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Papua New Guinea
Irrigation and drainage
Evolution of irrigation development
Subsistence agriculture is the largest single economic activity. Most of the crops are rainfed and there is very little irrigation. There is evidence that simple flood irrigation techniques began in the highlands at least 450 years ago. The traditional methods of water application include:
- Simple flooding, where water is led to the upper edge of the garden and then circulates down, usually with wood or stone barriers to slow the flow. This acts to control erosion and trap sediments. In some cases, rough terraces are constructed directly in small stream beds. This is a highland practice found in Enga, Madang, Western Highlands, Eastern Highlands and Morobe provinces. Irrigated garden areas are generally small.
- The pondfield system, where the planted area is an artificial pond through which water is kept constantly flowing. The system is reported on the Mussau islands.
- Corrugated or furrow irrigation, where water is applied to the ground in small, shallow furrows so that it soaks laterally through the soil, wetting the area between the corrugations. This system is used in west New Britain and Bougainville.
A FAO study in 1986 identified a land area of 36 000 ha as agronomically suitable for irrigated rice production (Table 4). A commercial company in the Markham-Ramu valley introduced limited supplementary irrigation early in its development to establish seed cane nurseries and initial wetting of plant cane to promote germination. However, the project was later abandoned for economic reasons.