![]() ![]() 21, so it allowed flows through the Delta to be curtailed for 16 days until it was reversed. The decision was a victory for environmentalists, but they say it comes too late. Sobeck wrote that the reversal was based on “improved hydrology and in consideration of the public comments and the petition (from environmental groups) for reconsideration.” “An urgent need for the changes no longer exists, the changes are no longer in the public interest, and the impacts of the changes on fish and wildlife are no longer reasonable,” Eileen Sobeck, the water board’s executive director, wrote in a new order reversing the earlier one. The reason for the state’s reversal, according to the State Water Resources Control Board, is that conditions in the Delta have changed as storms boost the snowpack and runoff used to supply water to cities and farms. Ten environmental groups had petitioned the board to rescind its order, calling it “arbitrary and capricious, contrary to law, and…not supported by substantial evidence.” Our results also suggest that temperature forcing may generate greater drought stress affecting soils and stream flows than can be estimated by variability in precipitation alone.As storms swell California’s reservoirs, state water officials have rescinded a controversial order that allowed more water storage in the Sacramento-San Joaquin Delta while putting salmon and other endangered fish at risk. Our results suggest that in arid environments characterized by high topo-climatic variability, land and water managers need indicators of local watershed hydrology response to complement regional temperature and precipitation estimates. Hydrologic variability within a single river basin demonstrated at the scale of subwatersheds may prove an important consideration for water managers in the face of climate change. For both high- and low-rainfall scenarios, by the close of this century warming is projected to amplify late-season climatic water deficit (a measure of drought stress on soils) by 8% to 21%. ![]() ![]() Temperature forcing increases the variability of modeled runoff, recharge, and stream discharge, and shifts hydrologic cycle timing. Precipitation projections for the 21st century vary between GCMs (ranging from 2 to 15% wetter than the 20th-century average). By the last 30 years of this century, North Bay scenarios project average minimum temperatures to increase by 1.0 ☌ to 3.1 ☌ and average maximum temperatures to increase by 2.1 ☌ to 3.4 ☌ (in comparison to conditions experienced over the last 30 years, 1981–2010). Historical climate patterns show that Marin’s coastal regions are typically on the order of 2 ☌ cooler and receive five percent more precipitation compared to the inland valleys of Sonoma and Napa because of marine influences and local topography. We then used the BCM to estimate hydrologic response to climate change for four scenarios spanning this century (2000–2100). We downscaled historical and projected precipitation and air temperature values derived from weather stations and global General Circulation Models (GCMs) to a spatial scale of 270 m. The BCM calculates water balance components, including runoff, recharge, evapotranspiration, soil moisture, and stream flow, based on climate, topography, soils and underlying geology, and the solar-driven energy balance. ![]() We modeled the hydrology of basins draining into the northern portion of the San Francisco Bay Estuary (North San Pablo Bay) using a regional water balance model (Basin Characterization Model BCM) to estimate potential effects of climate change at the watershed scale. ![]()
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