Hydrologic Drought Atlas for Texas
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abstract
2014 American Society of Civil Engineers. This paper presents a hydrologic drought atlas for the state of Texas. The atlas depicts the spatial variation of drought severity for durations of 3, 6, 12, and 24 months corresponding to the return periods of 10, 25, 50, and 100 years. Using the variable infiltration capacity model which is a large-scale land surface model, drought characteristics were derived from monthly stream flow simulated at 1=8 resolution over the state of Texas. Appropriate marginal distributions of drought severity and duration were selected from amongst exponential, gamma, log-normal, and Weibull distributions, whereas the joint distribution of severity and duration was selected from the Archimedean, extreme value, Plackett, and elliptical families. Then, severity-duration-frequency (SDF) curves were obtained which were used for preparing the drought atlas that depicts the drought severity for any drought duration and return period at any location in Texas. Results indicate a decreasing pattern of severities from west to east. Humid and semihumid regions show a concave pattern in the SDF curves, whereas arid and semiarid regions show a convex pattern. The nonparametric Mann Kendall test was used to analyze the long-term drought trend that indicated a downward trend in arid and continental regions and an upward trend along the Gulf Coast, humid, and semihumid regions.
