Aspect assessed multipurpose water-storage options to increase irrigation water supply for the Horse Heaven Hills area—the agricultural center of WRIA 31 and an American Viticultural Area. We initially assessed 13 surface reservoir sites and, based on preliminary cost-benefits, we arrived at a preferred alternative of two in-channel surface reservoirs comprising approximately 100,000 acre-feet of storage capacity and 10,000 acre-feet of aquifer storage and recovery (ASR). The follow-on assessment retained Switzler Reservoir and demonstrated substantial public benefit by using the new water supply to mitigate impacts from new Columbia River water rights. The project involves diverse watershed stakeholders and is currently in SEPA review.