Quality and Quantity of Return Flow as Influenced by Trickle and Surface Irrigation (Annual Report, Year 1)

This report describes the first year of a three year study on the quality of return flow from field plots irrigated by surface and trickle application and having different frequencies and efficiencies. Thirty plots, each 24 x 24 feet square, were constructed with polyethylene plastic surrounding the plots to a depth of 2.5 feet. Six plots, 20 x 60 feet square were constructed for irrigation by the trickle system. All plots were instrumented with triplicate tensiometers at two depth below the root zone and triplicate suction cups at a level between the tensiometers. Two neutron access tubes were installed in each plot. Cotton was planted in all plots. Collection of samples from the soil solution below the root zone of the cotton has started, and measurements of the hydraulic gradient of the water below the root zone are made. A detailed description of the experimental set up is presented.

The volume and quality of the water in the Del Rio drain was measured continuously. There is a direct correlation between the flow in the drain and the availability of surface water in the irrigation district. In general periods of high drain flow correspond with lower salt concentrations.

Project NO. 13030 GLM