Water profile of Papua New Guinea
Geography and Population
Papua New Guinea lies to the north of Australia just south of the equator. Apart from the mainland, Papua New Guinea consists of a collection of islands, atolls, and coral reefs scattered around the coastline. The total land area of Papua New Guinea is 452,860 square kilometers (km2) and the country encompasses a large marine jurisdictional zone covering 2.3 million km2. For administrative purposes, the country is divided into 20 provinces. The capital city is Port Moresby.
The principal topographical features of the mainland, the Bismarck Archipelago and the north Solomon Islands are the highly dissected mountain ranges which reach 4,509 meters (m) on the mainland. In the western half of the mainland are the extensive lowland plains and swamps of the Sepik-Ramu and Fly rivers, lying respectively north and south of the main mountain ranges.
In 1997, the cultivable area of the country was estimated at 12,500,000 hectares (ha), or about 27 percent of the total area. Some 540,000 ha were reported to be cultivated in 1996, mainly with starch food crops such as taro, sweet potato, yam, cassava, banana, and sago. Export crops planted in extensive plantations and by subsistence farmers include coffee, cocoa, oil palm, coconut, and minor export crops such as tea, cardamon, vanilla, and rubber.
In 1996, the total population was estimated to be at 4.4 million inhabitants with a growth rate of 2.23 percent. The rural population represented 84 percent of the total. The population density was approximately 9 inhabitants/km2. According to the 1990 census, population densities were higher in pockets such as Simbu, Western Highlands province, and Eastern Highlands province with 31, 48, and 29 inhabitants/km2 respectively.
In 1996, the Gross Domestic Product (GDP) per caput was US$420. The agriculture sector contributed 40 percent of the GDP. In 1996, about 77 percent of the total economically active population was engaged in agriculture.
Climate and Water Resources
The climate is humid and rainy. Temperatures are not extreme for tropical climates and most areas, apart from the high altitudes, have a daily mean temperature of 27°C with little variation. Humidity in the lowland areas varies around 80 percent. Varied topography and location determine localized climates in the country. There are two principal wind directions, which strongly influence the rainfall patterns of the country. They are:
- southeast, from May to October;
- northwest, from December to March.
April and November are transition months.
However, high mountain barriers across the path of these winds induce heavy orographic convective rainfall on the northern and southern slopes in the highlands themselves. Thermal convective rainfall is characteristic of the Fly and Sepik lowlands.
The average rainfall varies from one location to another. On the mainland, the mean annual rainfall ranges from less than 2,000 millimeters (mm) along the coast to more than 8,000 mm in some mountain areas. The island groups to the north and the northeast receive an average rainfall between 3,000 and 7,000 mm/year. Areas lying southwest of Fly River, west of Lae in the Markham valley, receive less than 2,000 mm of rain per year. The Port Moresby coastal area receives the least rain with less than 1,000 mm/year.
River Basins and Water Resources
Geologically, Papua New Guinea is a young country. The presence of high mountain ranges and abundant rainfall leads to high runoff over most of the country.
There are nine hydrological drainage divisions (basins) in the country. The largest river basins of the country are the Sepik, Fly, Purari, and Markham. Even though the Sepik has the lowest annual discharge, it has the largest catchment area, 78,000 km2, followed by the Fly River with 61,000 km2, Purari with 33,670 km2, and Markham with 12,000 km2. The other catchments are less than 5,000 km2 in area and are very steep.
The internal renewable water resources are estimated at 801.0 cubic kilometers per year (km3/year). As the country has an abundance of surface water resources and as there are few large-scale consumers, groundwater resources have not been developed much. However, there is evidence that groundwater is being used increasingly as a source of reliable high quality water. In 1974, 34 percent of the villages surveyed relied on groundwater from boreholes, dug-wells, or springs. In the 1970s and 1980s, groundwater was developed for urban water supply schemes in seven major towns. The bacteriological and chemical quality of most of the groundwater in Papua New Guinea is good. Groundwater resources have not been assessed but it is assumed that most groundwater returns to the river systems and is therefore included in the surface water resources.
