorus (mg/L) Minimum Maximum Median size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area Station name . Soluble reactive phosphorus concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration phosphorus reactive Soluble . . Soluble reactive phosphorus concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration phosphorus reactive Soluble . 1 First Creek(at Highway 28) Nev. near2 Crystal Bay, Second CreeknearLakeshore at Nev. Crystal Dr. 3 Bay, Creek near mouth (at Wood Lakeshore near Nev.Crystal Dr.) Bay, 4 Creek above Jennifer Wood St. nearInclineNev. Village, 5 1991–98 Third Creek Nev.near (atLakeshore Crystal Bay, Dr.) 6 1991–98 Nev. Village, Incline at Blvd. Village at Creek Third 7 1991–98 71 Nev. Village, Incline near tributary unnamed below Creek Third 8 72 1991–98 69 Incline Creek (above Lakeshore near Nev.9 Crystal Dr.) Bay, .005 0.005 Incline Creek at Highway 28 at Nev. InclineVillage, 1991–98 1988–98 62 .011 .066 1991–98 0.046 437 64 .006 1988–98 .043 68 .018 .001 0.010 .003 432 .033 1990–98 .017 .002 .003 .048 .030 .017 233 .030 .073 .008 .008 .003 .008 .011 .074 .012 11 Incline Creek Tributary near at County Nev. Incline ClubVillage, Dr. 1991–98 83 .003 .025 .009 12 Glenbrook Creek(near mouth) at Glenbrook, 13 Nev. Glenbrook Creek at 14 Old Highway near Glenbrook, Nev. Logan House Creek near Glenbrook, 15 Nev. NorthLogan HouseCreek above Highway 50 near Glenbrook, Nev. 16 1991–98 Edgewoodnear Creek Stateline,at 1988–98Lake 1991–88 Tahoe 17 Nev. Edgewood CreekTributary above Clubhouse 18 near Stateline,Nev. 69 333 66 Culvert intoEdgewood Creek above Highway 50Stateline, at Nev. .002 .001 1995–98 .002 1984–98 1995–98 1989–98 .017 291 .087 8 .028 10 174 <.001 .020 .006 .013 .012 .013 .003 .019 1.55 .206 .243 .002 .084 .090 .014 10 Nev. Village, Incline near Village Tyrol above Creek Incline 1990–98 243 .001 .086 .011 Map number Table 13 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations Table 13 Table than] less <, Symbol: liter. per milligram mg/L, [Abbreviation: stations and miscellaneous water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada and California Basin, Tahoe Lake in the area, by stations, water-quality miscellaneous and stations

48 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Soluble reactive phosphorus (mg/L) Minimum Maximum Median size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name belowCalif.confluence City, near Tahoe 1992–98 143 .001 .016 .005

. Soluble reactive phosphorus concentration data for current USGS LTIMP surface-water quality sampling/gaging sampling/gaging quality surface-water LTIMP USGS current for data concentration phosphorus reactive Soluble . 19 Edgewood Creek(at Highway50) 20 at Stateline,Nev. Edgewood CreekatNev. nearPalisade Kingsbury, Dr. 21 Eagle Rocknear Creek Stateline, Nev. 22 Edgewood CreekTributarynear Daggett 23 Pass, Nev. Edgewood Creekbelow South near Benjamin Daggett Pass, Dr. Nev. 1992–98 25 1990–98 1990–98Creek Trout (at Highway 50)South at Calif. 28 LakeTahoe, 170 219 Calif. Tahoe, Lake South near Trail Pioneer at Creek Trout 29 76 0.007 1990–98 Calif. Meyers, near 12N01 Rd. Service Forest U.S. at Creek Trout 31 .003 Calif. Tahoe, .003Lake South at 50) Highway (at River Truckee Upper 33 1990–98 0.045 47 1993–98 1990–98 Calif. Meyers, above 50 Highway at River Truckee Upper 36 1990–98 .179 1993–98 165 .032 Upper River Truckee at South Upper Rd. near Truckee Meyers, Calif. .002 0.012 168 151 208 37 184 .003 1990–98 .010 Calif. .003 .004 Bay, Meeks near 89) .011 Highway (at Creek General 38 .023 .002 1990–98 .001 Calif. City, Tahoe 205 near 89) Highway (at Creek Blackwood 39 .067 Calif. 225Pines, .030 Tahoe .033 near 89 Highway at Creek Ward 40 .010 .023 .001 Calif. City, .032Tahoe near crossing Trail Rock Stanford at Creek Ward 41 .001 .010 .008 1993–98 .009 Creek Ward .009 1993–98 1992–98 .017 .005 209 .034 232 154 1993–98 .004 .001 .001 .007 .001 231 .030 .014 .002 .021 .004 .005 .034 .007 .007 Map number Table 13 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and stations

RESULTS 49 Total phosphorusTotal (mg/L) Minimum Maximum Median size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area Station name . Total phosphorus concentration data for current USGS LTIMP surface-water quality sampling/gaging stations and and stations sampling/gaging quality surface-water LTIMP USGS current for data concentration phosphorus Total . . Total phosphorus concentration data for current USGS LTIMP surface-water quality sampling/gaging stations and and stations sampling/gaging quality surface-water LTIMP USGS current for data concentration phosphorus Total . 1 First Creek(at Highway 28) Nev. near2 Crystal Bay, Second CreeknearLakeshore at Nev. Crystal Dr. Bay, 3 Creek near mouth (at Wood Lakeshore near Nev.Crystal Dr.) Bay, 4 Creek above Jennifer Wood St. nearInclineNev. Village, 5 1991–98 Third Creek Nev.near (atLakeshore Crystal Bay, Dr.) 6 1991–98 Nev. Village, Incline at Blvd. Village at Creek Third 7 1991–98 71 Nev. Village, Incline near tributary unnamed below Creek Third 8 72 72 1991–98 Incline Creek (above Lakeshore near Nev.9 Crystal Dr.) Bay, .023 0.018 Incline Creek at Highway 28 at Incline Nev. 62Village, 1991–98 1988–98 .027 4.58 440 1991–98 0.308 64 .032 1988–98 1.29 68 .085 .002 0.045 432 .014 .848 1990–98 .069 .014 9.42 2.00 .004 233 .074 1.30 1.19 .048 .035 .007 .042 .051 1.02 .050 11 Incline Creek Tributary near at County Nev. Incline ClubVillage, Dr. 1991–98 84 .024 .361 .046 10 Nev. Village, Incline near Village Tyrol above Creek Incline 1990–98 246 .014 .368 .036 12 Glenbrook Creek(near mouth) at Glenbrook,13 Nev. Glenbrook Creek at 14 Old Highway near Glenbrook, Nev. Logan House Creek near Glenbrook, 15 Nev. NorthLogan HouseCreek above Highway 50 near Glenbrook, Nev. 16 1991–98 Edgewoodnear Creek Stateline,atLake 1988–98 1991–88 Tahoe Nev. 17 Edgewood CreekTributary above Clubhouse 18 near Stateline,Nev. 70 334 67 Culvert intoEdgewood Creek 19 above Highway 50Stateline, at Nev. Edgewood Creek .015(at Highway50) at Stateline,Nev. .008 1995–98 .016 1984–98 1995–98 1989–98 393 8 1.98 .114 10 .283 176 <.002 .049 .032 .041 .485 .038 .016 1992–98 .261 2.16 11.1 170 .811 .021 .009 .262 4.30 .055 .507 .041 Map number Table 14 Table than] less <, Symbol: liter. per milligram mg/L, [Abbreviation: miscellaneous water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous Table 14 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous

50 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Total phosphorusTotal (mg/L) Minimum Maximum Median size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name belowCalif.confluence City, near Tahoe 1992–98 143 .005 1.63 .021

. Total phosphorus concentration data for current USGS LTIMP surface-water quality sampling/gaging stations and and stations sampling/gaging quality surface-water LTIMP USGS current for data concentration phosphorus Total . 20 Edgewood CreekatNev. nearPalisade Kingsbury, 21 Dr. Eagle Rock Creeknear Stateline, 22 Nev. Edgewood CreekTributarynear Daggett 23 Pass, Nev. Edgewood Creekbelow South near Benjamin Daggett Pass, Dr. Nev. 25 1990–98 1990–98Creek Trout (at Highway 50)South at Calif. LakeTahoe, 28 221 76Creek Trout at Pioneer nearTrail Calif. South Lake 29 Tahoe, 1990–98Creek Trout at U.S. Forest Service Rd. 31 12N01near Meyers, Calif. 0.007 Calif. Tahoe, .016Lake South at 50) Highway (at River Truckee Upper 33 47 1990–98 1993–98 Calif. Meyers, above 50 3.92 Highway at River Truckee Upper 36 1990–98 1990–98 167 1.16 1993–98 168 Upper River Truckee at South Upper Rd. near Truckee Meyers, Calif. .015 152 211 184 0.043 37 1990–98 .007 Calif. .003 Bay, Meeks near 89) Highway .065 (at Creek General 38 .140 .004 1990–98 .014 206 .004 Calif. City, Tahoe near 89) Highway (at Creek Blackwood 39 8.34 227 .393 CreekatPines,Highway 1.75 Calif. 89 near Ward Tahoe 40 .030 .009 .453 Calif. City, .230Tahoe near crossing Trail Rock Stanford at Creek Ward 41 .009 .033 1993–98 .040 Creek Ward .027 1993–98 1992–98 .248 .031 .031 210 233 .147 155 .021 1993–98 .007 .010 .026 .008 232 .351 1.88 1.01 .008 .021 .037 .029 2.14 .036 Map number Table 14 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous

RESULTS 51 in the Incline, Trout, and Ward Creeks and Upper Truc- plotted in figures 15 and 16. The data in these plots kee River watersheds, and decrease slightly in a down- exhibit wide scatter also; relations between concentra- stream direction in the Edgewood Creek watershed. tion and streamflow are complex.

Biologically reactive iron Load Estimations Concentrations of biologically reactive iron (table m 15) ranged from 8 micrograms per liter ( g/L) at Ward Comparison of Nutrient and Suspended-Sediment Creek at Highway 89 and below confluence stations to Load Estimations 131,000 mg/L at Highway 50 Culvert to Edgewood Creek during storm runoff. For all stations, the highest A non-parametric Wilcoxon signed-rank test median concentration was 44,200 mg/L at Highway 50 (Helsel and Hirsch, 1992) was performed on the ESTI- Culvert to Edgewood Creek and the lowest was 63 mg/L MATOR and FLUX estimates for each constituent at Ward Creek below confluence. For primary and sec- across the 10 primary stations for the study period. ondary stations, the highest median concentration was Comparisons between ESTIMATOR and FLUX load 1,120 mg/L at Third Creek near Crystal Bay and the estimation programs for the 10 primary stations are lowest was 63 mg/L at Ward Creek below confluence. listed in table 17. The results of the two load estimation Iron concentrations were observed to increase in a programs were found to be not significantly different downstream direction in the Incline, Trout, and Ward for only three of the seven constituents tested. The Creeks and Upper Truckee River watersheds, and range of difference was from -96 to 710 percent. decrease in a downstream direction in the Edgewood Examination of table 17 shows ESTIMATOR- Creek watershed. FLUX monthly load differences of dissolved nitrite plus nitrate nitrogen ranged from -39 to 17 percent and Suspended Sediment the Wilcoxon test found the loads not to be statistically Suspended-sediment concentrations (table 16) different. Dissolved ammonia nitrogen load differences ranged from less than 1 mg/L at five stations to 12,500 ranged from -33 to 119 percent and the Wilcoxon test mg/L at Highway 50 Culvert to Edgewood Creek dur- found the loads to be statistically different. Total nitro- ing storm runoff. For all stations, the highest median gen load differences ranged from -13 to -2 percent and concentration was 3,900 mg/L at Highway 50 Culvert the Wilcoxon test found the loads to be statistically dif- to Edgewood Creek and the lowest was 3 mg/L at three ferent. Soluble reactive phosphorus load differences stations. For primary and secondary stations, the high- ranged from -78 to 4 percent and the Wilcoxon test est median concentration was 59.5 mg/L at Third Creek found the loads to be statistically different. Total phos- near Crystal Bay and the lowest was 3 mg/L at Logan phorus load differences ranged from -65 to -3 percent House Creek near Glenbrook and Upper Truckee River and the Wilcoxon test found the results to be statisti- at Highway 50 above Meyers. Suspended sediment cally different. Biologically reactive iron load differ- increased in a downstream direction in the Incline, ences ranged from -96 to 90 percent and the Wilcoxon Trout, and Ward Creeks and Upper Truckee River test found the loads not to be statistically different. Sus- watersheds, and decreased in a downstream direction in pended-sediment loads differences ranged from -33 to the Edgewood Creek watershed. 710 percent and the Wilcoxon test found the loads not to be statistically different. Concentration Versus Time and Streamflow Monthly Loads from Primary and Nutrient and suspended-sediment concentrations Secondary Stations for the two index stations, Incline Creek near Crystal Bay and Upper Truckee River at South Lake Tahoe, are Summary statistics (median, maximum, and min- shown as time-series plots in figures 13 and 14. The imum) for estimated monthly loads of nutrients (from data in these figures exhibit wide scatter, especially for ESTIMATOR) and suspended sediment (from FLUX) the Incline Creek stations, and trends are difficult to for the 10 primary and 10 secondary stations for various discern. Nutrient and suspended-sediment concentra- periods of record are listed in tables 18–23 and discussed tions versus streamflow for the two index stations are below.

