0023-6152

AA00697606

4103896

A distributed long–term rainfall–runoff model was developed to quantify the watershed scale impacts of water–saving measures in the Ibague watershed, Colombia. The water–saving effects were evaluated by scenario analyses that incorporated the introduction of a water–saving irrigation method (early stopping) to improve irrigation efficiency with respect to redundant paddy irrigation water. In addition to water stopping, the impacts of a new water–saving rice genotype are analyzed. To calculate rainfall–runoff, the Sugawara tank model was utilized. The tank model quantified runoff discharges from forest, upland, paddy field, and urban areas by incorporating each land type into every mesh for a distributed rainfall–runoff model. This quantified the rainfall–runoff characteristics for each land use. Agricultural ponds and irrigation canals were allocated to each corresponding mesh to model irrigation management practices in the watershed. Agricultural ponds, which have a significant effect on the water balance at the watershed scale, were detected by performing cluster analysis on the seasonal transition of the backscatter coefficient obtained from multi–temporal Sentinel–1 SAR images. Quantitative analyses of the impacts of water–conservation under various scenarios indicated that the early–stopping irrigation method reduced water consumption by 9.4%, compared to the conventional methods. The scenarios, which assumed the introduction of a new water–saving rice genotype, assumed regular irrigation intervals of one or two days and indicated 24.1% and 48.2% reductions, for water consumption, respectively, compared to conventional irrigation methods. Scenarios that implemented a new water–saving rice genotype, as well as the early–stopping irrigation method showed reductions of 30.7% and 53.2% in water consumption compared to the conventional irrigation method, for the one and two day irrigation periods respectively.