The Monitor 1998
Owens Valley Water Management
Inyo County and Los Angeles agreed to a maximum groundwater pumping limit of 64,000 acre-feet for the 1998-1999 runoff year (April 1, 1998-March 31, 1999). An additional amount of groundwater could be pumped by the Los Angeles Department of Water and Power during the winter, if necessary, to prevent the water in the Los Angeles Aqueduct from freezing. Actual pumping was 51,575 acre-feet. The pumping limit was based on predictions of water table responses at 18 indicator wells and in consideration of valleywide vegetation conditions.
Water uses on LADWP's Owens Valley lands for the runoff year were planned at about 92,860 acre-feet. These uses included 44,900 acre-feet for irrigation, 16,800 acre-feet for stockwater, 8,730 acre-feet for LADWP recreation and wildlife projects, and 22,430 acre-feet for enhancement/mitigation projects, including Klondike Lake, Lone Pine Riparian Park, treelots in Independence and Lone Pine, several native pastures and alfalfa fields, and the Lower Owens River rewatering project.
LADWP's April 27, 1998 snow survey reported water content in the Mammoth Pass snowpack as 64.1 inches. The 1998 snowpack varied throughout the Eastern Sierra from 163% of normal at Mammoth Pass to 119% of normal at Rock Creek. Measurements at LADWP's snow survey stations at Big Pine Creek and Cottonwood Lakes were 164% and 183%, respectively.
Runoff in the Owens Valley for April 1998-March 1999 was projected by LADWP at about
603,800 acre-feet or 152% of normal. Recharge to the valley's aquifers for the 1998 water
year (October 1, 1997September 30, 1998) was estimated to be 233,131 acre-feet.
Figure 1. Water levels as of April 1999 in selected shallow monitoring wells relative to baseline groundwater conditions.
These data are used each year to predict water level changes at selected indicator wells throughout the valley. Multiple linear regression equations developed for these monitoring wells allow ICWD and LADWP to predict the water table response to different groundwater pumping scenarios (see "Predicting Water Table Response to Groundwater Pumping" on page 16).
Under the conservative groundwater management of the Drought Recovery Policy, LADWP's pumping has been relatively low since 1990 and water tables have gradually climbed. In general, water tables continued their upward trend during 1998, due to high recharge and low pumping. Figure 1 shows that as of April 1999, water tables were approaching baseline levels over much of the valley. "Baseline" is the average April water-level from 1985-1987.