An Evaluation of Multi-Scalar Drought Indices in Nevada and Eastern California

Nevada and eastern California are home to some of the driest and warmest climates, most mountainous regions, and fastest growing metropolitan areas of the United States. Throughout Nevada and eastern California snow-dominated watersheds provide most of the water supply for both human and environmental demands. Increasing demands on finite water supplies have resulted in the need to better monitor drought and its associated hydrologic and agricultural impacts. Two multi-scalar drought indices, the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI), are evaluated over Nevada and eastern California regions of the Great Basin using standardized streamflow, lake and reservoir water surface stages to quantify wet and dry periods. Results show that both metrics are significantly correlated to surface water availability, with SPEI showing slightly higher correlations over SPI suggesting that the inclusion of a simple water balance demand in SPEI is useful for characterizing hydrologic drought in arid regions. These results also highlight the utility of multi-scalar drought indices as a proxy for summer groundwater discharge and baseflow periods.