|Ayars, James - Jim|
Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2010
Publication Date: 3/1/2011
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2236.pdf
Citation: Shouse, P.J., Ayars, J.E., Simunek, J. 2011. Simulating Root Water Uptake From a Shallow Saline Groundwater Resource. Agricultural Water Management. 98(5):784-790. Interpretive Summary: Disposal of saline drainage water is a significant problem for irrigated agriculture but our research resources would soon be depleted if we were to rely totally on experiments to solve this problem. Simulation modeling can reduce our dependence on empirical data by extrapolating experimental results to irrigated areas where disposal of drainage water is a concern. We found that HYDRUS 1-D simulations of our experimental results were quantitative and in good agreement with measured values of water use from different sources (i.e. shallow groundwater and soil). In addition we also used simulations to visualize system dynamics for which we had no direct measurements (i.e. salinity concentrations, pressure heads, and root water uptake patterns). These results will have great impact on soil and water resource planners, state soil scientists, and NRCS personnel.
Technical Abstract: Disposal of saline drainage water is a significant problem for irrigated agriculture. One proposal to deal with this problem is sequential biological concentration (SBC), which is the process of recycling drainage water on increasingly more salt tolerant crops until the volume of drainage water has been reduced sufficiently to enable its final disposal by evaporation in a small area. For maximum effectiveness this concept will require crop water reuse from shallow groundwater. To evaluate the concept of sequential biological concentration, a column lysimeter study was used to determine the potential crop water use from shallow groundwater by alfalfa as a function of ground water quality and depth to ground water. However, lysimeter studies are not practical for characterizing all the possible scenarios for crop water use related to ground water quality and depth. Models are suited to do this type of characterization if they can be validated. To this end, we used the HYDRUS-1D water flow and solute transport simulation model to simulate our experimental results. Considering the precision of the experimental boundary and initial conditions, numerical simulations matched the experimental results very well. The modeling results indicate that it is possible to reduce the dependence on experimental research by extrapolating experimental results obtained in this study to other specific sites where shallow saline groundwater is of concern.