DistrictCover.fm Page 1 Thursday, February 14, 2002 1:33 PM In cooperation with the Texas Water Development Board Results of Streamflow Gain-Loss Studies in Texas, With Emphasis on Gains From and Losses to Major and Minor Aquifers Open-File Report 02–068 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior U.S. Geological Survey Results of Streamflow Gain-Loss Studies in Texas, With Emphasis on Gains From and Losses to Major and Minor Aquifers By Raymond M. Slade, Jr., J. Taylor Bentley, and Dana Michaud U.S. GEOLOGICAL SURVEY Open-File Report 02–068 In cooperation with the Texas Water Development Board Austin, Texas 2002 U.S. DEPARTMENT OF THE INTERIOR Gale A. Norton, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. For additional information write to District Chief U.S. Geological Survey 8027 Exchange Dr. Austin, TX 78754–4733 E-mail: [email protected] Copies of this report can be purchased from U.S. Geological Survey Branch of Information Services Box 25286 Denver, CO 80225–0286 E-mail: [email protected] ii CONTENTS Abstract ................................................................................................................................................................................ 1 Introduction .......................................................................................................................................................................... 1 Purpose and Scope .................................................................................................................................................... 1 Ancillary Benefits ..................................................................................................................................................... 2 Method of Gain-Loss Studies ................................................................................................................................... 2 Results .................................................................................................................................................................................. 2 Studies in All Reaches .............................................................................................................................................. 2 Studies in Reaches Intersecting Aquifer Outcrops ................................................................................................... 3 Additional Information and Qualifications ............................................................................................................... 3 Selected References ............................................................................................................................................................. 4 PLATES 1–2. Maps showing: 1. Locations of streamflow gain-loss sites and outcrops of major aquifers in Texas 2. Locations of streamflow gain-loss sites and outcrops of minor aquifers in Texas TABLES [at end of report] 1. Characteristics of flow gain-loss studies in Texas ................................................................................................ 5 2. Inventory of daily mean streamflows for active and discontinued streamflow-gaging stations in Texas ............ 23 3. Median streamflow and associated hydraulic characteristics for streamflow-gaging stations in Texas .............. 45 4. Gains and losses from gain-loss studies in Texas ................................................................................................. 55 CONTENTS iii Results of Streamflow Gain-Loss Studies in Texas, With Emphasis on Gains From and Losses to Major and Minor Aquifers By Raymond M. Slade, Jr., J. Taylor Bentley, and Dana Michaud Abstract streamflow gains and losses from all available records of gain-loss studies done by the USGS in Texas. Data for all 366 known streamflow gain-loss Since 1918, the USGS has conducted streamflow studies conducted by the U.S. Geological Survey in gain-loss studies on streams throughout much of Texas. Texas were aggregated. A water-budget equation The usual objective of the gain-loss studies was to that includes discharges for main channels, tribu- obtain data that could be used to estimate discharge taries, return flows, and withdrawals was used to from or recharge to shallow aquifers. Most gain-loss document the channel gain or loss for each of 2,872 studies were done during low-flow conditions because subreaches for the studies. The channel gain or loss low flows are more likely to be steady (not changing with time) than other flows (except in reaches down- represents discharge from or recharge to aquifers stream from major springs or reaches downstream from crossed by the streams. Where applicable, the reservoirs where sustained releases account for most of major or minor aquifer outcrop traversed by each the flow). subreach was identified, as was the length and loca- In 1958, the data for all known streamflow gain- tion for each subreach. These data will be used to loss studies were compiled and published in a report by estimate recharge or discharge for major and minor the Texas Board of Water Engineers (currently the aquifers in Texas, as needed by the Ground-Water TWDB) and the USGS (Texas Board of Water Engi- Availability Modeling Program being conducted neers, 1960). The data for most of the studies done since by the Texas Water Development Board. The data 1958 have been published in annual data reports and also can be used, along with current flow rates for other reports by the USGS. This study carries the docu- streamflow-gaging stations, to estimate streamflow mentation of gain-loss studies a step farther: The gains at sites remote from gaging stations, including sites and losses in stream subreaches (channel segments where streamflow availability is needed for permit- between flow-measuring sites in a reach) were related to ted withdrawals. major and minor aquifer outcrops in digital and geo- graphic information system (GIS) databases. INTRODUCTION Purpose and Scope As part of the Ground-Water Availability Model- The purpose of this report is to summarize the ing (GAM) Program currently (2001) being conducted results of 366 gain-loss studies involving 249 unique by the Texas Water Development Board (TWDB), data reaches of streams throughout Texas since 1918. The are needed to quantify the interaction of surface water locations of subreaches for which gains and losses were and ground water for the nine major aquifers (Ashworth computed are indicated by streamflow-measurement and Hopkins, 1995) and most of the 20 minor aquifers sites on maps of major and minor aquifer outcrops. The in Texas. Where streams flow across aquifer outcrops, gain-loss studies are tabulated by sequential number, channel gains and losses constitute aquifer discharge major river basin, stream name, and reach identification, and recharge, respectively. To make this aquifer dis- and the total gain or loss for each reach is given. The charge and recharge information available for the GAM gains and losses for each subreach are tabulated by Program, the U.S. Geological Survey (USGS), in coop- sequential number for the gain-loss study and located eration with the TWDB, compiled data and computed by latitude and longitude of the upstream end of the Abstract 1 subreach. Where applicable, the major or minor aquifer upstream from its mouth. The channel gain or channel outcrop traversed by a subreach is identified. loss can be computed for the subreach between each main-channel measurement site by equating inflows to Ancillary Benefits outflows plus flow gain or loss in the subreach: The compilation of streamflow gain-loss data Qu + Qt + Qr = Qd + Qw + Qe + Qg,(1) could be beneficial to the Water Uses and Availability Section of the Water Resources Management Division where of the Texas Natural Resource Conservation Commis- Qu = streamflow in at upstream end of subreach; sion (TNRCC). That section is responsible for permit- Qt = streamflow from tributaries into subreach; ting surface-water withdrawals in Texas. Most of the Qr = return flows to subreach; recently issued permits represent contingency permits, Qd = streamflow out at downstream end of sub- which authorize surface-water withdrawals only when reach; the streamflow exceeds a threshold rate. The threshold Qw = withdrawals from subreach; streamflow rate for each contingency permit generally Qe = evapotranspiration from subreach; and represents the total discharge needed to sustain permit- Qg = gain (positive) or loss (negative) in subreach. ted withdrawals downstream from the withdrawal point Thus, for the contingency permit plus any streamflow required as inflow to receiving bays or estuaries. Contingency Qg = Qu + Qt + Qr – Qd – Qw – Qe.(2) permits are used to protect the existing water rights of For most streams, underflow (flow parallel to stream users downstream from newer users. through shallow channel-bed deposits) and bank stor- The TNRCC and others associated with surface- age are considered negligible or minimal. water usage often use USGS current streamflow data Many of the studies were done during winter to available on the World Wide Web to verify existing minimize evapotranspiration. Also, the short length of streamflow conditions pertinent to contingency permits. most subreaches and minimal width of the streams However, there are only about 350 existing streamflow-