Impacts of spatial variability of basins microtopography on irrigation performance

Land microtopography unevenness is a key variable affecting basin irrigation performances. Using stochastic modeling, a number of sets of spatially variable surface elevations were generated, and a two-dimensional basin irrigation model was used to simulate irrigation for the generated sets. Strip, narrow and wide basins, as well as graded and zero-levelled basins were analyzed. Results show that spatial variability of basin microtopography influences the infiltrated depth when the advance is completed (Z (adv)) and the irrigation uniformity (DUlq). When the degree of unevenness increases, the Z (adv) value and its range of variation also increase, thus indicating that overirrigation increases with unevenness, mainly when zero leveling is adopted, inflow rates are small, and basin length is larger. Differently, DUlq is relatively small and insensitive to unevenness in case of graded basins, but is much larger and sensitive in case of zero leveling. This indicates that when water saving is aimed, it is preferable to adopt graded basins and shorter cut-off times, while it is better to adopt zero leveling and high inflow rates when high DUlq is pretended.