Tuesday, October 14, 2008 : 4:30 p.m.

Fate of Dos Palmas Preserve and Vicinity Due to Lining of Irrigation Canals, Salton Trough, California

Barry Hibbs, Ph.D.1, Mathew A. Kelliher, PG, CHG2 and Rachel Andrus1, (1)California State University, Los Angeles, (2)Water Replenishment District of South California

The All American Canal and its Coachella Branch divert water from the Colorado Rivers for use in the Imperial and Coachella Valleys. On the northeast side of the Salton Trough, leakage from the unlined Coachella Canal recharged local aquifers.  At the contact between alluvial fan material and lacustrine sediments, spring discharge has created an extensive system of wetlands that have grown since the Coachella Canal was constructed in 1949. The wetlands were natural features prior to canal construction, but their areal extent was limited due to minimal natural recharge. Today the extensive wetlands support extensive habitat.

Lining of the entire canal was completed in December 2006. Before the canal was lined, we collected samples from several spring and well locations downgradient from Coachella Canal to assess geochemical and isotopic signatures for comparison to canal and native groundwater sources. Analysis of stable isotopes identifies three distinct groups of water.  One group consists of nearly pure canal water, a second group consists of nearly pure native groundwater, and a third group consists of various mixtures of canal and native groundwater.  Most of the waters at the preserve are derived from Colorado River-fed canal water. 

Now that lining of the canal has been completed, flow at the wetlands will decrease. As flow decreases the isotopic and hydrochemical signature of the waters should evolve toward that of native groundwater; this evolution will be a direct result of decreased recharge from the Coachella Canal. Wetland habitat will also decrease due to diminished recharge and a gradual salinization of groundwater. It is unknown how complete this transformation will be or how long it will take to occur; therefore, continued monitoring of these locations are being done to determine the effect of reduced spring and well flow on the current wetland areas.

Barry Hibbs, Ph.D., California State University, Los Angeles Dr. Barry Hibbs is Professor of Hydrogeology at California State University, Los Angeles. His professional and research interests include watershed and wetlands hydrology, arid zone hydrology, hydrogeochemistry of trace elements, and modeling groundwater flow.


The NGWA International Conference on Nonrenewable Ground Water Resources — Sociotechnological Aspects of Nonrenewable Ground Water Resources: Half-Empty, Half-Full, Top-Down, Bottom-Up, and Some Paths Forward