Regional water quality Evaluation of data for assessing conditions and trends
Janet Hren Carolyn J. Oblinger Childress
J. Michael Norris Thomas H. Cbaney Donna N. Myers US.Geological Survey Although large amounts of water quality data have heen collected, the prob lems of aggregating them into one data base for broad water quality assessments are unknown. The US. Geological Survey in 1984 undertook a study in Colorado and Ohio to determine bow well these data could be used to address such questions as, What are existing water quality conditions? How have they changed? and How do these conditions and changes relate to natural and human-induced activities? The major finding of this study was that few areas in either state had a d e quate numbers of samples or sampling sites for the constituents evaluated. This was because the benefits of aggregating data collected by various agencies were limited due to either the nature (e.g., effluent samples) or quality of the data with respect to regional assessments. Furthermore, more data were collected for gross indicators of water quality (e.g., dissolved solids) than for constituents specifically related to toxic contamination (e& organic compounds). Have U.S. rivers benefited from the expenditure of $40 billion since the passage of the Clean Water Act in 1972? With the reauthorization of the Act in 1987, it is estimated that an additional $60 to $70 billion will be required to meet its goals. Recent drought has caused shortages in some areas of the country, and contamination of supplies has increased the need to better determine the quantity and quality of the nation’s water resources. Despite this need, only a small part of existing data can be used to assess the status, trends, and causes of water quality conditions on regional and national scales. 1122
Environ. Sci. Technol., Val. 24, No. 8,
igg0
This article not subleot to U S . copyright. Published 1990 American Chemical Society
Blodgett (I) described monitoring programs as “fragmented, duplicative and wasteful, and in many cases. . . d e void of scientific validity and leadership.” Other studies have criticized programs as inadequate for effective management (2, 3, 4). The need for a national water quality monitoring and assessment program has been expressed by a number of federal, state, local, and private agencies (5). This need has been recognized by recent plans of the Department of Interior for full-scale implementation of the National Water Quality Assessment Program (NAWQA) by the U. S. Geological Survey (6). In 1986, a pilot NAWQA program was begun to develop, test, and refine methods useful for a full-scale national water quality assessment program. In late 1989 the Bush administration d e termined that the U S . Geological Survey (USGS) should proceed with imple mentation of the NAWQA program in FY 1991 and requested that Congress appropriate $18 million to begin the full program, which is planned to increase in four years to about $60 million annually. The goals of the NAWQA program are, first, to describe the status and trends in the water quality of the nation’s streams and aquifers and second, to provide an understanding of the natural and human causes of the o b served conditions and trends. Study unit investigations will be conducted in 60 areas throughout the nation to provide a framework for national and regional water quality assessments. The study unit areas are stream aquifer systems thousands to tens of thousands of square miles in extent. The study unit investigations will consist of intensive assessment activity for 4-5 years followed by 5 years of less intensive activity. Twenty study units will be in an intensive data collection and analysis phase during each fiscal year, and the first cycle of intensive investigations averidg the 60 study units will be comuleted in FY 2002. P r i o r to t h e initiation of t h e NAWQA program, the USGS undertook a comprehensive examination of programs in Colorado and Ohio to determine the characteristics of data a l lection activities of federal, state, and local agencies and universities and to determine the adequacy of resulting data. The goals were to improve the ability of USGS to define current water quality conditions, determine water quality changes, and establish cause and effect relationships between current conditions and anthropogenic activities. The programs were studied in three phases; objectives of the phases are shown in the box.
Phase I-Identify existing programs USGS compiled an inventory of 1984 data collection activities for all public agencies and academic institutions in Colorado and Ohio. Forty-eight organizations in Colorado with 115 programs were identified, and in Ohio 42 organizations with 88 programs. Each program was screened using the following criteria: (1) Were data MIlected from natural sources (e.g., streams, wells, lakes, etc.) as opposed to “in-line” sources (e.g., treated drinking water, sewage effluent)? Only natural sources were used in this USGS study. (2) Were data available for public use? (3) Were sampling sites readily located? (4) Was quality assurance documentation available? (5) Were data in accessible computer files?
