Ceylon can be divided into a Dry Zone and a wet Zone by a line following approximately the 75 inch isohyet. The wet zone corresponds roughly to the southwest quadrant , which covers about 30 percent of the island's area. However this area contains more than three quarters of the total population of Ceylon. It will be noted from figure I that the population of Ceylon has risen very sharply from around 1945, and the density in the Wet Zone has in fact reached a figure of around 1,200 people per square mile. This situation has brought clearly into focus the necessity to develop agricultural production in the Dry Zone.
As Agriculture in the Dry Zone is almost entirely development upon irrigation, its development is virtually impossible without securing an assured water simply. To this end the Government initiated several investigations of the area. Among them were those of the United States Operations Mission (1958-61) and the Canadian Hunting Survey Corporation (1961-62), Which , together with the Irrigation and Survey Department of the Ministry of Land , Irrigation and power, examined the water resources of the Mahaweli Ganga and possibility of an irrigation and hydropower development scheme. Missions of the international bank for reconstruction and Development visited the area in 1961 and reported that the development proposed for a multi-purpose scheme to meet Ceylon's economic needs was promising.
Initiation of present project
In 1961 the government of Ceylon requested assistance from the special fund of the united nations to survey the Mahaweli Ganga Basin and the Dry Zone areas in the North and Central Provinces. The request was approved by the governing Council of the special fund in june, 1964. The plan of operation was drawn up and signed on 12 october, 1964 on behalf of the government of Ceylon, the united Nations Special fund and the food and agriculture organization of the united nations acting as executing agency. The co-operating government agency was the ministry of land, irrigation and power . the UNDP allocated US $ 1,146,000 to cover the cost specialist personnel, contractual services, fellowships and equipment. The government contribution in kind was estimated at US $ 837,000.
Purpose of the project
The project was designed to achieve the following objectives :-
• To provide basic information on the land and water resources of the Mahaweli Ganga Basin and the Dry Zone areas of the North Central Provinces;
• To provide an overall water management plan with a view to the effective use of water for irrigation and power generation;
• To provide technical plans , preliminary design of works , cost estimates, priorities, phasing and financing needed for implementation of the plan.
Execution of the project
The project became operational on 27 October,1964 and field work was concluded in May, 1968. This was followed by UNDP/FAO Mission to investigate and report upon Organizational and Management requirements, from 15 June to 25 July.
The survey was carried out over a period of three years in two stages the field investigations of the first stage, carried out between March, 1965 and February, 1967 comprised mainly a reconnaissance of the entire project area. The principal aim was to work out an outline for a Master Plan for full development of the water resources for irrigation and hydropower.
The second stage of the survey was carried out between February , 1967 and May , 1968. During this period , all the three phases of development for the entire scheme were identified. Additional investigations were made of the areas selected, for the three projects to be included in the first phase of development and detailed designs were prepared.
The effect of the project on the social and economic structure of the country was also considered and analyzed in some detail. For example problems of settlement, of maintenance and operation of the project works, and of the development of a sound agricultural programme based on the optimum use of irrigation facilities ware considered. In addition , cropping patterns and farming practices and methods for the improvement of existing cultivation were studied and workable cropping patterns were devised for the new areas.
THE PROJECT AREA AND ITS BASIC RESOURCES
The project area
The project area covers 39 present of the whole island and 55 percent of the Dry Zone. It includes the mahaweli Ganga basin, the basin of the Maduru Oya and rivers in the north central part of the island.
The area classified as suitable for irrigation extends to approximately 1.5 million acres , of which 900,000 acres would be commended by the proposed irrigation systems (of this 246,000 acres are at present partially irrigated). There remains therefore 600,000 acres of land of which 54,000 acres presently cultivated, but not commanded by the irrigation systems. Its envisaged that the balance of 546,000 acres will remain under forests of the new land to be developed for irrigation, which is 654,000 acres (900,000 – 246,000),360,000 acres area in the basins of the Mahaweli Ganga and Maduru Oya, and 294,000 acres are in the north central part.
The long term mean annual yield of the Mahaweli Ganga river at the lowers diversion weir (Kandakadu) is 6,400,000 acre-feet. By constructing reservoirs on the Mahaweli and its tributaries it is possible to obtain a regulated flow of 400,000 acre feet can be obtained as a result of the lateral inflow from intermediate catchments. Thus the total useful water resources of the Mahaweli and its tributaries are estimated at 4,700,000 acre feet per year. The yield of the rivers in the North Central Province, Maduru Oya and the smaller streams in the Mahaweli Basin, which has already been or would be stored and regulated amounts to 900,000 acre-ft. finally the overall potential of water resources of the project area is around 5,600,000 acre-feet per year.
Hydro-electric power potential
The total hydropower potential of the rivers of Ceylon is estimated at about 6,300 million kWh per year; of this about 3,800 million kWh can eventually be obtained from Mahaweli and its tributaries alone .