Water Resource Management in Sri Lanka

WATER RESOURCE MANAGEMENT

Introduction

Water is the blood of our life. Simply water is everything. Every living being is created and live because of water. Water is an essential element to exist life.71% of the surface of our planet is covered with water. And also water can be found in air, soil, glacier, etc. Human life is heavily bonded with water. We have to deal with water for everything we do. The natural water circle is very helpful to distribute water around the earth and to balance the water level of soil and air. Natural water circle is the continuous movement of water around the earth and air. This is somewhat water management freely done by the mother of nature. As technology develops and human activities become more and more complex we need to plan, develop, protect, manage valuable water recourses. It is very important and essential.  This is called water resource management.

How much water do we have on the earth?

Water is the most valuable thing that humans have. Water can be found on everywhere because 72% of the surface of the earth is covered with water. However, we cannot consume all of them.97% of that water is salty water which cannot be used. Only 3% of them can be used for human activities. Only 1% of them are easily accessible.

Water can be found in

1. ·         Oceans, Seas
2. ·         Ice caps, glacier, snow
3. ·         Groundwater
4. ·         Moisture
5. ·         Lakes
6. ·         Atmosphere
7. ·         Swamps
8. ·         Rivers

What is water resource management?

Water is a very valuable limited source. Therefore, we have to manage it wisely. Planning, Developing and distributing the water throughout the country are main tasks of water resource management. And protecting and preventing water pollution is also a very important task to be done. The main purpose of water resource management is to satisfy the demand over time. It is very important to develop water resources and irrigation systems to face future expectations and to overcome future natural disasters like droughts.

 Water resources in Sri Lanka

Sri Lanka is an island located in The Indian subcontinent, north to the equator giving it monsoonal and tropical climate. Sri Lanka always exposed to the wind with high moisture that coming from the southwest and the north-east. Sri Lanka is feed with good annual rainfall. Sri Lanka has various water resources.

Ex:

• ·         River basins (Covering 90% of the island)
• ·         Rainfall
• ·         Lakes
• ·         Tanks
• ·         Dams
• ·         Groundwater

Sri Lanka has good natural water distribution system (Rivers) that carries surface water from higher lands to all over the lower lands covering dry zones and supplying water for human activities. For example, Mahaweli river starts from Samanala Kannda and flows to dry zone carrying a huge amount of water and meets the sea at Trincomalee.

Here are some river basins in Sri Lanka with their catchment area:

Name of Basin	Catchment area (sq. Km.)
Kalani Ganga	2278
Kaluganga	2688
Bentota Ganga	6622
Walawe Ganga	2442
Nilwala Ganga	960
Kirindi Oya	1165
Gal Oya	1792
Maduru Oya	1541
Mahaweli Ganga	10327
Malvatu Oya	3246

Historical profile of water resource management in Sri Lanka

Sri Lanka is a well-known country for its marvellous hydraulic engineering technologies and irrigation technologies dating from about 300 BCE. We had an unbelievable water resource management technology. The best example is Jaya Ganga which is constructed to one inch per mile slope. Sri Lanka has relied on water resources from the beginning of civilization. Our kings tried to make our country prosperous with agricultural development. Sri Lankan people’s life was heavily depended on connection with nature and water. They created tremendous water tanks and lakes to preserve water for use in dry session and they built an unbelievable irrigation system to distribute water across their kingdoms. The king Pandukhabhaya who ruled from 437 to 367 BC was the first king to build the first tank in Sri Lanka. He built Abhaya Weva, Gamini Weva, and Jaya Weva in his era. Thereafter the king Parakramabahu 1 built a number of tanks including the largest tank Parakrama Samudraya which is still supplying water for agricultural fields.

Sri Lanka has such a great history that no other country has. Here are some miracle works are done by ancient Sri Lankans:

• Parakrama Samudra
•  Kala Wawa
• Yodha Ala (Jaya Ganga)
• Sigiriya

Irrigation technology of ancient Sri Lanka

Ancient social structure in Sri Lanka was heavily bonded with agriculture. It is very difficult to cultivate in hill country but is it is very easy to cultivate in low lands like Anuradhpura and Polonnaruwa but the dry climate in those areas was the main problem. The annual rainfall in dry zone was very low. However, it is essential to have constant water supply throughout the season for paddy cultivation (Yala and Maha). Therefore, people built large tanks to store water and well-structured irrigation system at village level. King Pandukhabhaya started building the first tank known as Bassawakkulama Wawa and later kings constructed more and more tanks and small lakes and developed the irrigation system among those water systems.

