Environmental security

Throughout the Sacramento Basin a number of instream flow requirements are established through an anadromous fish recovery programme (AFRP). Meeting these requirements is vital not only on the main stem of the Sacramento, but also on tributaries that are critical for spawning. There is also a more general flow requirement downstream to maintain the estuary of the San Francisco Bay - a habitat that provides numerous ecosystem services to the region, including fish, wildlife, water quality, and recreational and aesthetic opportunities.

Four of these instream flow requirements are evaluated for each of the two scenarios and two strategies. Examining the flow requirement on the Feather River, the minimum flow requirements are essentially met under all scenarios and for both time periods. For the remaining three instream flow requirements (shown in Fig. 11.10) and flow requirement on the Sacramento at Freeport for environmental flows to the Delta, it is clear that these requirements are much harder to meet under climate change conditions. Furthermore, the frequency of unmet flow requirements increases in 2070-2099. For instance, for the Delta flow requirement, the frequency of unmet requirements increases by almost a factor 2. Similar to the situation for wetlands, the Water for Food strategy is more problematic for each of the instream flow requirements. Lastly, examining the American AFRP (Fig. 11.10), we observe that typically in the months of May-July the flow requirements are unmet.

Wetlands

Under the two adaptation strategies, unmet demands related to wetland areas on average increase over time due to climate change. For 2010-2039 under the Water for Environment strategy, unmet demands are 1.7%. However, this is largely due to additional environmental demands introduced (i.e. winter rice flooding) and the

Fig. 11.10. Frequency of unmet monthly flow requirements 2010-2039 (top) and average percentage unmet flow requirement 2070-2099 for the American AFRP (bottom).
Table 11.7. Frequency of annual flow events to the Yolo bypass relative to current conditions.

Adaptation strategy

2012-2039

2072-2099

Land use change

46%

41%

Land use and climate change

29%

32%

Water for environment

39%

32%

Water for food

29%

32%

restrictions on groundwater withdrawals imposed. Thus, effectively, despite these small unmet demands, total wetland area increases under this strategy. Under the Water for Food strategy, environmental unmet demands increase to 4.5%. This percentage increases to 5.1% under the 2070-2099 scenario. These demands are generally unmet during the autumn/winter months when the wetland and refuge requirements are the highest, thus the relative impact of these shortfalls are greater than indicated by the annual average percentage (Table 11.7).

0 0

Post a comment