Integrated Water Management in an Ancestral Water Scheme in a Mountainous Area of Southern Spain

The snow pack of Sierra Nevada, Southern Spain, melts during spring and early summer feeding ancestral irrigation canals in the region called Alpujarra. This study compared the traditional supply, based on proportional division, with the actual supply, based on up-downstream priority, in a representative watershed in the Alpujarra. A combination of three models was used for the analysis. Snow melt and runoff were simulated using the Snow Runoff Model and satellite images to determine snow cover. A second model (based on a water balance with capacity constraints) simulated the distribution of water either following proportional supply or up-downstream priority. Crop irrigation requirements were simulated using the FAO approach. The equity inherent to the proportional supply did not diminish adequacy overall. Because of the reuse of return flows in the watershed, irrigation efficiency at the watershed scale was significantly greater than irrigation efficiency at the irrigation canal scale.