The development of irrigation technology was come up with the civilization and impact of Buddhist teachings. The well-known quote “Gamai Pansalai Wawai Dagabai” inspired people to build a Sthoopa using good soil coming out by excavating the tank. Then they could have Temple and a complete village to live.

The main two eras which large irrigation systems were constructed was Anuradhapura and Polonnaruwa eras. Here are some constructions done in those eras.

Anuradhapura era

•  Kala Wawa – by King Dathusena (459-477)
• Jaya Ganga (Yoda ala)
• Tissa Wewa
• Nuwara Wewa
• Nachchaduwa Wewa

Polonnaruwa era

• Parakrama Samudraya
• Giritale Wewa

Parakrama Samudraya connected with three tanks and they are Thopa Wewa, Dumbutulu Wewa, and Erabadu Wewa.

King Wasabha constructed a canal from Elahera to Kantale including diversion structure at Elahera across Amban Ganga which is a part of Mahaweli Ganga. This canal is connected with Minneriya, Girithale and Kanthale reservoirs. And also, it had irrigated lots of small tanks for examples:

 lhakulu Wewa, RotaWewa, Matalu Wewa, and Konduru Wewa.

King Mahasena known as “Minneri Deviyo” (275 – 301) constructed Minneriya Wewa that has two spillways.

Techniques used in ancient irrigation

We can recognize unbelievable techniques used in ancient irrigation systems. They have all the water resource management techniques including protecting and preventing water pollution. One tank supplies water to paddy fields for cultivation there after water flow out from paddy fields is directed to another water tank. Like that the system was well organized to get the maximum use of water.

A tank or lake has some important components to manage its water body.

• Catchment forest (Mukalana)

Forest cover before the tank is the catchment area of the tank. It was highly protected by people. The role of the Mukalana is to increase the ground water level. And also, Mukalana was a nice place to find medicine plants when needed.

• Tree belt (Gasgommana)

This is the upper area of a tank where well-grown tree belt is situated, this act as a water filter as well as a barrier.

• Check dams (Potawetiya) and soil ridges (Iswetiya)

These dams help to reduce the velocity of water flow coming to the tank from upper catchment area. And also, it helps to store the excess water and to release gradually.

• Biso Kotuwa

Biso Kotuwa is an amazing engineering product of ancient Sri lankans.Biso Kotuwa is placed in the lowest side of a lake. It is generally made of stones. Its main purpose is to prevent overflowing situations in a lake and it also helps to stop gathering silt in the lake. They have used very high engineering technology to reduce the water pressure of water body that pouring into the Biso Kotuwa and finally flows out from it in very slow calm speed.

• Spill-gate (Sorrowwa)

 Sorrowwa is the most important part of a lake. It must have built in very high quality to sustain high pressure as it is the place where the highest water pressure is applied. Ancient people have decided the correct place for spill gate without any technical instruments. And Sorrowwa helps to maintain the water level of the tank and to distribute water for agricultural fields. In some tanks, there is an extra spill gate to remove silt.

There are lots of ancient contractions built using high engineering technologies and  amazing water management systems for examples

• Sigiriya water garden
•  Kuttam Pokuna

Current water management projects in Sri Lanka

Sri Lanka is not only an agricultural country anymore. We have developed and mostly today’s society is depending on a commercial market more than an agricultural market. And society has become more and more complex. As a developing country, we need more advance water resource management systems.

Currently, government build water reservoirs and dams mainly targeting power generating rather than for agricultural purposes. Therefore, the irrigation systems and water management techniques used for these are different and advance.

Mahaveli development project was the largest development project in Sri Lanka. It was finished in 1986 spending 38.26 billion rupees. The main purpose of this project was to generate hydroelectric power. And also, flood controlling, water supplying for agricultural lands in dry zone were other expected purposes.