52 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada 93 513 807 786 679 618 437 973 824 242 564 484 248 371 612 588 g/L) 1,120 1,560 Median m 44,200 4,880 8,350 4,700 8,170 9,450 2,750 2,920 7,100 6,300 6,540 20,000 63,700 33,300 14,300 18,000 28,500 23,700 27,700 Maximum 131,000 40 22 67 67 43 43 18 73 85 34 110 193 148 219 220 193 267 646 Biologically ( reactiveBiologically iron 14,900 Minimum 8 71 69 69 61 68 64 82 66 69 10 113 308 303 207 195 230 189 168 size Sample Sample record 1991–98 1991–98 1991–98 1991–98 1988–98 1991–98 1991–98 1988–98 1990–98 1990–98 1991–98 1988–98 1991–88 1984–98 1991–98 1989–98 1995–98 1995–98 1992–98 Period of of Period Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area Station name g/L, microgram Symbol: <, less than] per liter. m First Creek (at Highway 28) near Crystal Bay, Nev. Nev. (atFirst Highway Creek 28) near Crystal Bay, Nev. near Crystal Bay, Second CreekLakeshore at Dr. Creek near mouth (atWood Lakeshore near Nev. Crystal Dr.) Bay, Creek above JenniferWood St. nearInclineNev. Village, Nev. near Crystal Bay, Third CreekLakeshore (at Dr.) Nev. Village, Incline at Blvd. Village at Creek Third Nev. Village, Incline near tributary unnamed below Creek Third Incline Creek (above Nev. near Lakeshore CrystalBay, Dr.) Incline Creek at Highway Nev. 28 at InclineVillage, Nev. Village, Incline near Village Tyrol above Creek Incline Nev. Village, Incline near Dr. Club County at Tributary Creek Incline Glenbrook Creek(near mouth) at Glenbrook, Nev. Nev. Glenbrook, near Highway at Old Creek Glenbrook Logan House Creek near Glenbrook, Nev. NorthLogan HouseCreek above Highway 50 near Glenbrook, Nev. near Stateline, Edgewood Nev. at CreekLake Tahoe EdgewoodaboveTributary Creek Clubhouse near Stateline,Nev. Culvert intoEdgewood Creek above Highway 50Stateline, at Nev. Nev. Stateline, at 50) Highway (at Creek Edgewood . Biologically reactive iron concentration data for current USGS LTIMP surface-water quality sampling/gaging stations and and stations sampling/gaging quality surface-water LTIMP USGS current for data concentration iron reactive Biologically . . Biologically reactive iron concentration data for current USGS LTIMP surface-water quality sampling/gaging stations and and stations sampling/gaging quality surface-water LTIMP USGS current for data concentration iron reactive Biologically . 1 2 3 4 5 6 7 8 9 11 10 12 13 14 15 16 17 18 19 Map number Table 15 Nevada and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous Table 15 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous [Abbreviation:

RESULTS 53 g/L) m Biologically ( reactiveBiologically iron Minimum Maximum Median size Sample Sample record Period of of Period Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay (fig.6) Tahoe Station name belowCalif.confluence City, near Tahoe 1992–98 142 8 10,600 63

. Biologically reactive iron concentration data for current USGS LTIMP surface-water quality sampling/gaging stations and and stations sampling/gaging quality surface-water LTIMP USGS current for data concentration iron reactive Biologically . 20 Edgewood CreekatNev. nearPalisade Kingsbury, 21 Dr. Eagle Rock Creeknear Stateline, 22 Nev. Edgewood CreekTributarynear Daggett 23 Pass, Nev. Edgewood Creekbelow South near Benjamin Daggett Pass, Dr. Nev. 25 1990–98 1990–98Creek Trout (at Highway 50)South at Calif. Lake 28Tahoe, 204 73Creek Trout at Pioneer nearTrail Calif. South Lake 29 Tahoe, 1990–98Creek Trout at U.S. Forest Service Rd. 31 12N01near Meyers, Calif. 166 145 Calif. Tahoe, Lake South at 50) Highway (at River Truckee Upper 45 33 1990–98 1993–98 41,400 Calif. Meyers, above 50 Highway at River Truckee Upper 36 1990–98 22,400 151 1990–98 1993–98 167 Upper River Truckee at South Upper Rd. near Truckee Meyers, Calif. 140 18 197 182 698 37 2,000 1990–98 70 103 General Creek (at Highway Calif. 89) nearMeeks 38 Bay, 3,600 51 1990–98 193 94 Calif. City, Tahoe near 89) 53 Highway (at Creek Blackwood 39 57,600 213 8,750 17,900 CreekatPines,Highway Calif. 89 near Ward Tahoe 40 139 12,100 38 4,210 Calif. City, Tahoe near crossing Trail Rock Stanford at Creek Ward 41 250 46 571 Creek Ward 158 1993–98 1993–98 368 5,500 1992–98 373 208 231 4,560 153 212 1993–98 32 140 73 16 230 14,800 7,650 9,670 8 448 143 177 33,900 210 Map number Table 15 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous

54 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Suspended sediment (mg/L) sediment Suspended Minimum Maximum Median s a m p li n g/ g ag i ng st t o ns

size Sample Sample t er q u a l ity record Period of of Period M P s ur L TI f a c e- w

Stateline area (fig. 4) (fig. area Stateline Glenbrook area (fig. 3) (fig. area Glenbrook Incline (fig.Village2) area d a ta f or c urr e nt U S G

Station name d i m ent c o nc e nt r a t ion e nd d - s . Su s p . Suspended sediment concentration data for current USGS LTIMP surface-water quality sampling/gaging stations stations sampling/gaging quality surface-water LTIMP USGS current for data concentration sediment Suspended . 1 6

1 First Creek(at Highway Nev. 28) near2 Crystal Bay, Second CreeknearLakeshore at Nev. Crystal Dr. 3 Bay, Creek near mouth (at Wood Lakeshore near Nev.Crystal Dr.) Bay, 4 Creek above Jennifer Wood St. nearInclineNev. Village, 5 1991–98 Third Creek Nev.near (atLakeshore Crystal Bay, Dr.) 6 1991–98 Nev. Village, Incline at Blvd. Village at Creek Third 7 71 1991–98 Nev. Village, 72 Incline near tributary unnamed below Creek Third 8 69 1991–98 Incline Creek (above Lakeshore nearNev. Crystal9 Dr.) Bay, 1 62 Incline Creek at Highway 28 at Nev. InclineVillage, 1991–98 1988–98 1 2 392 4,500 65 1991–98 1988–98 1 644 69 2,300 381 1 45 1 1,270 1990–98 18 39 1 3,930 232 2,480 1 46 1,080 1,840 60 19 1 35 1,530 24 16 11 Incline Creek near Tributary at County Nev. Incline ClubVillage, Dr. 1991–98 85 3 348 14 10 Nev. Village, Incline near Village Tyrol above Creek Incline 1990–98 245 1 443 7 12 Glenbrook Creek(near mouth) at Glenbrook, 13 Nev. Glenbrook Creek at 14 Old Highway near Glenbrook, Nev. Logan House Creek near Glenbrook, 15 Nev. NorthLogan House Creek above Highway 50 near Glenbrook, Nev. 16 1991–98 Edgewoodnear Creek Stateline,at 1988–98Lake 1991–88 Tahoe 17 Nev. 70 Edgewood CreekTributary above 290 Clubhouse 18 near Stateline,Nev. 68 Culvert intoEdgewood Creek above 19 Highway 50Stateline, at Nev. Edgewood Creek(at Highway50) at Stateline,Nev. 1995–98 1 1 1984–98 1 1995–98 255 1989–98 8 8 547 606 177 187 17 1 630 1992–98 2 9 6 4 167 12,500 272 388 325 3,900 1 59 3 5 130 5 Map number T a b l e Nevada and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and than] less <, Symbol: liter. per milligram mg/L, [Abbreviation: Table 16 Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and

RESULTS 55 n s Suspended sediment (mg/L) sediment Suspended l i n g /g a gi n g s t at i o Minimum Maximum Median m p size Sample Sample ter qu a li t y s record Period of of Period M P s u r f a c e- w L TI

U S G

Stateline area (fig. 4) (fig. area Stateline South Lake Tahoe area (fig. 5) (fig. area South Lake Tahoe Tahoe City to Meeksarea Bay(fig.6) Tahoe f o r c u rre n t

Station name c on e n t r at i d ata

n t belowCalif.confluence City, near Tahoe 1992–98 140 <1 440 5

. Su s pe n ded - e di m 1 6

20 Edgewood CreekatNev. nearPalisade Kingsbury, 21 Dr. Eagle Rocknear Creek Stateline, Nev. 22 Edgewood CreekTributarynear Daggett 23 Pass, Nev. Edgewood Creekbelow South near Benjamin Daggett Pass, Dr. Nev. 25 1990–98 1990–98Creek Trout (at Highway 50)South at Calif. LakeTahoe, 28 221 77 Calif. Tahoe, Lake South near Trail Pioneer at Creek Trout 29 1990–98Creek Trout at U.S. Forest Service Rd. 31 12N01near Meyers, Calif. 1 Calif. Tahoe, Lake South at 50) Highway (at River Truckee Upper 47 33 1 1990–98 1993–98 Calif. Meyers, above 50 Highway at River Truckee Upper 36 1990–98 1990–98 167 3,320 1993–98 173 Upper River Truckee at South 2,080 Upper Rd. near Truckee Meyers, Calif. 152 211 <1 187 37 1990–98 1 General Creek (at Highway Calif. 89) nearMeeks 38 Bay, 9 2 1990–98 154 209 25 1 1 Calif. City, Tahoe near 89) Highway (at Creek Blackwood 39 1 230 4,070 Calif.Pines, Tahoe near 89 Highway at Creek Ward 40 335 <1 642 499 Calif. City, at CreekStanfordcrossing Rock nearTahoe Trail Ward 3 41 458 <1 Creek Ward 1993–98 7 1993–98 1992–98 14 176 208 231 7 5 155 16 153 1993–98 4 231 1 1 <1 3 1,620 2,840 1 452 3,000 21 8 6 12 Map number and miscellaneous water-quality stations, by area, in the Lake Tahoe Basin, California and Nevada—Continued and California Basin, Tahoe Lake the in area, by stations, water-quality miscellaneous and T a b l e

56 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Dissolved nitrite plus nitrate nitrogen Dissolved ammonia nitrogen 0.080 0.020

0.060 0.015

0.040 0.010

0.020 0.005 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER MILLIGRAMS PER LITER 0 0 1/1/87 12/31/89 12/31/92 1/1/96 1/1/99 1/1/87 12/31/89 12/31/92 1/1/96 1/1/99 DATE DATE

Total nitrogen Soluble reactive phosphorus 0.60 0.040

0.030 0.40

0.020

0.20 0.010 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER MILLIGRAMS PER LITER

0 0 1/1/87 12/31/89 12/31/92 1/1/96 1/1/99 1/1/87 12/31/89 12/31/92 1/1/96 1/1/99 DATE DATE

Total phosphorus Biologically reactive iron 0.200 4,000

0.150 3,000

0.100 2,000

0.050 1,000 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER MICROGRAMS PER LITER 0 0 1/1/87 12/31/89 12/31/92 1/1/96 1/1/99 1/1/89 7/3/91 1/1/94 7/2/96 1/1/99 DATE DATE

Suspended sediment 200

150

100

50 CONCENTRATION, IN MILLIGRAMS PER LITER 0 1/1/87 12/31/89 12/31/92 1/1/96 1/1/99 DATE

Figure 13. Time-series plots of nutrient and suspended-sediment concentrations for Incline Creek near Crystal Bay. Note: Data in shaded area are below method reporting level.

RESULTS 57 Dissolved nitrite plus nitrate nitrogen Dissolved ammonia nitrogen 0.120 0.020 0.100 0.015 0.080

0.060 0.010

0.040 0.005 0.020 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER 0 MILLIGRAMS PER LITER 0 1/1/76 10/1/81 7/2/87 4/1/93 1/1/99 1/1/88 10/1/90 7/2/93 4/1/96 1/1/99 DATE DATE

Total nitrogen Soluble reactive phosphorus 0.80 0.040

0.60 0.030

0.40 0.020

0.20 0.010 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER

0 MILLIGRAMS PER LITER 0 1/1/88 10/1/90 7/2/93 4/1/96 1/1/99 1/1/80 10/1/84 7/2/89 4/2/94 1/1/99 DATE DATE

Total phosphorus Biologically reactive iron 0.400 2,000

0.300 1,500

0.200 1,000

0.100 500 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER

0 MICROGRAMS PER LITER 0 1/1/80 10/1/84 7/2/89 4/2/94 1/1/99 1/1/80 10/1/84 7/2/89 4/2/94 1/1/99 DATE DATE

Suspended sediment 400

300

200

100 CONCENTRATION, IN MILLIGRAMS PER LITER 0 1/1/72 10/1/78 7/2/85 4/1/92 1/1/99 DATE

Figure 14. Time-series plots of nutrient and suspended-sediment concentrations for Upper Truckee River at South Lake Tahoe. Note: Data in shaded area are below method reporting level.

58 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Dissolved nitrite plus nitrate nitrogen Dissolved ammonia nitrogen 0.120 0.020 0.100 0.015 0.080

0.060 0.010 0.040 0.005 0.020 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER MILLIGRAMS PER LITER 0 0 1 10 100 1 10 100 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

Total Nitrogen Soluable reactive phosphorus 0.040

1.20 0.030

0.80 0.020

0.40 0.010 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER 0 MILLIGRAMS PER LITER 0 1 10 100 1 10 100 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

Total phosphorus Biologically reactive iron 0.400 6,000

5,000 0.300 4,000

0.200 3,000

2,000 0.100 1,000 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER

0 MICROGRAMS PER LITER 0 1 10 100 1 10 100 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

Suspended sediment 600

500

400

300

200

100 CONCENTRATION, IN MILLIGRAMS PER LITER 0 1 10 100 STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 15. Plots of nutrient and suspended-sediment concentrations versus streamflow for Incline Creek near Crystal Bay. Note: Data in shaded area are below method reporting level.

RESULTS 59 Dissolved nitrite plus nitrate nitrogen Dissolved ammonia nitrogen 0.120 0.040

0.100 0.030 0.080

0.060 0.020

0.040 0.010 0.020 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER 0 MILLIGRAMS PER LITER 0 1 10 100 1,000 10,000 1 10 100 1,000 10,000 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

Total nitrogen Soluable reactive phosphorus 0.040

1.20 0.030

0.80 0.020

0.40 0.010 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER

0 MILLIGRAMS PER LITER 0 1 10 100 1,000 10,000 1 10 100 1,000 10,000 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

Total phosphorus Biologically reactive iron 0.600 6,000

0.500 5,000

0.400 4,000

0.300 3,000

0.200 2,000

0.100 1,000 CONCENTRATION, IN CONCENTRATION, IN MILLIGRAMS PER LITER 0 MICROGRAMS PER LITER 0 1 10 100 1,000 10,000 1 10 100 1,000 10,000 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

Suspended sediment 800

600

400

200 CONCENTRATION, IN MILLIGRAMS PER LITER 0 1 10 100 1,000 10,000 STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 16. Plots of nutrient and suspended-sediment concentrations versus streamflow for Upper Truckee River at South Lake Tahoe. Note: Data in shaded area are below method reporting level.

