Final Water Supply and Demand Assessment
April 23, 2019
This year, the water supply outlook is optimal. Rainfall was abundant. The San Lorenzo River and local streams are flowing strong. Loch Lomond Reservoir is full and still spilling. Cumulative runoff from the San Lorenzo River registers 160 percent of average, making Water Year 2019 technically classified as Wet.
Across California, hydrologic conditions have improved dramatically from one year ago. Except for a small portion of southern California, virtually the entire state is mapped drought-free for the first time in nearly a decade.
The assessment of water supply and demand this year indicates that the Loch Lomond Reservoir will remain full through the month of June and will end the dry season in late 2019 at approximately 90 percent of capacity. In most years, the reservoir is usually drawn further down. This year, the combination of good flowing supplies and continuing low water demand system-wide means that treatment plant operators won’t have to depend on the reservoir as much as they normally do during the peak summer season to meet the community’s daily water needs, at least until later in the year. Accordingly, there is no reason the City needs to declare a shortage or impose temporarily restrictions on water use for 2019.
This is a summary of the Final Water Supply and Demand Assessment, for the more detailed version, click here.
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Figure 3 shows the mean monthly stream flow in the San Lorenzo River measured at the Big Trees gaging station in Felton for the season to date, along with the long-term average monthly values, and the mean monthly flow from last year for comparison.
The 2019 Water Year started October 1, 2018 with Loch Lomond Reservoir at about 90 percent of capacity. The lake elevation rose above the spill level on the evening of February 2nd and is currently spilling, as you can see in this photograph.
A chart of cumulative runoff from October 1, 2018 through April 17, 2019 is presented in Figure 4.
Figure 5 shows the latest chart from the US Drought Monitor
Figure 6 shows the Water Supply Scenario 1 Spreadsheet
Figure 7 shows the projected reservoir draw-down for WY2019