Results of Streamflow Gain-Loss Studies in Texas, With Emphasis on Gains From and Losses to Major and Minor Aquifers

Data for all 366 known streamflow gain-loss studies conducted by the U.S. Geological Survey in Texas were aggregated. A water-budget equation that includes discharges for main channels, tributaries, return flows, and withdrawals was used to document the channel gain or loss for each of 2,872 subreaches for the studies. The channel gain or loss represents discharge from or recharge to aquifers crossed by the streams. Where applicable, the major or minor aquifer outcrop traversed by each subreach was identified, as was the length and location for each subreach. These data will be used to estimate recharge or discharge for major and minor aquifers in Texas, as needed by the Ground-Water Availability Modeling Program being conducted by the Texas Water Development Board. The data also can be used, along with current flow rates for streamflow-gaging stations, to estimate streamflow at sites remote from gaging stations, including sites where streamflow availability is needed for permitted withdrawals. streamflow gains and losses from all available records of gain-loss studies done by the USGS in Texas. Since 1918, the USGS has conducted streamflow gain-loss studies on streams throughout much of Texas. The usual objective of the gain-loss studies was to obtain data that could be used to estimate discharge from or recharge to shallow aquifers. Most gain-loss studies were done during low-flow conditions because low flows are more likely to be steady (not changing with time) than other flows (except in reaches downstream from major springs or reaches downstream from reservoirs where sustained releases account for most of the flow). In 1958, the data for all known streamflow gainloss studies were compiled and published in a report by the Texas Board of Water Engineers (currently the TWDB) and the USGS (Texas Board of Water Engineers, 1960). The data for most of the studies done since 1958 have been published in annual data reports and other reports by the USGS. This study carries the documentation of gain-loss studies a ste