Domestic watersupply sector

Urban demands are given the highest priority in the Water for Food strategy. As a result, the percentage unmet demands are the lowest for this strategy Unmet demands in the Water for Environment strategy are due in large to the priority given to American AFRP requirements downstream of Placer and El Dorado counties. Unmet urban demands are comparable in terms of percentage to agricultural unmet demands and increase over time in the presence of climate change. Demand management is implemented as an adaptation to partly mitigate losses taken in the Environment and Food Security strategies, thus dampening the overall loss of water for this sector. Furthermore, under the B2 climate scenario, unmet urban demands increase because of less available water in the Sacramento system as a whole (Table 11.8).

Groundwater storage

Groundwater storage in general declines across all strategies. However, the rate of decline varies. For the Water for Environment strategy, the imposed groundwater withdrawal restrictions limit the decline in storage in both the 2010-2039 and 2070-2099 scenario. Storage still declines under this strategy at a rate of about 275 million m3/year, a factor of almost 3 less than in the Water for Food strategy (860 million m3/year). The effects of land use change and climate change on storage are also evident. More groundwater is extracted under the combined land use and climate change scenario because of increased evaporative demands for agriculture. Furthermore, under the Water for Food strategy, current rates of withdrawal are clearly unsustainable. These findings can be generalized across individual groundwater sub-basins, although the severity of depletion varies widely. For instance, in the Sacramento Stone Corral groundwater sub-basin, under the Water for Food and Land Use and Climate Change scenarios, the aquifer is near depletion by 2050.

Table 11.8. Average urban unmet demand (average % deficit).

Adaptation strategy

2010-2039

2070-2099

Land use change

6.5%

6.3%

Land use and climate change

9.5%

11.7%

Water for environment

8.3%

22.0%

Water for food

0.0%

10.4%

0 0

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