60 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada (kg) ESTIMATOR at Stateline Edgewood Creek Edgewood (kg) programs, programs, programs, programs, FLUX a a—Continued (kg) ESTIMATOR near Glenbrook (kg) FLUX Logan House Creek (kg) ESTIMATOR at Glenbrook Glenbrook Creek Glenbrook (kg) FLUX Total nitrogen Total (kg) Soluble reactive phosphorus Soluble reactive Dissolved ammonia nitrogen ESTIMATOR Dissolved nitrite + nitrate nitrogen + nitrate nitrite Dissolved Incline Creek Incline near Crystal Bay (kg) FLUX FLUX (kg) ESTIMATOR Third Creek Third near Crystal Bay (kg) FLUX . Comparison of monthly load summary statistics (sum, median, maximum, and minimum) and percent difference for load-estimation load-estimation for difference percent and minimum) and maximum, median, (sum, statistics summary load monthly of . Comparison . Comparison of monthly load summary statistics (sum, median, maximum, and minimum) and percent difference for load-estimation load-estimation for difference percent and minimum) and maximum, median, (sum, statistics summary load monthly of Comparison . SumMedianMaximumMinimumPercent difference in sumSum 1,550Median 5.95 83.8Maximum 1,530Minimum 1.50 1Percent difference in sum 5.91 85.7 3,320Sum .88 15.8 134 300Median 2,320 11.7 1.40Maximum 4.30Minimum .50 208 -31 9.65 86.4 sum in difference Percent 1.08 523 7.88 -30 1.30Sum 35,200 .20 1.65 349 32.9Median 317 2,335 1.90 117 8.00 31,100Maximum 0 27.3Minimum 17.1 272 1,900 .83 .90 -12 10.5 1.46 117Percent difference in sum -22 29,200 55.8 -39 10.3 .04 1,743 27,000 .29 3.70 .10 66.2 2.10 .40 101 65.2 798 41.0 3.10 1,947 18.2 5,210 0 3.49 55.5 0 3.17 .20 554 .70 827 .25 95.4 4 55.2 3.07 -8 15.3 4,950 -16 342 25.2 11.8 538 1,180 6.35 17 .01 .64 .90 0 .01 13.9 58.8 4.80 1,460 428 25.8 .30 1,170 25.9 5.20 1.74 1.80 12.4 1.10 1,360 0 69.4 5.17 .06 0.15 130 258 -1 19.0 249 -5 119 1.31 1.03 6,770 2.75 15.4 .80 2.60 .01 -3 125 0 294 53.7 256 6,270 0 2.65 18.8 0.74 1.72 .30 405 .07 104 76.2 .02 2.90 3 14 -7 .80 .11 425 17.8 53.1 23.3 2.08 0 .05 13.5 347 24.5 4.05 .01 -78 342 -7 27.5 3.82 1.50 1.40 -1 ESTIMATOR and FLUX, for the 10 primary LTIMP sampling stations, through water year 1998, Lake Tahoe Basin, California and Nevad and California Basin, Tahoe Lake 1998, year water through stations, sampling LTIMP 10 primary the for FLUX, and ESTIMATOR Table 17 [Abbreviation: kg, kilogram] ESTIMATOR and FLUX, for the 10 primary LTIMP sampling stations, through water year 1998, Lake Tahoe Basin, California and Nevad and California Basin, Tahoe Lake 1998, year water through stations, sampling primary 10 LTIMP the for FLUX, and ESTIMATOR Table 17 Table

RESULTS 61 . 0 2 - 1 4 (kg) (kg) ESTIMATOR ESTIMATOR 0 at Stateline Ward Creek at Ward Edgewood Creek Edgewood State 89 Highway (kg) (kg) programs, programs, FLUX FLUX a—Continued . 4 3 1 9 (kg) (kg) ESTIMATOR ESTIMATOR 1. 4 0 near Glenbrook near Tahoe City Tahoe near Blackwood Creek Blackwood (kg) (kg) FLUX FLUX Logan House Creek - 1 (kg) (kg) ESTIMATOR ESTIMATOR . 1 4 2 0 . at Glenbrook General Creek near MeeksBay near Glenbrook Creek Glenbrook (kg) (kg) FLUX FLUX 1 . 0 8 Total phosphorus Total - 33 Suspended sediment (kg) (kg) Biologically reactive iron ESTIMATOR ESTIMATOR Dissolved nitrite + nitrate nitrogen + nitrate nitrite Dissolved 2 . 0 Incline Creek Incline near Crystal Bay (kg) (kg) South Lake Tahoe South Lake FLUX FLUX FLUX FLUX Upper Truckee River at Upper Truckee 3 . 2 (kg) (kg) ESTIMATOR ESTIMATOR 4 . 6 0 Third Creek Third Trout Creek at Trout near Crystal Bay (kg) (kg) South Lake Tahoe South Lake FLUX FLUX sum 4 sum

. Comparison of monthly load summary statistics (sum, median, maximum, and minimum) and percent difference for load-estimation load-estimation for difference percent and minimum) and maximum, median, (sum, statistics summary load monthly of Comparison . d i f e r en c i n

SumMedianMaximumMinimumPercent difference in sumSum 8,930Median 26.0 875Maximum 8,180Minimum 6.20 -8 24.2Percent difference in sum 576 7,300 3.55 124,000Sum 15,700 25.3Median 550 580 6,990 132,000Maximum 4.00 130 6,980Minimum 22.9 121,000 610 -6 716 2,630P e rce n t -4 2.30 103,000 17,500,000 6,520 97.5 1,150 10.5 18,200,000 2,080,00 21,200 156 463 91,600 2,610,000 8,370,000 6,410 .40 1,840 21,000 96.8 5,630,000 2.59 13,400 147 397,000 135 544 6,430 1,240 -15 438,000 35,300Sum .09 76.1 906,000 -56 1,480 142Median .20 433,000 1,210 433 7,530 15.4Maximum 8,380 42,700 0 17.7M i n m u 1,380 1,580 83,200 137,000 .24 14.3 64.9 201 678 559 242,000 24,100 1,520 .62 -85 13,500 .02 9,320 17.2 169 431,000 23,300 198 27.4 316 -3 436 1.20 45,300 6.20 8,880 371,000 0 14.6 4.30 166 1,310 28.8 188 1.30 30,000 10.9 22,100 36.8 4.30 1,150 87,400 .04 279 22,900 59.2 729 -7 93.6 0 -4 70.4 233 64.0 1,220 4,450 848 2.70 47.9 1,340 2,120 1.55 55.9 631 11,700 -3 2.32 55.4 12,100 299 12.8 508 3,030 12.4 3,560 783 3.65 179 3.66 608 Percent difference in sum -5 4 10 3 17 ESTIMATOR and FLUX, for the 10 primary LTIMP sampling stations, through water year 1998, Lake Tahoe Basin, California and Nevad and California Basin, Tahoe Lake 1998, year water through stations, sampling primary 10 LTIMP the for FLUX, and ESTIMATOR Table 17 Table

62 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada (kg) ESTIMATOR Ward Creek at Ward State 89 Highway (kg) programs, programs, FLUX a—Continued (kg) ESTIMATOR near Tahoe City Tahoe near Blackwood Creek Blackwood (kg) FLUX (kg) ESTIMATOR General Creek near MeeksBay near (kg) FLUX Total nitrogen Total Total phosphorus Total Soluble phosphorus Soluble (kg) Biologically reactive iron Dissolved ammonia nitrogen ESTIMATOR (kg) South Lake Tahoe South Lake FLUX FLUX Upper Truckee River at Upper Truckee (kg) ESTIMATOR Trout Creek at Trout (kg) South Lake Tahoe South Lake FLUX . Comparison of monthly load summary statistics (sum, median, maximum, and minimum) and percent difference for load-estimation load-estimation for difference percent and minimum) and maximum, median, (sum, statistics summary load monthly of Comparison . SumMedianMaximumMinimum sum in difference Percent Sum 1,310Median 9.45 32.5MaximumMinimum 883 3.70 -33Percent difference in sum 5.74 24.65 1.68 3,530Sum 75,900 171 13.6Median 3,710 314 2,740 72,900Maximum .50 66.5Minimum 10.5 120 4,300 -4 293 211,000Percent difference in sum -22 385 48.0 13,700 .17 200,000Sum 6,160 20.4 .70 489Median 13,100 18.1 313 209 24,100Maximum 13.2 6,070 .10 18.6Minimum 0.73 3.00 413 23,700 -1 16.9 1,610Percent 1,140 difference in sum 249 14.3 -19 -5 8,110 .07 2.85 103,000 62.2 2.65Sum 77,600 1,550 1,080 26.1 14.1Median 5,990 140 356 8,080 36,200 1.60 73,000Maximum 53.2 2.73 10,600 .30 .40 12.6 1,910 22.1 591 14.3 -65 392 64,200 87.7 1.44 12,200 998 591 0 33.6 1.25 .32 4,820,000 .46 8.38 -5 -2 3,130 61,300 513 93.3 535,000 2.65 1,340 95.4 205,000 897 6.70 39.0 513 33.6 29.6 1.35 3,160 0 13,000 9,120 2.10 77.1 .30 1,060 646,000 2.32 101 6.84 30.9 2,260 29.6 -5 755,000 30,600 8,500 1.97 407 .65 1,010 -10 .01 1.25 2,230 4.40 107 -13 12.6 0 64,700 -6 24,800 43,700 1,160 425 1.40 1.35 3.92 1.00 2,550 30,000 11.3 127 30,100 1,960 .01 6,620 1.35 1,830 243,000 1.00 14.1 34.4 23,700 3,960 -7 31.9 97.5 420,000 6,180 -1 13,300 4.20 -13 32.5 11,500 3.84 .10 28.6 143,000 108 11,200 183,000 5.00 272,000 327 .03 2,240 15.3 24,100 -31 0 265 127,000 -28 15.3 0.09 60.7 51.7 -44 ESTIMATOR and FLUX, for the 10 primary LTIMP sampling stations, through water year 1998, Lake Tahoe Basin, California and Nevad and California Basin, Tahoe Lake 1998, year water through stations, sampling primary 10 LTIMP the for FLUX, and ESTIMATOR Table 17 Table

RESULTS 63 (kg) ESTIMATOR Ward Creek at Ward State 89 Highway (kg) programs, programs, FLUX a—Continued Results same/not Results (kg) ESTIMATOR near Tahoe City Tahoe near Blackwood Creek Blackwood (kg) FLUX Accept null hypothesis, Ho hypothesis, (kg) 3,670,000 31,500,000 255,000,000 17,200,000 46,500,000 ESTIMATOR Test statistic, Ts Test General Creek near MeeksBay near (kg) FLUX SUMMARY Suspended sediment Wilcoxon Wilcoxon (kg) Biologically reactive iron signed-rank test ESTIMATOR (kg) South Lake Tahoe South Lake FLUX FLUX Upper Truckee River at Upper Truckee Range of Range of percent difference difference percent (kg) ESTIMATOR Trout Creek at Trout (kg) South Lake Tahoe South Lake FLUX Constituent Nitrite + nitrateDissolved ammonianitrogen Total Soluble phosphorusphosphorus Total to -32 119 -39 to 17Biologicallyiron reactive Suspended sediment to -78- 5 to -13 -2 -96 to 90 -3 to -65 5 24 -33 to 709 5 27 0 0 25 8 8 8 8 8 Accept 8 Reject 8 Reject Accept Reject Different Same Reject Accept Different Different Same Different Same . Comparison of monthly load summary statistics (sum, median, maximum, and minimum) and percent difference for load-estimation load-estimation for difference percent and minimum) and maximum, median, (sum, statistics summary load monthly of Comparison . MinimumPercent difference in sumSum 250 -96 190 21,800,000 18,900,000 53,500,000 56,300,000 24.3 3,500,000 17 27.8 2.30 3.42 21 37.3 67.6 73 .10 .18 90 MedianMaximumMinimumPercent difference in sum 1,130,000 40,600 1,380,000 3,120 24,900 3,670,000 -13 7,950,000 40,900 432 914,000 34,200 986,000 227 6,450,000 785 207,000,000 384 5 4,470,000 37,600,000 789 54.4 6,010 83.8 4,240 5 129 3,950 178 1,750 710 15.4 32.2 170 ESTIMATOR and FLUX, for the 10 primary LTIMP sampling stations, through water year 1998, Lake Tahoe Basin, California and Nevad and California Basin, Tahoe Lake 1998, year water through stations, sampling primary 10 LTIMP the for FLUX, and ESTIMATOR Table 17 Table

64 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Dissolved nitrite plus nitrate nitrogen Total phosphorus Estimated monthly loads of dissolved nitrite plus Estimated monthly loads of total phosphorus for nitrate nitrogen for the study period ranged from 0.01 the study period ranged from 0.02 kg/mo at Logan kilogram per month (kg/mo) at Logan House Creek near Glenbrook and Ward Creek below confluence to House Creek near Glenbrook to 6,180 kg/mo at Black- 848 kg/mo at Upper Truckee River at South Lake wood Creek near Tahoe City. The highest median Tahoe. The highest median monthly load was 64.0 monthly load was 101 kg/mo at Upper Truckee River at kg/mo at Upper Truckee River at South Lake Tahoe and South Lake Tahoe and the lowest median was 0.25 the lowest median was 0.20 kg/mo at Logan House kg/mo at Logan House Creek near Glenbrook. Creek. Dissolved nitrite plus nitrate nitrogen accounted for about 25 percent of the total nitrogen load for all stations. Biologically reactive iron Estimated monthly loads of biologically reactive Dissolved ammonia nitrogen iron for the study period ranged from 0.04 kg/mo at Estimated monthly loads of dissolved ammonia Logan House Creek near Glenbrook to 183,000 kg/mo nitrogen for the study period ranged from 0.01 kg/mo at Blackwood Creek near Tahoe City. The highest at Logan House Creek, Glenbrook Creek at Glenbrook, median monthly load was 1,160 kg/mo at Upper Truc- Ward Creek at Highway 89 and Ward Creek below con- kee River at South Lake Tahoe and the lowest median fluence to 120 kg/mo at Upper Truckee River at South was 1.30 kg/mo at Logan House Creek near Glenbrook. Lake Tahoe. The highest median monthly load was 10.5 kg/mo at Upper Truckee River at South Lake Tahoe and the lowest median was 0.07 kg/mo at Logan House Suspended sediment Creek near Glenbrook. Dissolved ammonia nitrogen accounted for about 7 percent of the total nitrogen load Estimated monthly loads of suspended sediment for all stations. for the study period ranged from 0.1 kg/mo at Logan House Creek near Glenbrook to 6,500,000 kg/mo at Total nitrogen Blackwood Creek near Tahoe City. The highest median monthly load was 40,900 kg/mo at Upper Truckee Estimated monthly loads of total nitrogen for the River at South Lake Tahoe and the lowest median was study period ranged from 0.07 kg/mo at Logan House 36.8 kg/mo at Logan House Creek near Glenbrook. Creek near Glenbrook and Ward Creek below confluence to 13,100 kg/mo at Upper Truckee River at South Lake Tahoe. The highest median monthly load was 413 Index station monthly loads kg/mo at Upper Truckee River at South Lake Tahoe and the lowest median was 2.65 kg/mo at Logan House Plots of estimated monthly loads for nutrients and Creek near Glenbrook. suspended sediment for the two index primary stations, Incline Creek near Crystal Bay and Upper Truckee Soluble reactive phosphorus River at South Lake Tahoe, for various periods of record are shown in figures 17–22. Monthly loads for Estimated monthly loads of soluble reactive phos- Incline Creek near Crystal Bay are grouped by nitrogen phorus for the study period ranged from 0.01 kg/mo at (fig. 17), phosphorus (fig. 18), and biologically reactive Logan House Creek near Glenbrook and Ward Creek iron and suspended sediment (fig. 19). Upper Truckee below confluence to 392 kg/mo at Upper Truckee River at South Lake Tahoe. The highest median monthly load River at South Lake Tahoe monthly loads are grouped was 16.9 kg/mo at Trout Creek at South Lake Tahoe and by nitrogen (fig. 20), phosphorus (fig. 21), and biolog- the lowest median was 0.05 kg/mo at Logan House ically reactive iron and suspended sediment (fig. 22). Creek near Glenbrook. Soluble reactive phosphorus Median monthly loads for the period of record for these load accounted for about 18 percent of the total phos- two stations were summarized by months and seasons phorus load for all stations. and also included in figures 17–22.

