Annual compilation and analysis of hydrologic data for Escondido Creek, San Antonio River basin, Texas

Abstract

Introduction History of Small Watershed Projects in Texas The U.S. Soil Conservation Service is actively engaged in the installation of flood and soil erosion reducing measures in Texas under the authority of the "Flood Control Act of 1936 and 1944" and "Watershed Protection and Flood Prevention Act" (Public Law 566), as amended. The Soil Conservation Service has found a total of approximately 3,500 floodwater-retarding structures to be physically and economically feasible in Texas. As of September 30, 1970, 1,439 of these structures had been built. This watershed-development program will have varying but important effects on the surface and ground-water resources of river basins, especially where a large number of the floodwater-retarding structures are built. Basic hydrologic data under natural and developed conditions are needed to appraise the effects of the structures on the yield and mode of occurrence of runoff. Hydrologic investigations of these small watersheds were begun by the Geological Survey in 1951 and are now being made in 12 study areas (fig. 1). These investigations are being made in cooperation with the Texas Water Development Board, the Soil Conservation Service, the San Antonio River Authority, the city of Dallas, and the Tarrant County Water Control and Improvement District No. 1. The 12 study areas were chosen to sample watershed having different rainfall, topography, geology, and soils. In five of the study areas, (North, Little Elm, Mukewater, little Pond-North Elm, and Pin Oak Creeks), streamflow and rainfall records were collected prior to construction of the floodwater-retarding structures, thus affording the opportunity for analyses of the conditions "before and after" development. A summary of the development of the floodwater-retarding structures in each study areas of September 30, 1970, is shown in table 1. Objectives of the Texas Small Watersheds Project The purpose of these investigations is to collect sufficient data to meeting the following objectives: To determine the net effect of floodwater-retarding structures on the regimen of streamflow at downstream points. To determine the effectiveness of the structures as ground-water recharge facilities. To determine the effect of the structures on the sediment yield at downstream points. To develop relationships between maximum rates and/or volumes of runoff with rainfall in small natural watersheds. To develop a stream-system model for basins with floodwater-retarding structures. To determine the minimum instrumentation necessary for estimating the flood hydrographs below a system of structures, as needed for downstream water-management operation. Purpose and Scope of this Basic-Data Report This report, which is the tenth in a series of basic-data reports published annually for the Escondido Creek study area, contains the rainfall, runoff, and storage data collected during the 1970 water year for the 72.4-square-mile area above the stream-gaging station Escondido Creek at Kenedy, Texas. The location of floodwater-retarding structures and hydrologic-instrument installations in the Escondido Creek study area are shown on figure 2. This investigation is scheduled to continue through a period of both above- and below-normal precipitation to define the various factors used in the analyses of rainfall-runoff relationship. To facilitate the publication and distribution of this report at the earliest feasible time, certain material contained herein does not conform to the formal publication standards of the U.S. Geological Survey.