Climate change effects on water allocations with season dependent water rights

Abstract

Appropriative water rights allocate surface water to competing users based on seniority. Often water rights vary seasonally with spring runoff, irrigation schedules, or other non-uniform supply and demand. Downscaled monthly Coupled Model Intercomparison Project multi-model, multi-emissions scenario hydroclimate data evaluate water allocation reliability and variability with anticipated hydroclimate change. California's Tuolumne watershed is a study basin, chosen because water rights are well-defined, simple, and include competing environmental, agricultural, and urban water uses representative of most basins. We assume that dedicated environmental flows receive first priority when mandated by federal law like the Endangered Species Act or hydropower relicensing, followed by senior agricultural water rights, and finally junior urban water rights. Environmental flows vary by water year and include April pulse flows, and senior agricultural water rights are 68% larger during historical spring runoff from April through June. Results show that senior water right holders receive the largest climate-driven reductions in allocated water when peak streamflow shifts from snowmelt-dominated spring runoff to mixed snowmelt- and rainfall-dominated winter runoff. Junior water right holders have higher uncertainty from inter-annual variability. These findings challenge conventional wisdom that water shortages are absorbed by junior water users and suggest that aquatic ecosystems may be disproportionally impaired by hydroclimate change, even when environmental flows receive priority.

Climate Forecasts and Flood Mitigation

“…Figure 3 shows the percent difference in parameter estimates from the historical period for each of the 64 short-term climate projections . Differences in future 16 See Null and Prudencio (2016) for details on the GCMs and RCPs used in this study. Representative concentration pathways capture how different economic and technology assumptions influence carbon dioxide concentrations.…”

“…See Null and Prudencio () for details on the GCMs and RCPs used in this study. Representative concentration pathways capture how different economic and technology assumptions influence carbon dioxide concentrations.…”

“…Climate‐driven streamflow changes are most pronounced toward the end of the 21st century (Null and Prudencio ). Overall, average annual air temperatures are projected to increase by an average of 1.8, 2.7, 2.9, and 4.2°C by the end of the 21st century for RCP 2.5, 4.5, 6.0, and 8.5, respectively.…”

Water allocation under future climate change and socio-economic development : the case of Pearl River Basin

“…Water shortage has become a major challenge in these regions causing a bottleneck for socio-economic development. Allocating water resources is critical to meet human and ecosystem needs now and in the future (Bangash et al, 2012;Null and Prudencio, 2016). However, water resources allocation and management are being challenged by uncertainties associated with climate change.…”

“…This situation is likely to be aggravated over the next decades by decreasing water availability due to climate change (Alcamo et al, 2007;Arnell, 2011;Milly et al, 2005). Allocating water resources is critical to meet human and ecosystem needs now and in the future (Bangash et al, 2012;Null and Prudencio, 2016). However, water resource allocation in river basins are being challenged by uncertainties associated with climate change and socio-economic development.…”