Despite season ending lower than normal snowpack conditions, the regional water supply outlook is still very good. Upstream reservoir storage is in great shape at close to 75% of maximum capacity, and the projections are for most reservoirs to re-fill (or come close to it) over the course of the next several months. Lake Tahoe will begin the summer just about a foot shy of maximum capacity, which is very good news. 2020 will end up going down in the books as a relatively dry year, but because upstream reservoir storage is in such great shape right now, normal river flows are projected for the remainder of this year and the foreseeable future.
Water Supply
River Flows – Springtime runoff has begun, and the Truckee River is flowing swiftly in response to the warmer springtime temperatures. Runoff will continue to climb and begin to peak over the next week or two. Normal river flows are projected for this summer and through next winter. Flows this morning at the CA/NV state line were about 1,000 cubic feet per second which is about twice the amount of flow you would typically see in the middle of the summer.
Reservoir Storage – Truckee River reservoir storage is roughly about ¾ capacity (75%). The elevation of Lake Tahoe is 6227.57 feet (1.53’ below legal maximum storage elevation). Storage values for each reservoir as of 4/22 are as follows:
Reservoir……………… Current Storage (Acre-Feet)……………………… % of Capacity
Tahoe…………………… 556,600………………………………………………………………… 75%
Boca……………………. 14,220………………………………………………………………….. 35%
Donner ………………… 6,627……………………………………………………………………. 70%
Independence……….. 11,317………………………………………………………………….. 67%
Prosser…………………. 11,716………………………………………………………………….. 38%
Stampede……………… 194074…………………………………………………………………. 86%
In addition to roughly 18,000 acre-feet of storage in Donner and Independence reservoirs, TMWA has approximately 14,500 acre-feet of water stored between Lake Tahoe, Boca and Stampede reservoirs under the terms of the Truckee River Operating Agreement (TROA). TMWA’s total combined upstream reservoir storage is approximately 32,500 acre-feet as of 4/22.
Snowpack
The official April 1 snowpack numbers reported by the NRCS were well below normal. The Truckee Basin finished out the season at 72% of normal, and the Lake Tahoe Basin at 71% of normal. While noticeably lower than average, snowpack conditions in both basins are much improved from only a month ago where both the Truckee and Lake Tahoe basins were about 42% of normal. Significantly above average Eastern Sierra precipitation over the last 30 days (since the middle of March), added a tremendous amount of water content to the snowpack, helping to dramatically improve water supply conditions. As of this morning snowpack in the Lake Tahoe Basin was 79% of normal, and 74% of normal in the Truckee River Basin.