The North , , Water-Quality Monitoring Network

In February 1996, North­ U.S. Army Corps of Engineers released west Oregon experienced water from . This turbid lake some of the most severe flood­ water flowed downstream, keeping turbi­ ing in recorded history. dity values at the water-treatment facility Heavy, warm rain fell on intakes high until July 1996. The City of above average snowpack in Salem was forced to temporarily cease the Cascade Range of the Wil­ operations of the facility for 8 days and lamette River Basin, resulting acquire water from reserve sources and in 50- to 100-year flood events neighboring communities until an alter­ in many area rivers. The nate treatment scheme was developed. at In 1998, a monitoring program was Mehama crested at nearly initiated to better understand the sources 2½ feet above flood stage on and transport of sediment that causes high the afternoon of February 7, turbidity within the North Santiam River 1996. Although the water Basin. The project is a cooperative effort level returned to normal of the City of Salem, the U.S. Geological within a few weeks, the water The City of Salem water-treatment facility withdraws water Survey (USGS), the U.S. Forest Service, from the North Santiam River. Changes in water quality, as quality was affected for and the U.S. Army Corps of Engineers. In during floods, affect the facility’s operation. months to come. anticipation of future events like the 1996 flooding, the agencies now continuously monitor hydrologic and water-quality con- Why Monitor Water Quality? Lake was held back to prevent further ditions throughout the basin. The data col- flooding downstream. When the turbid lected by this program are available online The water quality of the North Santiam waters of the North Santiam tributaries River is important to more than 170,000 in real-time and are used by the coopera- flowed into the lake, the larger sand parti- tors for current operational decisions, residents of the Salem, Oregon area that cles settled out of the water. The fine silt rely on the river as their primary source of ongoing research projects and future basin and clay particles, stirred by currents, wind management. drinking water. The river normally runs so and waves, remained suspended. As the clear that the City of Salem is able to use a flood waters downstream receded, the relatively inexpensive and environmentally low-impact water-treatment process called slow-sand filtration. This process uses sand and gravel filters to remove suspended What Is TURBIDITY? organic and inorganic particles in conjunc­ Turbidity is a measure of the tion with natural biological processes to “muddiness” of water caused by remove dissolved organic contaminants. If suspended and dissolved material, the river turbidity (see inset) is greater than as well as organic matter. The cur­ 10 NTU, these filters can become clogged. rently accepted numerical mea­ To keep the facility running smoothly, the sure of turbidity is the nephelo­ intake water is tested daily. If the turbidity metric turbidity unit (NTU). An NTU value represents the amount remains consistently above 10 NTU, the of light scattered by particles in water intakes are closed. the water. As the number of sus­ During the 1996 flooding, the North pended particles in the water in­ Santiam River had turbidity values in creases, the intensity of scattered excess of 100 NTU at the water-treatment light increases, which results in facility intakes. (It is impossible to deter­ higher turbidity values. In this mine the exact maximum turbidity value photograph, the North Santiam because there was no continuous water- River near Detroit has a turbidity quality monitoring system in place at the of approximately 700 NTU. time.) Much of the water entering Detroit

U.S. Department of the Interior USGS Fact Sheet FS–2004–3069 U.S. Geological Survey December 2004

The North Santiam River Basin

Table 1. North Santiam River Basin monitoring stations.

