According to an independent hydrologists' evaluation of the proposed Cadiz Valley water project, project backers used flawed models and incomplete data to forecast the amount of water they could pump out of a desiccated valley in the Mojave Desert.
Cadiz project backers plan to pump up to 50,000 acre-feet of groundwater yearly for 50 years out of the hyperarid Cadiz Valley, moving the water via pipeline to coastal Southern California communities.
Cadiz Inc., owner of about 34,000 acres in the Cadiz Valley, has teamed up with the Santa Margarita Water District, Three Valleys Municipal Water District, Golden State Water Company, Jurupa Community Services District and Suburban Water Systems to propose the project.
The independent hydrological consultants, Johnson Wright Inc. (JWI) of Lafayette, CA, were hired by the National Parks Conservation Association (NPCA) to assess claims made in the Cadiz Valley Water Conservation, Recovery, and Storage Project's Draft Environmental Impact Report (DEIR).
The key to any environmental acceptance of Cadiz Inc.'s plans is the developers' estimates of available water in the Cadiz Valley hydrological system. The DEIR contends that the majority of the water Cadiz would be removing from the desert valley -- about 32,500 acre-feet -- would otherwise be lost to evapotranspiration from Bristol and Cadiz dry lakes, and that the other 17,500 acre-feet, which would have gone into the aquifer, would be replenished by precipitation each year. In Cadiz's words:
The Cadiz Valley Water Conservation, Recovery and Storage Project is designed to capture and conserve billions of gallons of renewable native groundwater flowing beneath our property in California's Mojave Desert that is currently being lost to evaporation and salt contamination at nearby dry lakes. Through the active management of the aquifer system and a state-of-the-art groundwater protection program, the Project will reduce the loss of groundwater to evaporation from the dry lakes, put this water to beneficial use and create a reliable water supply without adversely impacting the aquifer system or the desert environment.
Since the first version of the plan was proposed over a decade ago, environmentalists have charged that Cadiz's estimates of the amount of water it could extract sustainably are wildly optimistic.
In preparing the DEIR, Cadiz relied on aquifer recharge estimates from the environmental engineering firm CH2M Hill, which provided projected figures for the annual rate of replenishment of the Cadiz aquifer based on precipitation in the Fenner and Orange Blossom Wash watersheds, the aquifer's main catchment basins. JWI challenged those estimates:
Estimating groundwater recharge in arid or semiarid regions can be a difficult and complex task. Groundwater recharge in arid and semi-arid areas is dependent on a complex set of spatial and temporal hydrologic parameters and processes dependent on local climate, land surface properties and subsurface characteristics. Indeed, surface hydrology generating recharge in arid and semi-arid areas is complex and extremely difficult to quantify using conventional methods of analysis.
Instead of using the amount of precipitation, JWI calculated the amount of water discharged from the system, which should roughly match inflow if the watershed is at equilibrium. By that standard CH2M Hill's estimate of 32,477 acre-feet per year added back into the aquifer is more than twice the actual recharge -- around 14,000 acre-feet, a figure that corresponds with earlier independent estimates.
As JWI states to provide perspective on Cadiz's recharge figures of 32,477 acre-feet:
The following recharge volumes are provided to put in perspective the amount of groundwater estimated to recharge the Fenner and Orange Blossom Watersheds:
- This is greater than the natural recharge to the Coastal Plain of Orange County basin (29K AFY [acre-feet per year]).
- This is greater than the combined recharge from stream flow in the [very well-watered -cc] Bishop Creek to Big Pine Creek region (and inclusive of intermediate streams) of the eastern Sierra Nevada.
JWI also points out several places in the DEIR and various supporting documents where Cadiz or its consultants either misrepresented or misinterpreted outside data, for instance referring to:
and the Davisson and Rose (2000) Maxey-Eakin recoverable water estimate of 29,815 AFY
JWI pointed out that Davisson and Rose actually estimated that "recoverable water" recharge ranged from 7,864 AFY-29,185 AFY. Cadiz had taken the maximum estimate of recharge in an extremely wet year and presented it as the figure in an average year.
Throughout the DEIR, JWI says, references to data adjustments done by consultants are left undescribed, existing studies of the Cadiz and similar areas are unmentioned if they conflict with Cadiz's preferred data, and overall estimates of the amount of water available are generally significantly higher than a cautious researcher would suggest. The comments conclude by stating that Cadiz's conceptual model of the basin's hydrology is flawed, the company has paid insufficient attention to key details of the whole system, and too few "milestones" and "decision points" are spelled out in the management plan, calling into question the company's future responsiveness to changing conditions in the basin -- despite its ostensible plans for "active management of the aquifer system."
The omission which may have the greatest impact on the Mojave Desert ecosystem involves long-term changes to the aquifer. Pumping water out of the ground creates what's called a "cone of depression," a roughly conical lowering of the water table with its deepest point at the pump, formed as water flows through rock and soil toward the pump. If a cone of depression is large enough, it can continue to grow even after pumping stops as water seeps back into the depressed area from neighboring parts of the aquifer.
Many estimates have it that pumping from the Cadiz Aquifer over 50 years could well create a cone of depression that would still be growing another 50 years after the pumping stopped, lowering the water table in the southern reaches of the Mojave National Preserve and in a number of intact wilderness areas. Lowering the water table in the desert dries up streams and seeps with devastating consequences for wildlife, as well as air quality when the landscape's vegetative cover dies off.
Which raises an issue not discussed in JWI's comments. Cadiz Inc. lauds its project as "reclaiming" water that would otherwise be "lost" to evapotranspiration. Let's assume for a moment that their figures prove to be more or less accurate, as unlikely as that may be. "Evapotranspiration" looks like a compound word, and it is. It means the sum of water put into the atmosphere either from evaporation, as when a lakebed dries up in the desert, or transpiration, which means water vapor given off by living things.
Most of the evapotranspired water in the Cadiz basin is indeed evaporated from lakebeds. But not all of it. Implying that water used by desert wildlife is a "wasted" resource is essentially the same thing as saying that river water that makes it to the ocean is "wasted," and never mind how many salmon it keeps alive along the way. The "river" in the Cadiz Basin runs into the air rather than the sea, but the argument is still the same: a disregard for the rights of living things that happen not to be human customers of Cadiz, Inc.
"[JWI's] comments do contain some uncertainty," says Seth Shteir, California Desert Field Representative for the NPCA. "Even with that uncertainty, though, it's clear that this project poses enough of a threat to the groundwater, air resources, and wildlife that we think it should be stopped."
Shteir points out that the project's implications extend far beyond the Cadiz Lake watershed. "Essentially, what Cadiz proposes to do is to take a public resource -- the desert's groundwater -- privatize it, then sell it back to us. Not only does that make no sense from an environmental perspective, but we think it's just really bad policy."
Chris Clarke is an environmental writer of two decades standing. Author of Walking With Zeke, he writes regularly at his acclaimed blog Coyote Crossing and comments on desert issues here every week. He lives in Palm Springs. Read his previous posts here.
TrackBack URL: http://www.kcet.org/cgi-bin/mt/mt-tb.cgi/12913