Purpose of Dam	Dam
Hydroelectricity	Bowatenna,Broadlands,Canyon,Castlereigh,Deduru Oya,Gal Oya,Kotmale,Kukule Ganga,Laxapana,Maskeliya,Moragahakanda,Norton,Nilambe,Polgolla,Randenigala,Rantembe,Samanala,Udawalawe,Upper Kotmale,Victoria
Irrigation	Ingimitiya,Kulu Gaga,Kandalama,Kantale,Lunugamwehera,Maduru oya,Rajanganaya,Rambakan Oya,Ratkinda,Ulhitiya

There are different technologies use for build dams. They are,

1. ·         Gravity dams
2. ·         Arch -gravity dams
3. ·         Embankment Dams
4. ·         Arch Dams

Sri Lanka, we can see all of the above types of dams. It depends on the condition of the soil where the dam is located and the amount of water it holds. Each and every dam in Sri Lanka use a different kind of engineering techniques for its mechanisms and for irrigation systems.

Roles of a Dam

In ancient time people built dams to store water for irrigation and for water supply. But with the development of humankind, there was greater requirements like flood control, navigation, electric generation, sedimentation control. Dam’s major role is to manage water flowing in a river basin and fulfil those requirements. According to the purpose of the dam, we can categorize them in to groups.

1. Hydroelectricity dams
2. Irrigation dams
3. Water supply dam
4.  Flood control
5. Navigation water ways

Hydroelectricity dams

The main purpose of this kind of dams is to generate electrical power using the potential energy of the water. Electricity generated using hydroelectricity dams is the largest renewable energy source in the world. Typical hydroelectricity dam can produce several hundreds of kilowatts or several hundreds of megawatts. Hydroelectricity is generated using turbines.

Irrigation dams

Irrigation dams are built to supply water for agricultural purposes. These dams release continuous water supply for agricultural fields.

Dams in Sri Lanka

Victoria Dam

Victoria Dam is double curvature arch dam which is located in Theldeniya area. It is the tallest dam in Sri Lanka and its main purpose is to generates hydroelectricity and irrigation. Victoria power station generate 210MW and it is connected to the main power network of Sri Lanka. And also, it is the largest hydroelectric power station in the country. This project was started in 1978 and completed in April 1985.

Victoria dam 122m high with the crest length of 520m. Crest width 6m and base width of 25m.And it has a storage capacity of 722,000,000 m3 with a catchment area of 1,869 km².Victoria dam has 12.5m wide and 6.5m tall eight spill gates that automatically opens without consuming power when the water level is high. Those spill gates can discharge water body of 8,200 m3/s.

The power house of Victoria dam has three 70MW power generators which produce 210MW (780GWh) electricity.

Gal Oya Dam (Senanayaka Samudraya)

Gal oya dam known as Senanayake Samudraya is the largest reservoirs in Sri Lanka. It is an embankment dam which is located in Uva province. The main purpose of the dam is irrigation. But it also powers up a small hydroelectric power station. This project started in August 1949 and completed in 1953.

This special dam was built by Morrison Knudsen company using 1,500,00 m³ of soil in between 1,100 m apart two hills at Inginiyagala. Gal Oya dam has a total storage capacity of 950,000,000 m³ and it spreads over 91 km² Area.

Gal Oya dam has small power station at Inginiyagala. It consists of two 2.475 MW and two 3.15 MW turbine units.

Water-related problems in Sri Lanka

Floods and droughts are the extreme water-related problem in Sri Lanka. Sri Lanka has faced many such extreme weather situation in recent history affecting 50% or more of people in the country.

Serious floods have happened in the Kelani, Kalu and Mahaveli river basins. Most of the time the main reason was human activities. When intense rainfall and high wind speed may result in extreme flood situations even in the dry zone. There was such a situation in 1957 in Yan Oya basin.

Floods

Floods can be happened due to different reasons. They can be categorized as below.

1. River-Line floods
2. Flash floods
3. Localized floods
4.  Floods due to reservoir operations
5.  Floods due to reservoir breach

River line floods are the most common once. It is caused by overflowing of a river. Flash floods are as the name implies, quick once. These kinds of floods happen mostly in mountainous/hilly areas. This happens due to rushing water flows from hills to lowland. Flash floods can be very destructive and damage to the property. Localized floods are well known as urban floods or drainage congestion, this is kind of man-made flood. Floods due to reservoir operations happens usually in high rainfall situations. When the water level of the dam is high spill gates starts to open and release excess water from the dam. These water flow can result in a flood in the area below the dam. Floods due to reservoir breaching are the most dangerous flood type. Fortunately, there are no any report about such cases in Sri Lanka. This can be happed due to various reasons like extreme rainfall and flood situation, a fault in the structure of dam, lack of correct maintenance.