Subbasin area USGS station Date of water-quality Number of suspended- Map number Site name (square miles)1 number Station name probe installation2 sediment samples3 1 Mehama 655 14183000 North Santiam River at Mehama April 2000 156 2 Little North 112 14182500 Little North Santiam River near Mehama April 2000 150 3 Niagara 453 14181500 North Santiam River at Niagara April 2000 93 4 French 9.9 14179100 French Creek near Detroit June 2001 64 5 Breitenbush 108 14179000 near Detroit October 1998 131 6 North Santiam 216 14178000 North Santiam River near Detroit October 1998 4227 7 Blowout 26 14180300 Blowout Creek near Detroit October 1998 158 1Includes the area upstream from the station location and contributing subbasins. 2Includes water temperature, specific conductance, pH, and turbidity. 3Samples collected manually through June 30, 2004. 475 samples from automatic pumping sampler. The North Santiam River Basin flows and landslides that supply sediment Lake), formed by the damming of the Study to the rivers. The central basin is bounded river. The reservoirs are operated by the on the east by less steep and younger High Corps of Engineers for power generation, The North Santiam River Basin is volcanics and on the west by flood control, streamflow management, located on the western slopes of the Cas- alluvial lowlands. and recreation. cade Range in northwestern Oregon, east Average annual precipitation in the area of Salem. The river flows west from ranges from 45 inches in Stayton to over How Is Water Quality of the North to the , 200 inches at Mount Jefferson. The basin Santiam River Monitored? draining 766 square miles upstream from contains the main-stem North Santiam Salem’s water-treatment facility. The River, its major tributaries (Breitenbush The USGS operates a network of geology of the central part of the basin is River, Blowout Creek, French Creek, and monitoring stations (sites) throughout the dominated by Western Cascade volcanic the Little North Santiam River), and two North Santiam River Basin. Seven sites rocks. The steep terrain and older, weath- reservoirs (Detroit Lake and Big Cliff provide water-quality and streamflow ered soils of this area produce many earth- information (table 1). Three sites are located downstream from Detroit Lake tions of chemical ions in the water. Abrupt (map numbers 1–3), and four sites are conductance deviations may result from located on streams that flow into the lake chemical spills or sewage overflows (map numbers 4–7). Each site has equip­ entering a stream, lake, or other water- ment that measures the water level of the body. river and several water-quality parame­ ters. These data are recorded electroni­ cally every half-hour. Several times a day, the data are uploaded to the USGS Port­ land office, stored in a database, and made available through a Website (http:// The summer water temperature in the North or.water.usgs.gov/santiam). These provi­ Santiam River at Mehama (map number 1) o sional data are immediately available to sometimes peaks above 16 C on several the agencies involved in the study, as well consecutive days, potentially exceeding the as to the public. The USGS periodically Oregon standard, which is calculated by aver­ aging the maximum values of the previous 7 corrects or deletes the raw data according days. to routine field checks of the water-quality A dramatic spike in conductivity appeared in probes and other calibration or perfor­ the Breitenbush River (map number 5) over Turbidity mance issues. The final data are then pub­ just a few hours. Periods of regularly occur­ lished in a year-end report. ring spikes such as this may lead to an investi­ Turbidity is used as a monitoring and gation of possible causes of contamination regulatory parameter in the industrial, Multiparameter Water-Quality upstream of the monitoring station. sanitation, and environmental fields, and Probes can be used as a substitute for suspended- pH sediment concentration. Elevated turbid­ Water-quality probes in the North San­ pH is the measure of the alkaline or ity reduces the transparency of water due tiam River Basin measure specific con­ acidic properties of water. Proper pH is to the presence of suspended and dis­ ductance, pH, water temperature, and tur­ important for the survival and abundance solved materials. Increases in turbidity bidity. These physical and chemical of aquatic plant and animal communities, can reduce biological primary production characteristics are important indicators of as well as for the aesthetic qualities of (algal growth), important to the health and the overall health of the aquatic system. drinking water, such as taste, odor, and balance of the aquatic ecosystem, and may color. aid in transporting contaminants attached to suspended particles. Turbidity can be an indicator of water suitability for fish­ ery, drinking, industrial, and recreational uses, and has been used to evaluate the effects of mining, dredging, stream-side construction, wastewater effluent, log­ ging, road building, and other land use activities.

