PROGRAMS AND PLANS--A U.S. Geological Survey (USGS) Climatological Discharge Data Network In Reply Refer To: February 4, 1988 WGS-Mail Stop 415 REPLY REQUESTED BY MARCH 1, 1988 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 88.05 Subject: PROGRAMS AND PLANS--A U.S. Geological Survey (USGS) Climatological Discharge Data Network The Water Resources Division (WRD) is seeking to define a climatologic dis- charge data network by identifying those stations in WATSTORE which would be suitable for mesoscale climatic analyses. Jim Slack (Branch of Regional Research/WR) and Jurate Landwehr (Branch of Regional Research/NR) have been working with Charlie Riggs (Office of Surface Water (OSW)) and myself to identify stations appropriate for inclusion in such a network. Several different collections of stations that have been used for climatologic or related analyses by researchers in the WRD were merged into a single col- lection. This station list was given an initial review by OSW. Annual water summaries for each State were also reviewed for possible additions to this list. We are now requesting your help in reviewing the compiled station list. BACKGROUND: The USGS collects discharge information for several thousand stations through- out the United States and its territorial areas. This data-collection effort is motivated by societal concerns, e.g., establishing information with which to secure public water supplies or to mitigate against flood damages. It must be an ongoing activity because the phenomenon of interest--streamflow--varies over time. The variability of streamflow is a function not only of the inherent variabil- ity of the hydrologic cycle, but also the variability of the climatic system in which the cycle is embedded, as well as the variability of the economic and social demand for water. However, in many areas, though certainly not all, it is the climatic variability which is dominant, and a major shift in the climate system would engender a major shift in the hydrologic regime as well. Consequently, for both operational and research interests of the Division, it will be useful to have one commonly defined data set of high-quality discharge stations identified as the "USGS Climatological Discharge Data Network." CRITERIA: A network such as we are discussing cannot be all things to all people. In particular, it cannot be expected to characterize the stochastic behavior of micro-hydrologic conditions. Such questions must be addressed on a local, case-by-case basis. Rather, the spatial scale of the basins which would com- prise this network should be in the mesoscale range, i.e., comparable in size to hydrologic units of the WRD as well as to the climatological divisions of the National Weather Service. Such a scale is fine enough to distinguish be- tween climatologically distinctive areas as well as appropriate for aggrega- tion upward to a general circulation model (GCM) scale. Initially, the resolution for the variability of interest will be on a rather gross time scale, such as monthly or even seasonal averages. The pattern of diurnal or even weekly cycles will not be captured. Consequently, criteria by which stations should be considered for inclusion in such a network are: 1. Long records: n>=20 Preferably, n>=50, but the 20-year threshold was chosen to allow the inclusion of the benchmark stations. 2. Good quality data. This pertains to the quality of the stage record, the discharge measure- ments, and the stage-discharge relation. 3. Broad geographic and diverse climatologic representation across the country. 4. Minimal anthropogenic effects in basin, including minimal regulation of the stream discharge or reduction of base flow due to extreme ground-water pumping. 5. Basin size generally should be mesoscale, i.e., 100 to 1,000 square miles. However, this need not be a hard and fast rule: there is some merit in including the records from the "Big Five" rivers at one end of the scale and the benchmark stations, at the other, if criteria number 2 is met. In striving for geographic coverage, particularly in the Southwest, the ques- tion of including ephemeral streams may arise. If such a stream should meet the above-stated criteria, it may be considered for inclusion but should be identified as such. There may be several strategies that could be used to obtain appropriate geographic density. For example, Byron Aldridge, WR, has suggested two approaches which could be considered: (1) choose one or two stations within each hydrologic accounting unit which is most representative of hydrologic conditions in that unit; or (2) select one station for each rectangular area unit that is 1 degree of latitude by 2 degrees of longitude, starting with a few minutes between odd longitudes in the mountainous regions. The number of stations in the network should not exceed 500; the more realis- tic number is probably 300 nationwide. STRATEGY: There are several different collections which have been or still are in use by different offices of WRD, although none completely satisfy the above criteria. These include National Water Conditions data set (C); NASQAN, active and inactive (N and n); Benchmark (B); Miniregions (M); Langbein-Slack (L); and Alley-Lins (A). (See attached footnotes for further explana-tion.) These are termed "Other Compilations." Charlie Riggs, OSW, has provided an initial screening of this mega-list as well as examining the State data reports for other prospective stations, identified as "OSW." The list of stations by District can be found in the file JRS.BIGLIST which is located in the RVARES FTS_DEPOT. For each State, these is a subdivision into two lists, namely "Stations suggested by OSW" and "Stations in other compila- tions." Other compilations in which stations appear are identified in the left margin. We ask that you consider the stations in your District and indicate agreement or disagreement with the stations suggested by OSW, in light of the forestated criteria. Are there any stations from the other compilations that also should be considered? Are there any other additions which do not appear in any of the compilations that also should be considered for inclusion in such a data base? Comments as to why further additions should be considered, especially in preference to the listed stations, would be helpful in our deliberations. If you have further questions, please do not hesitate to call Jurate Landwehr (FTS 959-5893) or Jim Slack (FTS 459-7201). Please return comments to J. M. Landwehr (USGS, MS-430, Reston, Virginia 22092) before March 1, 1988. Verne R. Schneider Attachment WRD Distribution: A, B, S, FO Footnotes (C) The National Water Conditions data set is the subcollection of discharge stations (besides reservoirs and wells) used in the monthly National Water Conditions report of the USGS. (N and n) See "The National Stream Quality Accounting Network (NASQAN) - Some Questions and Answers" by J. Ficke and R. Hawkinson, Geological Survey Circular 719, 1975. (Stations designated "N" were active as of 1985.) (B) See "A National Network of Hydrologic Benchmarks" by L. B. Leopold, Geological Survey Circular 460-B, 1962. (M) The miniregions data set was compiled by N. C. Matalas and J. M. Landwehr, with the help of Don Thomas and Gary Tasker, then in the Branch of Surface Water , drawing upon, but also expanding, the data set of Hardison. (See Water Resources Research, v. 10, no. 5, 1974.) Unlike the latter, which had specifically been con- structed to examine peak discharge records, the miniregions data set was constructed with the goal of looking at the spectrum of flow conditions, low to high, with minimal controls imposed on the low end. (L) See "Yearly Variations in Runoff and Frequency of Dry Years for the Conterminous United States, 1911-1979" by W. B. Langbein and J. R. Slack, Open-File Report 82-751, 1982. (A) The Alley-Lins data set was compiled for hydro-climatic data analysis by informal poll of all District offices, drawing on the Langbein and Slack work and on the National Water Conditions stations. See "Interannual Streamflow Variability in the United States" by H. Lins, Water Resources Research, v. 21, no. 5, May 1985.