RESULTS 65 .1 6.2 6.80 52.7 36.8 eriod of eriod 908 559 p period of of period 2,200 4,450 15,700 42,700 13,500 30,000 ( k g / m o ) 1988–98 1988–98 1988–98 1988–98 1988–98 401,000 sediment 1,840 1,360 Suspended 21,200 2,080,000 Basin, California and California Basin,

Basin, California and Nevada and California Basin, .62 .04 .24 6.12 1.30 97.5 45.9 76.1 31.4 64.9 716 544 198 233 ( k g / m o ) 1990–98 1990–98 1990–98 1990–98 1990–98 6,980 6,410 1,210 1,150 Biologically Biologically reactive iron reactive iron .09 .24 .25 .02 .04 3.55 1.55 2.30 1.32 2.59 24.2 22.9 14.3 14.6 Total 576 610 135 166 ( k g / m o ) 1988–98 1988–98 1988–98 1988–98 1988–98 phosphorus phosphorus .64 .20 .30 .02 .07 .05 .01 .01 3.07 5.17 1.03 0.74 2.08 3.82 55.2 69.4 18.8 27.5 ( k g / m o ) 1988–98 1988–98 1988–98 1988–98 1988–98 phosphorus phosphorus Soluble reactive .15 .07 .49 7.50 5.51 1.17 2.65 p e r m o n t h] 10.3 95.4 15.3 12.4 53.1 Total

117 428 125 425 ( k g / m o ) 1988–98 1988–98 1988–98 1988–98 1988–98 nitrogen nitrogen 1,900 1,950 EdgewoodStatelineat Creek Third Creek nearCrystalThird Bay Creek Inclinenear Crystal Creek Bay Glenbrook Creek at Glenbrook at Creek Glenbrook k i l o g ram

Logan House Creek near Glenbrook near LoganHouse Creek .20 .07 .29 .08 .25 .01 .02 .07 .01 .01 1.08 7.88 1.46 3.17 1.74 1.72 10.5 53.7 ) nitrogen 4 ( k g / m o ) 1988–98 1988–98 1988–98 1988–98 1988–98 ammonia Dissolved k i l o m e t r; g / ; (NH

per s q ua r e

) nitrogen nitrate ( nitrate 3 + .88 .38 .56 .83 .04 .08 .20 .01 .04 5.91 9.65 1.30 3.49 5.20 85.7 86.4 17.1 25.8 (k g / m o ) 1988–98 1988–98 1988–98 1988–98 1988–98 NO , k i l ogr a m Dissolved + 2 2 m nitrite nitrite NO k i l ogr a m ; g /

) ) ) ) 2 2 2 2 k g,

. Nutrient and suspended-sediment monthly load summary statistics (median, maximum, and minimum) and median monthly yields for for yields monthly median and minimum) and maximum, (median, statistics summary load monthly suspended-sediment and Nutrient . . Nutrient and suspended-sediment monthly load summary statistics (median, maximum, and minimum) and median monthly yields for for yields monthly median and minimum) and maximum, (median, statistics summary load monthly suspended-sediment and . Nutrient i a t ons: Median Maximum Minimum (kg/km Yield Median Maximum Minimum (kg/km Yield Median Maximum Minimum (kg/km Yield Median Maximum Minimum (kg/km Yield Median Maximum Table 18 Table Tahoe Lake the in stations sampling primary 10 LTIMP the for record of period complete for and 1988–98) years (water comparison Nevada—Continued Comparison period Comparison period Comparison period Comparison period Comparison period Table 18 Tahoe Lake the in stations sampling primary LTIMP 10 the for of record period complete for and 1988–98) years (water comparison [ A bbr e v

66 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada period of period ( k g / m o ) sediment Suspended Basin, California and and California Basin, ( k g / m o ) Biologically Biologically reactive iron reactive iron Total ( k g / m o ) phosphorus phosphorus ( k g / m o ) phosphorus phosphorus Soluble reactive Total ( k g / m o ) nitrogen nitrogen EdgewoodStatelineat Creek General Creek near Meeks Bay Meeks near Creek General Trout Creek at South Lake Tahoe Creek Trout Upper Truckee River at South Lake Tahoe River Truckee Upper ) nitrogen 4 ( k g / m o ) ammonia Dissolved (NH ) nitrogen ) nitrate 3 + NO (k g / m o ) 1988–98 1988–98 1988–98 1988–981988–98 1988–98 1988–98 1990–98 1988–98 1988–98 1988–98 1988–98 1990–98 1988–98 1982–98 1988–98 1988–98 1982–981983–98 1982–98 1988–98 1990–98 1988–98 1982–98 1983–98 1983–98 1983–98 1983–98 1985–98 1988–98 1988–98 1985–98 1985–98 1990–98 1985–98 Dissolved + 2 nitrite (NO ) .36) .12 3.66 .21 .26 .05) 1.01 2.79 .38 16.1 .13 307 .08 .59 2.95 9.52 .08 219 .55 8.57 237 2 2 2 . Nutrient and suspended-sediment monthly load summary statistics (median, maximum, and minimum) and median monthly yields for for yields monthly median and minimum) and maximum, (median, statistics summary load monthly suspended-sediment and Nutrient . MedianMaximumMinimum (kg/km Yield 119 22.0 3.83Median 5.74Maximum 24.6Minimum 1.68 (kg/km Yield 4,300 293 48.0 848 53.0 1.08 168 13.8 3.98 10.5 120 860 61.9 .17 12.41 13,100 413 13,000 1,000 14.3 123 392 820,000 23,000 11.1 3,120 .46 3,160 76.7 1.97 64,700 1,200 3,670,000 27.8 33,200 227 MedianMaximumMinimum 188 28.8 3.23Median 5.74Maximum 24.6Minimum 1.68 4,300 293 48.0 848 64.0 1.08 249 16.9 2.85 10.5 120 1,910 87.7 .17 8.38 13,100 413 13,000 1,000 14.3 123 392 1,130,000 14.3 40,600 .46 3,120 3,160 101 1.97 64,700 1,160 27.8 3,670,000 40,900 227 MedianMaximumMinimum 55.4 2.32 .14 18.6 0.73 .07 1,550 22.1 1.44 30.9 2.32 .65 425 11.3 1.35 3,960 32.5 3.42 914,000 785 54.4 Minimum (kg/km Yield 1.31 .11 13.5 1.40 4.30 47.9 631 comparison (water years 1988–98) and for complete period of record for the 10 primary LTIMP sampling stations in the Lake Tahoe Lake the in stations sampling primary 10 LTIMP the for record of period complete for and 1988–98) years (water comparison Nevada—Continued Comparison period Comparison period Table 18 Table Period of record Period of record Period of record

RESULTS 67 period of period ( k g / m o ) sediment Suspended Basin, California and and California Basin, ( k g / m o ) Biologically Biologically reactive iron reactive iron Total ( k g / m o ) phosphorus phosphorus ( k g / m o ) phosphorus phosphorus Soluble reactive Total ( k g / m o ) nitrogen nitrogen General Creek near Meeks Bay Meeks near Creek General Ward Creek at State Highway Ward 89 Blackwood Creek near Tahoe City BlackwoodnearTahoe Creek ) nitrogen 4 ( k g / m o ) ammonia Dissolved (NH ) nitrogen nitrogen ) nitrate 3 + NO (k g / m o ) 1988–98 1988–98 1988–98 1988–981988–98 1988–98 1988–98 1990–98 1988–98 1988–98 1988–98 1988–98 1990–98 1988–98 1988–98 1988–981986–98 1988–98 1988–98 1988–98 1988–98 1988–98 1990–98 1986–981986–98 1988–98 1986–98 1988–98 1986–98 1988–98 1986–98 1986–98 1986–98 1986–98 1986–98 Dissolved + 2 nitrite (NO ) .08 .04) 1.16 .40 .11 .10) .51 2.69 .15 1.70 .13 30.2 .05 1.00 1.94 11.0 .15 238 .63 2.84 165 2 2 2 . Nutrient and suspended-sediment monthly load summary statistics (median, maximum, and minimum) and median monthly yields for for yields monthly median and minimum) and maximum, (median, statistics summary load monthly suspended-sediment and Nutrient . MedianMaximumMinimum (kg/km Yield 783 11.4 .43Median 2.73Maximum 53.2Minimum .32 (kg/km Yield 12,200 77.1 608 3.82 6.84 127 .02 3.83 1.00 1.35 29.6 6,180 28.6 .01 5.00 5,540 183,000 48.8 316 6,500,000 .23 84.6 108 3.88 6,820 129 .03 2,240 15.8 127,000 .09 71.5 4,470,000 4,160 .30 15.4 MedianMaximumMinimum (kg/km Yield Median 43.5 1.58Maximum 0.14Minimum 18.6 0.73 783 12.4 0.07 .43s 1,550 22.1Median 1.44 2.73Maximum 53.2Minimum 30.9 .32 2.10 12,200 0.65 77.1 425 608 6.84 3.66 9.74 1.35 127 .02 3.92 3,960 32.5 1.00 1.35 29.6 6,180 3.42 28.6 914,000 .01 576 5.00 5,540 183,000 48.8 54.4 265 6,500,000 .23 67.6 108 3.84 6,000 129 .03 2,240 15.3 127,000 .09 51.7 4,470,000 3,950 .18 32.2 comparison (water years 1988–98) and for complete period of record for the 10 primary LTIMP sampling stations in the Lake Tahoe Lake the in stations sampling primary 10 LTIMP the for record of period complete for and 1988–98) years (water comparison Nevada—Continued Comparison period Comparison period Table 18 Table Comparison period Period of record Period of record

68 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada ( k g / m o ) sediment Suspended Suspended e in sums between between sums e in e in sums between between sums e in ( k g / m o ) Biologically Biologically reactive iron ing stations in the Incline Creek Creek Incline the in stations ing ing stations in the Incline Creek Creek Incline the in stations ing Total ( k g / m o ) phosphorus Soluble reactive ( k g / m o ) phosphorus Total ( k g / m o ) nitrogen , kilogram, per squarekilometer; kg/mo.,kilogram permonth. Symbol:—,not applicable] 2 ) nitrogen Incline Creek at Highway 28 Highway at Creek Incline 4 Incline Creek near Crystal Bay Crystal near Creek Incline ( k g / m o ) ammonia ammonia Dissolved Incline Village Creek aboveTyrol (NH + 2 ) nitrogen ) nitrogen 3 ( k g / m o ) NO + nitrate (NO + nitrate Dissolved nitrite Dissolved , acre-feet, per squaremile; kg, kilogram; kg/km runoff 2 annual (acre-ft) Average Average 90————— )930—— )1,040——————— )1,180——————— 2 2 2 ) —) .62 — .08) 6.76 .52 .41 — .09 1.79 4.93 .61 32.2 .35 2,710 .04 1.68 5.15 27.2 .30 1,310 1.04 4.75 257 2 2 2 . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary runoff and load monthly suspended-sediment and . Nutrient . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary runoff and load monthly suspended-sediment and Nutrient . Unit runoff (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit Percent change in sum54402831352517 23 sum2439235234434441 in sum2221491731323936 in sum54402831352517 in change change change Sum —MedianMaximumMinimum 1,960Percent (kg/km Yield 206 6,220 (average)Sum —Median 23,900 10.8 —MaximumMinimumPercent 1,040 86.4 1.46 (kg/km Yield 1.30 (average) 4,730 6,500 117Sum 10.5 — —Median 6.19 .28 —Maximum 99,400 1,950Minimum 1,200 7.12 4,370,000 Percent 16.2 55.0 1.05 (kg/km Yield 69.4 .91 30.9 159 3,370 (average) 58.2 1.03 — 8.17 — 610 11,600 558 4.53 — .19 833 4.13 3.96 776 6,410 20,200 48.3 689 6.89 .31 19.8 76.1 .17 401,000 41.2 57.5 3,680 38.0 3.34 .54 2,200 321 278 .08 7,470 55,500 630 2.25 15,400 2.29 2,590,000 3,210 2.51 364 23.2 44.1 7.66 142,000 1,620 .26 2,730 152 56.0 16,300 .92 1,900 1,840 1,003,000 168,000 4.56 94.5 Table 19 stations, and monthly median units/yields between stations for period of comparison (water years 1991–98) for three LTIMP sampl LTIMP three for 1991–98) years (water comparison of period for stations between units/yields median monthly and stations, Nevada—Continued Basin, Tahoe Lake area, Village Incline the in watershed, stations, and monthly median units/yields between stations for period of comparison (water years 1991–98) for three LTIMP sampl LTIMP three for 1991–98) years (water comparison of period for stations between units/yields median monthly and stations, Nevada Basin, Tahoe Lake area, Village Incline the in watershed, Table 19 [Abbreviations:acre-ft, acre-feet; acre-ft/ mi

RESULTS 69 (kg/mo) sediment Suspended e in sums between between sums e in e in sums between between sums e in (kg/mo) Biologically reactive iron f record for three LTIMP sampling sampling LTIMP three for f record f record for three LTIMP sampling sampling LTIMP three for f record Total (kg/mo) phosphorus (kg/mo) phosphorus Soluble reactiveSoluble Total (kg/mo) nitrogen , acre-feet, per square mile; kg/mo., kilogramper month. Symbol:—,not applicable] 2 Edgewood at Stateline Creek Edgewood Creek at Palisade Dr. at Palisade Creek Edgewood Eagle Stateline near Creek Rock ) nitrogen 4 (kg/mo) ammonia Dissolved (NH + 2 ) nitrogen ) nitrogen 3 (kg/mo) , kilogram per square kilometer; acre-ft/ mi acre-ft/ kilometer; square per , kilogram 2 NO + nitrate (NO Dissolved nitrite runoff (acre-ft) Average annual annual Average )620——————— )345——————— 2 2 ) —) .36 — .12 3.66 .17 .26 .03 1.01 3.09 16.1 .13 307 .64 12.9 1,200 2 2 . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary runoff and load monthly suspended-sediment and . Nutrient . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary runoff and load monthly suspended-sediment and . Nutrient Unit runoff (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit ecn nu193553 6 31515137 input169 Sum —MedianMaximumMinimum 171Percent input (kg/km Yield 1,080 (average) — 20.0Median — 1.41 31MaximumMinimum 3,080 8.12 .23Sum — 32 .08Median — —Maximum 97.7Minimum — 25.1 .89Percent 51.1 .03 7 719 565 (average) 1.16 254 8.12 1.08 — .08 9.58 .84 13,100 — 49 .55 .19 .89 5.75 5.21 965 850,000 .03 2.09 .12 29 .12 17.3 254 .09 105 83.0 53.1 .84 .31 .50 13.0 9,740 47 894 .02 .54 5.75 193 40.8 .12 5.56 87,700 .78 2.44 83.0 56 3.25 1,700 163 1.88 .50 894 72.9 2.75 .19 52,000 94 7.21 5.56 5,300 87,700 23.1 .51 163 64.9 711 4.30 3,420 30.7 Percent change in sum53599036564037-52 in change Sum —MedianMaximumMinimum 538Percent (kg/km Yield (average) 3,480 — 294 5.20 — 6,270 25.8 1.72 1.31 342 53.1 53.7 .11 1,520 425 3.82 13.5 23,300 14.6 27.5 431,000 1.40 233 166 4.30 4,450 1,150 47.9 30,000 631 Table 20 o period complete and 1992–98) years (water comparison of period for stations between units/yields median monthly and stations, Nevada—Continued Basin, Tahoe Lake area, Stateline the in watershed, Creek Edgewood the in stations Comparison period: record: of Period Comparison period: Table 20 [Abbreviations: acre-ft, acre-feet; kg, kilogram; kg/km stations, and monthly median units/yields between stations for period of comparison (water years 1992–98) and complete period o period complete and 1992–98) years (water of comparison period for stations between units/yields median monthly and stations, Nevada Basin, Tahoe Lake area, Stateline the in watershed, Creek Edgewood the in stations

