PUBLICATIONS: Reports on Data Networks September 29, 1975 QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 76.02 Subject: PUBLICATIONS: Reports on Data Networks During the recent months, members of the staff of the Quality of Water Branch have completed two papers on networks for monitoring water quality which may be of interest to our field offices. Copies of the reports are enclosed. U.S. Geological Survey Circular 719, "The National Stream Quality Accounting Network (NASQAN)--Some Questions and Answers," by Ficke and Hawkinson, is intended to answer some of the frequently-asked questions concerning concepts used in establishing NASQAN--its purposes, design value, and future plans. This Circular was written for use in describing this important national network to other Federal agencies, cooperators and the public. But I hope that it will be widely read also within the Geological Survey, and particularly in our field offices by the people who provide the important functions which make the network operate. Copies of the Circular may be obtained free through the Branch of Distribution. Article 1.04.3 of the WRD Publications Guide requires that orders for multiple copies be sent to the Publications Unit, National Center, Mail Stop 435, Reston. The paper, "Design of Nationwide Water-Quality Monitoring Networks," by Pickering and Ficke, was prepared for and presented at the recent International Conference on Environmental Sensing and Assessment that was held in Las Vegas during September 14-19. We wrote the paper for a broad international audience, and intended it to apply to nationwide networks. However, some of the concepts described in the paper also apply in the design of water- quality networks at regional and local levels. I invite your comments on the paper. Also enclosed is a Geological Survey news release covering the NASQAN Circular and the Las Vegas paper. We have received several calls at Headquarters as a result of the news release. Because you may receive inquiries about it at your local offices, you will probably wish to see that it receives wide distribution among your employees. The Water Resources Division Training Center has completed a short video tape describing NASQAN. Copies of the tape may be obtained from the Center. R. J. Pickering Attachments - 3 WRD Distribution: A, FO-LS, PO DESIGN OF NATIONWIDE WATER-QUALITY MONITORING NETWORKS R. J. Pickering and John F. Ficke Hydrologists, U.S. Geological Survey, National Center, Reston, Va. Abstract The many facets of "water quality," which include physical, chemical, and biological characteristics of water, make it impossible to design an all-purpose water-quality monitoring network. The specific objectives of the monitoring program must be clearly defined before a proper mix of sampling sites, characteristics to be measured, and frequency of measurement can be selected. Design of ground-water quality networks, for example, must be based on a knowledge of direction and rate of water movement, while proper sampling in streams requires a knowledge of velocity distribution in the cross section and expected variation in streamflow and water quality with time. Funding and manpower are commonly the primary constraints for network design, rather than acceptable error or ideal coverage of water-quality characteristics. The U.S. Geological Survey, as the agency responsible for describing and evaluating the water resources of the United States, has designed several networks for monitoring water quality on a national and regional scale. The largest of these is the National Stream Quality Accounting Network (NASQAN), which is designed to monitor quantity and quality of streamflow as it moves from one hydrographic "accounting unit" to another or to the oceans. Reports from NASQAN will describe geographic and year-to- year variations in streamflow and water quality, their probable causes, and detectable long-term trends. Organic and radioactive substances and biological characteristics are measured at selected network stations that constitute subnetworks of NASQAN. The subject of this paper, national networks for monitoring quality of water, is an extremely broad one. Its full scope could be the subject of many papers. I will address the subject in general terms at first, and then turn to a specific example of such a network that is being operated by the U.S. Geological Survey. First, some definitions would seem to be in order. By "monitoring" I refer to successive measurements over a period of time for the purpose of detecting change, or lack of it. "Network," in the broadest sense, refers to an organized system for collecting a specific kind of information. In the narrower sense, as used in this paper, "network" refers to a series of points at which one or more measurements are made, and which have been selected to satisfy a specific objective. For example, an objective might be to detect changes in the quality of the Nation's large rivers, or to measure the beneficial effects of our Nation's pollution- abatement efforts, or to provide an early warning of intrusion of salt water into a fresh-water aquifer. Water quality can be defined as "the wide variety of physical, chemical, and biological characteristics of water that make it fit or unfit for a particular use." The several hundred inorganic chemical constituents and tens of thousands of organic compounds that can occur in water serve to demonstrate that not all aspects of water quality can be addressed by any one monitoring network. h~cn reference is made to "water-quality monitoring network," we must immediately ask "what kind of network?