Lakes and Dams
There are around 5,383 freshwater lakes in the country. The lakes are mostly small, and only 22 have a surface area exceeding 1,000 ha. Lake Murray is the largest with a surface area of 64,700 ha.
In 1986, there were three dams in the country over 15 m high. The gross theoretical hydropower potential for Papua New Guinea is 175,000 gigawatt hours per year (GWh/year). In 1990, the total installed capacity was 163 megawatts (MW) and the annual generation was 438 GWh/year.
In 1987, the total water withdrawal was 0.1 km3. The main consumer was the agriculture sector with 49 percent, followed by the domestic (29 percent) and industrial sectors (22 percent) (Figure 1). In 1990, 94 percent of the urban population and 20 percent of the rural population had access to water supply.
Irrigation and Drainage Development
In Papua New Guinea, 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. In Papua New Guinea, 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 simple wood or stone barriers to slow down 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 in Papua New Guinea's 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 1986 FAO study identified a land area of 36,000 ha as agronomically suitable for irrigated rice production. A commercial company in the Markham-Ramu valley introduced limited supplementary irrigation early in its development for the purpose of establishing seed cane nurseries and initial wetting of plant cane to promote germination. However, the project was later abandoned for economic reasons.
Papua New Guinea is rich in natural resources including water. However, due to a lack of both human resources and political interest, and also to underlying financial constraints, it has not been able to achieve sustainable development in the water sector. The water sector in Papua New Guinea is fragmented and poorly coordinated. The Water Resources Act (1982) regulates the use of water.
The major government institutions involved in the water resources and irrigation sector are:
- the Department of Environment and Conservation (DEC), which is responsible for: the management and protection of the country's water resources; pollution control; and water related laws and regulations, and their enforcement. Its hydrological survey branch is responsible for monitoring surface water and rainfall stations. The DEC's activities have been severely curtailed by lack of funds;
- the Geological Survey of the Department of Mineral Resources (GSPNG), which is responsible for providing advice on groundwater exploration, assessment, management, and protection of resources;
- the Water Board, which is a statutory organization responsible for water supply and sewerage in 11 towns throughout the country, though not the capital city. The development and management of rural water supply and sanitation has been delegated to the Department of Health since 1987.
Trends in Water Resources Development
The fourth directive principle of Papua New Guinea's national constitution is to conserve its natural resources (including water), use them for the collective benefit and ensure that they be replenished for the benefit of future generations.
Papua New Guinea is a rural country, where up to 90 percent of the population is reported to depend mainly on subsistence or semi-subsistence agriculture. There is hardly any significant irrigation development program or proper irrigation policy. Although the country receives abundant rainfall, droughts do occur, the most recent one being in 1997, and can have a severe impact on the agriculture sector.
This experience has led the Government to seriously consider irrigation development as announced by the Minister for Agriculture and Livestock in a 1997 World Food Day message. According to this message:
- There is a need to develop small-scale village water supply, irrigation, and water management
- The Government and policy-makers need to examine irrigation development as a component of the strategy for increased food production.
- It is important to establish an irrigation development unit within the Department of Agriculture and Livestock and to develop a national irrigation policy.
Irrigation will be introduced for the first time in a pilot area, under the FAO's Special Programme for Food Security, where subsistence farming is the norm.
- Department of Environment and Conservation, Conservation Resources Center, and the Africa Center for Resources and Environment. 1995. Papua New Guinea country study on biological diversity, p. 437.
- FAO. 1975. Irrigation development in selected areas of Papua New Guinea, p. 15.
- FAO. 1986. Rice development policy, Papua New Guinea, p. 7.
- Hunter, J. 1985. Papua New Guinea handbook - business and travel guide, p. 280. Pacific Publications (Aust.) Pty. Ltd.
- Osborne, P.L. 1988. Bibliography of fresh ecology in Papua New Guinea. Biology Department Occasional Paper 9. Papua New Guinea.
- Petr, T. 1980. Purari river environment (Papua New Guinea), p. 57. A summary report of research and surveys during 1977-1979. Office of Environment and Conservation, Waigani and Department of Minerals and Energy, Konedobu, Papua New Guinea.
- World Bank. 1997. Papua New Guinea accelerating agriculture growth, an action plan, p. 92.Report No 16737-PNG.
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