Module 9 - Investments in Shallow Tubewells for Small-Scale Irrigation

Shallow groundwater supplies provide a basis for small tubewells providing both domestic and irrigation water. Water supplies for garden areas and small fields are pumped using human or animal power, but mechanized pumps are becoming common in all parts of the world. Small engines constitute about two-thirds of shallow tubewell costs, but they can be used for other purposes such as powering boats, hand tractors, and other farm machinery. Shallow tubewells contribute to diversification of cropping systems and improve economic and social conditions. Problems arise, however, if tubewells overexploit the groundwater supply or contribute to salinization of groundwater. Evaluation of groundwater supply and quality, regulation of tubewell establishment, and technical support to farmers are essential for sustainable tubewell systems to contribute to poverty reduction.

Tubewells are a cost-effective source of irrigation water for many small-scale farmers, where groundwater is close to the surface (less than 20 meters deep) and soils are productive. These wells can irrigate up to 5 hectares, depending on the soil, crop, and water conveyance losses. The technology is not complicated, and acceptance by farmers and poor rural communities is rapid. Tubewells can be one of the better investments for poverty reduction, and they are already common in many parts of the world, particularly in Asia and Africa.

Shallow tubewell irrigation generally results in some form of crop diversification for home or local consumption or for export. Niger, for example, has developed a good export market for green beans shipped by air to Europe, with much of the production related to shallow tubewells. Conjunctive use of tubewell water (mostly shallow) to supplement inadequate supplies of surface water or water that is not available when needed to optimize crop production, is also common in many countries, particularly in Pakistan and India (box 9.18).

Investments

Shallow tubewells can be drilled by hand with simple soil auger-type tools, by power rotary drilling, or with a drilling method called jetting or washboarding. The wells represent a relatively inexpensive way of supplying water for drinking and irrigation. In Bangladesh, wells are typically hand drilled even to depths of 60 meters and cased with galvanized iron or plastic pipe that is slotted to allow water to enter while keeping the aquifer material out of the well. Wells are normally equipped with centrifugal surface-mounted pumps with 5 to 10 horsepower diesel engines. Each well can provide enough water to irrigate about 4 or 5 hectares.