Water productivity: A basic tool for sustainable irrigation

Abstract

The rapid population, economic and standard of living growth with the global climate changes is increasing the per capita demand on water. This increase in water demand is resulting in less available fresh water supply for agriculture. To sustain irrigated agriculture, better water management is necessary at all levels. Water supply in the Middle East and North Africa region (MENA) is unequally distributed in space and time. This region has among the lowest per capita water supply in the world. On the other hand, the intensive extraction and use of water without proper planning and provisions for the protection of their water resource has led to serious water pollution. Agriculture consumes 70-80% of water in this region. This leads to a fundamental problem for water-short countries that should manage between their renewable water resources and their capacity for food production. Water-short countries do import food commodities, which has imbedded water called "virtual water". The aim of this paper is to present a model with the general objective to maximize water productivity (monitory units per cubic meter of water). The mathematical model resulted in a maximum water productivity of 6.92 $/m3 with eight crops out of 43 crops grown on site. The remaining 35 crops induced a saving 3,408 m3/ha, which equals the virtual water. Three sets of scenarios were tested. First a decrease in available water from 100% to 50% showed a decrease in the objective function value from 6.92 to 4.727 $/m3, second a decrease in on farm crop prices by 10, 20 and 40% caused decreases in the objective function value by 4.8%, 9.66% and 20.29% respectively, while an increase in prices increased the objective function value and third an imposition of certain crops in the project area decreased water productivity.