Modernizing water distribution networks Lessons from the Bembezar MD irrigation district, Spain

In many arid and semi-arid countries, traditional irrigation schemes have been modernized, with open channel networks replaced by new on-demand pressurized systems. In this study, this conversion is evaluated using performance indicators derived both before and after the modernization of an irrigation district (Bembezar MD) in Andalusia, southern Spain. The analysis shows a reduction of approximately 40% in water diverted for irrigation due to a more efficient distribution system. However, this has led to changes in crop rotation, with higher-value and more water-demanding crops being introduced. As a consequence, crop evapotranspiration has increased considerably (21%). Modernization has also led to a dramatic increase (fourfold) in management, operation and maintenance costs. Much of this cost is due to the high energy dependency of the new pumped system (0.15 kWh/m(3)). Such costs were negligible prior to modernization due to the scheme being gravity-fed. The implications for modernizing such traditional schemes are highlighted.