Low-cost irrigation project interests other developing countries.

Low-cost irrigation project interests other developing countries

DRIP irrigation is gaining popularity in dry areas of rural China, thanks to a series of innovations by Chinese engineers and scientists at the Beijing-based Institute of Water Conservancy and Hydroelectric Power. They have turned this normally expensive technique into the most economic and efficient irrigation method in the country.

The Chinese version has aroused the interest of water conservation engineers in other countries. The institute has received inquiries from corporations in Malaysia, Thailand, Peru and the United States, expressing their intention to buy the technique and necessary equipment. A Malaysian businessman, for example, has requested that China help him build a drip irrigation project for his 200-hectare cocoa plantation.

Drip irrigation requires a network of polyethylene pipes of different diametres laid on the cropland. Through emitters, these pipes deliver water directly to the subsurface soil around crop roots so that the soil maintains suitable moisture for crop growth.

China imported the drip irrigation technique from Mexico in 1974. At first, its application was limited because of the high cost of large quantities of pipe.

Cost-cutting innovations by Chinese engineers, however, quickly changed this. The cost of installing drip irrigation now comes to about 600 yuan (US $200) per hectare on cropland and about 1,800 yuan (US $600) in orchards. This is 80 to 90 per cent less than the costs outside China, according to Institute estimates.

Lower costs, less water

Compared with sprinkler irrigation and conventional surface irrigation, drip irrigation also saves 30 per cent on operating costs, so more Chinese farmers can afford it. At present, some 13,300 hectares of farmland are under drip irrigation.

The technique uses little water. It saves water by 70 to 80 per cent compared with surface irrigation, and by 40 per cent compared with sprinkler irrigation. In addition, Chinese farmers can use small streams, wells and ponds--an impossibility with other methods. Engineers say a well with a water flow of 10 cubic metres an hour can irrigate 6 to 7 hectares of farmland if the technique is applied.

The technique can be employed to irrigate wheat, cotton, corn, peanut, vegetables, sweet potatoes, trees and flower gardens. Drip-irrigated crops and fruit trees usually yield twice as much as unirrigated crops, Institute scientists say.

A case in point is the Dazhigou village in Zunhua county, 140 kilometres east of Beijing. Villagers began in 1982 to use a well with a water flow of only 6 cubic metres an hour to drip-irrigate 7 hectares of chestnut trees. The per hectare yield of chestnuts that year shot up to 1,425 kilogrammes, twice that of unirrigated chestnuts. The output continued to rise last year, to 3,630 kilogrammes per hectare.

"This low-cost, water-saving irrigation method will play an especially important role in agricultural and forestry production in Northern China where water is scarce,' says Dr. Qiu Weiduo, an engineer at the Institute.

Fewer pipes

Among the innovations Dr. Qiu and his colleagues have introduced is a new pressure-regulating technique which uses half as many main polyethylene pipes.

Another device cuts down the use of lateral pipes by 96 per cent. By making them movable manually instead of fixed in the field, they are spaced 30 metres apart instead of 1 metre, requiring much fewer pipes.

A new arrangement of microtube emitters also reduces use of lateral pipes. Emitters of an orchard network are laid in groups of 3 or 4 underground and radiate from the tree trunk, instead of on the ground and around the tree as is the usual arrangement abroad. This improvement cuts the amount of lateral pipes by two-thirds.

Also, Chinese emitters are different from those used abroad. They are actually microtubes with an inner diametre of less than 1 millimetre twining around lateral pipes. They cost 4 or 5 cents each, much less than their foreign counterparts.

Photo: Irrigation projects are crucial for ultimately improving the quality of life in the developing world.