Warm, sunny afternoons result in increased photosynthetic activity from instream algae and rooted aquatic plants. This can be ob­ served in daily variations of pH values at Little North Santiam River near Mehama (map num­ ber 2). Summer heat and low-flow conditions can cause pH to exceed the Oregon standard of 8.5. A USGS scientist calibrates a water-quality The sudden increase in turbidity at Blowout instrument at the Breitenbush monitoring sta­ Water Temperature Creek (map number 7) reached the sensor’s tion. Optimal water temperature is impor­ maximum value (about 1,350 NTU) in just min­ utes, gradually dropping after remaining for tant for the survival and vitality of fish and Specific Conductance 2 hours at the sensor limit. A site visit and in­ aquatic insect populations. Changes in spection of the area upstream of the station Specific conductance is the measure of river temperatures can affect these popu­ revealed that a washed-out road and related the capacity of water to conduct electricity lations, as well as algal, plant, and debris flow resulted in sediment transport, at 25 degrees Celsius. A change in con­ amphibian species. causing increased turbidity (see photograph ductance signals a change in concentra­ at the end of the report). Suspended-Sediment Samples these sampling methods has equipment samples under certain conditions. The designed specifically for the task, includ­ sampler is positioned on the river bank At each of the seven monitoring sites, ing different size and weight samplers, along with flexible tubing deployed from the USGS collects water samples that are cranes, and reels. Samples are collected at the sampler into the water. When the tur­ analyzed for suspended-sediment concen­ each site on a regular basis and during bidity reaches a certain value, the sampler tration. The USGS adheres to strict qual- high-turbidity events. It is particularly pumps water into bottles stored within it. ity-assurance and quality-control proto­ important to collect samples during Unlike manually collected samples, these cols to assure the reliability of the intense precipitation periods that produce “point” samples (samples collected at a resulting data. The sampling procedure high streamflows, since this is when most single point) do not necessarily provide a requires that water be collected across the of the sediment is transported down­ sediment and water mixture representa­ entire cross-section of the river, ensuring a stream. tive of the river cross-section. A correla­ representative sample. The samples are tion must be developed between the cross- collected in one of three ways: (1) Sites Automatic Pumping Samples sectional samples and point samples by where the river is typically over 3 feet When time or personnel constraints collecting both types at the same time deep have a suspended cableway across make it impossible to sample all seven during a variety of flow conditions. Once the river from which samples are col­ sites during a high-turbidity event, at night this correlation is established, the point lected. (2) Other sites can be sampled or on weekends, automatic samplers are samples can be used to estimate the sus- from a bridge. (3) Smaller streams and useful. These devices are programmed to pended-sediment concentration of the rivers at low-flow conditions can some­ automatically collect suspended-sediment river cross section. times be sampled by wading. Each of

Capturing the Unexpected On October 21, 2003, the automatic sampler deployed at the North Santiam River near Detroit station was triggered to begin sampling by a sharp rise in turbidity. The turbid water entered the North Santiam River from Pamelia Creek, 11 miles upstream from the monitoring station (photo at left). The sediment plume moved quickly downstream. The automatic sampler collected 24 samples over the 16-hour event. Peak turbidity in these samples exceeded 5,000 NTU (center samples in photograph at right). About 4 hours after the peak, a USGS technician arrived at the site and manually collected a sample, which showed a sharp decrease to 560 NTU. Typically, stream turbidity increases during periods of storm runoff; however, this turbidity event was not associated with rainfall. Glacial melt and related landslide activity on Mount Jefferson were the most likely cause. Persistent-Turbidity Samples Detroit Lake Samples Thus, the monitoring network allows the City of Salem to better manage the water- Another important aspect of the water To better understand the processes of treatment facility and to provide clean quality is “persistent turbidity.” This term sediment transport through Detroit Lake, water to its customers. refers to material that remains in suspen­ the USGS collected lake samples regu­ sion for a long period of time. Fine silt and larly at three locations from April 2002 to U.S. Geological Survey clay particles settle through the water October 2003. Samples were collected more slowly than larger sand particles. A throughout the water column and ana­ The sediment-concentration and other higher percentage of fine material results lyzed for suspended-sediment concentra­ water-quality data collected from Detroit in more persistent turbidity. Samples are tion and persistent turbidity using the Lake are being used by USGS researchers collected at the monitoring sites during same methods as for the samples from the in a water-quality model of the lake to fur­ high-turbidity events for persistent-turbid- rivers. The resulting data allow research­ ther the understanding of the overall water ity analysis. In the USGS laboratory, the ers to model the movement of sediment quality in the North Santiam River Basin. turbidity of these samples is measured at through the lake. The model utilizes data from the continu- regular time intervals. As the sediment ous-monitoring sites on the tributaries in settles, the turbidity near the surface of conjunction with the lake data. Stream- the water sample decreases. The rate of flow, water quality, and environmental the decrease depends on the amount of factors are used to describe sediment fine material in the sample. These data transport and thermal structure within the help to determine the proportion of clays lake. This model provides information to and silts that enter the stream network the agencies involved in this study, as well from each of the monitored watersheds as to those studying water quality farther upstream from Detroit Lake. downstream in the Willamette Valley.

