Excessive Groundwater Pumping
Figure 1
Because of the consecutive years of high runoff and low pumping high water tables can be found throughout the valley (Figure 1). During this year of below normal runoff water table decline can be expected throughout the Valley. Pumping will cause additional decline in most well fields.
(Pg.1, Annual Owens Valley Operations Plan 2000-2001 Runoff Year)Due to consecutive years of low pumping, high water tables can be found throughout the valley. During this year of below normal runoff, the water table can be expected to decline naturally throughout the valley. In addition, the limited pumping outlined below will likely lead to some decline in parts of most wellfields.
(Pg. 1, Annual Owens Valley Operations Plan 2001-2002 Runoff Year)Due to the success of the Drought Recovery Policy and the associated ten consecutive years of low pumping, high water tables persist throughout the valley. The limited pumping will likely lead to temporary water table decline in parts of most well fields.
(Pg. 1, Annual Owens Valley Operations Plan 2002-2003 Runoff Year)Although high water tables persist throughout the valley, the limited pumping plan outlined below will likely lead to temporary decline in parts of most well fields.
(Pg.1, Annual Owens Valley Operations Plan 2003-2004 Runoff Year)…groundwater levels are generally high throughout the valley considering previous five years of relatively dry conditions.
(pg. 3-1)
Abstract
As of spring 2004, monitoring data show water tables have been held below the grass rooting zone under selected meadow parcels for the entire 14 year period of management under the LTWA. These parcels are spread throughout all of DWP's wellfields in Owens Valley. Total perennial and grass cover in these parcels are correspondingly diminished relative to the baseline values (Manning 2002). There is a correlation between perennial cover and annual precipitation in some of these parcels which suggests they have converted from groundwater-dependence to precipitation-dependence (Manning 2004). Decreases in cover and changes from groundwater- to precipitation-dependence are exactly the changes the LTWA is intended to avoid. In monitored parcels containing groundwater-dependent vegetation not subject to pumping-induced drawdowns, on the other hand, perennial cover has not diminished over the same period — if anything it has increased (Manning 2002). Patterns in cover change documented in field data have recently been independently corroborated with Landsat satellite imagery (Manning 2004).
The EIR to the LTWA emphasizes that management to avoid impacts is a primary goal (2-58) and that such management is required (2-45). Under current management there are no plans to restore water tables to grass rooting zones under the parcels in question. This cannot be considered management to avoid impacts.
The Technical Appendix to the LTWA (the Green Book) sets out specific steps for the Technical Group to take to determine if impact avoidance has failed and mitigation is necessary. The Technical Group has never undertaken this process. Under current management, impacts are thus neither avoided nor mitigated. While a reliable water supply to LA is being provided, the environmental protection goal and management requirements to meet it are being ignored for these parcels.
Another line of evidence supports the conclusion of excessive pumping. The average annual pumping since the implementation of the LTWA is approximately 95,800 af/runoff year (Coufal 2004b). Danskin (1998) estimated evapotranspiration requirements of vegetation in the baseline period would cap the long term annual average pumping at about 70,000 af/yr. Subsequent research on evapotranspiration suggests Danskin, if anything, may have underestimated the water requirements of the baseline vegetation (Steinwand 2000). This suggests, in turn, the maximum long term average pumping should be even less than 70,000 af/yr.
Finally, hydrologic modeling by ICWD also shows excessive pumping is occurring. In 2003, probabilities for water table recovery by 2005 were calculated for indicator wells and permanent monitoring sites. Even with the assumption of normal runoff every year, the probabilities of water table recovery for many sites were virtually nil (Steinwand and Harrington 2003).