70 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada (k g / m o ) sediment Suspended e in sums between between sums e in (k g / m o ) Biologically reactive iron f record for three LTIMP sampling sampling LTIMP three for f record Total (k g / m o ) phosphorus (k g / m o ) phosphorus Soluble reactiveSoluble Total (k g / m o ) nitrogen Eagle Stateline near Creek Rock ) nitrogen 4 (k g / m o ) ammonia Dissolved (NH + 2 ) nitrogen ) nitrogen 3 (k g / m o ) NO + nitrate (NO Dissolved nitrite runoff (acre-ft) Average annual annual Average )897——————— 2 ) — 0.34 0.07 7.98 0.48 1.69 14.2 436 2 . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary runoff and load monthly suspended-sediment and . Nutrient MedianMaximumMinimum — — — 2.09 .51 .09 .31 .10 .02 40.8 7.33 1.91 1.88 .35 .18 7.21 2.48 .51 64.9 12.4 3.55 3,420 225 30.7 Unit runoff (acre-ft/mi runoff Unit Yield (kg/km Yield Table 20 Period of record: stations, and monthly median units/yields between stations for period of comparison (water years 1992–98) and complete period o period complete and 1992–98) years (water comparison of period for stations between units/yields median monthly and stations, Nevada—Continued Basin, Tahoe Lake area, Stateline the in watershed, Creek Edgewood the in stations

RESULTS 71 (kg/mo) sediment Suspended Suspended e in sums between between sums e in (kg/mo) Biologically Biologically reactive iron f record for three LTIMP sampling sampling LTIMP three for f record Total (kg/mo) phosphorus , acre-feet per square mile. Symbol: —, not applicable. applicable. not —, Symbol: mile. square per acre-feet , 2 Soluble (kg/mo) reactive phosphorus Total (kg/mo) nitrogen Trout Creek at Pioneer Trail Trout Trout Creek Creek at South Lake Tahoe Trout ) nitrogen 4 (kg/mo) ammonia Dissolved Trout Creek at U.S. Forest ServiceRd. Forest 12N01 atU.S. Creek Trout (NH + 2 ) nitrogen ) nitrogen 3 (kg/mo) , kilogram, per square kilometer; kg/mo.,kilogram month; per acre-ft/ mi NO 2 + nitrate (NO + nitrate Dissolved nitrite Dissolved runoff (acre-ft) Average annual annual Average )744——————— )840——————— )744——————— 2 2 2 ) —) .22 — .05) 3.09 .15 .15 — .03 .62 2.73 .14 10.1 .16 .04 335 .52 2.82 5.85 .23 132 .56 3.23 141 2 2 2 . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary and runoff load monthly and suspended-sediment . Nutrient Percent change in sum2947564037414456 sum3937253738394145 in sum3216192325201519 in in change change change Sum —MedianMaximumMinimum 2,890Percent (kg/kmYield 27,300 (average) 656 —Sum — 23.2Median —Maximum 65,900Minimum 1,520 119 4.92Percent (kg/kmYield 4.16 2,770 (average) 19,400 287 324 21.4 — 464Sum 8.84 13,800Median — 1.68Maximum 39,900 4,300Minimum 15.4 201,000 72.4 121 1.68Percent 62.7 (kg/kmYield 1.09 1,750 (average) 8,690 168 10,300,000 15,300 163 65.2 13.2 — 4.26 2.77 — 8,170 .58 1,060 3,100 860 709 9.78 112,000 12.75 26.0 .71 30.1 1.09 13,000 2,800 107 35,200 31.1 190 4,680,000 54.1 7.05 2.93 29,700 .28 820,000 728 350 1,590 4,480 4.40 8.48 2,000,000 16.3 11,300 43.7 7,900 10.8 78.0 1.53 572,000 335 62.0 4.22 500 4,630 2,700 17.6 391,000 279 Unit runoff (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit Average annual runoff for Trout Creek at South Lake Tahoe is taken from Trout Creek near Tahoe Valley, upstream] annualCreekfor is taken runoff Valley, from Trout Average Creek at South Trout Lake near Tahoe Tahoe Table 21 Table [Abbreviations: acre-ft, acre-feet; kg, kilogram; kg/km stations, and monthly median units/yields between stations for period of comparison (water years 1991–98) and complete period o period complete and 1991–98) years (water of comparison period for stations between units/yields median monthly and stations, Nevada Basin, Tahoe Lake area, Tahoe Lake South watershed, Creek Trout the in stations

72 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada (kg/mo) sediment Suspended Suspended e in sums between between sums e in (kg/mo) Biologically Biologically reactive iron ing stations in the Upper Truckee Truckee in the Upper stations ing Total (kg/mo) phosphorus , acre-feet, per squaremile; —, not applicable] 2 (kg/mo) phosphorus Soluble reactive Total (kg/mo) nitrogen ) nitrogen 4 (kg/mo) ammonia Dissolved Upper Truckee River River at South Lake Tahoe Upper Truckee (NH Upper Truckee River at Highwayat River Meyers 50 above Upper Truckee Upper Truckee River at South Upper Truckee Road at Truckee South Upper River Truckee Upper + 2 ) nitrogen ) nitrogen 3 (kg/mo) , kilogram, per square kilometer; kg/mo.,kilogram month; per acre-ft/ mi NO 2 + nitrate (NO + nitrate Dissolved nitrite Dissolved runoff (acre-ft) Average annual annual Average )1,370——————— )1,660——————— )2,060——————— 2 2 2 ) —) .38 — .07) 4.04 .27 .12 — .04 .68 2.76 .32 9.14 .10 .04 394 .44 2.85 4.53 .19 121 .52 3.56 68.2 2 2 2 . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary and runoff load monthly and suspended-sediment . Nutrient Percent change in sum1237483942476068 sum4941313918292724 in sum392221224024138 in in change change change Sum —MedianMaximum 11,800MinimumPercent (kg/kmYield 74,200 (average) 2,100 — —Sum 53.0Median — 173,000MaximumMinimum 7,470 848 10.0Percent 4,860 (kg/kmYield 1.08 65,400 (average) 1,090 565 108 34,700 —Sum — 27.2Median — 106,000 .17Maximum 515,000 13,100Minimum 2,630 16.8 503 3.86Percent 2,840 14.3 (kg/kmYield 1.41 35,200,000 29,200 (average) 392 441 94.8 282 18,300 83.2 — 11.6 — .46 .25 3,160 1,280 38,900 10,000 206,000 10.1 168 1.63 64,700 16.4 1.97 1.83 1,940 11,300,000 261 55,100 45.3 105 44.6 27.8 7,670,000 1.00 8,390 .14 2,070 462 3,350 7.00 68,900 3.58 22,000 227 8.63 2,730,000 152 12,300 19.0 35.3 1,550,000 1.45 896 131 3.66 153 7,340 2,510 12.0 352,000 97.2 Unit runoff (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit Table 22 Table [Abbreviations: acre-ft, acre-feet; kg, kilogram; kg/km stations, and monthly median units/yields between stations for period of comparison (water years 1991–98) for three LTIMP sampl LTIMP three for 1991–98) years (water comparison of period for stations between units/yields median monthly and stations, Nevada Basin, Tahoe Lake area, Tahoe Lake South watershed, River

RESULTS 73 (kg/mo.) sediment Suspended Suspended e in sums between between sums e in (kg/mo.) Biologically Biologically reactive iron ing stations in the Ward Creek Creek in the Ward stations ing Total (kg/mo.) phosphorus , acre-feet, per squaremile; —, not applicable] 2 Soluble reactive (kg/mo.) phosphorus Total (kg/mo.) nitrogen Ward Creek below confluence below Creek Ward Ward Creekat State Highway Ward 89 ) nitrogen 4 Ward Creek at Stanford Rock Crossing Rock Stanford at Creek Ward (kg/mo.) ammonia Dissolved (NH + 2 ) nitrogen 3 (kg/mo.) , kilogram, per square kilometer; kg/mo.,kilogram month; per acre-ft/ mi NO 2 + nitrate (NO + nitrate Dissolved nitrite Dissolved runoff (acre-ft) Average annual annual Average )2,270——————— )2,340——————— )2,660——————— 2 2 2 ) —) .22 — .05) 3.08 .30 — .20 .08 2.80 .86 .50 4.84 .19 .08 290 2.70 .71 5.17 .15 466 .69 2.21 430 2 2 2 . Nutrient and suspended-sediment monthly load and runoff summary statistics (sum, median, minimum, and maximum), percent chang percent maximum), and minimum, median, (sum, statistics summary and runoff load monthly and suspended-sediment . Nutrient Percent change in sum517-3129114056 in sum6075704243451925 in change change Sum —MedianMaximumMinimum 2,890Percent (kg/kmYield 22,100 (average) 335 —Sum — 5.46 —MedianMaximum 36,900Minimum 2,410 608Percent change in sum 1.26 (kg/kmYield 21,000 (average) .02 1,350 35 347 77.5 —Sum — 25.5 7.07Median — 11,000Maximum .01 32,600Minimum 5,540 2,170 8 260,000 5.03 217Percent 1.75 (kg/kmYield (average) 13,200 16,000,000 .23 .12 1,220 108 21.7 242 65.0 — 30 23.8 6.39 — 9,810 .03 .08 2,240 15,600 122 4,730 4.48 196 155,000 46 1.04 127,000 1.76 .01 .09 7,130 577 7,030,000 92.2 16.4 4,470,000 34.5 19.1 48 .51 4,970 .01 .30 2,160 120 1,410 1.94 44 48,400 81,800 20.9 1.33 10,800 .07 3,970,000 46.1 8.78 614,000 41 12.6 .01 558 28.3 387 19 5,500 16,400 .03 521,000 .05 206 Unit runoff (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit (acre-ft/mi runoff Unit Table 23 Table [Abbreviations: acre-ft, acre-feet; kg, kilogram; kg/km stations, and monthly median units/yields between stations for period of comparison (water years 1992–98) for three LTIMP sampl LTIMP three for 1992–98) years (water comparison of period for stations between units/yields median monthly and stations, Nevada Basin, Tahoe Lake area, Bay Meeks and City Tahoe watershed,

74 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Incline Creek near Crystal Bay sediment constituents occurred in the spring (April, May, and June) during periods of snowmelt. March also The monthly load plots for Incline Creek near had high loads when snowmelt begins. For all constit- Crystal Bay (figs. 17–19) show a pattern typical for the 2 uents, the largest median monthly loads occurred in smaller streams (drainage area less than 8 mi ) in the May and the lowest median seasonal loads occurred basin. Loads during water years with below-normal during the summer period (July, August and Septem- precipitation (1988–92 and 1994) generally were low, ber). The lowest median monthly loads occurred in var- whereas loads for water years of above-normal precip- ious months but usually in August, September, or itation (1993 and 1995–98) were higher. The highest October. monthly load at this medium-smaller watershed station occurred in spring of 1995 for all nutrients and sedi- Watershed-Load Comparison ment except dissolved nitrite plus nitrate and ammonia nitrogen. Dissolved nitrite plus nitrate nitrogen had the The period of comparison is 1988–98, except highest monthly load in the spring (June) of 1996. Dis- Edgewood Creek at Stateline, which was sampled only solved ammonia nitrogen had the highest monthly load from 1992 to 1998 after this station was relocated in in spring (June) of 1998. The highest monthly load for 1992. The original station, Edgewood Creek at Lake the non-spring period all occurred during January 1997 Tahoe, was located about 0.5 mi downstream and was for all nutrients and suspended sediment. in operation from 1989 to 1992. Because streamflow at The seasonal load plots for Incline Creek near Edgewood Creek at Lake Tahoe was affected by vari- Crystal Bay (figs. 17–19) show the highest median sea- ous diversions upstream and impoundments down- sonal loads for this station occur in the spring during stream, the stage-streamflow relation was determined periods of snowmelt. The highest median monthly to be of poor quality. Although samples were collected loads occurred in April for dissolved nitrite plus nitrate from this discontinued gaging station, estimated loads nitrogen, soluble reactive phosphorus, and total phos- were not calculated due to the poor streamflow record. phorus; May for dissolved ammonia nitrogen, total Median monthly loads for nutrients and suspended sed- nitrogen, and suspended-sediment; and June for iron. iment for the 10 primary stations for the comparison The lowest median seasonal loads occurred during the period are shown in figures 23–29. summer period (July, August and September) for nitrite The Upper Truckee River at South Lake Tahoe plus nitrate, soluble reactive phosphorus and total phos- had the largest median monthly loads for five of the six phorus; and the fall period (October, November, and nutrients with 53.0 kg/mo nitrite plus nitrate; 10.5 December) for ammonia, total nitrogen, iron, and sus- kg/mo ammonia; 413 kg/mo total nitrogen; 76.7 kg/mo pended sediment. The lowest median monthly loads total phosphorus; 1,200 kg/mo biologically reactive occurred in various months but usually in October. iron; and 40,900 kg/mo suspended sediment. Trout Creek at South Lake Tahoe had the largest median of monthly loads for soluble reactive phosphorus at 13.8 Upper Truckee River at South Lake Tahoe kg/mo. Logan House Creek near Glenbrook had the The monthly load plots for Upper Truckee River smallest median monthly loads for all nutrients and sus- at South Lake Tahoe (figs. 20–22) show a pattern typi- pended sediment with 0.20 kg/mo dissolved nitrite plus cal for larger streams (greater than drainage area of 10 nitrate, 0.07 kg/mo dissolved ammonia, 2.63 kg/mo mi2) in the basin. Loads for water years with below- total nitrogen, 0.05 kg/mo soluble reactive phosphorus, normal precipitation years (1985, 1987–92, and 1994) 0.25 kg/mo total phosphorus, 1.30 kg/mo biologically generally were low, whereas loads for water years of reactive iron, and 36.8 kg/mo suspended sediment. above-normal precipitation (1984, 1986, 1993, and 1995–98) were much higher. The largest monthly load Within-Watershed Station Load Comparisons for this larger watershed station occurred in January of The within-watershed comparison of summary 1997 for all nutrients and sediment except ammonia, statistics (sum, median, maximum and minimum), per- which occurred in April 1989. cent input of estimated monthly loads of nutrients and The seasonal load plots for Upper Truckee River suspended sediment and percent differences in sums at South Lake Tahoe (figs. 20–22) show the highest between 10 secondary stations the period of compari- median seasonal loads for all nutrient and suspended- son for stations, by area, are listed in tables 19–24. The

RESULTS 75 AB Dissolved nitrite plus nitrate nitrogen Dissolved nitrite plus nitrate nitrogen 90 45

80 40

70 35

60 30

50 25

40 20

30 15

20 10 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 10 5 MEDIAN MONTHLY LOAD, IN KILOGRAMS LOAD, MEDIAN MONTHLY

0 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 5.88) (median = 16.3) (median = 27.8) (median = 4.19) MONTH/SEASON

Dissolved ammonia nitrogen Dissolved ammonia nitrogen 12 5.0

4.5 10 4.0

3.5 8 3.0

6 2.5

2.0 4 1.5

1.0 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 2

MEDIAN MONTHLY LOAD, IN KILOGRAMS LOAD, MEDIAN MONTHLY 0.5

0 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 0.92) (median = 1.52) (median = 3.25) (median = 1.14) MONTH/SEASON

Total nitrogen Total nitrogen 2,000 300

1,800 250 1,600

1,400 200

1,200 , IN KILOGRAMS

, IN KILOGRAMS 1,000 150

800 100 600

400 MONTHLY LOAD MONTHLY 50

200 LOAD MEDIAN MONTHLY

0 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 71.1) (median = 110) (median = 219) (median = 71.5) MONTH/SEASON

Figure 17. Plots of nitrogen nutrients for Incline Creek near Crystal Bay for water years 1988–98: (A) monthly loads, and (B) loads by month and season with seasonal medians.

