PUBLICATIONS -- Transmittal of the report "Summary of the nationwide analysis of the cost effectiveness of the U.S. Geological Survey stream-gaging program (1983-88)" by W. O. Thomas, Jr. and K. L. Wahl In Reply Refer To: October 18, 1994 Mail Stop 415 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 94.08 Subject: PUBLICATIONS -- Transmittal of the report "Summary of the nationwide analysis of the cost effectiveness of the U.S. Geological Survey stream-gaging program (1983-88)" by W. O. Thomas, Jr. and K. L. Wahl The subject report summarizes a nationwide analysis of the cost effectiveness of the stream-gaging program that was operated by the U.S. Geological Survey (USGS) during 1983-88. The subject report should be of interest to those individuals who operate and manage the USGS stream-gaging program. The objective of the nationwide study was to define and document the most cost-effective methods of furnishing streamflow information. The study involved three phases: (1) an analysis of the data uses and availability and documentation of the sources of funding for each streamflow station; (2) an evaluation of the utility of using less costly alternative methods, such as hydrologic flow routing models and statistical methods, to provide the needed streamflow information; and (3) an analysis of the cost-effective operation of the stream-gaging program that relates the accuracy of the streamflow records to various operating budgets. A prototype study for the nationwide analysis was described by Fontaine and others (1984). Statewide analyses were performed by hydrologists in District offices throughout the Water Resources Division (WRD). The reports describing the analyses for the individual States are summarized and referenced in the subject report. The nationwide analysis documented that (1) multiple uses were being made of data collected at stations in the USGS stream-gaging program, (2) simulated flows from hydrologic flow routing models and statistical methods were not generally of sufficient accuracy for most uses, and (3) the stream-gaging program was being operated in an efficient and cost-effective manner. The cost- effectiveness techniques developed in this study provide an objective way to compare the relative accuracy of streamflow records at several locations as a function of the number of visits to the station. The USGS has a long history of analyzing and evaluating the stream-gaging program. The subject report describes the third nationwide analysis of the USGS stream-gaging program. A brief history of surface-water network analysis within USGS follows. The first known nationwide review of the stream-gaging program was conducted in 1953-58. The purpose of the review was to design a hydrologic network of stream-gaging stations in accordance with principles described by Langbein (1954). During this review, stations were classified as either water management or hydrologic network (regional hydrology). Within the hydrologic network, the concept of primary and secondary stations was developed. The primary stations were for obtaining a long-term sampling of streamflow and the secondary stations, operated for 5-10 years, were for obtaining geographic coverage of streamflow characteristics. Estimation of long-term statistics at the secondary stations was based on correlation of monthly flows with the long-term primary stations. Recommendations for improving the stream-gaging program are summarized in a June 1958 Administration Report entitled "Progress Report to Chief, Surface Water Branch on the Nationwide Review of Stream-Gaging Program". The second national study of the streamflow data-collection program was conducted in 1969-70. The general procedures for evaluating the available data, codifying the purposes of stream gaging and determining the desirable program of the future were described by Carter and Benson (1969). The stations were classified by data uses as current use (water management), planning and design (regional hydrology), long-term trends and stream environment. Within planning and design, unregulated minor and principal streams (over 500 square miles) were identified. The goals of the study were to obtain 25 years of record at stations on principal streams and obtain 25 years of equivalent record at points intermediate to gaging stations. The goal for minor streams was to obtain 10 years of equivalent record through the use of regression equations that related a variety of streamflow characteristics to watershed and climatic character- istics. The regression equations developed in this study and the results of the program analysis are described in a series of statewide reports entitled "A Proposed Streamflow Program for [State Name]." A summary of the nationwide study, including recommendations for improving the program, is provided by Benson and Carter (1973). As an outgrowth of the 1969-70 nationwide analysis, a new network analysis technique, regression analysis simulation, was developed by Moss and Karlinger (1974). Ordinary least squares regression equations, relating streamflow characteristics to watershed and climatic characteristics, were used to evaluate the time-sampling and spatial-sampling errors in order to design a more optimal regional-hydrology network. These techniques, known as Network Analysis for Regional Information (NARI), are described by Moss and others (1982). The NARI techniques were used to determine a more appropriate stream-gaging strategy for reducing the standard error of the regional regression equations. This strategy may involve operating the existing stations longer, adding new stations to the network or some combination of both. The results of applying these techniques are described in several statewide reports. The nationwide cost effectiveness analysis described in the subject report was conducted during the mid-1980's (Thomas and Wahl, 1993). The recent emphasis on surface-water network analysis within the WRD is the use of Generalized Least Squares (GLS) regression analysis to analyze the regional-hydrology network. The GLS procedures build on the techniques described by Moss and others (1982) by utilizing GLS regression procedures that incorporate the time-sampling error in streamflow characteristics and an improved measure of the correlation in streamflow characteristics between stations. The objective is the same as in NARI and that is to determine if the existing stations should be operated longer, whether new stations should be installed or some combination of both. More details on applying these procedures are given in Office of Surface Water Technical Memorandum No. 87.08. The technical aspects of the GLS procedures are described by Tasker and Stedinger (1989) and an example of applying these techniques to a surface-water data network in Kansas is described by Medina (1987). Network analysis techniques have evolved over the years from (1) correlation of monthly mean flows as recommended by Langbein (1954), to (2) the use of regional regression equations to determine the equivalent years of record of estimated streamflow characteristics at ungaged sites, to (3) the use of regional regression equations to evaluate the trade-off between time- sampling and spatial-sampling errors in the design of a regional hydrology network. Network analyses and program evaluation will continue to play a prominent role in the management of the USGS stream-gaging program. Future directions will likely involve the development of techniques for a more coordinated analysis of water-quality, ground-water and streamflow networks. References Benson, M. A. and Carter, R. W., 1973, A national study of the streamflow data-collection program: U.S. Geological Survey Water-Supply Paper 2028, 44 p. Carter, R. W. and Benson, M. A., 1969, Concepts for the design of stream-flow data programs: U.S. Geological Survey open-file report, 20 p. Fontaine, R. A., Moss, M. E., Smath, J. A., and Thomas, W. O., Jr., 1984, Cost effectiveness of the stream-gaging program in Maine - A prototype for nationwide implementation: U.S. Geological Survey Water-Supply 2244, 39 p. Langbein, W. B., 1954, Stream gaging networks: International Association of Hydrological Sciences (IAHS) Publication No. 38, pp. 293-303. Medina, K. D., 1987, Analysis of surface-water data network in Kansas for effectiveness in providing regional streamflow information [with a section on Theory and Application of Generalized Least Squares by G. D. Tasker]: U.S. Geological Survey Water-Supply Paper 2303, 28 p. Moss, M. E. and Karlinger, M. R., 1974, Surface water network design by regression analysis simulation: Water Resources Research, vol. 10, no. 3., pp. 427-433. Moss, M. E., Gilroy, E. J., Tasker, G. D., and Karlinger, M. R., 1982, Design of surface-water data networks for regional information: U.S. Geological Survey Water-Supply Paper 2178, 33 p. Tasker, G. D. and Stedinger, J. R., 1989, An operational GLS model for hydrologic regression: Journal of Hydrology, 111, pp. 361-375. Thomas, W. O., Jr., and Wahl, K. L., 1993, summary of the nationwide analysis of the cost effectiveness of the U.S. Geological Survey stream-gaging program (1983-88): U.S. Geological Survey Water-Resources Investigations Report 93-4168, 27 p. Ernest F. Hubbard Acting Chief Office of Surface Water Attachment WRD DISTRIBUTION: FO