There are few areas in Sri Lanka where 100% flood free. The following chart shows the flood events in Sri Lanka.

Current utilization of water resources

Hydroelectric power

Hydroelectric power is the cheapest method among power generating methods uses in Sri Lanka. And also, it was the first public electricity supplying method. In 1895 a UK company named Messrs Bousteds introduced hydroelectricity to our country. In 1950, the first hydro-project was completed. It is known as Laxapana power scheme. It has gravity dam which is 35m high and 105m long. And from the dam, there is a 2560m long 2.7m diameter tunnel to carry the water to power the station at old Laxapana. Stage 2 of this project completed in 1958. The Wimaladasa power station was built in this stage.

The Maskeli Oya project was commenced in 1966 and was finished in 1969. In this project Maussakelle Dam and reservoir was constructed across Maskeli oya. It is 35m high 188m wide concreate dam. This reservoir holds 109,000,000 m³ of water

Polgolla Barrage was constructed under the first stage of Mahaveli development project and. It was built to turn Mahaveli Ganga to Amban Ganga generating 38MW at Ukuwela power station. The 8 km long tunnel was built to carry water from Polgolla to Ukuwela. In next stage, Bowatenna reservoir was constructed which has two tunnels, one for irrigation and other for power generation. The irrigation tunnel connected to three tanks Dambulu Oya, Kandalama Wewa, and Huruluwewa. Power tunnel carries water to Bowatenna power station.

Kotmale, Victoria and RAndenigala are major power stations in Sri Lanka. Those were constructed under “Accelerated Mahaweli Development Project (AMDP)” 

Name of Project	Installed Capacity (MW)
Old Laxapana	50
Wimalasurendra [Northon Bridge]	50
Polpitiya	75
New Laxapana	100
Canyon	60
Victoria	210
Kotmale	134
Randenigala	122
Rantambe	49
Samanalawewa	240

Irrigation

The position of Sri Lanka in the world and its monsoonal pattern is the main reason of development of irrigated agriculture. There are different kind of irrigation systems that suitable for different areas in Sri Lanka. For example, there are flood irrigations, Furrow irrigations, Sprinkler irrigations. The most commonly used type of irrigation in Sri Lanka is flood type irrigations. In dry zone, there are flood type irrigated paddy fields. In the dry zone, rain fall is enough in north-east monsoonal period. But during south-west monsoon (Known as Yala Kannaya) it is essential to have irrigation water. Paddy is the main plant in the dry zone which needs irrigation water. Furrow irrigation is used to grow crops such as chillies, onions, soya beans, cowpea. Sprinkler irrigation systems are hardly found in Sri Lanka.

Systems of Irrigation

• Flood irrigation
• Furrow irrigation
• Sprinkler irrigation
• Drip irrigation

In flood irrigation method water is made to flood the land of cultivation. In this method, water should be everywhere in the land and cover the entire surface of the soil. The best example for this method is paddy fields. Water enters the highest paddy field and slowly flow to lower levels before being drained into channels.

In Furrow irrigation water is flowing through furrows between the rows of plants. When water flowing through the furrows water is absorbed to the soil. Furrow irrigation method usually use for dry food crops.  However, this method needs higher labour cost for maintenance.

Sprinkler irrigations are the permanent installation. There are lines between every plant and water is delivered above the crops or soil surface trough sprinkler heads connected to water lines. Properly installed sprinkler systems have a number of advantages.

Drip irrigation system also another piped water supply method. In this method, water drips near the plant root. Even though it is a costly method using this method we can minimize the water consumption. In Sri Lanka, this method is used only in two or three places. Agricultural research station at Eluwankulam uses this kind of irrigation method.

Irrigation works in Sri Lanka

Irrigation works in Sri Lanka can be categorized according to their scale of covering-area. These groups are

·         Village works

·         Medium works

·         Major works

Village works are the area less than 80 ha and medium works are the area over 80ha and less than 600ha. Major works are those which has an area above 600 ha.