66
Have U.S. rivers benefited from the expenditure of $40 billion since the passage of the Clean Water Act in
1972?” Sources of samples. Most samples were from surface water sources. Groundwater represented only 9% of the samples reported from Colorado and 4% of those from Ohio. The dominance of surface water samples reflected its greater public use in both states (e&, drinking water). The predominance of surface water sampling may also reflect the opinion that because groundwater moves more slowly than surface water its quality should change more slowly (assuming no introduction of contaminants). Therefore, less f r e auent samDline would he needed to d e iect changes in groundwater quality. In addition, much of the sampling effort in both states was for mandated purposes, such as meeting permit requirements for monitoring drinking water or waste water effluent. Most of these oermits involve surface waters and reqhre r e petitive sampling. Data cdectioa purposes. water quality data collected by identified organizations were classified by purpose: to meet permit requirements, to fulfill
...
compliance and enforcement needs, or to characterize ambient water quality conditions. The data collection purposes largely dictated the location and f r e quency of sample collection, methods used, and the constituents analyttd. These data attributes, in turn, affect the availability and applicability of the data for broad-scale studies. As indicated in Figure I, 46% of the Colorado samples and 84% of the Ohio samples were collected to meet permit requirements. None of the samples from programs required for permits passed the initial screening test primarily because they did not represent ambient water conditions. We recognized that when used with predictive techniques and instream data, these analyses are useful for conducting certain water quality evaluations. For example, effluent analyses are useful for modeling certain constituents (e.g., dissolved oxygen) in specific waste load allocation studies and for evaluating alternative wastewater treatment technologies. However, for many other constituents (e.g., heavy metals and pesticides), knowledge of in-stream reactions and processes was inadequate for sound modeling-based assessments. Therefore, samples required for permits were considered inappropriate for constructing a data base to define ambient conditions and to address fundamental water quality issues. Property and constituent groups. U s e fulness of the existing data for addressing critical water quality issues depends largely on the specifi~rnnrtitm-ntc that
-
objecliveg ot the USGS water WW mr*m F+haseI-ldentify, inventory, and estimate costs of the 1984 water quality data collectin programs in Colorado and Ohio and Identify specific programs Dduclng data that satisfy requirements r brcad-scale water quality assess-
ment. Phase ILEvaluata the quality assur-
ance of programs mat meet the broad criteria of Phase I; only data meeting phase I criteria were evaluated in Phase II
the
I
7:”;:
~~~~~d~~ which it cBn be used addresssBIect. ed wa,e, quality issues for ,he two
states, We have reported in detail elsewhere on results of phase I (7), Phase II (8h and phase 111 (9). Major findings of all *rP w me summarized in this ar-
:le.
Environ. Sci.Technoi., Vol. 24, No. 8, I900 H 2 3
have been measured. For this study, 1 I major groups were evaluated (Figure 2). Of the total number of samples passing the screening criteria, relatively few were directed a t concerns about toxic pollution. For example, priority pollutants, pesticides, and radiochemicals amounted to only 0.5% of the Colorado samples and 5% of the Ohio samples. Screening results. Of about 308,000 samples reported for Colorado and about I million samples reported for Ohio, only a fraction met all the screening criteria. Thirty-four percent of the samples reported for Colorado and 5% of the Ohio samples met all five of the Phase I screening criteria. Most of the data failed the screening step because of the ambient conditions criterion; that is, they did not represent generally prevailing water quality conditions. Laboratory costs. An estimated $13.5 million was spent during 1984 in Colorad0 and $49.6 million in Ohio for the laboratory analyses. Of this amount, about $6.1 million for Colorado and $35.7 million for Ohio were spent s p cifically to meet permit requirements. These samples accounted for 45%of the total estimated laboratory costs for Colorado and 72% of the total for Ohio. For Colorado, 17%of the total estimated laboratory costs was for samples for compliance and enforcement activities, and the remaining 38% for samples to characterize ambient conditions. For Ohio, 2% of the estimated laboratory costs was for compliance and enforcement activities and the remaining 26% for characterization of ambient conditions.
I
FIGURE 1
Regknal water aualiIy samples reported in 1984, by collection purpose
hlorac
Ohio
Of an estimated $21.3 million spent
on analyses of samples collected to characterize ambient conditions or for compliance and enforcement activities in the two states, about $7.1 million represents data from samples that met all Phase I screening criteria. Thus, only about 11% of the total estimated laboratory costs (of $63.1 million) produced data that are readily available and are considered to be potentially applicable to fundamental, broad water quality issues. These laboratory costs, of course, represent only a part of the total expenditures of data collection programs.
