Sustainable Water Management in Drylands

View as PDF File

Drylands are, by definition, regions of water scarcity. Though they occupy 40 percent of the earth’s surface and provide a home for a third of its people, drylands possess only an estimated 8 percent of the global renewable water supply, and only 88 percent of this is accessible for human use. Thus, per capita availability of water in drylands is just 1300 cubic meters per year, substantially below the global average and even lower than the amount (2000 cubic meters) regarded as the minimum required to meet human needs.

The implications for agriculture and rural livelihoods are obvious. Low and highly variable rainfall in drylands places strict limitations on agricultural productivity. In the semi-arid tropics, for example, erratic and torrential rain storms occur during the cropping season, followed by long dry spells. The storms result in the loss of nutrient-rich topsoil, worsening the effects of drought.

Improved water management is thus essential for improving agricultural productivity and ecosystem health in dry areas. There is much scope to use scarce rainfall more efficiently through better crop and soil management. In the West African Sahel, for example, natural vegetation in the zone that receives 450mm of rainfall annually uses only 15 percent of this precipitation. Most of the rest is lost to evaporation. Soil degradation makes the problem far worse by impeding the infiltration of water and causing much of it to be lost as runoff. In contrast, when soil fertility is improved, vegetation is able to use 50 percent more of the rainfall, and agricultural productivity can be increased by several orders of magnitude.

Achieving more efficient use of water in drylands, and thus boosting agricultural productivity while reducing risk, requires that scientists and development professionals work with rural people at different scales – from individual farm plots to entire landscapes – to develop better management practices.

Selected Highlights from Research for Dryland Development

Getting more crop per drop: The CGIAR’s Water and Food Challenge Program, which is coordinated by the International Water Management Institute (IWMI), provides a comprehensive framework for developing and promoting approaches likes those described above. It aims to strengthen food security and improve rural livelihoods without increasing water use in agriculture.

One promising approach to accomplish those ends is referred to as the Sahelian Eco Farm. Developed by the International Crop Research Institute for the Semi-Arid Tropics (ICRISAT) and its partners in Niger and now being further refined by the Water and Food Challenge Program, the Eco Farms blend traditional and introduced components, such as the use of hedges of leguminous shrubs to act as wind-breaks and improve soil fertility and the creation of half-moon shaped earth bunds to serve as micro-catchments for the collection of rainwater. In testing at 35 sites in northern Ghana and Burkina Faso, the Eco Farms are increasing water-use efficiency and soil fertility, mitigating the effects of drought, reducing soil erosion, providing better animal feed during the dry season, and diversifying farmers’ income sources.

Increasingly, the Water and Food Challenge Program is going beyond its focus on “more crop per drop” to consider how farmers and herders can intensify livestock production without exerting unmanageable demand on water resources. Livestock are often overlooked in water management programs. Yet, to produce livestock feed, like growing food for humans, requires 50 to 100 times more than what the animals actually drink. As a result, in regions such as the Nile River Basin, people and animals already compete for access to water. To avoid increased competition and conflict, the International Livestock Research Institute (ILRI) and various Challenge Program partners have embarked on a project aimed at identifying technologies and policies that reduce livestock pressure on water resources in the Nile Basin.

Water harvesting for olive production: One local innovation is enabling farmers in northwestern Syria to grow olive trees sustainably in an area normally considered too dry for this crop, with average rainfall at just 220 millimeters per year.

Traditionally, farmers in this area have used the lower slopes of degraded hills for extensive livestock grazing or barley cultivation. Some of them have managed to establish olive orchards, but their normal practice of plowing up and down the slopes to control weeds results in furrows, which worsen water runoff and erosion. Through participatory research, however, facilitated by scientists from the International Center for Agricultural Research in the Dry Areas (ICARDA), farmers have found that, if they manually form V-shaped earthen bunds, reinforced with stones, around individual trees, the furrows, rather than worsen runoff, actually serve to harvest scarce rainfall. They do so by channeling runoff into the micro-catchments formed by the bunds, where it is concentrated in basins around the trees. The research that led to this innovation is part of a widely applicable, integrated approach for achieving sustainable land management in dry areas.

More efficient use of groundwater: In northwestern India’s parched Rajasthan and Gujarat States, the rural poor depend on groundwater from wells for drinking and for cattle and crops. With increasing demand, though, groundwater levels have dropped, while concentrations of pollutants have risen. Using satellite images, scientists at IWMI have determined that small-scale water harvesting – that is, capturing rainwater – is effective for restoring local groundwater reserves. As a result of this practice, vegetation has increased significantly over large areas over the past several years – a change that is evident from the satellite images.