# Monitoring the Water Quality of the Nation's Large Rivers

## Columbia River Basin NASQAN Program

##  In 1995, the U.S. Geological Survey's (USGS) National Stream QualityAccounting Network (NASQAN) Program began monitoring the water quality ofthe Columbia River Basin, applying a basinwide approach in order to understandwater quality on a regional scale. A primary objective of the Columbia NASQANProgram is to provide an ongoing characterization of the concentrationsand mass flux (amount of material or load passing a location per unit time,generally expressed as tons per day) of sediment and chemicals at key locationsin the basin. These data can then be used to determine regional source areasfor these materials, and to assess the effect of human influences on observedconcentrations and constituent loads. NASQAN complements the ongoing USGSNational Water Quality Assessment (NAWQA) Program, which is performing adetailed assessment in three subbasins of the Columbia River Basin. NASQANmonitors the larger rivers in the basin, downstream of NAWQA study units.

### Environmental Setting

The Columbia River (figure 1) is a vital culturaland economic resource in the Pacific Northwest. The waters of the ColumbiaRiver Basin provide spawning grounds for Pacific salmon, a cornerstone ofthe regional identity. In addition, hydroelectric projects on the riverproduce nearly 70 percent of the region's electric power. The river alsosupplies irrigation water for millions of otherwise nonarable acres in thedry interior basin, a navigation channel that extends inland for 465 miles,water-supply and waste-disposal sites for an expanding urban population,and considerable recreational opportunities and wildlife habitat.

Scenes along the Columbia River (Photographs courtesy of the U.S. Army Corpsof Engineers, Portland District)   

### Water-quality issues

Water quality in the main-stem Columbia River has historically been perceivedto be good, largely because of the dilution effect of the nearly pristinesnowmelt that constitutes the bulk of streamflow. Within the last 10 years,however, evidence has been accumulating that hazardous chemicals presenta significant threat to wildlife and potentially to human health. In theupper basin, elevated concentrations of trace elements such as cadmium,arsenic, lead, mercury, and zinc have been observed in fish tissue and bedsediments in Lake Roosevelt. Concentrations of trace elements such as copper,lead, and zinc that violate State water quality standards have been observedin the Willamette River and in water and sediment samples collected throughoutthe Columbia River Estuary, an important component of the central PacificOcean coastal ecosystem.

In the lower Columbia River Basin, contamination by organochlorine pesticidesand PCBs has been found in tissues of mink and river otter, and eggs ofthe bald eagle, currently listed as a threatened species. Fish advisorieshave been issued throughout the basin. Dioxin also has been identified asa concern, resulting in the establishment of a TMDL (Total Maximum DailyLoad) for dioxin in 1991 for the entire Columbia River Basin by the U.S.Environmental Protection Agency.

### Measuring Flux

Because flux measurement is the primary objective in NASQAN, a relativelyhigh sampling frequency is required. Additionally, the emphasis on fluxcharacterization dictates that more samples must be collected during periodsof higher streamflow. The water chemistry measured at any one point in theriver reflects a complex combination of natural processes and human activitiesthat occur upstream. The flux-based approach allows the river network tobe treated as an integrated system, providing data to describe and compareyields of nonpoint-source contaminants across large regional basins, calculateloads to receiving waters, including off-continent flux, and test regionalmodels of the influence of land use on water quality. Because of the smallnumber of samples collected during low flow, however, the data may not satisfyregulatory requirements during the most critical conditions of the yearfor aquatic biota.

### Station Selection

Six NASQAN sampling stations were selected at critical locations in theriver system to provide the essential framework for evaluating flux of materialswithin the basin and to the ocean. An important consideration was the influenceof the extensive reservoir system, especially the centrally coordinatedsystem of large-scale Federal projects that extend throughout all but asmall fraction of the main-stem Columbia River. Construction of dams andreservoirs has transformed the river from a system characterized by swift-flowingrapids and spectacular waterfalls to a series of quiet pools, carefullymanaged to reduce the potential for flooding and to provide maximum benefitfor hydropower, navigation, irrigation, and recreation. The annual patternof streamflow in the Columbia River has been significantly altered by theoperation of the dams, as illustrated by mean monthly streamflow at TheDalles during the pre- and post-dam periods (figure2).

