The Mahaweli River report, by Paul van Zandvoort
Characteristics
Length: 355 km (longest River in Sri Lanka)
Climate: equatorial and tropical
Precipitation: wet zone: +250 centimetres; dry zone 120 to 190 centimetres.
Problems
- Irrigation-induced salinity was reckoned as a pervasive threat to agricultural production and the environment in view of its adverse effects on sustainable use of land and water resources
- Ground water is the main source of drinking water in Sri Lanka. In certain areas the ground water contains salts causing hardness, bad colour and bad taste.
Important projects
1. The MAHAWELI GANGA development project - Generation of hydroelectric power
- Providing irrigation facilities for Dry Zone cultivation’s settlement
- Settlement of landless
- Helping unemployed families by constructing and developing a social infrastructure required for human habitation, by harnessing the waters of the Mahaweli Ganga.
(Note: largest multipurpose river basin development project ever undertaken by Sri Lanka.)
2. Development of large-scale irrigation projects - Diversion of rivers
- Construction of large reservoirs
- The irrigation of large landscapes
3. Subsidising - Households are encouraged to construct wells for water consumption
- Providing of pumps for areas where the groundwater lies deeper.
Conclusion
Sri Lanka is aware of their problems when it comes to water awareness and water used as a resource. To deal with these problems, several projects are created and executed to accommodate industry, nature and habitants. However some recommendations can be made: for better water management and environmental protection, continuous monitoring of soil and water salinity in the field and drainage area is important to prevent the build-up of salinity in the long run. Also preventive measures for soil salinity problem, appropriate to the soil condition, will help in minimizing the loss caused by soil salinity. These solutions for the salinity problem must be made financial and technological feasible.
Abstract
The Mahaweli is the longest river in Sri Lanka (335 km). It originates from the central highlands, proceeds through the Central, Uva, North-Central and Eastern Provincials, and discharges into the Ocean at Trincomalee on the East Coast.
The climate in the watershed is equatorial and tropical, influenced by elevation above sea level, but marked by only slight diurnal and seasonal variations. The annual precipitation in wet zone averages 250 centimetres; in dry zone precipitation varies from 120 to 190 centimetres.
The river basin of the Mahaweli River
The biggest project started in the Mahaweli basin is the Mahaweli Program. In this abstract there are given a few highlights, irrigation and drinking water supply. These subjects are chosen because the have to do with awareness for water.
Mahaweli Program
The MAHAWELI GANGA development project, the largest multipurpose river basin development project ever undertaken by Sri Lanka, involves production of 508 MW of power and development of 364 000 Ha. of land for irrigated agriculture and human settlement.
The major components of the program are;
1. Generation of hydroelectric power.
2. Providing irrigation facilities for Dry Zone cultivation’s settlement.
3. Settlement of landless.
4. Helping unemployed families by constructing and developing a social infrastructure required for human habitation, by harnessing the waters of the Mahaweli Ganga.
Irrigation
The project area has been divided into13 irrigation systems, with natural features forming the boundaries. Agricultural lands with high water tables are usually surrounded by hamlets. Irrigation-induced salinity was reckoned as a pervasive threat to agricultural production and the environment in view of its adverse effects on sustainable use of land and water resources. Excessive irrigation and inadequate drainage are the principal causes of salinity. They contribute to water logging and waste the water itself. Approximately 40% of the world’s irrigated area is affected by salinization. When the major irrigation projects where developed, it resulted in a differed composition of the water systems.
When a large-scale irrigation project is developed, this involves diversion of rivers, construction of large reservoirs and the irrigation of large landscapes, causing large changes in the natural water and salt balances of the entire hydrologic system.
This is all based on studies and experience, and some recommendations can be made: for better water management and environmental protection, Continuous monitoring of soil and water salinity in the field and drainage area is important to prevent the build-up of salinity in the long run.
Preventive measures for soil salinity problem, appropriate to the soil condition, will help in minimizing the loss caused by soil salinity. These solutions for the salinity problem has to be financial and technological feasible.
Drinking water
Ground water, which does not need treatment to be safe for consumption forms the source for household consumption.
Each household is encouraged to construct their wells by providing a subsidy. In places where the groundwater is much deeper, tube wells fitted with simple Indian made hand pumps have been provided.
Most of the wells desiccate during the driest spell in Augustus- September. In certain areas the ground water contains salts causing hardness, bad co lour and bad taste.
The town centre, which is the main centre of the Mahaweli settlements, has a population of around 10.000 on the average. When the water demand is high, the source of water is the Mahaweli River, with its widely fluctuating sediment and other problems.
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