--What is the objective? What water quality characteristics are of interest? Once the objective of the water-quality monitoring network is defined, decisions must be made on (l) water-quality characteristics to be measured, (2) sites at which measurements are to be made (objectives may be 2-dimensional or 3-dimensional with depth the third dimension), (3) frequency of measurement for each characteristic and at each point, and (4) the statistical parameter that will be used to report each characteristic. Almost all networks rely on point measurements, and interpolation and extrapolation therefrom -- both in space and in time. Exceptions include certain measurements that can be made by aircraft or satellite, such as temperature, or for which sensors have been developed that can be used to record variations with time at a point at streamside, or variations in space by being towed in a boat -- for example, specific conductance, an indirect measure of dissolved solids; dissolved oxygen; pH; turbidity; radioactivity; and a few other water-quality characteristics. This paper will review some of the principles of design and operation of water-quality monitoring networks, and in doing so will concentrate on the techniques and experience of the U.S. Geological Survey. Design of Networks In designing any kind of water-data network, one must initially decide (l) the function of the network, and (2) the geographic scope and network must cover. It is clear that a pollution- surveillance network will not call for measurement of the same water-quality characteristics as a network designed to define the "natural" quality of water. It is clear also that selection of monitoring sites for a network that can be used to describe streamflow quality on a nationwide or broad regional basis will be on a different scale than for a network aimed at quantifying non- point pollution sources in a small river basin. The U.S. Department of the Interior's Office of Water Data Coordination has developed a function-and-level concept of network design which it has been using in its efforts to coordinate water- data collection or acquisition in the United States (figure 1), and to develop a National System for Water Data. The horizontal axis on the diagram corresponds to functional categories, that is, general objectives for gathering data. The vertical axis refers to the geographic scope of the data-gathering effort, and thereby indicates the level of detail of the information needed. Within this generalized conceptual model, there is much room for differences in approach to network design. For example, a "systems concept," or hierarchical approach, could be used for selecting data-collection sites and water-quality characteristics to be measured. A carefully-designed random sampling procedure might be employed in other circumstances, such as to describe water-quality in an aquifer for which variability is poorly known. Or a hydrographic basis, calling for measurement of water quality at successive downstream points, could be used to illustrate incremental changes in water quality as surface water moves toward the sea. Figure l.--Relation of levels of information to functional categories in the National System for Water Data. Design of surface-water quality monitoring networks differs from that of ground-water networks in several respects. Because surface flow is confined to a stream channel, there is usually no question about the direction of movement of the water, and techniques are available by which to measure or estimate the length of time it takes the water to move from one point to another under different streamflow conditions. Nevertheless, a representative sample of water in the stream cross-section at a particular time may require a series of depth-integrated samples along the cross section because of non-homogeneous distribution of the water-quality characteristics of interest. The sampling or measurement pattern should be determined through a site evaluation study made at the time the measurement site is first selected. Ground water, on the other hand, is much less accessible than is surface water, sampling points necessarily are fewer in number, and the hydrologic characteristics of the aquifer are seldom known well enough to predict in detail either the exact direction or the rate of movement of the water. A general knowledge of the hydrology of the aquifer must be acquired before the significance or cause of changes in water quality with time can be assessed. Monitoring of pollution sources and other factors affecting water quality, such as land use and natural basin or aquifer characteristics, will provide a basis for postulating causes of water-quality changes and identify tools for predicting and modifying such changes if necessary. Funding and manpower are commonly the primary constraints to network design, rather than acceptable error or ideal coverage of water-quality characteristics. The U.S. Geological Survey has utilized all the above concepts in designing its water-data collection networks. Its Benchmark Network, which is aimed at defining the range of "natural" streamflow and water quality and the factors controlling them, consists of data-collection sites in small stream basins that are unaffected by man. The basins in the network were selected to cover the station geographically and to represent a good mix of basin characteristics. Our National Stream Quality Accounting Network (NASQAN) consists of data-collection sites at the mouth of each of 325 hydrographic "accounting units," and is designed to provide a measure of the quantity and quality of water moving from one accounting unit to the next. NASQAN data thus provides