The Owens Valley Monitor 2002-2003

Figure 2. Shallow monitoring well changes in depth to
groundwater from 1985-87 to 1992 (2a) and through 2002 (2b).
Gray and black circles show drop in groundwater of at least
2 and 4 feet, respectively. Open circles represent wells with
groundwater drop less than 2 feet. Wells with water in 1985-87
that were dry in 1992 (2a) and 2002 (2b) are marked with an "x."
Numbers in parentheses are the number of wells in each category.

Groundwater Conditions

When LADWP inventoried Owens Valley vegetation between 1984 and 1987, water tables were generally high throughout the valley because of a series of wet years (1982-1986) and relatively low groundwater pumping. The vegetation mapped during that period, which became the baseline for management under the Inyo/Los Angeles Water Agreement, reflected these conditions.
     Following the inventory, during the first three years of the 1987-1992 drought, LADWP pumped approximately 210,000 acre-feet (1987), 200,000 acre-feet (1988), and 155,000 acre-feet (1989). Water tables declined in most wellfields below the plant root zones, and as a result, the vegetation declined.
     In 1990, in recognition of the decline in water tables and vegetation and the experimental nature of the management techniques of the Water Agreement, the Inyo/LA Standing Committee adopted a Drought Recovery Policy. The policy required that groundwater pumping be managed conservatively to allow substantial recovery of water tables, soil moisture, and vegetation. Since then, LADWP’s pumping has been lower than the pumping of the late 1980s (see page 4). In response to both lower pumping and several high runoff years, water tables rose during the 1990s, peaking in 1999. More recently, pumping and four years of below normal recharge have led to gradual water table declines. These declines have not been as severe as during the late 1980s because the Drought Recovery Policy held pumping to relatively low levels.
     Figure 2a shows three categories of drawdown that occurred at 220 shallow monitoring wells between the average April depth to water in 1985-1987 and April 1992, the last of six consecutive dry years. Figure 2b shows the difference between April 1985-1987 water levels and April 2002 levels at 219 monitoring wells. The gray background shows the area within 1.5 miles of LADWP pumping wells.
     The circles in Figure 2 are shaded according to how close the wells are to baseline levels. Areas of greatest water table decline in Figure 2a (black circles) coincide with the locations of highest groundwater extraction. In Figure 2b, many of the monitoring wells that are the furthest from recovery to 1985-1987 levels (black circles) are also near areas where the greatest amount of pumping has occurred. Comparison of Figures 2a and 2b shows that some monitoring wells have recovered in response to the high recharge and reduced pumping managed under the Drought Recovery Policy; however, many wells remain below baseline levels (black and gray circles).

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