Table 1: Description of NASQAN sampling stations and subbasins in the ColumbiaRiver Basin Map NumberSampling StationDrainage area (square miles)Incremental Increase in drainage area (square miles)Mean streamflow (cubic feet per second)Incremental Increase in streamflow (cubic feet per second)
 1 Columbia River at Northport, Washington
60,200
 60,200
 99,100
 99,100
2 Columbia River at Vernita Bridge near Priest Rapids Dam, Washington
96,000
 35,800
 118,600
 19,500
 3 Snake River at Burbank, Washington
 108,800
 108,800
 57,700
 57,700
4 Columbia River at Warrendale, Washington
240,000
 35,500
 202,600
 26,300
5 Willamette River at Portland, Oregon
11,100
 11,100
 38,000
38,000
6 Columbia River at Beaver Army Terminal near Quincy, Oregon
257,000
5,500
270,000
29,400

Because of the focus on regional scale in NASQAN, the station networkwas not designed to assess the influence of each main-stem reservoir separately.Instead, a series of reservoirs is treated as a "black box" andtheir influence is evaluated as a single unit. Generally, stations wereselected where significant changes in mass flux were expected, or at thelower ends of reservoir reaches.
Columbia River at Northport
. This site monitors the inflow to  Lake Roosevelt, water that originates primarily in Canada and represents  a large component of both the drainage area and streamflow at the river  mouth.   
- Columbia River at Vernita Bridge . This site does not represent  a large incremental increase in either drainage area or streamflow, but  it is located below a series of seven reservoirs and just upstream of a  free-flowing reach. This station provides a measure of the sediment and  chemicals removed by the reservoirs.   **Snake River at Burbank**. This site is located at the mouth of  the large and hydrologically complex Snake River Basin, which represents  a significant portion of the drainage area in the Columbia River Basin.    Columbia River at Warrendale
. This site is located downstream  of the lowermost reservoir series on the main-stem river and upstream of  major industrial and urban areas.   
- Willamette River at Portland . This site is operated in collaboration  with the USGS NAWQA program. The Willamette River is a major source of  trace elements and organic chemicals, and contributes a significant portion  of streamflow during the winter rainfall season.    **Columbia River at Beaver Army Terminal**. This site is located  at the mouth of the river, and monitors the inflow into the Columbia Estuary.Sampling Strategy
A broad range of chemical constituents is measured in the NASQAN program.These include 47 water-soluble pesticides, suspended and dissolved traceelements, major nutrients, carbon, and suspended sediment. Samples are collected12 to 15 times per year, depending on the local site characteristics. Inthe Columbia River Basin, runoff patterns fall into two general categories:snowmelt-dominated, in the interior portions of the basin (figure2), and rainfall-dominated, in the coastal region (figure3). Sampling strategies are structured differently in these differentregions and will be modified in an iterative process as more is learnedabout patterns of concentration and flux in the basin.