76 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada AB Soluble reactive phosphorus Soluble reactive phosphorus 70 10

9 60 8

50 7

6 40 5 30 4

20 3 2 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 10

MEDIAN MONTHLY LOAD, IN KILOGRAMS LOAD, MEDIAN MONTHLY 1

0 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 4.80) (median = 4.26) (median = 8.76) (median = 3.84) MONTH/SEASON

Total phosphorus Total phosphorus 700 50 45 600 40

500 35

30 400 25

300 20

15 200 10 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 100

MEDIAN MONTHLY LOAD, IN KILOGRAMS LOAD, MEDIAN MONTHLY 5

0 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 16.2) (median = 21.2) (median = 44.0) (median = 13.1) MONTH/SEASON

Figure 18. Plots of phosphorus nutrients for Incline Creek near Crystal Bay for water years 1988–98: (A) monthly loads, and (B) loads by month and season with seasonal medians.

RESULTS 77 AB Biologically reactive Iron Biologically reactive Iron 7,000 2,200

2,000 6,000 1,800

5,000 1,600 1,400 4,000 1,200

1,000 3,000 800

2,000 600 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 400 1,000

MEDIAN MONTHLY LOAD, IN KILOGRAMS LOAD, MEDIAN MONTHLY 200

0 0 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 4,120) (median = 8,910) (median = 27,600) (median = 5,320) MONTH/SEASON

Suspended sediment Suspended sediment 1,000,000 60,000

900,000 50,000 800,000

700,000 40,000 600,000

500,000 30,000

400,000 20,000 300,000 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 200,000 10,000

100,000 IN KILOGRAMS LOAD, MEDIAN MONTHLY

0 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep FALL WINTER SPRING SUMMER WATER YEAR (median = 349) (median = 596) (median = 1860) (median = 395) MONTH/SEASON

Figure 19. Plots of biologically reactive iron and suspended-sediment concentrations for Incline Creek near Crystal Bay for water years 1991–98 and 1988–98, respectively: (A) monthly loads, and (B) loads by month and season with seasonal medians.

78 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada AB

Dissolved nitrite plus nitrate nitrogen Dissolved nitrite plus nitrate nitrogen 900 300

800 250 700

600 200

500 150 400

300 100

200

MONTHLY LOAD, IN KILOGRAMS 50 100 MEDIAN MONTHLY LOAD, IN KILOGRAMS

0 0 1984 1986 1988 1990 1992 1994 1996 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 34.8) (median = 152) (median = 227) (median = 15.3) MONTH/SEASON

Dissolved ammonia nitrogen Dissolved ammonia nitrogen 140 60

120 50

100 40

80 30 60

20 40

MONTHLY LOAD, IN KILOGRAMS 10 20 MEDIAN MONTHLY LOAD, IN KILOGRAMS

0 0 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 3.25) (median = 17.6) (median = 46.3) (median = 3.13) MONTH/SEASON

Total nitrogen Total nitrogen 14,000 3,500

12,000 3,000

10,000 2,500

8,000 2,000

6,000 1,500

4,000 1,000 MONTHLY LOAD, IN KILOGRAMS 2,000 500 MEDIAN MONTHLY LOAD, IN KILOGRAMS

0 0 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 186) (median = 889) (median = 2,870) (median = 123) MONTH/SEASON

Figure 20. Plots of nitrogen nutrients for Upper Truckee River at South Lake Tahoe for water years 1984–98 and 1989–98: (A) monthly loads, and (B) loads by month and season with seasonal medians.

RESULTS 79 AB

Soluble reactive phosphorus Soluble reactive phosphorus 400 120

350 100

300 80 250

200 60

150 40

100

MONTHLY LOAD, IN KILOGRAMS 20 50 MEDIAN MONTHLY LOAD, IN KILOGRAMS

0 0 1984 1986 1988 1990 1992 1994 1996 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 8.67) (median = 23.0) (median = 78.5) (median = 5.64) MONTH/SEASON

Total phosphorus Total phosphorus 3,500 900

800 3,000 700 2,500 600

2,000 500

400 1,500

300 1,000

MONTHLY LOAD, IN KILOGRAMS 200 500 100 MEDIAN MONTHLY RUNOFF, IN ACRE FEET 0 0 1984 1986 1988 1990 1992 1994 1996 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 52.3) (median = 207) (median = 605) (median = 30.0) MONTH/SEASON

Figure 21. Plots of phosphorus nutrients for Upper Truckee River at South Lake Tahoe for water years 1984–98, : (A) monthly loads, and (B) loads by month and season with seasonal medians.

80 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada AB Biologically reactive iron Biologically reactive iron 70,000 12,000

60,000 10,000

50,000 8,000

40,000 6,000 30,000

4,000 20,000

MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 2,000 10,000 MEDIAN MONTHLY LOAD, IN KILOGRAMS LOAD, MEDIAN MONTHLY 0 0 19841985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 516) (median = 2,570) (median = 7,200) (median = 266) MONTH/SEASON

Suspended sediment Suspended sediment 8,000,000 700,000

7,000,000 600,000

6,000,000 500,000

5,000,000 400,000 4,000,000 300,000 3,000,000

200,000 2,000,000 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 1,000,000 100,000 MEDIAN MONTHLY LOAD, IN KILOGRAMS LOAD, MEDIAN MONTHLY

0 0 19841985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep WATER YEAR FALL WINTER SPRING SUMMER (median = 13,900) (median = 82,300) (median = 409,000) (median = 7,000) MONTH/SEASON

Figure 22. Plots of biologically reactive iron and suspended-sediment concentrations for Upper Truckee River at South Lake Tahoe for water years 1984–98: (A) monthly loads, and (B) loads by month and season with seasonal medians.

RESULTS 81 five watersheds that are compared are Incline Creek, (the other Edgewood Creek watershed input station) at Trout Creek, and Upper Truckee River, 1990–98; and 11 percent. The upstream Edgewood Creek watershed Edgewood Creek and Ward Creek, 1992–98. stations are not in direct sequence and both are consid- For each watershed, summary statistics were cal- ered “input” stations, so were included in an upstream/ culated for runoff and constituent loads using methods downstream station comparison. Edgewood Creek at described in Helsel and Hirsch (1992). Median values Stateline station did not show increases from the com- were chosen as preferable summary statistics because bined two upstream “input” stations, except with sus- they are not strongly influenced by extreme values. For pended sediment. A portion of the suspended-sediment the within-watershed comparison for the five multiple- load in the Edgewood Creek watershed may be stored station watersheds (Incline, Edgewood, Trout and Ward in a pond upstream of Edgewood Creek at Stateline Creeks and Upper Truckee River), monthly loads were station. compared among stations. Each multiple-station water- A summary of average percent changes of sums shed was measured at no less than three points: an for the five multiple-station watersheds is listed in table upstream station in the headwaters, a middle station 24. Four of the multiple-station watersheds showed between the headwaters and the mouth, and a down- increases in average percent gains going downstream, stream station at or near the mouth of the stream. For between the upstream “input” and middle station and each watershed, the monthly load for the upstream sta- the middle and downstream “near mouth” stations. tion was considered an “input” amount. The differences Ward Creek watershed had decreasing percent gains in monthly loads between the upstream/middle and going downstream, with the largest average percent middle/downstream stations were then calculated. gain coming from above the upstream station. The larg- These values were divided the downstream station load est increase between the upstream (input) and middle to calculate the percent monthly load contributed by the stations occurred in Trout Creek watershed at 36 per- reach in question. Where more than one station was cent. The largest increase between the middle and measured in the headwaters part of the watershed, all downstream (near mouth) stations occurred in Upper headwater stations were totaled as the upstream input. Truckee River watershed at 42 percent. Two water- Monthly nutrient and suspended load plots and sheds had losses (minus percent) between stations for the hydrograph for the comparison period (1991–98) two constituents. Edgewood Creek watershed had a -34 for the two index watersheds (Incline Creek and Upper percent change in suspended sediment between the Truckee River) are shown in figures 30 and 31. The downstream and two combined upstream stations (table three Incline Creek watershed stations (near mouth = 20). Ward Creek watershed had a -3 percent change in near Crystal Bay, middle = at Highway 28, and dissolved ammonia between middle and downstream upstream = above Tyrol Village) are shown in figure 29 stations (table 23); this may be due to the presence of and the three Upper Truckee River watershed stations beaver dams between the stations. (near mouth = at South Lake Tahoe, middle = above Tables of monthly and daily load estimation val- Meyers, and upstream = at South Upper Truckee Road) ues, along with statistical estimates (SE, SE PRED, and are shown in figure 31. 95-percent confidence intervals), for periods of record The upper Ward Creek watershed station (below for the 20 primary and secondary stations are presented confluence) had largest inputs, in terms of percentage, in appendix 2. from the upstream watershed area for runoff (60 percent of the total watershed runoff comes from above this station), nitrite plus nitrate (75 percent), ammonia Yields and Ranks (70 percent) and soluble reactive phosphorus (43 percent). Edgewood Creek at Palisade Drive had largest Median monthly yields, in kilograms per square inputs, in terms of percentage, for total nitrogen (49 kilometers per month (kg/km2/mo), were calculated by percent), total phosphorus (47 percent), iron (56 per- dividing median monthly loads by drainage area, in cent) and suspended sediment (91 percent). The station square kilometers. The resulting yields were compared with the largest average input percentage for all eight and ranked for each constituent for each of the 10 sam- constituents was Ward Creek below confluence at 46 pled watersheds. Median monthly yields for each con- percent. The station with the lowest average input per- stituent were assigned a rank 1 for the highest yield to centage for all eight constituents was Eagle Rock Creek a rank 10 for the lowest yield. Overall ranks were deter-

RESULTS 89 A 150 Incline Creek near Crystal Bay, Nevada (at mouth) Incline Creek at Highway 28 at Incline Village, Nevada (at Hwy 28) Incline Creek above Tyrol Village near Incline Village, Nevada (above Tyrol)

100

50 STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, 0 1990 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR B C Dissolved nitrite plus nitrate nitrogen Dissolved ammonia nitrogen 90 12 at mouth at mouth at Highway 28 at Highway 28 80 above Tyrol above Tyrol 10 70

60 8

50 6 40

30 4

20 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY MONTHLY LOAD, IN KILLOGRAMS LOAD, MONTHLY 2 10

0 0 1991 1992 1993 1994 1995 1996 1997 1998 1991 1992 1993 1994 1995 1996 1997 1998 D WATER YEAR E WATER YEAR Total nitrogen Soluble reactive phosphorus 2,000 70 at Mouth at mouth at Highway 28 at Highway 28 1,800 above Tyrol above Tyrol 60 1,600

1,400 50

1,200 40 1,000 30 800

600 20

MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 400 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 10 200

0 0 1991 1992 1993 1994 1995 1996 1997 1998 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR WATER YEAR Figure 30. Within-watershed comparison of streamflow and nutrients and suspended-sediment concentrations at three Incline Creek watershed stations, water years 1991–98.

90 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada F G Total Phosphorus Biologically reactive Iron 700 7,000 at mouth at mouth at Highway 28 at Highway 28 above Tyrol above Tyrol 600 6,000

500 5,000

400 4,000

300 3,000

200 2,000 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 100 1,000

0 1991 1992 1993 1994 1995 1996 1997 1998 0 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR WATER YEAR H Suspended sediment 400,000 near mouth middle upper 350,000

300,000

250,000

200,000

150,000

MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 100,000

50,000

0 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR

Figure 30. Continued.

RESULTS 91 A

4,000 Upper Truckee River at South Lake Tahoe, California (at South Lake Tahoe) Upper Truckee River at Highway 50 above Meyers, California (above Meyers) Upper Truckee River at S Upper Truckee Road near Meyers, California (at Upper Truckee Road) 3,000

2,000

1,000 DISCHARGE, IN CUBIC FEET PER SECOND

0 1990 19911992 1993 1994 1995 1996 1997 1998 WATER YEAR B C Dissolved nitrite plus nitrate nitrogen Dissolved ammonia nitrogen 900 120 at South Lake Tahoe at South Lake Tahoe above Meyers above Meyers 800 at S Upper Truckee at S Upper Truckee 100 700

600 80

500 60 400

300 40

200 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 20 100

0 0 1991 1992 1993 1994 1995 1996 1997 1998 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR WATER YEAR D E Total nitrogen Soluble reactive phosphorus 14,000 400 at South Lake Tahoe at South Lake Tahoe above Meyers above Meyers 12,000 at S Upper Truckee 350 at S Upper Truckee

300 10,000

250 8,000 200 6,000 150

4,000 100 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 2,000 50

0 0 1991 1992 1993 1994 1995 1996 1997 1998 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR WATER YEAR

Figure 31. Within-watershed comparison of streamflow and nutrients and suspended-sediment concentrations at three Upper Truckee River watershed stations, water years 1991–98.

