The importance of water cannot be overemphasized. Water covers 71% of the earth’s surface, and makes up more than two-thirds of the human body weight. According to the Food and Agriculture Organization of the United Nations (FAO), food and agriculture are the largest consumers of water; requiring one hundred times more water than we use for personal needs. An FAO report in 2003 highlighted that up to 70% of the water we take from rivers and groundwater goes into irrigation, about 10% is used in domestic applications and 20% in industry. The report further said that about 3600 km3 of freshwater is withdrawn for human use, of which only half is really consumed as a result of evaporation, incorporation into crops and transpiration from crops.
This increasing demand for scarce water supplies is stimulating competition between agricultural production and other municipal and environmental demands. As a result, there is need for effective indicators to measure water performance and support water allocation planning processes. Such indicators should be suitable for multiple use systems, particularly those with high re-use and non-depleting uses of water. Water productivity (defined as the ratio of net benefits from crop, forestry, fishery, livestock and mixed agricultural systems, to the amount of water required to produce those benefits) is an indicator which has gained prominence as a measure of water use performance. However, the water productivity (WP) approach is limiting in that it is well suited only to single-use systems where water use is directly attributable to well-defined benefits.
A newly published journal article by Randall Ritzema, a systems scientist at the International Livestock Research Institute (ILRI), recommends an alternative indicator that addresses some limitations of the WP approach and enhances productivity estimates for water in integrated systems. The ‘aqueous productivity’ (AP) method uses a systems approach to integrate consumptive and non-consumptive water uses, hence providing an improved productivity estimation of water. As an enhanced indicator, AP also aids communication across disciplines and stakeholders, and supports studies between system components, between management and policy alternatives and across systems.
In the article, Ritzema presents the AP conceptual framework and analytical methodology, and provides two examples of hydro-economic systems and compares this to equivalent WP analysis.