Insights on the Energy-Water Nexus from Modeling of the Integrated Water Cycle at Regional Scales L. Ruby Leung Pacific Northwest National Laboratory With Hongyi Li, Xiao Zhang, Mohamad Hejazi, Nathalie Voisin, Lu Liu Visiting students: Wenhua Wan, Wei Wang JGCRI Integrated Assessment Workshop College Park, MD, October 11-12, 2016
Science questions! How does climate change influence water, energy, and their connections?! How does human intervention (mitigation, adaptation, and management) alter climate change impacts?! What are the regional characteristics of the above impacts and their drivers? 2
Scale adaptive river transport Real River Network Conceptualized River Network Tributary Main channel Watershed boundary Model for Scale-Adaptive River Transport (MOSART)! Hillslope routing:! Account for impacts of overland flow on soil erosion, nutrient loading, etc.! Sub-network routing:! Scale adaptive across different resolutions to reduce scale dependence! Main channel routing:! Explicit estimation of in-stream conditions (velocity, water depth, etc.)! Model streamflow and stream temperature! Being extended to include river biogeochemistry (Li et al. 2013; 2015 JHM; Li et al. 2016 JAMES) 3
Large human influence on streamflow Global distribution of dams 4
Water management! Local water extraction: first from local surface and subsurface runoff and then from the river channel storage! Reservoir operations: based on generic operating rules! Each reservoir has multiple purposes: Flood control; Irrigation; or Combined irrigation and flood control! Generic release targets and storage targets for each purpose! Configured independently for each reservoir based on hydro-climatological conditions and demand associated with the reservoir Irriga&on Rules release targets Flood Control Rules release targets (Voisin et al. HESS, 2013) Monthly release targets at Grand Coulee for different rules scenarios 5
Numerical experiments Not just GHG and aerosol emissions; LULC and water use are important parts of the mitigation RCP4.5 (1975-2100) RCP8.5 CESM è RESM (Atmospheric forcing) RCP4.5_NAT RCP8.5_NAT RCP4.5 RCP8.5 CLM (Runoff and soil temperature) MOSART (Streamflow and stream temperature) RCP4.5_WM RCP8.5_WM GCAM (Water demand) WM (Local extraction / reservoir operations) 6
Water management in the US rivers! A total of 1839 reservoirs in the US are represented! Water demand for withdrawal and consumption includes: irrigation, electricity generation, livestock, domestic purposes, primary energy production, and manufacturing 7
Climate change impacts: emission mitigation vs. water management Emission mitigation reduce increase increase Local water extraction reduce Reservoir operations increase Surface warming reduce Irrigation water demand Streamflow??? Stream temperature? Cooling water availability?? Thermoelectric power generation Hydrological drought
Changes in stream temperature Climate change effects (future minus historical) Mitigation effects (RCP8.5 minus RCP4.5) Water management effects (with WM minus without WM) % change in seasonal amplitude 9
Likelihood of extreme high stream temperature! Water management substantially reduces the likelihood of extreme high stream temperature in western river basins by enhancing summer low flows Exceedance Probability of high stream temperature Stream temperature ( o C) Without water management With water management Exceedance probability 10
Frequency changes for stream temperature > 27oC Emission mitigation reduces exceedance frequency Water management reduces exceedance frequency % change in number of hours with stream temperature > 27oC 11
Impacts of stream temperature on thermoelectric power production! Estimated based on 177 once-through power plants, which account for about 76% of once-through thermoelectric power plants in the US! Both emission mitigation and water management reduce power loss from climate change by about 5% Loss (%) Nat4.5 Nat8.5 WM4.5 WM8.5 2040s 10.6 11.1 10.0 10.5 2080s 14.0 15.1 13.3 14.4 12
Impacts of cooling water availability on thermoelectric power production! There is no consistent difference in cooling water availability between RCP4.5 and RCP8.5 due to large interdecadal variability in precipitation! Water management alleviates the duration of low water availability by 5%-14% Percentage of time when projected inflows (2040s and 2080s) are lower than the historical average (1991-2000) during summer 13
Two characteristics of water management effects on hydrological droughts Local water extraction: reduce flow year round All grid cells Reservoir operations: enhance summer low flow Grid cells affected by reservoirs 14
Changes in hydrological droughts! Water demand determines whether WM alleviates or intensifies drought WM alleviates moderate drought (-1.00 <SSI< -1.5) WM intensifies extreme drought (SSI -2.0): driven by intense water demand (e.g., in CA) Percentile Without water management With water management Percentile Without water management With water management % area under drought % area under drought 15
Water demand dominates the impacts Comparing RCP4.5 and RCP8.5 without WM Effects of WM: only increase drought in areas with high water demand Increased likelihood of drought 16
Summary! How does climate change influence water, energy, and their connections?! Warming increases stream temperature reduces thermoelectric power generation! Warming has variable effects on regional precipitation, cooling water availability, and hydrologic drought! How does human intervention (mitigation, adaptation, and management) alter climate change impacts?! Emission mitigation reduces warming, but its impacts on regional water availability are variable! Water management consistently alleviates high stream temperature and reduces thermoelectric power generation loss and moderate-to-severe droughts! What are the regional characteristics of the above impacts and their drivers?! Regional drivers: local water extraction, reservoir regulations, and water demand! Impacts of different scenarios must account for LULC and water use 17
Ongoing and future work! Extend the regional framework to global modeling ongoing work with ACME! Distinguish sources of irrigation water and methods of application water use efficiency! Represent return flow withdrawal vs. consumption influence spatial redistribution of water resources! Investigate climate change effects on hydropower! Investigate the effects of impoundment and groundwater use on sea level rise 18