Watershed influences and in-lake processes - A regional-scale approach to monitoring a water-supply reservoir, Lake Houston near Houston, Texas

Created in 1954 by an impoundment on the San Jacinto River, Lake Houston currently (2008) supplies about 20 percent of the total source water for the city of Houston. Houston historically has relied on ground water as the major source of supply. As a result of regulations to limit ground-water withdrawals because of associated land subsidence (effective in 2010), the lake will become the primary source of water supply for the city in the future. Since 1983 the U.S. Geological Survey (USGS), in cooperation with the City of Houston, has collected water-quality and lake-level data at Lake Houston, as well as discharge and intermittent water-quality data at its major inflowing tributaries. Previous studies indicate that Lake Houston is shallow, eutrophic, light limited and has a variable hydrologic regime with water residence times ranging from 12 hours to 400 days. Spring Creek, a tributary that drains the western, more urban, part of the Lake Houston watershed, contributes more sediment and nutrients than East Fork San Jacinto River, a tributary that drains the more rural, eastern part of the watershed. This fact sheet explains the importance of monitoring for management of the resource and describes ongoing research in the Lake Houston watershed by the USGS and the City.