Hydrologic investigations of urban drainage basins in Texas were begun by the U.S. Geological Survey in 1954. These studies are now in progress in Austin, Houston, and San Antonio. Studies were completed in the Fort Worth metropolitan area at the end of the 1977 water year, and in the Dallas metropolitan area at the end of the 1979 water year.

The Geological Survey, in cooperation with the Texas Department of Water Resources, expanded the existing streamflow network in the San Antonio metropolitan area in May 1968 to begin urban hydrology studies in this area. In September 1968, the program was further expanded to include the collection of water-quality data.

The operation and maintenance of stations 08178000, San Antonio River at San Antonio; 08178700, Salado Creek (upper station) at San Antonio; and 08178800, Sal ado Creek (lower station) at San Antonio are funded by the San Antonio River Authority in conjunction with the Texas Department of Water Resources and the U.S. Geological Survey.

The operation and maintenance and collection of water-quality data at station 08178720, Lorence Creek at Thousand Oaks Blvd., San Antonio, station 08178640, West Elm Creek at San Antonio, and station 08178645, East Eln Creek at San Antonio, are funded by the Edwards Underground Water District in cooperation with the Texas Department of Water Resources and the U.S. Geological Survey. Station 08178640, West Elm Creek at San Antonio, and station 08178645, East Elm Creek at San Antonio will provide hydrologic data on similar and adjacent watersheds. The West Elm watershed is still predominately rural but is undergoing extensive urbanization in some areas. The East Elm watershed is relatively stable and undeveloped.

The objectives of the San Antonio urban hydrology study are:

1. To provide data showing the effects of various stages of urbanization on flood discharge and runoff.
2. To provide water-quality data on surface-water runoff from floods of various magnitudes, during all seasons of the year from areas with different types of urban development.

Annual publication of the San Antonio urban studies was initiated in 1969.

A defination of terms related to streamflow, water quality, and other hydrologic data, as used in this report, are defined in the U.S. Geological Survey's 1979 and 1980 "Water resources data for Texas" reports.