Table of Contents
Cover Page
Director's Report
ICWD Staff
Saltcedar
Precipitation
Mitigation Status
Vegetation Conditions
Soil Water Conditions
Groundwater Conditions
Historic Pumping
Current Pumping

Groundwater Conditions

Inyo County, through the Inyo County Water Department (ICWD), and the Los Angeles Department of Water and Power (LADWP) entered into an Interim Management Plan (IMP) for groundwater management within the framework of the Water Agreement during the next three runoff-years beginning in Runoff-year 2007-08. The IMP was implemented to provide an environment conducive to the successful performance of the Green Book Revision Cooperative Study.  Documents concerning the IMP can be found here.

The IMP provides for specific sole-source uses in Owens Valley and curtails export pumping if it causes groundwater levels to decline below April 2007 levels. The IMP will terminate on March 31, 2010 unless terminated sooner as provided by the provisions of the IMP agreement.  Groundwater pumping in the Owens Valley under the IMP will be managed with the goal of having average forecasted wellfield groundwater levels on April 1, 2008, April 1, 2009 and April 1, 2010 (wellfield target levels) at or greater than the average measured wellfield groundwater levels on April 1, 2007, subject to criteria described in the IMP agreement.  April groundwater levels are forecasted using the IMP monitoring wells shown in Table 1, below and their associated regression models contained in the documentation in the link provided above. A list of exempt pump-equipped wells is also provided in the IMP documentation.  The Lone Pine and Bishop Wellfields are not managed under the water level provisions of the IMP. Instead, the Bishop Wellfield will be managed in accordance will the Hillside Decree, the Water Agreement and applicable court rulings, and in Lone Pine pumping will be limited to supplying the town water system and Enhancement/Mitigation project irrigation and possibly an operational test of a new well.

Runoff during the 2007-2008 runoff-year was forecasted at 58% of normal on April 1, 2007. Runoff-year 2007-2008 is defined as April 1, 2007 through March 31, 2008.  In the runoff-year 2007-2008, 60,338 acre-feet of groundwater was pumped from Water Agreement-controlled wells in the Owens Valley.  Table 2 shows pumping for the runoff-year 2007-2008 by wellfield within the Owens Valley.  This was within the 63,232 acre-feet prescribed under the IMP for 2007-2008. The IMP capped pumping and the below runoff-year runoff combined to produce a relatively stable shallow water table with small increases and decreases in the shallow groundwater table in the 20 IMP indicator test holes and other indicator test holes (See Table 1, and Map at right).  The Laws Wellfield was one notable wellfield exception.  In 2005-2006, court mandated water spreading developed relatively high water tables in Laws and in 2007-2008 the water tables declined due to drainage of groundwater to the Owens River, evapotranspiration and pumping for use in the Laws Wellfield (See Table 1).

Water levels generally remain below the levels of the mid-1980’s baseline vegetation mapping period (See Table 1, last column). Of the 36 test holes in Table 1, seven were above the baseline in April 2008.

The groundwater recharge estimation methods used for the groundwater mining calculations mandated by the Green Book show approximately 129,000 acre-feet of recharge for the 2007 water-year (October 1, 2006 through September 30, 2007) for the Owens Valley. In contrast, pumping for the 2007 water-year was 65,230 acre-feet.

Review of conditions by area for the 2007-2008 runoff years

Laws Wellfield

In the Laws Wellfield, located north and east of Bishop, the shallow water table responds dramatically to pumping and recharge from the McNally Canals. Shallow water table hydrographs for test holes T107, T436, T438 T490 and T492 are shown in Figure 1.  Pumping was 6,286 acre-feet which was used in the immediate wellfield. Groundwater levels declined to below April 2007 levels and three test holes are below baseline water levels (See Table 1). Declines were due to the mound decay from previous court mandated recharge, pumping for uses in the wellfield and evapotranspiration of vegetation.  No water was diverted from the Owens River into the McNally Canals during 2007-2008.

Bishop Cone Wellfield

Pumping on the Bishop Cone was 10,018 acre-feet.  Shallow water table hydrographs for test holes T387 and T479 are shown in Figure 2. Generally, pumping from wells on the Bishop Cone and recharge from the extensive network of canals, ditches and creeks balance to produce stable water levels.  The Bishop Cone Wellfield is exempted from the groundwater level provisions of the IMP and it will be managed consistent with the Hillside Decree, the Water Agreement and applicable court rulings.  A draft of the Bishop Cone Audit for the 2007-2008 runoff-year indicates that total groundwater extraction did not exceed water usage on Los Angeles-owned land on the Bishop Cone.

