Multiple Uses Of Water In Irrigated Areas

Water is being transferred out of agriculture to meet the growing demand in other areas, often without an agreement of or compensation to farmers with irrigated land and water rights. Furthermore, there is a failure to recognize that irrigation systems supply water not only for the main fields, but also for domestic uses, home gardens, trees and other permanent vegetation, and livestock. Other productive uses include fishing, harvesting of aquatic plants and animals, and a variety of other enterprises such as brick making. In addition, irrigation systems can have a positive or negative effect on wildlife habitats. Thus, the withdrawal of water affects the rural household, rural economy, and the environment in a number of ways. This paper argues that to ensure efficient, equitable, and sustainable water use, to reduce poverty and improve the well-being of the community, irrigation and water resources policies need to take into account all uses and users of water within the irrigation system. The multiple uses of water in the Kirindi Oya irrigation system are examined in this paper. An interdisciplinary group of scientists have investigated a number of areas including water accounting, water quality, household water use, the valuing of water for alternative uses, and the complementarities, competition, and conflicts among uses and users.

In many countries irrigated agriculture consumes a large proportion of the available water resources, often over 70% of the total. There is considerable pressure to release water for other uses and, as a sector, irrigated agriculture will have to increase the efficiency and productivity of its water use. This is particularly true for manually operated irrigation systems managed by government agencies, which provide water for a large number of users on small landholdings and represent 60% of the total irrigated area worldwide. --

Irrigated agriculture produces about 40% of all food and fibre on about 16% of all cropped land. As such, irrigated agriculture is a productive user of resources; both in terms of yield per cropped area and in yield per volume of water consumed. Many irrigation projects, however, use (divert or withdraw) much more water than consumed by the crop. The non-consumed fraction of the water may cause a variety of undesirable effects ranging from water-logging and salinity within the irrigated area to downstram water pollution. This book discusses all components of the water balance of an irrigated area; evapotranspiration (Ch.2), effective precipitation (Ch.3) and capillary rise from the groundwater table (Ch.4). Chapter 5 then combines all components into a water management strategy that balances actual evapotranspiration (and thus crop yield) with the groundwater balance of the irrigated area (for a substainable environment). Chapter 6 presents CRIWAR 3.0, a simulation program that combines all water balance components into a single simulation procedure. The chapter describes the use of the CRIWAR software for developing water requirement tables and other useful information based on the selected water management strategy. This version greatly expands upon the capabilities of previously published programs.

The Mapping Systems and Services for Multiple Uses of Water Services (MASSMUS) methodology is a special module that addresses multiple uses of water. It is part of Mapping Systems and Services for Canal Operation Techniques (MASSCOTE), developed by the Food and Agriculture Organization of the United Nations (FAO), it has been in use since 2000 for the auditing of medium to large irrigation systems, and for planning modernization of their operation and management.

The use of urban wastewater in agriculture is receiving renewed attention, with the increasing scarcity of fresh water resources in many arid and semi-arid regions of the world. Wastewater is a low-cost alternative to conventional irrigation water, although it may carry health and environmental risks. This book critically reviews experience worldwide of these issues. Emphasis is placed on untreated wastewater use by means of field-based case studies from Asia, Africa, the Middle East and Latin America. It brings together a range of perspectives including economic, health, agronomic, environmental, institutional, and policy dimensions.

"This publication expresses the rationale for multiple use of water services for large irrigation systems and demonstrates how managers can optimize, rather than simply tolerate, multiple uses. It also illustrates how consideration and appropriate management of multiple uses can benefit an irrigation system by improving performance and enhancing sustainability. The aim is to provide readers - irrigation managers and designers - with guidelines, steps to follow and leads that will allow them to perform multiple uses or services investigations in their own irrigation systems unearthing all services, the obvious and the hidden, and to document them using local data and surveys"--Publisher's description.

This publication contains background documents and papers presented at a workshop on integrated irrigation aquaculture (IIA), held in Mali in November 2003, as well as the findings of FAO expert missions on IIA in the West Africa region. The rationale for IIA development lies in its potential to increase productivity of scarce freshwater resources and to reduce pressure on natural resources, issues of particular important in the drought-prone countries of West Africa.