BOARD AGENDA MEMORANDUM
SUBJECT:
Title
Update on Capture of Stormflow in the Uvas-Llagas Watershed (Responding to Board Member Request R-18-0005).
End
RECOMMENDATION:
Recommendation
Receive update and provide direction to staff.
Body
SUMMARY:
This memorandum is a response to board member request R-18-0005 from the February 27, 2018 Board meeting. The Board requested information regarding options to capture storm water in the Uvas and Llagas watersheds to increase water supply. The following discussion provides a brief background on the existing infrastructure in these watersheds and analyses regarding expanding the ability to capture additional water.
The District operates two reservoirs in the Uvas-Llagas Watershed that impound local rainfall for water supply:
* Uvas Reservoir, built in 1957 on Uvas creek, has a capacity of 9,835 acre-feet (AF) and water rights for up to 24,400 AF each year.
* Chesbro Reservoir, built in 1955 on Llagas Creek, has a capacity of 7,945 AF and a water right of 7,200 AF per year.
These reservoirs were designed to take advantage of Californian climate - filled by winter rains with summer water releases to recharge the groundwater basin. In drought years, the reservoirs may have limited inflow; while in wet years, upland runoff can result in rapid fill and spill of excess flows over the spillways to downstream creeks then to the Pajaro River and out to Monterey Bay.
Historically, Uvas Reservoir spills more often than Chesbro due to its location in a watershed. Table 1 below shows recent spill events. To take advantage of this productive watershed, the Uvas/ Llagas transfer pipeline was constructed in 1955 to transfer water from Uvas Reservoir to Llagas Creek, just below Chesbro Reservoir for groundwater recharge. The pipeline is operated under the terms of a Lake or Streambed Alteration Agreement (LSAA or "permit") issued by the California Department of Fish and Wildlife. The permit allows transfers when Uvas is above a ...
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