River System Hydrology

Hydrologic conditions in Texas vary greatly both spatially and temporally. This chapter explores the characteristics of precipitation, reservoir surface evaporation, and stream flow with a particular focus on variability and stationarity. River system hydrology is fundamental to the development and operation of reservoir projects and other water management endeavors. The chapter discusses natural pollution of surface stream flow from salts dissolved from underlying geologic formations that occurs in portions of the upper watersheds of several major river basins in Texas and neighboring states. The large land area of Texas encompasses multiple regions with distinct climates. Texas is viewed in this chapter as hydrologically comprising western, central, and eastern thirds. The Texas Water Development Board maintains annually updated datasets of monthly precipitation rates and monthly reservoir surface evaporation rates for 92 1-degree latitude by 1-degree longitude quadrangles comprising a grid that encompasses the state. Precipitation in Texas is mainly rainfall.