92 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada F G Total phosphorus Biologically reactive iron 3,500 70,000 at South Lake Tahoe at South Lake Tahoe above Meyers above Meyers at S Upper Truckee at S Upper Truckee 3,000 60,000

2,500 50,000

2,000 40,000

1,500 30,000

1,000 20,000 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 500 10,000

0 0 1991 1992 1993 1994 1995 1996 1997 1998 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR WATER YEAR H Suspended sediment 4,000,000 at South Lake Tahoe above Meyers 3,500,000 at S Upper Truckee

3,000,000

2,500,000

2,000,000

1,500,000

1,000,000 MONTHLY LOAD, IN KILOGRAMS LOAD, MONTHLY 500,000

0 1991 1992 1993 1994 1995 1996 1997 1998 WATER YEAR

Figure 31. Continued.

Table 24. Average percent change of sums among the downstream, middle, and upstream stations for nutrient and suspended-sediment monthly loads and runoff, for the periods of comparison, in the five multiple-station watersheds in the Lake Tahoe Basin, California and Nevada

[Symbol: *, comparison between downstream (near mouth) and two combined upstream (input) stations]

Downstream (near Middle Upstream (input) Total Multiple station watershed mouth) stations stations stations percent

Incline Creek 38 31 31 100 Edgewood Creek (46)* (43 = input) 11 100 Trout Creek 41 36 23 100 Upper Truckee River 42 34 24 100 Ward Creek193447100

RESULTS 93 mined by averaging the ranks of all seven constituents Within-Watershed Stations for each watershed station and ranking these average Median monthly nutrient and suspended-sedi- ranks among the stations. ment yields and average annual unit runoff data for the Median monthly yields for nutrients and sus- five multiple stations watersheds are presented with the pended sediment for the 10 primary stations are listed load summary data in tables 19–23. All five multiple- with load summary data in table 18 and shown in fig- station watersheds decreased in unit runoff from the ures 32–38. Unit values for average annual runoff for upstream station to the downstream station, except the period of record are listed in table 4 and shown in Edgewood Creek. For example, Incline Creek figure 10. decreased from 1,180 acre-ft/mi2 at the upstream site to 1,040 acre-ft/mi2 at the middle station to 930 acre- 2 Primary Stations ft/mi at the downstream (near mouth) station, which is typical for the smaller streams. Yields for dissolved Comparing primary stations for the study period nitrite plus nitrate nitrogen increased slightly to moder- (1988–98), Incline Creek near Crystal Bay had the ately in downstream order in four of five watersheds. largest median monthly yields for dissolved nitrite plus Ward Creek stations decreased from 0.50 to 0.22 2 nitrate, 0.56 kg/km /mo, and soluble reactive phospho- kg/km2/mo between the upstream and downstream 2 rus, 0.30 kg/km /mo. Third Creek had the largest stations. Dissolved ammonia nitrogen yields increased median monthly yields for total nitrogen, 7.50 slightly in four watersheds between the upstream and 2 2 kg/km /mo, total phosphorus, 1.55 kg/km /mo, biolog- downstream stations, with Ward Creek showing a 2 ically reactive iron, 45.9 kg/km /mo, and suspended decrease. Total nitrogen and total phosphorus yields 2 sediment, 1,360 kg/km /mo. Edgewood Creek at State- increased between the upstream and downstream sta- line had the largest yield for ammonia, 0.12 tions in four watersheds but decreased in Edgewood 2 kg/km /mo. Logan House Creek had the smallest yields Creek. Soluble reactive phosphorus yields increased in for all nutrients and sediment with nitrite plus nitrate, Incline, Edgewood and Ward Creeks and decreased in 2 2 0.04 kg/km /mo, ammonia, 0.01 kg/km /mo, total Trout Creeks and Upper Truckee River. Iron increased 2 nitrogen, 0.49 kg/km /mo, soluble reactive phospho- between the upstream and downstream stations in all 2 2 rus, 0.01 kg/km , total phosphorus, 0.05 kg/km /mo, five watersheds while suspended sediment increased in 2 biologically reactive iron, 0.24 kg/km /mo, and sus- Incline, Trout and Upper Truckee River watersheds and 2 pended sediment, 17.3 kg/km /mo. decreased in the Ward and Edgewood Creeks. Median monthly suspended-sediment yields were highest for Third Creek, followed in order by Incline Trends in Concentrations Creek, Blackwood Creek, and the Upper Truckee River. These yields are similar to another suspended- Trends in constituent concentrations over time sediment study from 1981 to 1985 on nine Lake Tahoe from the Seasonal-Kendall test for all 10 primary and Basin watersheds by Hill and Nolan (1988). This study 10 secondary stations are summarized in table 25 and found that the highest annual suspended-sediment for the 10 primary stations by constituent in figures 40– yields were from, in descending order, Blackwood 46. Over time 69 percent of constituent concentrations Creek, Ward Creek, Upper Truckee River, and Third decreased, 26 percent had no significant trend, and 5 Creek. Note that eight of their stations are existing percent increased. LTIMP stations. Comparison of the primary stations (fig. 40) Ranks of median monthly yields for each primary showed five stations with decreasing trends in dis- station for each constituent are shown along with yields solved nitrite plus nitrate nitrogen concentrations and in figures 31–37. The overall average ranks are shown five stations with no significant trends. Seven stations in figure 39. Incline Creek had the highest average rank had decreasing trends in dissolved ammonia nitrogen of median monthly yield and Logan House Creek near concentrations and three stations had no significant Glenbrook had the lowest. Edgewood Creek actually trends. Six stations had decreasing trends in total nitro- came in third, but was downgraded to fourth as the gen concentrations and four had no significant trends. comparison period for that watershed was only from Four stations had decreasing trends in soluble reactive 1992 to 1998. phosphorus concentrations and six had no significant

94 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Table 25. Trends, P values, and probability plot correlation coefficient (PPCC) values from Seasonal Kendall and ESTIMATORTable 25. Trends, results P values,for 10 primary and probability and 10 secondaryplot correlation LTIMP coefficient stations in(PPCC) the Lake values Tahoe from Basin, Seasonal California Kendall and and Nevada ESTIMATOR results for 10 primary and 10 secondary LTIMP stations in the Lake Tahoe Basin, California and Nevada— [Symbols: *, P value <.05 = significant trend; **, P value >.05 to <.10 = less-significant trend; ***, P value >.10 = no significant trend; —,Continued no significant trend] Seasonal Kendall Seasonal Kendall Estimator Estimator Constituent PPCC trend P value trend P value Third Creek near Crystal Bay Dissolved nitrite + nitrate — 0.102*** positive 0.866*** 0.99 Dissolved ammonia negative .005* negative .000* .99 Total nitrogen negative .021* negative .000* .98 Soluble reactive phosphorus — .423*** — .303*** .99 Total phosphorus negative .021* — .296*** .99 Biologically reactive iron negative .002* positive .000* .98 Suspended sediment negative .070** positive .000* .99 Incline Creek near Crystal Bay Dissolved nitrite + nitrate negative .003* negative .813*** .98 Dissolved ammonia negative .011* negative .004* .99 Total nitrogen negative .051** positive .000* .98 Soluble reactive phosphorus negative .019* negative .002* .81 Total phosphorus — .260*** — .107*** .99 Biologically reactive iron — .535*** negative .001* .97 Suspended sediment — .110*** negative .000* .98 Incline Creek at Highway 28 Dissolved nitrite + nitrate negative .002* — .526*** .98 Dissolved ammonia negative .013* — .488*** .98 Total nitrogen negative .002* negative .000* .97 Soluble reactive phosphorus negative .088** — .720*** .96 Total phosphorus negative .009* negative .000* .97 Biologically reactive iron negative .003* negative .000* .96 Suspended sediment negative .036* negative .000* .98 Incline Creek above Tyrol Village Dissolved nitrite + nitrate negative .000* — .608*** .98 Dissolved ammonia negative .002* negative .010* .98 Total nitrogen negative .001* negative .000* .97 Soluble reactive phosphorus negative .001* negative .026* .95 Total phosphorus negative .000* negative .001* .94 Biologically reactive iron negative .001* negative .057** .94 Suspended sediment negative .002* negative .000* .98 Glenbrook Creek at Glenbrook Dissolved nitrite + nitrate negative .002* negative .048* .96 Dissolved ammonia negative .001* negative .000* .99 Total nitrogen negative .000* negative .000* .96 Soluble reactive phosphorus — .304*** —.217*** .98 Total phosphorus negative .025* negative .001* .96 Biologically reactive iron negative .037* negative .001* .96 Suspended sediment — .713*** negative .010* .98 Logan House Creek near Glenbrook Dissolved nitrite + nitrate — .168*** —.444*** .98 Dissolved ammonia negative .003* negative .000* .92 Total nitrogen negative .009* negative .000* .98

RESULTS 103 Table 25. Trends, P values, and probability plot correlation coefficient (PPCC) values from Seasonal Kendall and ESTIMATOR results for 10 primary and 10 secondary LTIMP stations in the Lake Tahoe Basin, California and Nevada— Continued

Seasonal Kendall Seasonal Kendall Estimator Estimator Constituent PPCC trend P value trend P value Logan House Creek near Glenbrook Soluble reactive phosphorus negative .001* negative .000* .74 Total phosphorus negative .000* negative .000* .99 Biologically reactive iron negative .008* negative .021* .97 Suspended sediment negative .005* negative .000* .86 Edgewood Creek at Stateline Dissolved nitrite + nitrate negative .052** —.262*** .96 Dissolved ammonia — .187*** —.626*** .99 Total nitrogen negative .002* negative .000* .99 Soluble reactive phosphorus negative .011* —.192*** .98 Total phosphorus negative .011* negative .060** .95 Biologically reactive iron negative .004* negative .077** .94 Suspended sediment negative .065** negative .007* .97 Edgewood Creek at Palisade Drive Dissolved nitrite + nitrate negative .008* —.134*** .99 Dissolved ammonia negative .004* —.375*** .99 Total nitrogen negative .017* negative .000* .95 Soluble reactive phosphorus negative .007* negative .053** .93 Total phosphorus negative .001* negative .000* .91 Biologically reactive iron negative .001* negative .008* .92 Suspended sediment negative .004* negative .000* .95 Eagle Rock Creek near Stateline Dissolved nitrite + nitrate negative .080** negative .071** .99 Dissolved ammonia negative .004* negative .023* .98 Total nitrogen — .552*** negative .000* .85 Soluble reactive phosphorus — .159*** negative .066** .92 Total phosphorus negative .011* —.863*** .80 Biologically reactive iron — .216*** negative .007* .84 Suspended sediment negative .074** negative .000* .89 Trout Creek at South Lake Tahoe Dissolved nitrite + nitrate — .479*** negative .000* .99 Dissolved ammonia — .115*** negative .000* .99 Total nitrogen — .227*** negative .236*** .98 Soluble reactive phosphorus — .374*** — .662*** .96 Total phosphorus negative .044* negative .000* .98 Biologically reactive iron — .112*** — .832*** .96 Suspended sediment — 1.00*** negative .000* .99 Trout Creek at Pioneer Trail Dissolved nitrite + nitrate negative .038* -negative .055** .98 Dissolved ammonia negative .014* negative .020* .99 Total nitrogen negative .060** negative .000* .93 Soluble reactive phosphorus negative .020* — .816*** .98 Total phosphorus negative .016* negative .000* .89 Biologically reactive iron negative .011* negative .000* .91 Suspended sediment negative .003* negative .000* .97

104 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada Table 25. Trends, P values, and probability plot correlation coefficient (PPCC) values from Seasonal Kendall and ESTIMATOR results for 10 primary and 10 secondary LTIMP stations in the Lake Tahoe Basin, California and Nevada— Continued

Seasonal Kendall Seasonal Kendall Estimator Estimator Constituent PPCC trend P value trend P value Trout Creek at U.S. Forest Service Rd. 12N01 Dissolved nitrite + nitrate negative .000* negative .076** .99 Dissolved ammonia negative .007* negative .000* .99 Total nitrogen negative .001* negative .000* .98 Soluble reactive phosphorus negative .029* negative .918*** .97 Total phosphorus negative .000* negative .003* .95 Biologically reactive iron negative .045* negative .000* .87 Suspended sediment negative .001* negative .000* .93 Upper Truckee River at South Lake Tahoe Dissolved nitrite + nitrate negative .000* negative .000* .99 Dissolved ammonia — .136*** negative .000* .99 Total nitrogen negative .006* negative .000* .98 Soluble reactive phosphorus negative .036* negative .000* .99 Total phosphorus negative .005* negative .000* .98 Biologically reactive iron — .404*** — .385*** .96 Suspended sediment negative .005* negative .000* .98 Upper Truckee River at Highway 50 above Meyers Dissolved nitrite + nitrate negative .000* negative .000* .98 Dissolved ammonia negative .036* — .198*** .98 Total nitrogen negative .000* negative .000* .97 Soluble reactive phosphorus negative .000* negative .000* .97 Total phosphorus positive .000* negative .000* .95 Biologically reactive iron negative .000* negative .000* .94 Suspended sediment negative .000 negative .000 .96 Upper Truckee River at South Upper Truckee Road Dissolved nitrite + nitrate negative .001* — .528*** .99 Dissolved ammonia negative .041* negative .006* .98 Total nitrogen negative .001* negative .000* .97 Soluble reactive phosphorus — .193*** — .628*** .97 Total phosphorus negative .001* negative .000* .96 Biologically reactive iron negative .028* negative .000* .94 Suspended sediment negative .000* negative .000* .98 General Creek near Meeks Bay Dissolved nitrite + nitrate — .935*** negative .002 .99 Dissolved ammonia negative .003* negative .000* .97 Total nitrogen — .893*** — .565*** .99 Soluble reactive phosphorus — .603*** — .556*** .99 Total phosphorus negative .004* — .182*** .83 Biologically reactive iron positive .003* positive .000* .97 Suspended sediment positive .000* positive .000* .99 Dissolved nitrite + nitrate — .279*** negative .001* .89 Blackwood Creek near Tahoe City Total nitrogen — .447*** — .136*** .99 Dissolved ammonia negative .000* negative .000* .79

RESULTS 105 Table 25. Trends, P values, and probability plot correlation coefficient (PPCC) values from Seasonal Kendall and ESTIMATOR results for 10 primary and 10 secondary LTIMP stations in the Lake Tahoe Basin, California and Nevada— Continued

Seasonal Kendall Seasonal Kendall Estimator Estimator Constituent PPCC trend P value trend P value Blackwood Creek near Tahoe City Soluble reactive phosphorus — .396*** positive .000* .99 Total phosphorus negative .020* negative .003* .97 Biologically reactive iron positive .018* positive .000* .99 Suspended sediment positive .000* positive .000* .99 Ward Creek at State Highway 89 Dissolved nitrite + nitrate negative .041* negative .000* .99 Dissolved ammonia negative .044* negative .000* .98 Total nitrogen — .893*** negative .013 .99 Soluble reactive phosphorus — .462*** — .962*** .83 Total phosphorus negative .007* negative .000* .96 Biologically reactive iron positive .004* positive .000* .99 Suspended sediment positive .058** positive .000* .98 Ward Creek at Stanford Rock Crossing Dissolved nitrite + nitrate negative .035* negative .000 .99 Dissolved ammonia negative .084*** — .796*** .99 Total nitrogen negative .043* negative .000 .98 Soluble reactive phosphorus negative .050* — .992*** .97 Total phosphorus — .154*** — .507*** .98 Biologically reactive iron negative .060** negative .000 .98 Suspended sediment — .238*** negative .072** .98 Ward Creek below confluence Dissolved nitrite + nitrate — .154*** negative .000* .98 Dissolved ammonia — .822*** positive .082** .99 Total nitrogen negative .060** negative .000* .97 Soluble reactive phosphorus negative .084** negative .003 .98 Total phosphorus — .154*** negative .098** .91 Biologically reactive iron — .940*** — .234*** .96 Suspended sediment — .822*** negative .001 .98