The Big Pine Wellfield

Pumping in the Big Pine Wellfield was 20,406 acre-feet.  Pumping has been historically relatively high compared to other wellfields because of LADWP pumping for the Fish Spring Fish Hatchery.  Shallow water table hydrographs for test holesT425, T426 and T469 are shown in Figure 3.  Groundwater levels in April 2008 were slightly below April 2007 levels in Table 1. In all three test holes in Table 1 shallow groundwater water levels remain approximately a foot below baseline levels (See Table 1).

The Taboose-Aberdeen Wellfield

Pumping in the Taboose-Aberdeen Wellfield was 932 acre-feet. Shallow water table hydrographs for test holes T417, T418, T419, T421, T502, T504 and T505 are shown in Figure 4.  Groundwater levels in April 2008 were slightly above April 2007 water levels in Table 1.   In three of the seven test holes in Table 1,  groundwater levels remained above baseline levels.  In the past this wellfield has undergone large pumping induced fluctuations (See Figure 4).

The Thibaut-Sawmill Wellfield

Pumping in the Thibaut-Sawmill Wellfield was 12,732 acre-feet.  Historically, pumping has been approximately this amount or higher for the Blackrock Fish Hatchery.  Shallow water table hydrographs for test holes T413, T414, T415 and T507 are shown in Figure 5. Groundwater level in April 2008 was mixed, with two test holes being above April 2007 levels and two test holes being below April 2007 levels (See Table 1).  In all indicator test holes in the Thibaut-Sawmill Wellfield water levels remain below the baseline levels (See Table 1). In the past this wellfield has undergone large pumping-induced fluctuations (See Figure 5).

The Independence-Oak Wellfield

Pumping in the Independence-Oak Wellfield was 7,035 acre-feet.  Shallow water table hydrographs for test holes T407, T406, T408, T409, T546, T412 and T453 are shown in Figure 6. Groundwater levels in four of the seven test holes in April 2008 were above April 2007 levels (See Table 1).  In all of the seven indicator test holes in the Independence-Oak Wellfield water levels remain below the baseline levels (See Table 1). In the past this wellfield has experienced sustained pumping due to the large number of exempt wells.

The Symmes-Shepherd Wellfield

Pumping in the Symmes-Shepherd Wellfield was 1,267 acre-feet, entirely used for irrigation.  Shallow water table hydrographs for test holes T401, T402, T403, T404, T510, T447 and T511 are shown in Figure 7. Groundwater levels in six of the seven test holes in April 2008 were above April 2007 levels (See Table 1).  In all of the seven indicator test holes in the Symmes-Shepherd Wellfield water levels remain below the baseline levels (See Table 1). Historically, pumping has varied greatly from this wellfield.

The Bairs-Georges Wellfield

Pumping in the Bairs-Georges Wellfield was 466 acre-feet.  Shallow water table hydrographs for test holes T398, T399 and T400 are shown in Figure 8. Groundwater levels all three of indicator test holes in April 2008 were slightly below April 2007 levels (See Table 1).  In two of the three indicator test holes in the Bairs-Georges Wellfield water levels remain above the baseline levels (See Table 1). Historically, pumping has varied greatly from this wellfield.

The Lone Pine Wellfield

Pumping in the Lone Pine Wellfield was 1,196 acre-feet, used for irrigation and town supply.  Shallow water table hydrographs for test holes T564 and T591 are shown in Figure 9 for reference. There are no indicator test holes in this wellfield.  Pumping in this wellfield has been principally for town supply, Diaz Lake and an Enhancement/Mitigation project east of the town.  LADWP has constructed a new production well west of the town of Lone Pine to supply the Los Angeles Aqueduct (W416).  LADWP and ICWD are currently developing a process and plan for testing this well and implementing management to protect groundwater dependent natural resources and private wells.

Shallow Groundwater Adjacent to the Lower Owens River

The court decided that base flows of 40 cubic feet per second were established in the Lower Owens River on  February 27, 2007.  A shallow test hole, T467 was monitored by ICWD staff during the establishment of base flows.  T467 is located approximately 700 feet east of the Owens River near the return of the Blackrock Ditch.  Shallow groundwater levels have increased by approximately two feet at T467 and other wells adjacent the river. in response to the increase in stage associated with the establishment of base flows in this section of the Lower Owens River where the channel was previously dry.

Projections Concerning the 2008-2009 Runoff-year

The April 1, 2008 LADWP runoff forecast for 2008-2009 was 86% of normal.  Although 2008-2009 was forecast to be below normal, it was not as dry as 2006-2007 which was forecast to be 48%.  Using the IMP regression equations and the planned pumping in the LADWP 2008-2009 Owens Valley Operations Plan (Table 3), projections concerning April 2009 water levels in the 20 IMP Indicator wells have been made by ICWD and LADWP Staff.  Those projections by ICWD are shown in Table 4 below.