The scoping study aims to identify a promising approach for estimating unregulated streamflow in the Deschutes River basin for both historical and projected future conditions that does not require a computationally intensive coupled groundwater surface water model. The Deschutes River flow can be characterized as dominated by groundwater discharge (Gannett et al. 2017). Prior hydrologic modeling studies have not produced simulated streamflow of adequate quality. The study team explored a modeling approach similar to that taken in the recent St Mary and Milk River Basin Study Update, which includes a precipitation-runoff model with routing module that represents both a storage term that simulates the quick component of the runoff, as well as a lower storage term which describes the slow component of the runoff and the groundwater extraction and losses. This scoping study provides an overview of historical climate and hydrology in the Deschutes River basin, describes methods employed to improve simulated streamflow estimates, and summarizes next steps for follow on study.