New Drought Index to Characterize Droughts Within a Snowmelt and Reservoirs Dominated Watershed

A new and integrated drought index was developed by combining data from the total water supply available (TWSA) in a river, precipitation, snow conditions, soil moisture, and reservoir storages. The index allows to simultaneously account the different climatic and hydrologic conditions that contribute to drought in snowmelt and reservoir dominated watershed. The performance of the index is evaluated using historical droughts and by comparing the commonly applied drought indices, such as the standard precipitation index (SPI), standardized runoff index (SRI), and Palmer Drought Severity Index (PDSI). The preliminary results, based on the Yakima River basin case study, show that the proposed index effectively captures historical droughts in the basin and perform better than the SPI, SRI, and PDSI. Furthermore, the new index in conjunction with the traditional indices is expected to shed insight on roles of the climatic and hydrologic factors affecting droughts and to evaluate performance of basin-wide water management practices for mitigating future droughts.