Reuse of drainage water from irrigated areas

Increasing competition for water of good quality and the expectation that at least half of the required increase in food production in the near-future decades must come from the world's irrigated land requires to produce more food by converting more of the diverted water into food. Reuse of the non-consumed fraction ('drainage water') of the irrigation water already diverted is a proven but risky option for better fresh water management. This paper presents an overview of different options for reuse of drainage water and guidelines for its safe use. Criteria for maximum irrigation water salinity to prevent soil deterioration and crop yield reduction, for the maximum concentration of toxic substances and limits for bacteriological water quality are given. Examples of sustainable reuse of drainage water in Egypt, India and the USA are presented. The usefullness of simulation models for the analysis of regional water and salt balances is demonstrated

Agricultural drainage: towards an integrated approach

Drainage needs to reclaim its rightful position as an indispensable element in the integrated management of land and water. An integrated approach to drainage can be developed by means of systematic mapping of the functions of natural resources systems (goods and services) and the values attributed to these functions by people. This mapping allows the exploration of the implications of particular drainage interventions. In that sense an analytical tool for understanding a drainage situation is proposed. The process dimension of the functions and values evaluation and assessment is participatory planning, modelled on co-management approaches to natural resources management. This provides a framework for discussion and negotiation of trade-offs related to the different functions and values related to drainage. In that sense the approach is a communication, planning and decision-making tool. The tool is called DRAINFRAME, which stands for Drainage Integrated Analytical Framework. The implementation of an integrated approach posits challenges for the governance, management and finance of drainage, as well as for research and design of drainage infrastructure and operation. Both have to be rethought from the perspective of multi-functionality. The paper concludes with five main policy messages