Trend summary: Number Both negative 77 Both positive 6 Both undetected 16 1 negative/1 undetected 35 1 positive/1 undetected 2 1 positive/1 negative 4 Total 140

106 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada trends. Nine of the 10 stations had decreasing trends in ranged from 7.3 to 10.6 with a median of 8.8. Field pH’s total phosphorus concentrations and one had no signif- were higher on the east side of the basin, but consis- icant trend. Three stations in General, Blackwood, and tently less than the median and maximum values Ward Creeks had increasing trends in biologically reac- observed at Edgewood Creek. tive iron, four had decreasing trends, and three had no The highest concentrations for four of the six significant trends. The same three stations had increas- nutrients (dissolved nitrite plus nitrate nitrogen, dis- ing trends in suspended-sediment concentrations, four solved ammonia nitrogen, total phosphorus, and bio- stations had decreasing trends, and three stations had no logically reactive iron) and suspended sediment, and significant trends. second highest concentrations of 2 other nutrients (sol- Decreasing trends in undeveloped watersheds, uble reactive phosphorus and total ammonia and such as Logan House Creek, may be due to a variety of organic nitrogen) were found at a miscellaneous urban causes, although none are clearly indicated. Potential runoff station (Highway 50 Culvert to Edgewood causes include changes in weather patterns during the Creek). The highest concentrations of other nutrients study period, such as the lack of intense summer thun- were found at another miscellaneous urban runoff sta- derstorms. Cooler spring snowmelt periods during the tion (Tributary to Edgewood Creek above clubhouse) latter years of the study led to longer, more moderate for soluble reactive phosphorus and Third Creek near runoff patterns, in general, and may have resulted in Crystal Bay (a primary station) for total ammonia and less channel erosion. In addition, decreasing trends for organic nitrogen. The higher total concentrations usu- developed watersheds also may be due to the increased ally occurred during summer thunderstorm events and restoration projects and installation of best manage- during rain-on-snow events in the winter/ spring peri- ment practices, resulting in overall greater efficiency in ods. Lowest total constituent concentrations occurred these watersheds. Increasing concentrations in biologi- during fall and winter periods, when streamflow was at cally reactive iron and suspended sediment at the three its lowest. Dissolved constituent concentrations and stations noted previously seem to be based primarily on samples collected during and after the January 1997 specific conductance tend to increase in the low flow flood. periods and tend to be lowest during prolonged snowmelt period. Concentrations of dissolved ammonia nitrogen were low for the study and had a large number SUMMARY of below detection limit values (less than 0.003 mg/L).

Concentrations and loads of six nutrients and sus- The emphasis in LTIMP sampling was placed on pended sediment and rates of streamflow varied widely storm runoff and spring snowmelt runoff. As a result, in the 14 sampled watersheds of the Lake Tahoe Basin. samples collected under this study may have higher Greater amounts of precipitation generally fall on the maximum concentration values, medians, and sums western side of Lake Tahoe Basin and the streamflow than from other water quality studies in the basin. runoff and nutrient and suspended-sediment concentra- The Upper Truckee River watershed shows the tions and loads reflect that. largest monthly loads of all nutrients and suspended The highest mean annual runoff and instanta- sediment of the 10 primary watersheds. The Upper neous peak and measured streamflow for the 20 pri- Truckee River is the largest watershed and has the mary and secondary stream gaging stations were found greatest annual runoff of the monitored watersheds in at the Upper Truckee River at South Lake Tahoe, which the Lake Tahoe Basin. Factors contributing to this high has the largest drainage area. The highest unit runoff runoff are that the Upper Truckee watershed, located on occurred at Blackwood Creek. The lowest runoff, the west side of the Lake Tahoe Basin, receives among instantaneous peak and measured streamflow, and unit the highest amounts of precipitation in the basin and runoff were all found at Logan House Creek, which has has large amounts of developed area. The smallest the smallest drainage area. loads for the 10 primary watersheds are from Logan Water-quality data mostly fell within expected House Creek, which is the smallest of the watersheds levels for the sampled stations in the LTIMP network, and has the least annual runoff for the 10 monitored with the exception of elevated pH values for the Edge- watersheds. Logan House Creek generally is undevel- wood Creek at Lake Tahoe. Field pH values there oped (at least above the sampling station) watershed.

114 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada The highest monthly loads for the 10 primary REFERENCES CITED watersheds generally occurred during snowmelt in June Boughton, C.J., Rowe, T.G., Allander, K.K., and Robledo, 1995 or January 1997, which included a major rain-on- A.R., 1997, Stream and ground water monitoring pro- snow event. The lowest monthly loads occurred during gram, Lake Tahoe Basin, Nevada and California: U.S. base-flow periods in August-September 1992, a Geological Survey Fact Sheet FS-100-97, 6 p. drought year. Median monthly loads for the 10 primary Buchanan, T.J., and Somers, W.P., 1969, Discharge measure- watersheds also showed seasonality patterns, with most ments at gaging stations: U.S. Geological Survey Tech- of the loading occurring during the spring snow-melt niques of Water-Resources Investigations, book 3, chap. A8, 65 p. period (April, May, June). The smaller loads occurring Cartier, K.D., Peltz, L.A., and Long, Kati, 1995, Hydrologic during the summer (July, August, and September) and basins and hydrologic-monitoring sites of Lake Tahoe fall (October, November, and December) periods. Basin, California and Nevada. U.S. Geological Survey Open-File Report 95-316, 1 sheet. The largest median monthly yields occurred in the Cartier, K.D., Peltz, L.A., and Smith, J.L., 1994, Develop- northeast part of the basin in the Incline Village area. ment and documentation of spatial databases for the Third Creek near Crystal Bay had the highest yields for Lake Tahoe Basin, California and Nevada: U.S. Geolog- total nitrogen, total phosphorus, biologically reactive ical Survey Open-File Report 93-4182, 65 p. iron and suspended sediment. Incline Creek near Crys- Cohn, T., 1988, Adjusted maximum likelihood estimations tal Bay had the highest yields for nitrite plus nitrate and of the moments of lognormal populations from type I censored samples: U.S. Geological Survey Open-File soluble reactive phosphorus. Edgewood Creek at State- Report 88-350, 34 p. line had the highest yield for ammonia. Logan House Cohn, T.A., DeLong, L.L., Gilroy, E.J., Hirsch, R.M., and Creek had the lowest yields for all nutrients and sus- Wells, D.K., 1989, Estimating constituent loads: Water pended sediment. Of the 10 primary watersheds, the Resources Research, v. 25(5), p. 937–942. higher yields were from watersheds which receive Cohn, T.A., Caulder, D.L., Gilroy, E.J., Zynjuk, L.D., and greater precipitation and are more developed. The low- Summers, R.M., 1992, The validity of a simple statistical model for estimating fluvial constituent loads: an est yields were from two watersheds which receive less empirical study involving nutrient loads entering precipitation and are less developed. Chesapeake Bay: Water Resources Research, v. 28(9), The 10 primary watersheds were ranked based on p. 2353–2364. Crawford, C.G., 1996, Estimating mean constituent loads nutrient and suspended-sediment yields. The rankings in rivers by the rating-curve and flow-duration, rating for the primary watersheds are listed from highest curve methods: Bloomington, Indiana, Indiana Univer- to lowest: Incline Creek, Third Creek, Blackwood sity, Ph.D. dissertation, 245 p. Creek, Edgewood Creek, Upper Truckee River, Trout Crippen J.R., and Pavelka, B.R., 1970, The Lake Tahoe Creek, Ward Creek, General Creek, Glenbrook Creek, Basin, California–Nevada: U.S. Geological Survey and Logan House Creek. Water-Supply Paper 1972, 56 p. Edwards, T.K., and Glysson, G.D., 1988, Field methods Constituent concentrations in the 10 primary for measurement of fluvial sediment: U.S. Geological watersheds showed decreasing or no significant trends, Survey Open-File Report 86-531, 118 p. with the exception for biologically reactive iron and Glancy, P.A., 1988, Streamflow, sediment transport, and suspended-sediment concentrations. These two constit- nutrient transport at Incline Village, Lake Tahoe, Nevada, 1970–73: U.S. Geological Survey Water- uent concentrations decreased or were undetected Supply Paper 2312, 53 p. at 7 of the 10 stations and increased at 3 stations. Goldman, C.R., and Byron, E.R., 1986, Changing water Decreasing trends for developed watersheds may be quality at Lake Tahoe—The first five years of the Lake due to restoration projects or the introduction of best Tahoe Interagency Monitoring Program: Tahoe management practices. Causes of decreases in rela- Research Group, Institute of Ecology, University of tively undeveloped watersheds are unclear, but may be California at Davis, 12 p. Guy, H.P., 1969, Laboratory theory and methods for sedi- related to climatic variations. Increased trends of con- ment analysis: U.S. Geological Survey Techniques of centrations likely are influenced by samples collected Water-Resources Investigations, book 5, chap. C1, during and after a large flood event in January 1997. 58 p.

REFERENCES CITED 115 Goldman, C.R., and Byron, E.R., 1986, Changing water ——— 2000, Lake Tahoe Interagency Monitoring Program: quality at Lake Tahoe—The first five years of the Lake Tributary sampling design, sites, and periods of record: Tahoe Interagency Monitoring Program: Tahoe U.S. Geological Survey Fact Sheet FS-138-00, 4 p. Research Group, Institute of Ecology, University of Rowe, T.G., Rockwell, G.R., and Hess, G.W., 1998, California at Davis, 12 p. Flood of January 1997 in the Lake Tahoe Basin, Guy, H.P., 1969, Laboratory theory and methods for sedi- California and Nevada: U.S. Geological Survey Fact ment analysis: U.S. Geological Survey Techniques of Sheet FS-005-98, 2 p. Water-Resources Investigations, book 5, chap. C1, 58 p. Rowe, T.G., and Stone, J.C., 1997, Selected hydrologic features of the Lake Tahoe Basin, California and Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in Nevada: U.S. Geological Survey Open-File Report water resources: Studies in Environmental Science 49, 97-384, 1 sheet. Amsterdam, Elsevier, 522 p. Hill, B.R., and Nolan, K.M., 1988, Suspended-sediment Smith, J.L., Stone, J.C., Rowe, T.G., and Gardener, J.V., factors, Lake Tahoe Basin, California-Nevada, in 1999, Selected hydrologic features of the Lake Tahoe Poppoff, I.G., Goldman, C.R., Loeb, S.L., and Leopold, Basin and surrounding area, California and Nevada, L.B., eds., Proceedings, International Mountain 1998 U.S. Geological Survey Water-Resources Investi- Watershed Symposium, Lake Tahoe, June 8–10, 1988: gations Report 99-4031, 1 sheet. South Lake Tahoe, Calif., Tahoe Resource Conserva- Thomas, B.E., Hjalmarson, H.W., and Waltemeyer, S.D., tion District, p. 179–189. 1997, Methods for estimating magnitude and frequency Hunter, D.A., Reuter, J.E., and Goldman, C.R., 1993, of floods in the southwestern United States: U.S. Standard operating procedures—Lake Tahoe Inter- Geological Survey Water-Supply Paper 2433, 195 p. agency Monitoring Program: University of California U.S. Geological Survey, 1989–99, Water resources data, at Davis Tahoe Research Group, 79 p. Nevada, water years 1988–99: U.S. Geological Survey Jeton, A.E., 1999, Precipitation-runoff simulations for the Water-Resources Data Report, published annually. Lake Tahoe Basin, California and Nevada: U.S. Geo- logical Survey Water-Resources InvestigationsReport U.S. Geological Survey, 1998, National field manual for the 99-4110, 61 p. collection of water-quality data: Techniques of Water- Resources Investigations — Handbook for Water- Jorgensen, L.N., Seacer, A.L., and Kaus, S.J., 1978, Hydro- Resources Investigations, book 9, chaps. A1–A9, logic basins contributing to outflow from Lake Tahoe, 2 volumes. California–Nevada: U.S. Geological Survey Hydro- logic Investigations Atlas HA-587, scale 1:62,500. U.S. Interagency Advisory Committee on Water Data, Kennedy, E.J., 1983, Computation of continuous records 1982, Guidelines for determining flood flow frequency: of streamflow: U. S. Geological Survey Techniques Bulletin 17B of the Hydrology Subcommittee: Reston, of Water-Resources Investigations, book 3, chap. A13, Va., U.S. Geological Survey, Office of Water Data 53 p. Coordination, 183 p. Rowe, T.G., 1999, Comparison of water quality for upstream Walker, W.W., 1996, Simplified procedures for euthrophica- and downstream sites in the Incline Creek watershed, tion assessment and prediction: User manual, Chapter 2 Lake Tahoe Basin, Nevada, 1990–98: Sixty-seventh FLUX: U.S. Army Corp of Engineers, Water Opera- Annual Meeting, Western Snow Conference, South tions Technical Support Program, Instruction report Lake Tahoe, Calif., April 1999, Proceedings, p. 35–44. W-96-2, p. 2-1 to 2-61.

116 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada APPENDICES

APPENDICES

APPENDICES 117 APPENDIX 1

Water-Quality and Streamflow Information on the Internet USGS/LTIMP water-quality data and daily, monthly, and annual mean streamflow and instantaneous streamflow measurements are available to the public through several USGS websites on the World Wide Web. Real-time and historical streamflow data and site information are available from the Nevada USGS National Water Information System (NWIS) site at: . This website includes information for Nevada and California stations in the Lake Tahoe Basin. Information also is accessible at the following websites: the USGS Nevada District at , the Lake Tahoe Data Clearinghouse at , and the USGS California District NWIS at . Streamflow data by water year are published annually in the USGS Water Resources Data Report for Nevada and California.

APPENDIX 2

Estimated Nutrient and Suspended-Sediment Monthly Loads Estimated nutrient daily and monthly loads from the ESTIMATOR program are listed in Appendix 2, with estimated standard errors, estimated standard error of prediction and 95-percent confidence intervals. Also listed in Appendix 2 are stimated suspended- sediment monthly loads from the FLUX program. Appendix 2 is available on the Internet as a Microsoft Access database file. This file can be downloaded from the online version of this report, which is at URL: .

118 Streamflow and Water-Quality Data for Selected Watersheds in the Lake Tahoe Basin, California and Nevada