a measure of the quality of the Nation's major rivers. Let us look at the design of NASQAN in more detail. As stated above, the United States has been subdivided into 325 hydrologic accounting units. For units with regular, well-integrated drainage, one station was placed as near to the downstream end of the unit as was practical. Our goal was to measure and have access for sampling of 90 percent of the streamflow moving from one accounting unit to the next. This is what we mean by accounting. However, because of parallel drainage patterns along coastal areas, and complex hydrologic situations elsewhere caused by dams and reservoirs, it was necessary to have more than one station in a number of accounting units. Indeed, in coastal regions it has been necessary for us to use a "representative station" concept. NASQAN stations have been located to provide a sampling of from 30 to 50 percent of the outflow of each coastal accounting unit. This water-quality information, together with more extensive streamflow data, will be used to estimate the quality of the remainder of the outflow of a particular accounting unit. To allow for the above considerations, the design of NASQAN calls for 525 stations when the network is completed, To date, 345 stations have been established at the locations shown in figure 2. Note that a large share of the stations are along coastlines, along international boundaries, or near the mouths of tributaries to major rivers where they monitor the drainage from tributary basins. A modified accounting approach has been used in the design of NASQAN subnetworks for monitoring radiochemicals and pesticides. Because money was not available to operate other full-scale networks the size of NASQAN, 153 NASQAN stations were randomly selected for monitoring of pesticides, and 51 stations were selected for monitoring of radiochemicals. The pesticide subnetwork is operated in cooperation with the U.S. Environmental Protection Agency (EPA) and will be described in more detail by another speaker in this symposium. The Geological Survey also operates the bulk of the stations in EPA's National Water Quality Surveillance System, which provides a sampling of selected pollution problem areas throughout the Nation. Operation of Networks Once station locations have been selected, the next issue that must be considered is what to measure and how often. There are many possible courses of action, and again the objective of the network must be the controlling factor. There usually is a strong temptation to select a suite of measurements that will attempt to address all needs but, as noted before, this is clearly impossible. The water-quality characteristics listed by the U.S. National Academy of Sciences as controlling the suitability of water for the six broad uses that the Academy has addressed, number close to a hundred. The often-asked question, "What do you measure, and why?" should be turned around to first approach the subject of why one is measuring water quality. Is the purpose to appraise the water's suitability for drinking, for support of fish life, for irrigation or industrial use; or is it to monitor for suspected pollution? If the purpose is to evaluate suitability for a particular use, the National Academy of Sciences' compilation is probably the best general source of information that is available. Determinations required by recent Federal legislation must be Figure 2.--Locations of stations in the National Stream Quality Accounting Network in operation as of January 1, 1975. included also if the intended water use falls within their purview. Thus, in most cases a list of standards or criteria is already available. Clearly, high costs and limited amounts of money often will limit the length of the list of chemical constituents and physical characteristics to be monitored. A selection must be made of the water use or uses of primary interest, and the water-quality characteristics that are most critical to the suitability of water for those particular uses. In some situations it is practical to use broad "indicator" measurements or to estimate the concentration of certain chemical constituents from measurements of other water-quality characteristics, such as electrical conductance. Studies of stream quality records in the United States have revealed many situations where it is possible to closely estimate the concentration of dissolved solids and of many major inorganic constituents from specific conductance data. In some situations, data on total and dissolved organic carbon can be used to determine changes in concentration of a particular organic compound which is present in relatively high concentrations. Biological information, such as amounts of or changes in numbers of cells, biomass, diversity, or other factors may be used as estimators of water quality, although in many cases such data do not directly relate to standards or criteria for use. The U.S. Geological Survey presently is collecting several types of biological data in our national networks in order to provide information that can be used to evaluate the potential application of biological measurements for judging the suitability of stream waters for specific uses. Frequency of measurement often is decided by a compromise involving two factors: (l) the need to define the variations over time of a particular water-quality characteristic, and (2) limitations imposed by the amount of money available to make the necessary measurements. It is necessary, for example, to make frequent measurements and estimate controlling factors if one hopes to define the range of concentration of a constituent. If the load, or