Project Number: 5310-61000-013-01
Project Type: Reimbursable

Start Date: Jul 01, 2005
End Date: Dec 31, 2008

Objective:
To determine the relative contributions of on farm deep percolation and associated use of Colorado River water and natural recharge, to the ground water and salt loading from Grand Valley. Comparison to 20 y unpublished data will also allow evaluation of the impact of management changes and land use practices within that time period.

Approach:
Ground water samples and samples from washes and the Colorado River will be collected in Grand Valley at the end of the 2005 irrigation season. These samples will all be analyzed for 18O/O16, D/H as well as tritium and other tracers for age dating waters of less than 50 y. using acceptable protocols. Additional samples from the same locations will be analyzed for chemical composition of major dissolved ions and several trace elements. These analyses will be utilized to evaluate the assumption that the ground water composition is integrating local precipitation and irrigation conditions over a series of years rather than reflecting climation conditions of 2005. Calculations will be made to estimate the relative salt loadings from natural recharge and Colorado River derived water. These data will be compared to data collected in 1984 (Suarez, unpublished) to allow evaluation of the impact of land use changes and irrigation project improvements (canal lining, changes in irrigation practices etc) on salt loading to the Colorado River. Documents Reimbursable with Bureau of Reclamation. Log 28824. Formerly 5310-61000-012-01R (FEB 07)