Predicting regional climate change and its impacts is of vital importance as we journey into a world of non-stationarity. Indeed, the IPCC, NSF, DOE, and many other organizations have identified regional climate change as one of the grand challenges humans will face in the 21st century. However, key questions remain on how best to determine the impacts of regional climate change. The goal of our IWG was to outline a clear path forward in approaching one of these key questions: what are the most relevant spatial and temporal scales of climate change with respect to surface hydrologic processes? To achieve this goal, experts in a broad swath of earth science fields congregated in a three-day workshop to distill what the essential problems and possible solutions are, identify who would be best suited to undertake these issues, and which grant opportunities and granting agencies would be more appropriate for the proposed research topics. Our IWG will help further our understanding of the effects climate change will have on our mountain sources of water, and as warming trends continue and droughts increase in intensity and frequency in the Western U.S., this will become of the utmost importance.