Adapting to Variable Water Supply in the Truckee-Carson River System, Western USA
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In snow-fed inland river systems in the western United States, water supply depends upon timing, form, and amount of precipitation. In recent years, this region has experienced unprecedented drought conditions due to decreased snowpack, exacerbated by exceptionally warmer winter temperatures averaging 3-4 degrees C above normal. In the snow-fed Truckee-Carson River System, two sets of interviews were conducted as part of a larger collaborative modeling case study with local water managers to examine local adaptation to current drought conditions. A comparative analysis of these primary qualitative data, collected during the fourth and fifth consecutive years of continued warmer drought conditions, identifies shifts in adaptation strategies and emergent adaptation barriers. That is, under continuous exposure to climate stressors, managers shifted their adaptation focus from short-term efforts to manage water demand toward long-term efforts to enhance water supply. Managers described the need to: improve forecasts and scientific assessments of snowmelt timing, groundwater levels, and soil moisture contentincrease flexibility of prior appropriation water allocation rules based on historical snowpack and streamflow timingand foster collaboration and communication among water managers across the river system. While water scarcity and insufficient water delivery infrastructure remain significant impediments in this arid region, climate uncertainty emerged as a barrier surrounding adaptation to variable water supply. Existing prior appropriation based water institutions were also described as an adaptation barrier, meriting objective evaluation to assess how to best modify these historical institutions to support dynamic adaptation to climate-induced water supply variability. This study contributes to a growing body of research that assesses drought adaptation in snow-fed inland river systems, and contributes a unique report concerning how adaptation strategies and barriers encountered by local water managers change over time under continuous exposure to climate stressors. These locally identified adaptation strategies forward a larger collaborative modeling case study by informing alternative water management scenarios simulated through a suite of hydrologic and operations models tailored to this river system.