Los Angeles Department of Water and Power will be pumping approximately 65,000 acre-feet during the 2014 runoff year.
The figure represents nearly half the volume – 134,411 acre-feet – that the Inyo-L.A. Long Term Water Agreement identifies as being available for pumping. Runoff for this year is forecast to be 42 or 43 percent of normal, down from last year’s forecast of 46 percent of normal when LADWP pumped about 70,000 acre-feet of groundwater. The utility pumped 88,681 acre-feet in 2012-13.
The department’s Annual Operations Plan was released April 28 and the groundwater pumping plan was agreed to by the Inyo County Water Department staff during the May 7 meeting of the Technical Group. The 2014 runoff year began on April 1 and will run through March 31, 2015. The LTWA requires that LADWP’s Annual Operations Plan propose pumping for the first six months of the runoff year during drought conditions. In the past, pumping in the last six months of a runoff year, October 1 to March 31, has been primarily for hatcheries, town uses and mitigation projects only.
In his response to the plan, Water Department Director Bob Harrington called the pumping volumes “substantially more conservative than pumping plans developed during the dry years of the early 1990s.” LADWP’s pumping activity, as outlined, would result in a total estimated low of 36,920 acre-feet to a high of 47,930 acre-feet during the time period, April 1 through Sept. 30,
The first six-month extraction represents 70-73 percent of the total year’s volume.
The department’s plan identifies pumping per wellfield. Laws, where, according to the county’s response, vegetation in the wellfields has been below baseline for years, will supply 5,760 to 7,200 acre-feet during the first six months of the year, well below the available annual capacity of 22,885. The volume “appears to accommodate irrigation, town and mitigation project needs” according to the county’s response and should result in little change to the water table. Baseline vegetation and water table levels were determined in the mid 1980s.
Pumping in Bishop wellfields will range from 7,200 to 8,700 acre-feet, roughly half of the available capacity.
Big Pine wellfields delivered 23,866 acre-feet of water during the 2013 runoff year and those numbers will be cut in half this year with anticipated levels ranging from 10,200 to 11,650 acre-feet for the first six months. Water tables in those wellfields have been below baseline (3.7 to 6.39 feet below); the county estimates changes would range from an increase of 0.63 feet to a drop of 1.3 feet.
Groundwater extraction in the Taboose Aberdeen wellfields will range from a tenth to a third of available capacity at 1,500 to 4,500 acre-feet. Last year, 9,593 acre-feet were pumped from the wellfields.
The impact of reduced pumping at the Blackrock Fish Hatchery, a result of the Blackrock 94 dispute resolution, will be seen in the Thibaut-Sawmill fields. The department proposes to pump 4,600 acre-feet, compared to the 12,717 extracted during the 2013 runoff year. The county anticipates a rise in the groundwater level of 2.13 feet to a drop of 0.63 feet.
Water tables from Aberdeen to below Independence have indicated the greatest decline, as low as 23.6 feet in the Symmes Shepherd wellfields. Those levels could see a slight increase under the 2014 pumping plan. Independence Oak fields will pump 5,280 to 6,600 acre-feet during the first six months; Symmes Shepherd wellfields will deliver 720 to 2,760 acre-feet with LADWP requesting a reduction in irrigation or mitigation project water.
Pumping proposed for the Bairs Georges wellfields is 1,080 to 1,440 acre-feet with 580 acre-feet extracted in the Lone Pine fields.