total weight of a particular constituent is desired, measurements must be made over a range of streamflow conditions; and a basis for estimation or indirect measurement must be developed, because continuous measurements are practical only for a few water-quality constituents, such as dissolved oxygen and electrical conductance. It is important to consider network objectives in selecting sampling frequency. Referring back to the classification of water- data collection then. 1), it may be possible to greatly reduce measurement frequency for a Level I accounting network once the variability of a water-quality characteristic has been defined over the expected range of streamflow, or after the nature of the variations has been defined--over time, with water discharge, and with variations in other characteristics. On the other hand, measurement frequency cannot so easily be relaxed for surveillance, which includes monitoring for hazards and collecting data on the nature and extent of pollution. Surveillance must, by definition, be designed to detect the unexpected, if and when it occurs. Surveillance monitoring usually involves .automatic monitors or samplers, frequent visits to the monitoring station and, commonly, immediate, automatic data transmission. The state of the art in automatic monitoring is changing every day; but there is one aspect of it that has not changed in recent years -- it is expensive. Rugged, dependable field monitors are available for recording temperature and specific conductance. Good equipment also exists for monitoring dissolved oxygen, pH, turbidity, and chloride, and for collecting representative sediment samples; but the equipment is expensive, requires frequent servicing, and even when working well commonly results in loss of a significant fraction of the record. Sophisticated equipment also exists for monitoring selected ions and certain organic compounds; but again, cost is high and reliability varies, especially in the case of field installations. Telemetering equipment has been used for many years in hydrologic monitoring, and it will see far greater use in critical situations in the future. Telemetry is expensive, but the cost often can be justified if there is a real need for immediate information. In many cases, however, the weak link in a system for telemetering data is in the sensors and equipment which supply the basic measurement signal. Without adequate servicing, the information obtained will be equivocal, and unusable for regulatory or management agencies. However, an incidental benefit of immediate, automatic data-reporting is the advantage of being immediately aware of malfunctions of field equipment. In operating any monitoring network, it is desirable to strive for uniformity--in space and in time--in equipment, in methods, and in operating standards. So far this paper has dealt with field considerations, but laboratory performance must also be considered. In the Geological Survey, we have attempted to gain uniform quality in laboratory data by standardizing methods; by generally adopting a system of fewer, larger, and more highly automated laboratories; and by constantly checking and evaluating analytical performance through carefully-designed quality control programs. It has been estimated that quality control accounts for from 10 to 20 percent of the cost of operating the Survey's three central laboratories, which annually process more than 90,000 samples and make more than l,OOO,000 individual physical, chemical and biological determinations. Beyond this, we are working with other data-collecting agencies and technical organizations to develop a National Handbook of Recommended Methods for later Data Acquisitions which will provide for improved comparability, reliability, and usability of the resultant data. Reporting Results When it comes to reporting results of monitoring networks, the objectives of network operation again must be considered. The commonly-used tables of numbers or computer printout often do not meet the needs of the busy planners and decision makers who must know the quality of water within their jurisdictions; or the statistical parameters used for reporting the water quality information may not provide the perspective the water manager may need to make his decision. During the past several months, the Geological Survey has devoted considerable thought and effort to determining how to report information on water quality. An interagency research project, conducted in cooperation with the U.S. Environmental Protection Agency (EPA) and the Council on Environmental Quality (CEQ) is providing comparative evaluations of water quality indices for use in reporting water-quality data. Ways of presenting water-quality information in relation to water-quality criteria or standards are being studied also. The search for simpler, more practical and useful ways of reporting water quality information will remain a continuing challenge in the years ahead. Summary The many facets of "water-quality," which include physical, chemical, and biological characteristics of water, make it impractical and too costly to design an all-purpose water-quality monitoring network. Specific objectives of the monitoring program must be clearly defined before a proper mix of sampling sites, characteristics to be measured, and frequency of measurement can be selected. In addition, one must have some knowledge of the functioning of the part of the hydrologic system to be monitored. Presentation of the information collected through network operations in the form that is most suited to the needs of water managers and decision makers is a major challenge for technicians in the field of environmental sensing and assessment. References 1. Biesecker, J. E., and Leifeste, D. K., 1971, Water Quality of Hydrologic Bench Marks - An Indicator of Water Quality in the Natural Environment: U.S. Geological Survey Circular 460-E, 2L p. 2. Cobb, E. D. and Biesecker, J. E., 1971, The National Hydrologic Bench-Mark Network: U.S. Geological Survey Circular 460-D, 38 p. 3. Ficke, J. F., and Hawkinson, R. 0., 1975, The National Stream Quality Accounting Network (NASQAN) - Some Questions and Answers: U.S. Geological Survey Circular 719, 23 p. 4. Langford, R. H., and Davis, G. H., 1970, National System for Water Data: Am. Soc. Civil Engineers Proc., Hydraulics Div. Jour., v. 96, no. HY 7, paper 7392, p. 1391-1401. 