Field-scale evaluation of water and solute transport in different irrigation technologies.

Abstract

Groundwater contamination has many sources, the routine agricultural application of fertilizers and pesticides are recognized as significant sources. This field study was initiated and designed to evaluate if there were differences among different irrigation technologies on water and solute transport under field conditions. The modes of water application were flood, sprinkler and drip (line source) with the same amount of water but different water application rates. Potassium bromide was applied along with irrigation water to assess the leaching behavior of chemicals. The three methods of water application yielded similar patterns of moisture regimes as a function of time. As the flow rate decreases, the gradual transition of moisture was observed with long peaks indicating more uniform water distribution and water availability in the case of drip irrigation. The moisture distribution for post irrigation was not significantly different with time among different irrigation systems. The moisture distribution profiles with depth were statistically different for sprinkler irrigation compared to flood and drip irrigations. There was no significant difference between flood and drip irrigations. The solute concentration distribution as a function of time exhibited solute pattern differences among irrigation methods. The concentration distribution in flood irrigation was quite different from sprinkler and drip irrigations due to high input flow rate. The post irrigation concentration distribution with time was higher in drip irrigation than those of flood and sprinkler irrigations. The solute concentration profiles in flood, sprinkler and drip irrigations showed no big differences among irrigation methods with depth up to 55 cm. But the drip irrigation had more solute retained and more uniformity in the soil profile than flood or sprinkler irrigations. The numerical model "HYDRUS" was used for the simulation of one-dimensional water flow and solute transport in flood, sprinkler and drip irrigations. The dispersivity versus solute profiles exhibited greater vertical variability with depth in flood irrigation than for sprinkler and drip irrigation. The comparative results of model simulation and field observed data for moisture distribution showed good agreement between the observed and the simulated water contents. The model prediction for solute concentration distribution also showed comparable results with field measurements.