PNNL

Abstract

The state of Texas in the United States is highly susceptible to drought, and its major rivers are subject to extensive water management activities. Water management alters streamflow regimes, thereby influencing the propagation processes of drought from meteorological to hydrological types and changing the characteristics of hydrological drought. Nevertheless, the impact of water management on drought properties in Texas is not yet fully studied. This study aims to fill this gap by leveraging an extensive observation-based naturalized streamflow dataset constructed by the Texas Water Development Board (TWDB). Observation-based naturalized streamflow offers a direct representation of complex hydrological conditions and is less prone to uncertainties than simulation-based estimates. Using the naturalized streamflow as a benchmark, this study quantifies the influence of water management on drought characteristics across 32 streamflow gauges along the mainstems of seven major rivers in Texas by comparing drought conditions under natural and managed conditions. Results indicate that water management has delayed the hydrological drought across Texas’ major rivers by a median of 2.5 months. The impact of the water management on the propagation rate varies across different locations but was found approximately linearly related to the change in the low flow. While the total duration and severity of hydrological droughts were alleviated at more than half of the gauges, average hydrological drought events intensified in most locations due to the significantly decrease in drought frequency. Water management was also found to greatly increase spatial variability of drought characteristics across the region. This study enhances our understanding of the influence of human disturbance on hydrological droughts in Texas and similar regions, which is essential for ensuring the sustainable management of water resources and building resilience to droughts in the changing world.