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Groundwater Management

In 2014 California passed a law regulating groundwater. It was intended to foster local control of groundwater resources and was based on the concept of “safe yield.”

Given the colonial status of Owens Valley, it might be thought that this new law would have been welcomed in Owens Valley as a way to weaken DWP’s control.  To the contrary, DWP and Inyo county staff negotiated with the groundwater law’s sponsors in the legislature to add (at the last minute) an exemption for DWP land in Inyo County.  The legislature passed the bill, with the exemption, before County Supervisors and the public had any chance to discuss the exemption at all.

Assuming the exemption is implemented, groundwater will continue to be managed under terms of the 1991 Inyo-LA Long Term Water Agreement (LTWA).  While the overall goals of the LTWA sound reasonable (i.e. to “avoid” creating significant impacts while providing a “reliable” supply of water), there are crippling flaws in its groundwater management protocol which prevent the goal of impact avoidance from being attained.

The concept on which LTWA groundwater management is based is simple: rotational pumping. At any given time pumping would be allowed in some areas to create water table draw-downs, while pumping elsewhere would be curtailed to allow water table recovery.  By carefully rotating areas of drawdown and areas of recovery, it would be, in theory, possible to “avoid” creating any further significant environmental impacts and also provide a “reliable” supply of water. Wellfield vegetation (an indicator of wellfield ecosystem conditions) was thought to be “drought hardy,” meaning it could tolerate cycles of water table drawdown and recovery

Unfortunately, the concept is not being successfully applied.

The protocol by which wells are turned on and off, (aka the “on/off protocol”) has proven to be ineffective in implementing rotational pumping.  It is ineffective for several reasons.

First, because approximately one-third of DWP’s wells –including several of the largest in the valley–have been exempted from the protocol or are simply not linked to on/off monitoring sites.  This means many wells are never rotated out of production, and some are actually operated continuously, year-round.  Anywhere from 70% to 100% of pumping in any given year usually comes from exempt or un-linked wells. As a result there are areas of permanent water table draw-downs which are never allowed to recover.  In 2006 Inyo County Water Department Director Tom Brooks told Inyo County Supervisors, “We cannot pretend managing 20-25 percent of pumping is really managing the resource.” Nine years later (in 2015) the problem as worsened, as even more exemptions have been granted.

Another problem is that the on/off protocol is not based on direct measurement of water table depth.  Instead, water availability is based on a complicated calculation of soil water measured at several different depths.  Relatively high precipitation in a given year may thus turn a given well to “on” status even though the water table may be deeply drawn-down.  If the following year is dry, the pump my go off, but water table recovery is not instantaneous and plants will be denied access to shallow groundwater when they need it most.

A similar problem pertains to the vegetation water requirements used in on/off calculations.  The LTWA goal is to manage pumping so as to avoid vegetation impacts relative to conditions as measured in 1984-87 (the “baseline period”), when DWP inventoried all its holdings and developed quantitative estimates of percent cover and species composition. On/off water requirements are based on measurements of current vegetation conditions at monitoring sites—not the water requirements of vegetation as measured in the 1984-1987 baseline period.  Had on/off been implemented as soon as baseline conditions had been measured, it might have had a chance of success.  Unfortunately, it was not implemented until several years of drought in conjunction with record high levels of pumping had dramatically lowered water tables and seriously reduced vegetation cover below baseline.  The protocol was not designed to raise cover, but to keep it from declining. Were on/off based on estimated water requirements of baseline vegetation the protocol would have been much more effective at raising vegetation cover to baseline conditions.

Apart from poor vegetation conditions, the clearest evidence of the failure of on/off is seen in valleywide pumping totals.  According to the USGS, long term average pumping should not exceed ~70,000 acre feet per year (excluding artesian flows) if water tables are to remain high enough to meet LTWA goals of impact avoidance.  However, DWP reports its actual long term average pumping to be almost 90,000 af/yr.

One reason long term average pumping is too high is because, on any given year, the on/off protocol permits far more than 70,000 af of pumping.  For example, according to DWP, in 2011, (the last year before the current drought), on/off allowed pumping 197,284 af of water.  Even during the four years of the current (as of 2015) record-breaking drought the average allowable pumping has been 133,357 af/yr, a volume almost 50% greater than the USGS ceiling of 70,000 af/yr.  On/Off permits so much pumping DWP doesn’t pump all it is allowed.  This lets the agency claim it is pumping “conservatively” and complying with the LTWA because it is pumping far less than is allowable, even while it pumps far more than it should were it seriously trying to avoid impacts.

A final problem with the on/off protocol is that it favors deep-rooted shrubs over meadow grasses.  Most DWP pumping is in areas of (formerly) shallow groundwater (formerly) dominated by groundwater-dependent grasses (aka “alkali meadows”).  As water tables are drawn-down due to pumping, grasses experience water stress before invasive shrubs, because the shrubs typically have deeper roots.  Likewise, shrubs recover from water stress in a period of rising water tables before grasses, due to the shrubs’ deeper roots.  This potential for conversion from grass to shrub dominance was recognized as a potential problem with rotational pumping when the LTWA was negotiated and vegetation monitoring data provide clear evidence it is occurring.

In 2005 Inyo County Water Department began developing a replacement for on/off based on direct management of groundwater.  This led to the 2007 decision by the Inyo-LA-Standing Committee to initiate a joint Inyo-DWP facilitated process for revising the on/off protocol and the entire technical appendix to the LTWA.  The process was to last three years – far longer than the two months it took to write the original LTWA technical appendix.  The revision process is now in its ninth year with no results.  Without court involvement there is no reason to believe agreement will ever be reached.

Why is groundwater important?

Three of the many reasons why groundwater is important are: 1) to sustain biodiversity; 2) to preserve beauty; and 3) to support economic activities in the form of livestock grazing and tourism.  When Euro-Americans first saw the valley, they marveled at beautiful extensive meadows, and diverse wildlife habitats all sustained by surface water and shallow groundwater.  Under current management, wellfields are becoming steadily drier, less diverse, browner, dustier and uglier.

A better way to implement GroundWater based Management is contained in this presentation:


Related links to the old OVC website

Introduction to GW
Desertification as usual