Phase II-Quality kosmpoce Water quality data are collected by many organizations for diverse purposes that range from meeting statutory re quirements to basic research. Combining these individual data bases is an a p
pealing and potentially cost-effective way to develop a data base adequate for regional or national assessments. However, to combine data from diverse sources, field and laboratory procedures used to produce the data need to be equivalent and need to meet specific quality assurance standards. A total of 44 programs in Colorado and 29 programs in Ohio passed the Phase I screen and were examined in Phase 11. These programs accounted for an estimated 165,000 analyses in Colorado and 76,300 analyses in Ohio for 20 constituents selected for Phase 11. Each of the eight criteria that comprise the Phase I1 screen fall into one of two major categories: field practices or laboratory practices. Field practices included the use of documented sample collection techniques, collection of samples representative of stream or aquifer
FIGURE 2
Number of surface and gmundwater samples repolted in 1984 be4-- --* tuent gmup
w Phr-
+
weening, by prop-.
Colorado
-
Ohio
isicai properties
62.270
nic constituents Trace elements
13,940 13,810
M=ior metals Nutrients ibstances mllutants 'esticides :hemicais 9 t a
?nt
4410 244
28,110 14.540 35,870 6570
370.2M 91,210 7990 31.910 37w - 69,990 8820
50 )
-15.160
11w
b, 4940 2120
\119,3
,
1124 Environ. SdTechnol.. Vol. 24, No.8, lgS0
52,460
71.730
conditions, use of other established field practices, use of established sample handling and sample preservation procedures, and use and maintenance of analytical instruments in the field in accordance with established procedures. Laboratory practices included maintenance of a quality assurance program, maintenance of laboratory quality control procedures, and use of appropriate analytical methods. About 11% of analyses reported for Colorado and 14% of analyses reported for Ohio passed both Phase I and Phase I1 screening steps. Effect of screening criteria. The smallest percentage of analyses met the representative-sampling criterion. Analyses that failed this criterion were from stream samples that could not be verified as being representative. Generally, these were point (or “grab”) samples; that is, samples collected from a single point near the water surface without any knowledge of mixing conditions. Point samples may be collected for several reasons, but savings of time and cost probably are dominant factors. A representative stream sample is best obtained by combining depth integrated samples collected at several locations in the stream cross section. For Colorado, about 115,000 surface water analyses met all of the field and laboratory practices criteria except the representative-sample criterion. For Ohio, about 118,000 analyses met all the criteria except the representative-sample criterion. The sample handling and sample preservation criterion was met by the second smallest percentage of analyses for both states. In contrast to the field practices criteria, most analyses in both states met each of the laboratory practices criteria. This was because of more detailed description and widespread publication of guidelines for laboratory practices compared with guidelines for field collection practices. Few of these field guidelines emphasize the need for, or methods of, collecting representative samples. Furthermore, little has been published about the sources and magnitude of errors associated with collection of water samples for chemical analysis. Most of the data passing both the Phase I and Phase I1 screening were pH, alkalinity, specific conductance, and dissolved oxygen-factors that broadly characterize water quality. Therefore, the Colorado and Ohio data bases contain a relatively large amount of data needed to address issues of longstanding concern (e.g., sanitary quality and salinity). The fewest acceptable analyses were for trace constituents (atrazine, polychlorinated biphenyl, and lead). As a result, these data bases contain relatively few analyses that are needed to address current issues of con-
tamination by potentially toxic substances. The Phase I1 screening had little effect on the few groundwater analyses identified in Phase I. Sixty-nine percent of the groundwater analyses for Colorado and 100%of those for Ohio passed the Phase I1 screen.
