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88 Part I California Water But statewide totals are misleading, because the share of environmental water varies considerably across California. The wet, North Coast region is distinct in two respects: It is largely isolated hydraulically from the rest of California (the major exception being diversions from the Trinity River to the Sacramento River for CVP water supply) and its water is dedicated over- whelmingly to environmental flows. Excluding the North Coast and North Lahontan—another hydraulically isolated region—to look at California's main interconnected water system,average gross water use is 61 maf/year,with about 52 percent agricultural, 14 percent urban,and 33 percent environmental. The environmental share of net use is even lower-23 percent—because much of the environmental water in these regions is available for reuse downstream as Delta exports. In net terms, agriculture accounts for more than three-fifths of the total(62%),urban uses 16 percent,and environmental uses 22 percent. Looking across hydrologic regions, California has essentially specialized many of its river systems.North Coast rivers are more specialized in environ- mental flows,whereas many other regions are more specialized for agricultural and urban uses(Figure 2.1).The one other region with a large volume and share of net environmental water use is the Sacramento River Basin, which sends significant net outflows through the Delta and the San Francisco Estuary. In contrast, environmental water use in the Tulare Basin is almost entirely in upstream areas,with almost all of that water subsequently consumed by agri- culture downstream. The effectiveness of dedicated environmental flows has been hampered by a range of water and land management practices,including legacies from past land uses,dams,contaminants,and other problems.Chap- ter 5 examines approaches for improving the effectiveness of environmental water management. Where watersheds and streams can provide more envi- ronmental benefits with only limited economic losses (or vice versa), more deliberate specialization may be a key to better performance. Farms'and Cities'Adaptation to Water Scarcity California's agricultural and urban water users have been adapting to increasing water scarcity. Over time, the urban sector's share of total human water use has increased with population growth.In 1960,agriculture accounted for 90 percent of gross human water use,but by 2005 this share had fallen to 77 percent(Figure 2.8). Gross urban and agricultural water use appears to have leveled off or declined in recent years,following decades of expansion.(Note that Figure 2.8 shows long-term trends calculated to reflect"normal"water years,so the declines are not the result