BOARD00345

• Board Meeting Date: 11/19/2001
• Description: ISF Section - Proposed ISF Recommendations for 2002
• Board Meetings - Doc Type: Memo

Pitt et ,II, August 2001. Replacing the Bypass Flow On The Colorado River

augment flows to the Colorado River delta in Mexico, as long as the addition of this water to the
mainstem does not violate the Minute 242 salinity standard.40 ..

Ecological Advantages of Leasing WelIton-Mohawk Water and Securing Federal Credit
for Yuma Mesa Groundwater
There are two important ecological advantages to this alternative: I) bypass flows will be
replaced without creating new storage for Colorado River water and the ecological damage
created by reduced flood flows to the Colorado River delta would be avoided, and 2) salinity of
flows to the Cienega de Santa Clara will be reduced.

Flood flows have restored considerable native habitat in the Colorado River delta, and must be
protected. Minute 30641 of the International Boundary and Water Commission commits the
United States and Mexico to a collaborative process to identify mechanisms to supply the delta
with water to sustain its ecosystems. The United States will violate the spirit of Minute 306 if
actions are taken to further reduce the probllbility of flood flows to the delta. In addition, the
United States may be obligated not to diminish flood flows to the delta by the Endangered
S . A 42
pecles ct.

Of note, groundwater pumped from the Yumll Mesa area is slightly brackish (1400 ppm).43 BaR
analysis indicates that addition of pumped Yuma Mesa groundwater to the Colorado River
mainstem is likely to cause violations of the Minute 242 salinity standard during dry winter
months.44 Diverting some groundwater pumped from the Yuma Mesa area would reduce the
probability of these violations, and would have the additional benefit of reducing the salinity of
flows to the Cienega de Santa Clara. Water in the MODE averages 2400 ppm; the addition of
25,000 acre-feet of l400ppm water annually would reduce MODE water salinity to 2200 ppm.

2. OPERATION OF THE YUMA DESAL1"ING PLANT

BOR has proposed that it could replace bypass flows by treating the bYPllss flow itself, or
another source of brackish water, at the Yuma Desalting Plant (YDP).45 The YDP, with capacity
to produce 68,000 acre-feet of treated water l1111lually, was completed in 1992 at a total cost of
$258 million and todal sits idle on "ready reserve" status, costing approximately $2.2 million
per year to maintain.4 BaR estimates YDP operational costs at approximately $21.1 million
annually, resulting in a cost of over $310 per acre-foot for treated water.

4() At such time that addition to the Colorado River mainstem of pumped Yuma Mesa groundwater would violate the
salinity standard, it could be diverted to the MODE to temporarily increase flows to the Cioneg. de Santa Clara.
41 Full Text of Minute 306 is available at htto://www.ibwc.state,20v/lFiles/Minutes/Min306.odf.
42 See supra note 13,
43 U.S. Bureau of Reclamation, supra note 35.
44 U,S, Bureau of Reclamation, handout at Las Vegas briefing 5/8/01.
4S U.S. Bureau of Reclamation, handout at Las Vegas briefing 5/8/01.
46 Pontius, Dale, (1997) Colorado River Basin Study: Report to the Western Water Policy Review Advisory
Commission, p, 68.

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