Efficiency of water use in irrigation

Efficiency can be described according to their application of irrigation method. Including timing, the design of the system. The water supply for irrigation must be managed by understanding the relationship between the supply and distribution. The method of irrigation, Climate, Soil properties, Crops cultivated are the main areas to draw the attention. Fertilizers, diseases and pest control is essential for proper management in water resources

Problems associated with irrigated agriculture

In old days’ crops cultivate only once a year and also insects, pest and other various chemicals could not reach a harmful level. As the result of the competitive market, farmers tend to do fast and easy method rather than correct method. Because of chemical fertilizers, a large number of chemical compounds and heavy metals were applied to soil and water.

These kinds of agricultural activities pollute waterways very badly. And it finally results in serious health problems.

Several suggestions have been made to overcome these waters related problems due to pollution. Some fertilizers were prohibited to import. But most important thing is the knowledge of the farmers and society. 

Industrial water supply

Industrial development in Sri Lanka increased in recent past. Industrial water supply is a major problem due to the large amount of water requirement and water pollution. Many of industries which require a large amount of water are located close to water resources like rives. However, discharge of those factories without any water management results in huge water pollution. Here are   some industrial complexes that use surface water resources

1.  Tyre Corporation – Kalaniya
2. Steel Corporation – Oruwla
3. Leather Corporation – Mattakkuliya
4. Pugoda Textiles – Alawwa
5. Plywoods coporation
6.  Ruhunu cement
7. Associated motor ways and tyres - Kaluthara

Government has specified several laws and regulations about disposal standards in environment act to stop water pollution

Public water supply

Piped born water supply is a very important service in any country. Currently, all urban areas of Sri Lanka are covered and some rural areas also have covered. National water supply and drainage board have already established a number of water schemes for urban and rural areas. The government has made a planes to supply drinking water to all people in Sri Lanka with the assistance of UNDP. 

Policy level recommendations and avenues for further development

As water is a limited natural resource. It is essential to protect water resource for our existence. We need to develop and manage water resources according to future requirements and risks. The further development must be carried out by understanding priorities and evaluating current projects.

• Water Laws

National Policy on Watershed Management, National Land Use Policy, National Forest Policy are some laws previous governments has made to conserve water resources. But still, there are areas to cover in law to stop polluting water. The government must take strict decision to make new laws to protect water resources and to stop harmful activities done by people.

•  Legislation

There are many legislations in Sri Lanka to preserve water resources. New legislations must be carried out to prevent harmful chemical disposal and to prohibit importing fertilizers with harmful heavy metals.

• Water waste quality and pollution control

We should be more responsible about water waste and water pollution. The government must implement new methods to water waste management and pollution control. This can be done in the small sector or in house wise. And also, factories which use water resources must be strictly monitored.

• Empowering the institutions related to conservation of water recourses

Private and non-profitable institutions can do large service to protect water resources. Government and others who understand the situation can empower institutions related to water conservation to start their campaigns.

• Improve the awareness of people

It very important task to be done. People must understand the value of water and the risk they have made for future. Government and social service institutes must encourage the community participation on the protecting water resources. First of all, it is essential to educate the community to understand the value of water. For that, we can conduct awareness programs in locally and in school level. And encourage private sector participant to protect our water recourses.

• Research

We must develop our technologies by researching. This can be done in universities and other technical institutions. It is very important to find new methods to preserve and manage water resources rather stay stuck on old methods 

• New technologies

The government must introduce new technologies to water resource management. There are a lot of new successful technologies that other countries use to manage and protect their water resources. We must go with new technologies to protect our valuable water resource in Sri Lanka

Finally

From the beginning of our nation, our economy and society depend on our mother Sri Lanka’s water resources. Sri Lanka is a prosperous country which is rich in water resources. And there is a rich diversity of ecosystem with wonderful nature. Waterfalls, Wetlands, Rainforests and much more. Sri Lanka is one of the word’s most beautiful country which has wonderful biodiversity. We have given everything by mother nature. But do we respect her? Do we protect what she gave to us?

It is time to think and change this is our country and this is our life. Therefore, it is our utmost responsibility to save our valuable water resources for future generations.

END.