Based upon an analysis of the amount of water being put into and taken out of Lake Arrowhead for all purposes, together with rainfall and evaporation, the level of water at the lake in June 2018 compared to June 2017 shows there was 21.05 fewer acre-feet (6,859,164 gallons) in the lake this year than last year.
In June 2018, 92.50 acre-feet (30,141,218 gallons) were extracted from Lake Arrowhead for treatment. That treatment did not take place at the Bernina Water Treatment Plant, which was off-line in order to reconstruct the North Bay water intake system. Rather the water was treated at the Cedar Glen Water Treatment Plant.
The Lake Arrowhead Community Services District took 57.12 acre-feet (18,612,609 gallons) from the Crestline Lake Arrowhead Water Agency to replenish the lake. Wells in Grass Valley produced 11.78 acre-feet (3,838,525 gallons) that was directed into the lake.
In the first six months of 2018, 85.36 fewer acre-feet (27,814,641 gallons) were taken out of the lake for the nearby community’s water supply compared to the first six months of 2017.
No water was transferred to Grass Valley Lake from Lake Arrowhead for irrigation at the Lake Arrowhead Country Club, a repeat of what occurred in 2017. The discontinuation of water transfers to the Lake Arrowhead County Club came about because irrigation at that facility is now predominantly reliant upon recycled water. In April, 30.31 acre-feet of recycled water were used for irrigation at the Lake Arrowhead Country Club and its golf course and 35.13 acre-feet were used in May for the same purpose. In June, another 45.30 acre-feet of recycled water was diverted to the country club and its golf course, and was used exclusively for irrigation. Had the 110.74 acre-feet (36,084,740 gallons) of recycled water provided to the golf course and country club for irrigation been obtained directly from the lake, it would have diminished the lake’s level by 1.85 feet.
As of June 1, the lake’s level stood at was 5100.48 feet, which is 6.22 feet or 74.64 inches below what is deemed to be its full level.
On July 1, the lake level was 5099.81 feet’, which is 6.89 feet or 82.68 inches below being full.
In this way, the lake’s level dropped two-thirds of a foot, or 8.04 inches during June 2018. The lake is now 89.1 percent full.
There was no rain in Lake Arrowhead in June 2018. Lake Arrowhead on average experiences .16 inches of rain in June. The water year runs from October 1 to September 30. For the 2017-18 Water Year to date (since Oct. 1, 2017) total precipitation has been 15.3 inches, or roughly 41.6% of the 126-year average to date. This is an indication of the continuing drought, which underwent a respite in 2017. Average yearly precipitation over the last 126 years in Lake Arrowhead has been 37.9 inches. If the trend thus far continues, Lake Arrowhead will receive less than 50 percent of its annual average.
The Lake Arrowhead Community Services District calculates that water evaporation from the lake from January 1 through June 30 was about 1,700 acre feet, which translates to a draft of 28.35 inches.