Phase In-Utility of data Phase 111 evaluated the extent to which ambient water quality data that met the Phase I and Phase I1 criteria can be used to answer major regional and national questions such as: What are existing water quality conditions? Has water quality changed? and How do the existing water quality conditions and trends relate to natural versus anthropogenic factors? This evaluation focused on the first two questions by examining the number of measurements of different constituents at sampling sites and site areal distributions. In Phase 111, 12 of the 20 constituents evaluated in Phase I1 were selected for further study. To define existing conditions, both surface water and groundwater data collected during 1980-84 were used. For defining changes or trends, the period 1977-84 was used for surface water and 1972-84 was used for groundwater. Number of measurements at each data collection site. The number of measurements made at each of the data collection sites has a large effect on meeting the goals of ambient water quality assessments. Single or a few measurements at sites may be adequate for describing current groundwater quality conditions and are useful for reconnaissance level assessments of streams. However, because of the inherent variability of streams, measurements with concurrent streamflow data are needed to develop models of seasonal variation and long-term trends at a site. Most (75% or more) data from surface water sites in both Colorado and Ohio also had concurrent streamflow measurements. Although no single frequency of sampling or number of measurements is ideal for all conditions, 10 analyses were considered the minimum number needed to define existing conditions. Because groundwater quality changes more slowly than surface water quality, only one observation for the period 1980-84 was considered necessary to define existing groundwater conditions. For the different constituents evaluated in Phase 111, an average of 123 (26%) of the surface water sites in Colorado and 36 (12%) of the sites in Ohio yielded 10 or more analyses and concurrent streamflow data for the period 1980-84. All groundwater sites that met
the Phase I1 criteria in Colorado and Ohio yielded at least one analysis and were suitable for defining existing conditions. Estimates of constituent load (mass per unit time) also are used to compare contributions of various constituents from different streams and to estimate rates of erosion, deposition, and reservoir sedimentation. Accurate calculation of loads requires daily streamflow data and frequent water quality measurements. For this study, a minimum of 10 water quality measurements and daily streamflow data were required for estimating loads. In Colorado, 105 sites (22%) and in Ohio only 30 sites (10%) met this requirement. Computation of changes or trends in conditions generally requires uniform data collection over a long period of time (IO,11, 12). For this study, at least quarterly surface water quality measurements and concurrent streamflow data collected over 5 years were used. Fewer than 10% of the sites in both states met this requirement. For groundwater, only 1%, or 10 sites, in Colorado and 13%, or 23 sites, in Ohio had at least one sample per year over at least 5 years. Areal distribution of data collection sites. Data collection sites with an adequate number of measurements were mostly in relatively small areas with known or suspected water quality problems and/or high water use. For example, in Colorado, most sites with streamflow data and 10 or more dissolvedsolids and suspended-sediment measurements were clustered in the northwestern part of the state, in response to concerns about salinity and mining effluent effects on the Colorado River (Figure 3). In Ohio, sites with streamflow data and 10 or more total phosphorus measurements were more concentrated in the Lake Erie basin, a heavily populated, high-water-use area (Figure 4). Although important to specific water resource management objectives, the focus on known or suspected water quality problem areas and high-water-use areas results in a biased assessment of conditions and trends. For an unbiased assessment, additional data collection sites are needed so that the full range of hydrologic and land use conditions in the states are represented.
Implications of study results This study was undertaken in part because of concerns and criticism raised that existing monitoring programs were “fragmented, duplicative, and wasteful” and inadequate for effective management of water resources. Accordingly, the U.S. Geological Survey examined water quality programs in Colorado and Envlron. Sci. Technol., Vol. 24, No. 8,1990
1125
Ohio to determine whether existing data can he aggregated into a consistent and technically sound data base that is appropriate for assessments on the regional or national scale. Although the study results were specific to Colorado and Ohio, many of the conclusions have implications for a national assessment. Expenditures for data collection activities in the nation were large and difficult to estimate. In Colorado and Ohio during 1984, an estimated $63 million was spent for laboratory analyses of water samples. Laboratory costs represent generally less than 50% of the total costs of data collection programs. Assuming that these costs are representative, an estimated $2.5-3.0 billion was spent annually on water quality data collection activities in the United States. The magnitude of funding for these activities fails to reliably indicate the quantity or usefulness of data for assessing regional and national conditions and trends. There are several major reasons for this conclusion. First, most of the funding is for programs that have limited potential for producing the ldnds of data needed for regional amhient assessment. Environmental laws and sampling programs initiated in the 1970s focused on pollution discharges rather than on the receiving waters. The result has been large expenditures for end-of-pipe effluent sampling. For example, in 1984.45% of the estimated laboratory costs in Colorado and 72% of the costs in Ohio were for samples that represented effluent or treated water conditions rather than ambient stream or groundwater conditions. These programs have not provided the kind of information necessary to answer the types of regional and national questions facing the nation. More emphasis on in-stream sampling both upstream and downstream of discharge points, combined with effluent sampling, would increase our ability to determine improvements in water quality resulting from expenditures on treatment facilities. Second, several key aspects of these programs seemed to he out of balance. One aspect of this imbalance was that more than 9 W of the samples inventcried for this study were from surface water sources. Increased effort needs to be focused on groundwater to address growing concerns about groundwater contamination. Another area of imbalance was the limited effort directed toward the determination of potentially toxic constituents. Of the samples meeting Phase I screening criteria, samples for the determination of priority pollutants, pesticides, and radiochemicals amounted to 1126
Envlron. Scl. Technol., VOl. 24, No, 8, 19W
I
0
-.