5. U.S. National Academy of Sciences and National Academy of Engineering, Environmental Studies Board, 1972, Water Quality Criteria 1972: Washington, D.C., U.S. Environmental Protection Agency rept. EPA.R3.73.033, Mar. 1973, 594 p. news release GEOLOGICAL SURVEY Kelly (703) 860-7444 For Immediate Release (September 18, 1975) NATIONAL WATER QUALITY MONITORING NETWORK A new water-quality monitoring network designed to provide a balanced yearly picture of water quality in U.S. streams on a national and regional scale is now in operation according to the U. S. Geological Survey report. Known as the National Stream Quality Accounting Network (NASQAN), the network now consists of 345 stations that measure 46 physical, chemical, and biological water-quality characteristics, including temperature, specific conductance, and a variety of bacteria, dissolved minerals, trace elements, nutrients, and organic, and biological constituents. Measurements are made either continuously, daily, monthly, or quarterly, and the network will be expanded to 525 stations by October 1976. Speaking before a recent (September 15, 1975) International Conference on Environmental Sensing and Assessment in Las Vegas, Nev., Dr. R.J. Pickering, Chief, Quality of Water Branch, National Center, Reston, Va., said, "Previous attempts by the U.S. Geological Survey and other Federal organizations to clearly document changes or lack of changes in water quality with time, on a nationwide basis, have been largely unsuccessful because data-collection programs were designed to meet local needs or to provide data for special programs or problems." "A balanced large-scale picture of the Nation's stream quality could not be drawn because data-collection sites were operated for short periods of time and were moved frequently, measurements were made at irregular intervals, or the parameters being measured were changed to meet different needs," the USGC spokesman said. "NASQAN will not have these problems because it is set up on a national basis; its stations are operated uniformly; and the program is committed to long-term objectives." "The primary objectives of NASQAN," Pickering explained," are to account for the quantity and quality of water moving within and from the United States, to depict areal variability of water quality, to detect changes in stream quality, and to lay the groundwork for future assessments of changes in stream quality." "The USGS-designed network measures a broad range of physical, chemical, and biological characteristics that were selected in response to the information needs of groups involved in water planning and management on a national or regional scale. NASQAN sampling sites are selected on the basis of hydrologic subdivisions of the United States that have been adopted by the U.S. Water Resources Council. The Council, with the help of the USGS Office of Water Data Coordination, has divided the country into 23 regions, 220 subregions, and 324 accounting units. Locations of II SQ~ monitoring stations have been chosen to measure the quantity and quality of approximately 90 percent of the surface water leaving each inland accounting unit. Stations located in accounting units which discharge into the Great Lakes, oceans, across international boundaries, or into closed basins, ~here no single stream drains the entire accounting unit, have been selected so that 30 to 50 percent of the water draining from these units is measured. Because adjacent basins usually have similar land and water characteristics, water-quality data collected from these sites will be used in conjunction with more extensive streamflow measurements to estimate the quality of the remainder of the discharge. Most NASQAN stations are operated and maintained by the USGS, and most of the samples collected at the stations are analyzed in USGS laboratories. Some of the USGS stations are paid for by monies from other Federal agencies, from State and local cooperators, or from other more specialized programs of the USGS . A few of the stations are operated by other Federal agencies, such as the Environmental Protection Agency and the U. S. Army's Corps of Engineers, who furnish their data to the USGS . NASQAN data will be published in three forms: (l) annual Geological Survey has data reports on a State-by-State basis, (2) an annual summary report depicting the Nation's surface-water quality, and (3) a series of reports, published every three to five years, that will deal with long-term changes (or lack thereof) in water quality. NASQAN is more fully described in a new report, "The National Stream Quality Accounting Network (NASQAN)--Some questions and Answers, " by John F. Ficke and Richard 0. Hawkinson, published as U. S. Geological Survey Circular 719. Copies of the report are free upon request to the Branch of Distribution, U.S. Geological Survey, 1200 South Eads Street, Arlington, Va. 22202.