A wise irrigation to contribute to integrated water resource management

Abstract

Irrigated agriculture accounts for about 20% of cultivated lands worldwide while currently generating an estimated 40% of crop production, and two-thirds of future gains in crop production are expected to come from irrigated lands. Therefore, irrigation is strategic to ensure food for the world’s increasing population and slow down the pace of deforestation. Irrigated agriculture also accounts for more than 70% of global water withdrawals, and the way agriculture uses freshwater is crucial for ensuring availability for other activities and preserving water-related ecosystems. To give an agri-environmental interpretation of the water fluxes involved in irrigation, the total amount of water withdrawn from a source is called white water (W) and subdivided as follows: gold water (G) is the amount that is actually used by the crops. This fraction represents the ultimate goal of irrigation, which is to increase crop productivity and food availability. We can also consider this amount as the irrigation water for crops. The gold color means an income for the farm; emerald water (E) is the amount of water withdrawn for irrigation that does not reach the crops but provides ecosystem services, i.e., the benefits that people get from ecosystems. This amount of water is useful for the community and can be identified as irrigation of the territory; red water (R) is losses, i.e., the fraction of water that has to be reduced as much as possible if not eliminated. It is an economic, social and environmental cost; the red color is associated with the red traffic light that means STOP! The quantification of W has to be preceded by a careful evaluation of the benefits achievable with irrigation in relation to the environmental characteristics of the cultivation area. Strategic issues at this stage are the choice between full or deficit irrigation and the individuation of opportunities to exploration of opportunities to increase the availability of water resources by using non-conventional sources. The quantification of G and E fluxes is necessary to reduce losses, while strategies/techniques useful to reduce irrigation needs at the field level are key factors to allocate irrigation water within the framework of an integrated and sustainable management of water aimed at turning user conflicts into synergies. This implies multiple subjects and actors in a multi-disciplinary approach.