Co-developing drought indicators for Pacific Northwest state water managers

Though numerous drought indices have been developed by the research community, operational adoption of these indices by state water managers has been limited. While these indices purport to support management decisions, reasons for not considering them in practice are plenty. Some indices include mismatches in time scales and spatial scales between the indices supplied and the operational decisions (e.g. water managers often work within political boundaries, such as states or counties, or by administrative hydrologic basins, whereas drought indices may not be provided at such spatial units). The focus of drought indices tends to be on physical parameters with little regard to actual available water supply or societal demand, which is crucial in the Western US. The objective of this project is to co-develop an index with an advisory group of state water managers (Oregon, Washington, and Idaho) in the Pacific Northwest (PNW) to ensure that the result is useful and applicable for water management and drought declarations in the respective states. State water managers are often tasked with considering individual county drought declarations that have political consequences. State drought declarations help users cope with drought by relaxing the current water rights structure to allow for flexibility in use and delivery. Co-developing this work with this advisory group was an iterative process, with multiple conversations between the research team and the managers, who provided input on data sources and final products. The current product under development considers of total moisture for the PNW states and probability of recovery. Total moisture is derived from snow water equivalent (SWE) and soil moisture modeled by the VIC (Variable Infiltration Capacity; 6-km horizontal resolution) hydrologic model using observed historical temperature and precipitation as model inputs. We have developed a product that displays the current drought status and also projects how the year may progress in a county based on historical patterns. This allows for water managers to understand the probability of recovery from current drought conditions at various points in the water year and can aid in making drought declarations in counties across the region.