The sustainable management of water in agriculture is becoming a key issue for policy makers. Globally, demand for water for human needs has been growing at more than twice the rate of the population increase during this century, and already a number of regions are chronically short of water. Over the last decades, most of the increase in the world’s food supply has come from the expansion of irrigated lands, which now account for around 20 per cent of the volume and about 40 per cent of the value of crop production on 17 per cent of agricultural land. The productivity of irrigated land is, globally, double that of rain-fed land. This expansion of irrigation — combined with increased use of high-yielding crop varieties, fertilisers and pesticides — has enabled growth in world food production to outpace demographic growth. It has also helped reduce the uncertainty associated with variable rainfall. Over two-thirds of the water used in agriculture arrives directly as rainfall, while the remaining third is supplied to farmland either via surface diversions or is pumped from underground reservoirs.
Globally, 70 per cent of the freshwater diverted for human purposes goes to agriculture. In some countries, there has been an excessive use or abstraction of water. Whether there will continue to be a sufficient quantity of water available in the future to meet not only the requirements of agriculture but also the needs of industries, households, and the environment is an emerging policy issue. Advances in irrigation technology, and the ability and willingness of agencies responsible for water supply and farmers to adopt water-conserving practices, and recognising the economic and environmental dimensions of this scarce resource will therefore be crucial. Agricultural land can play an important role in absorbing rainfall — thus helping to prevent flooding — and in recharging groundwater aquifers. But as water runs off from or percolates through farmland it picks up nutrients, pesticides and other elements that have been added to the soil. Whether and to what extent such pollution causes problems for the environment depends on a wide range of often site specific factors, some under the control of farmers, others (such as the weather) not.
The effect of agriculture on water quality is potentially greater in irrigated areas, since the intensification of production methods and the high rate of evapo-transpiration associated with irrigation practices tends to concentrate not only farm chemicals but also those elements that occur naturally in the source water itself. Governments are also under growing domestic pressure to address the environmental impacts of agricultural policies. Governments have often responded to perceived problems of water management in agriculture by spending money. Increasingly, public funds have also been used to encourage producers to adopt or maintain good farming practices, to help underwrite farmers’ costs of mitigating pollution, or of enhancing environmental protection. Examples include paying farmers to lower input use through changing production practices or to restore wetlands so that they again become attractive to wildlife, or through removing dikes.
Sustainable water resource management can contribute to the goals of economic and environmental efficiency, and to broader social goals. An important step towards achieving these goals is to make policies and programmes related to water management in agriculture more transparent, and to undertake regular monitoring and evaluation of policies, and cost-benefit assessments of projects. Continue to reform agricultural policies in ways that contribute to reduce distortions in agricultural production and the use of water resources, improve the quality of water, and enhance environmental benefits associated with water use in agriculture. Improve the information available to policy makers, including clarifying the extent and nature of environmental impacts. Improve the information on the agri-environmental processes involved in the linkages between agriculture, water and environment. Establish mechanisms to enable the introduction or strengthening of pricing, charging and allocation methods for users and beneficiaries of water (including farmers). Where a payment is deemed necessary to help farmers adjust to higher prices for water resulting from the implementation of reforms, such as the adoption of greater water cost recovery, or the adoption by farmers of water conserving methods, it should be in the form of income support not linked to commodity production or past crop yield, be transparent, and provided only as long as necessary to meet clearly stated objectives. Ensure that all stakeholders are involved in the design of policies, and the planning and management of water resources.
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