I
L
0.5% of the samples in Colorado and 5% of those samples in Ohio. In contrast, most of the samples were analyzed for traditional constituents and properties associated with acidification, sanitary
quality, salinity, and eutrophication. There was also an apparent imhalance in the areal and temporal scales of the assessments. Most of the programs in Colorado and Ohio were directed tc-
ward small-scale, transient assessments that characterized individual problem areas associated with known or suspected point and nonpoint sources of contaminants. For large areas information was inadequate to perform an unbiased assessment of regional surface water and groundwater quality conditions. Similarly, there were relatively few sites in either state where samples were collected over a long enough period to define trends in water quality. A critical factor in understanding water quality is the ability to make comparisons among different locations and over time. The third finding of this study was the increased need to define field proce dures, especially the collection of representative water samples. Improvements to field procedures would result in more reliable data suitable for water quality assessments. Maintaining high quality assurance standards in the laboratory is equally important, but precise laboratory analysis is of little benefit if the samples are unrepresentative. In spite of the criticisms of long-term networks (4). these networks provide adequate data for regional-scale assessments of conditions and changes. At many of the sites in these networks, samples were collected only once each month, but the record of surface water flow was long enough that the range of flows generally was well represented. The data were adequate to define not only the water quality at a site but also, in conjunction with synoptically collected data around a river basin, were adequate for describing general water quality conditions and changes for a number of constituents in a basin.
References
Report 90-174; USGS Washington, DC. 1990. Hrcn, J. el al. “Water-Quality Data-Collection Activities in Colorado and Ohio: Phase I-Inventory and Evaluation of 1984 Programs and Costs”; US.Geological Survey Water-Supply Paper 2295-A; USGS: Washington, DC, 1987. Childress, C.J.O. et al. “Water-Quality Data-Collection Activities in Colorado and Ohio: Phase 11-Evaluation of 1984 Field and Laboratory Quality-Assurance Practices”; U.S. Geological Survey Waterdupply Paper 2295-8: USGS: Washington, DC. 1989. Norris, J. M. et al. “Water-Quality Data Collection Activities in Colorado and Ohio: Phase Ill-Evaluation of Existing Data for Use in Assessing Regional WaIerQuality Conditions and Trends”; US. Geological Survey Water-Supply Paper 2295-C; USGS: Washington. DC, in preSs. Hirsch, R. M.; Slack, J. R.; Smith, R. A. Wore, Resow. Res. 1982 18. 107-21. Hirsch. R. M., Wale? Resour. Bull. 1988, 24.493-503. Lettenmaier, D. P. Waler Resour. Bull. 1978.14, 884-902.
Janet H m is a hydrologist with the U S .
Geological Suruey, Water Resources Diuision, Western Region O p in Fenlo Park, CA. She has a B.S. egree in brology f r o m Kent State University and an M.S. degree in biology from the Uniuersit y ofAkron. OH.
J. Michael Norris is a hydroloflit for the U.S. Geological Survey in Lakewood. CO. He har an M.S. denee in hydrolow and water resources /;om color ado^ State University. For thepast 10 years his work has ocused on various as ects of water qua rty, hydrologic mode&, and hazardous waste contamination in both surface water and groundwater.
lhonus H. C h m y is a hydrolo ‘ v i wirh the Water Rerources Division oflhe U S . Geolo cal S u n e y in Dewer. CO. He has B S 8gree.v i n ’ z w l o m rom Ohio Slate Unirererty. Columbus. I I , and in h e r tehrate iwlow from Wright State Uniiwvirj,. Dayron. OH Hi
