News
Plans to catch our runaway rainfall
Despite the torrential rains that beat the country for weeks last month, triggering floods and landslides and driving thousands of people from their homes, many areas of the Northern Province and the dry zone are in the grip of a severe drought.
Up to 300,000 families are suffering hardship from drought in the districts of Jaffna, Vavuniya, Kilinochchi and Mannar in the Northern Province, and the Polonnaruwa, Anuradhapura and Kurunegala districts in the dry zone. People have to walk miles in search of drinking water.
There are 103 river basins in Sri Lanka the main among them being the Mahaweli, Kelani, Kalu, Walawe and Gin Ganga. It is estimated that more than 50 per cent of the water flows to the sea during heavy rains.
So where does all the water go, is the question The Sunday Times posed to the authorities concerned with water management in the country.
National Water Supply and Drainage Board (NWSDB) Chairman K.A. Ansar explained that rains are often heavy falls that wash off the ground surface into rivers without collecting in underground basins where it could be used by people who do not receive pipe-borne water – only half the population has pipe-borne water, with the rest depending on groundwater.
For this reason, he said, the board is building reservoirs for groundwater collection.
“We are planning to build 24 mega-projects to stock water in tanks and will have them completed in three years,” he said. The cost of building the tanks is estimated at Rs. 386 billion. The tanks will range in size up to 1000 acres with a capacity of up to one million cubic metres.
Fifteen such projects have been completed in the past two years, with the focus on dry zone areas such as Badulla, Vavuniya, Puttalam and Moneragala.
By 2020, when the building of the tanks is completed it is expected that 60 per cent of the country’s population will receive pipe-borne water.
Director of the Lanka Rainwater Harvesting Forum, Dr. Thanuja Ariyananda, concurred that a great deal of rainwater goes direct to the sea without being used, and she put the figure at 60 per cent of rainfall.
Due to climatic changes it rains in torrents with the ground unable to absorb the water, she said.
Dr. Ariyananda said in urban areas it was difficult to retain rainwater for storage in underground basins because most areas are covered by roads and buildings.
These prevent the rain from seeping into the water table to be used as a water bank that can be relied on in times of drought.
In Colombo, although the soil quality is good for groundwater collection, the numerous buildings and tarred roads are a hindrance. The cutting down of trees to clear land for construction exacerbates the problem.
In Sri Lanka, the wet zone receives 70 per cent of the country’s rains and the dry zone, 30 per cent. In Colombo, the groundwater level would be high because the area’s sandy soil retains water, but the rain washes off the hard surfaces of the buildings and tarred roads into the sea.
Dr. Ariyananda said it was important to collect as much rainwater as possible by channeling roof water into tanks placed underground or in backyards. Even small barrels could be used to collect rainwater for domestic use.
Farmers in Sri Lanka use excess water on paddy fields to control weeds and this is later drained off, a practice that uses up a great deal of water, Dr. Ariyananda said. “We get around 2000mm of rainfall and still cry out each year that there is not enough water for cultivation. In other countries such as China, famers used only a tenth of the water for the same extent of cultivation.
She said, that there was not enough public awareness about conserving water. Sanctions and rewards should be employed to avoid serious water shortages: these could include restricting the time spent in showers, using a dual mode of commode flushing, prohibiting the use of clean water for gardening and vehicle washing, giving incentives to urban citizens for rainwater harvesting, and motivating them to save water through the systematic monitoring of water consumption.
The Irrigation Department (ID) said it managed some 30,000 irrigation tanks including 400 major and medium-sized reservoirs.
After the recent rains, the reservoirs were 40 per cent full and about a quarter of this capacity was used up for the Yala season two months ago. With this the farmers have cultivated 60 per cent of the cultivable land in the Central, North Central, Eastern, Northern and Southern provinces, the department’s Director of Irrigation, Water Management and Training, W.B. Palugaswewa said.
Water is obtained from streams by farmers – with paddy needing a great deal of water – and is pumped away through drainage outlets.
The ID plans to build about 25 reservoirs for irrigation, including the Mundini Oya, Pahala Malwathu Oya, Kumbukkan Oya, Yan Oya and Hatto Oya but is facing severe opposition by residents in some areas. These people fear inundation of their homes and are demanding compensation and not allowing the upgrading of existing tanks.
“Apart from this, our major concern is the lack of funds to complete projects,” Mr. Palugaswewa said. The government has allocated only Rs. 9 billion in the 2018 Budget for agriculture and allocations have been meagre in previous years too, he said.
Plans are also afoot to divert the Kalu Ganga and the Gin Ganga to the Hambantota area.
Professor Siri Hettige of the University of Colombo’s Department of Sociology said the authorities should start thinking “out of the box” and blamed the scarcity of water in the dry zone on the failure to try innovative methods.
He recalled that in 2000 he had approached the NWS&DB about an initiative to harvest rainwater at the University of Colombo, only to be turned down because the NWS&DB said the proposal did not come under its purview.
“If only it had been carried out it would have served as a role model for other institutions to follow,” Prof. Hettige said.