U.S. Army Corps of Engineers The Corps of Engineers relies on streamflow data from the stream-gaging network to manage the water budget of the basin. Accurate water volume input and output values allow them to plan for flood control, flow augmentation, power gener­ A USGS scientist collects water samples from ation, and recreation. Data from the sam­ Detroit Lake for water-quality analysis. pling program will assist the Corps in esti­ mating sedimentation rates in Detroit Who Uses the Water-Quality Data? Lake.

City of Salem Local Governments, Industry, and the Public The USGS water-quality monitoring network serves as an early warning Communities, municipalities, industry, system for Salem’s water-treatment facil­ and the general public use the data to ity. During storms, water managers can make informed decisions about water use, monitor the major tributaries of the North fishing, and other recreational activities. Santiam River for changes in streamflow and turbidity. The ability to anticipate the Land Managers Persistent-turbidity lab analysis begins with a arrival of excessively turbid water allows Turbidity sensors allow the estimation well-mixed sample of water and sediment. water-treatment facility operators to close of real-time sediment concentrations at Subsamples are collected [at a specific depth water intakes before damage occurs to the each of the monitored sites. The sediment from the sample water surface] after approxi­ sand filters. When the turbidity returns to mately 0, 2, 4, 8 and 24 hours of settling time. data can be used to calculate the quantity The turbidity values of these subsamples are 10 NTU or less, the intakes are reopened, of suspended material being transported then plotted to determine the decrease of tur­ and water can once again enter the filtra­ downstream past each monitoring station bidity over time. Cylinders A through E demon­ tion system. During periods of prolonged and to identify the source of the sediment. strate the results of a typical persistent- high turbidity, water is diverted to a pre­ Knowing which subbasins produce the turbidity experiment. The graph (top) shows treatment facility, where chemical pre­ most turbidity-causing material can aid the actual results of the analysis. Notice how treatment removes the turbidity-causing in the understanding of processes related the turbidity decreases over the 24-hour peri­ material before the water enters the sand to glacial activity, landslides, and earth- od of settling (cylinder A to cylinder E). filters. This diversion is no longer neces­ flows, and thus in the management of land sary once the monitors show that turbidity use, such as streamside construction, values have stabilized below 10 NTU. timber harvesting, and road building. Heavy rain in December 2001 triggered a road failure on a tributary of Blowout Creek. The result- ing debris flow caused increased turbidity at the monitoring station for several days.

Working together, the City of Salem, USGS, land managers, and local agencies have developed a water-quality monitoring network that benefits a large segment of Oregon’s population. The cooperative rela­ tionship has helped foster an environment that balances drinking-water needs, land use Detroit Lake, January 29, 2004, looking westward from near where the Breitenbush River enters and forest activities, and recreation with the the lake. Note the turbid water entering the main body of the lake after more than 3 inches of rain maintenance of a healthy ecosystem in the fell over a 3-day period. North Santiam River Basin.

By Heather M. Bragg and Mark A. Uhrich U.S. Army Corps of Engineers Portland District Where can I learn more? P.O. Box 2946 Portland, OR 97208 City of Salem Drinking Water Program http://www.nwd-wc.usace.army.mil/nwp/ 555 Liberty SE Salem, OR 97301 (Use the “dataquery” button to obtain data http://cityofsalem.net/~swater/ for the Willamette River Basin.) North Santiam River Turbidity Study Website Willamette National Forest http://or.water.usgs.gov/santiam Detroit Ranger District HC73, Box 320 Report: Monitoring Instream Turbidity to Estimate Mill City, OR 97360 Continuous Suspended-Sediment Loads and Yields http://www.fs.fed.us/r6/willamette/ and Clay-Water Volumes in the Upper North Santiam River Basin, Oregon, 1998–2000 U.S. Geological Survey http://pubs.water.usgs.gov/wri034098 10615 SE Cherry Blossom Drive Portland, OR 97216 http://or.water.usgs.gov/

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