Table 2: Constituents measured in the NASQAN programMeasurement Class  ExamplesSuspended sedimentConcentration of fine and coarse sediment particlesPesticidesCommon water-soluble pesticides, including atrazine and metalochlorSuspended and dissolved trace elementsLead, cadmium, copper, and zincCarbonDissolved and suspended organic carbon; dissolved inorganic carbonNutrientsTotal and dissolved nitrogen and phosphorusMajor IonsCalcium, sulfate, and chlorideSupport VariablesStream discharge, temperature, pH, dissolved oxygen, conductivity
Examples of questions to be addressed
Specific questions that can be answered by NASQAN data in the ColumbiaBasin include the following:
Which pesticides can be detected in the Columbia River? How do frequency  of detections, concentrations, and flux of pesticides vary in response  to land and water use, season, and climatic and hydrologic factors in the  various subbasins? What proportion of pesticides applied in the various  subbasins is delivered to the Columbia River Estuary?
- What is the effect of land and water use (such as mining, smelting  operations, and urban activities), reservoir regulation, season, and streamflow  on the flux of trace elements from the the various subbasins? What are  the dominant modes of transport, suspended or dissolved, for trace elements  in the Columbia River?    Do concentrations of dissolved trace elements and pesticides exceed  established standards and health advisories at key locations in the Columbia  River Basin? If so, what are the associated seasonal and hydrologic factors?National NASQAN program
The Columbia River Basin NASQAN program is part of a national programthat was redesigned in 1995 to focus on monitoring water quality in fourof the Nation's largest rivers-the Mississippi (including the Missouri andOhio), the Colorado, the Rio Grande, and the Columbia. In these four basins,the USGS currently operates a network of 40 NASQAN stations, applying aconsistent flux-based river basin approach to characterize the transportof selected chemicals through the river systems. 

Together, NASQAN and NAWQA provide water-quality information on bothlarge and small river basins. A central feature of NAWQA is the examinationof the role of land use on water quality. Because comparable data are collectedby both programs, findings from NAWQA may be used in the development ofregional models describing the influence of land use on water quality inNASQAN basins.
Products of the NASQAN program
Data from the NASQAN program are published annually in USGS data reportsissued by each State in the network. Additionally, NASQAN data are beingreleased electronically on the World Wide Web (http://water.usgs.gov/nasqan);flux estimates for selected constituents at NASQAN stations will also bepublished periodically.

In addition, interpretive products for the NASQAN program are planned,based upon four levels of analysis of the data. These levels progressivelyincrease in complexity, beginning with a simple description of relativeoccurrence of contaminants in different subbasins. The next step is to determinethe correlation between subbasin fluxes or yields and various governingfactors, both hydrologic and anthropogenic. Additionally, comparison ofsuccessive downstream fluxes will provide information about the characteristicsof mass transfer of material within a river system, and possibly allow inferencesabout the relative importance of instream processes and nonpoint-sourcecontributions. Finally, the most complex level of analysis will includean investigation of how contaminants are processed and transformed as theyflow through the basin.
Evolution of NASQAN in the Columbia River Basin
After the initial 3 to 5 years of data collection have been completedand baseline conditions have been established for the measured constituentsin the basin, the Columbia River Basin NASQAN program may be altered tomore closely address specific water-quality issues. Of particular concernis the occurence and distribution of organochlorine compounds in the basin,which are relatively insoluble in water and tend to accumulate in sedimentsand biological tissue. These compounds are not presently included in thesuite of NASQAN constituents because they are difficult to sample in waterusing conventional sampling methods. 

In 1997-1998, the Columbia River Basin NASQAN and Lower Columbia RiverEstuary Program are jointly funding a special study that employs a new samplingtechnology utilizing semipermeable membrane devices (SPMDs). These deviceswill be used to collect time-weighted samples for hydrophobic organic compoundsat NASQAN stations in the basin. Also, fish tissue and bed sediment sampleswill be collected at selected NASQAN stations, providing a comparison ofresults from the different sampling media. Additional sampling using SPMDsmay be incorporated into the Columbia River Basin NASQAN program in thefuture, depending on the results from this study.

In addition, the Columbia National Estuary Program is developing an interagencylong-term monitoring plan for the Columbia River Basin in conjunction withthe USGS and the NASQAN program, as well as with many other Federal andState agencies. The issues identified as major priorities for monitoringas part of this long-term plan will also provide essential guidance forthe evolution of the Columbia NASQAN program in the future.

*-By Valerie J. Kelly and Richard P. Hooper*

*For additional copies of this report, or for more informationabout the Columbia NASQAN program, please contact-*

NASQAN Columbia Basin Coordinator10615 SE Cherry Blossom DrivePortland, OR 97216(503) 251-3200

Fact Sheet FS-004-98

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This page maintained by rphooper.Last updated December 27, 1998URL: *http://water.usgs.gov/nasqan/clmbfact/clmbfact.html*