Pacific Water Safety Plans Programme
Tonga Water Safety Plans Country Reports
1. Scoping Mission Report
2. National Training and Planning Workshop
3. Tonga Water Supply System Description
4. Tonga Follow Up Mission I Report
5. Tonga Follow Up Mission 2 Report
Tonga Water Supply System Description
Nuku’alofa
Introduction
The importance of safe drinking water for health and development in the Pacific Island Countries (PICs) has been reflected in many regional action plans and policies. Through the Regional Action Plan on Sustainable Water Management (Sigatoka, Fiji, 2002) Pacific Island Countries outlined actions that were needed to achieve sustainable water management through collaborative efforts by water sector authorities and inter-sectoral partners.
The WHO workshop on Drinking Water Quality Standards and Monitoring in Pacific Island Countries (Nadi, Fiji, 2005) developed a Framework for Action on Drinking Water Quality and Health in Pacific Island Countries, designed to support the implementation of drinking water quality actions envisioned in the Regional Action Plan.
The Pacific Island Countries embraced the Water Safety Plan concept during the workshop and this was reflected in the Regional Framework. It was recommended that PICs should use Water Safety Plans to better manage their water supplies to ensure safe quality drinking water for Pacific communities.
The Government of Tonga, through various government and non-government agencies including Tonga Water Board, Ministry of Health, Ministry of Lands and Survey, NGOs and Community Groups, are committed to establish Water Safety Plans for urban, rural and outer-island water supplies.
A Steering Committee for the Tonga Water Safety Plan Programme has been established and consists of relevant agencies, both government and non-government. The Tonga Water Board is the secretariat for the Steering Committee as well as the lead implementing agency. (Refer to Figure: 1 below)
Other agencies such as the Ministry of Health, Ministry of Lands, Survey and Natural Resources, Department of Environment, National Planning Office, Tonga Association of Non Governmental Organization, Tonga Community Development Trust, Ministry of Finance and Ministry of Fisheries and Forestry have committed to support the programme.
Since there are a number of agencies involved in water supply in different roles it is vital to include them in the functional structure. The use of authority in their specific areas and organizational networking is also important for the water safety programme at country level. It was noted that Tonga Water Board is the water supplier and owned the infrastructure whereas the role of Ministry of Health is seen as the regulator. The Department of Environment is monitoring the natural resource and educating the public on sustainable development. The other Non-governmental Organizations such as Tonga Trust is working very closely with the community in raising the public awareness in aspects of health and environment.
Figure: 1- Functional Structure Water Safety Plans (WSP Tonga Mission Report 2006-SOPAC)
Background
The Kingdom of Tonga is a Polynesian country located in the South west Pacific between Fiji Western Samoa and New Zealand. It is a Monarchial state with defined borders of longitudes 117degree West and latitude 15-30 degree south. The kingdom is comprised of 176 islands of which 35 are inhabited. These islands fall into the four major island groups namely Tongatapu, Haapai, Vavau and the Niuas. (Refer to Map 1)
In 1996 Tonga had an estimated population of 100,000 dispersed throughout the six island groups. Of the total population 98 % had access to water supply in urban areas and only 63% had access in rural areas. As noted in the WHO Guidelines for Drinking Water Quality Volume 3, access to water supply is of paramount importance. The capital and seat of government is Nuku’alofa where most of the population of about 50,000 resides. Access to water can be defined by factors such as the population served, the reliability of the supply, and the cost of the water to the consumer.
Map: 1- Main Islands of Tonga
Climate and Geology
The climate is semi-tropical with moderate rainfall and high humidity during the wet seasons which extends from December to April. The mean temperature is 13.5 degree C and the mean humidity is 76.9. The mean annual rainfall is 1801 mm. in Nuku’alofa.
The Tonga ridge is a young volcanic island arc uplifted between the Tonga trench to the east and the Lau basin in the west. The ridge originated in the Tongatapu and is formed of mildly metamorphosed basic- intermediate lavanas, gabbros and tuffs. All the islands on the eastern side of the ridge are limestone covered. On the Tongatapu, oil drill holes penetrated through 137 m of reef limestone and alternating coarse and fine detritus sediments rich in volcanic litholastics to a total depth of 1685 m.
It is considered that a wide area of the Tonga platform is covered by thick sediments ranging from Lower Miocene to Lower Pliocene age and that these are at least 1500 m thick beneath Tongatapu. The area was probably dotted with intermittently active volcanoes, between which sediments are deposited in shallow to deep water environments. The sediments are mainly coarse to fine grained volcaniclastics, but reef, biostatic, and foraminifer’s limestone are also present.
Photo: 1 showing rocky coastal area of limestone in Tongatapu (Davendra Nath-SOPAC)
Ground Water Resource
There are no large surface water supplies in Tonga and the source of domestic, agricultural and industrial water is either roof catchment or hand dug or drilled wells tapping a lens of fresh water floating on denser sea water.
More than 50 dug or drilled wells from a few meters to 62.5 m deep are recorded in coral limestone in Tongatapu. The logs are all broadly similar and record hard and soft coral limestone beneath weathered superficial clay. The softer limestone, open textured and composed mainly of comminuted coral fragments, transmits water rapidly. It is estimated that 25 % to 30 % of the average rainfall penetrates to the water table, and that permeability may reach 1300 inches/day.
At the Mataki- Eua water reserve the surface of the fresh water lens is from 50cm to 75 cm above sea level. The lens does not occur at the coats and reaches a total thickness of about 20 m in the interior. Draught from the fresh water lens on Tongatapu amounts to about 300m3 /day (1978)
The main drinking water source in urban areas of Tonga is groundwater and for rural areas rainwater, with some utilization of surface river water. Due to the hardness and taste of the ground water Tongans supplement their drinking water supply with rainwater catchment system and purchase filtered ground water.
Photo: 2 Borehole overhead mechanical pumps (Davendra Nath-SOPAC)
On the majority of the islands, the ground water resource is located in the shallow and highly porous limestone aquifers Conjunctive use of ground water and rainwater resources is a preoccupation throughout the islands due to the omnipresence of saline intrusion into groundwater resources. For instance in the main island of Tongatapu, groundwater was noted to be as little as 0.6 meters above sea level. Consequently, the town of Nuku’alofa water supply is supplied by ground water from 31 boreholes in a borehole field to the south west of the town.
The rain water catchment system is predominantly based on corrugated iron roof which collect water in Ferro- cement tanks. The majority of tanks is equipped with an inspection hatch and soaks away facility; however none were noted as having the first flush systems. The rainwater tanks provide the annual principal source of drinking water. However 10% of Tonga’s population was recorded as living in thatched roof dwellings during the 1996 census. In these households rainwater catchment is not possible due to the low roof and the material used.
Responsibility for water supply, distribution operation and maintenance in urban areas and of village committee in rural areas is that of the Tonga Water Board. Monitoring of water quality is carried out by the board in urban areas and by the Ministry of Health in rural areas, though both monitoring and surveillance activities are generally poor. The urban area under Tonga Water Board includes Nuku’alofa the capital of Tongatapu, where ground water is the normal supply, together with the sale of rain water which is rarely inspected or monitored for quality. Consumption of water is high and a programme of installing water meters in urban areas is underway to help reduce abuse and monitor the water demand.
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