Climate change moves towards extremes, says scientist

By Dhaneshi YATAWARA

Heavy rains have caused flooding in wet zone including Colombo and suburbs. Higher rainfalls in Nuwara Eliya and Ratnapura areas could cause floods and landslides in those areas. The unusually dry weather in the Northcentral and Northern and northeastern parts of the island raised an impact on the agriculture specially paddy cultivation, making the farmer community helpless.

Extreme rainfall affects the urban squatters living close to marsh lands that are liable to flooding. High incidents of rainfall leads to infrastructure damages such as inundation of low lying road sections, the erosion of road sides, displacement of railway tracks and track bed material, creation of voids under railway sleepers and erosion of bridge piers and culverts. This is to name a few of the possible damages that can happen.

According to a study done by a Sri Lankan scientist impacts of the climate change is predicted up until 2050. The study done by Prof. Shanthi de Silva attached to the Agricultural Engineering Department of the Sri Lanka Open University predicts increasing rainfall for the wet zone and a significant drying up in the dry zone of Sri Lanka. It explains the unexpected high rainfall to wet zone areas and the extreme dry conditions experienced in the dry zone of the country.

“There wasn't much studies done in this area predicting future impacts. We were mostly analysing the past data but lacked knowledge on what is going to happen in future,” Prof. de Silva said, explaining about her study on climate change impacts on Sri Lanka.

Accordingly, the North-east monsoon rainfall that gives a significant amount of rainfall to the dry zone areas such as Trincomalee, Anuradhapura and Batticaloa, is going to decrease by 2050. On the other hand rainfall in the wet zone areas is predicted to increase. Both the decrease and the increase will have a serious impact on the country's infrastructure in coping with its consequences, said Prof. de Silva.

The temperature increases mainly in north, northeastern and northwestern regions

The average annual rainfall increase across the country

The increasing frequency and intensity of extreme weather events in future could bring about illness and deaths as well as injuries. Destruction of infrastructure and the displacement of affected persons and their physical and psychological trauma will need heavy attention and its going to be a lot of work for the responsible officials.

“The farmer community feels that rains get delayed whereas actually the rainfall has decreased in the dry zone,” she explained. Her study reveals that the current change in weather pattern in Sri Lanka can be explained through the predicted scenarios of the global phenomenon of climate change.

Scientists need a predicting tool which is technically known as a General Circulation model. This special system is developed in many ways by different institutes of the world and in her study Prof. de Silva used the model developed by the Hadley Centre for Climate Change in the United Kingdom named HadCM – precisely it is the Hadley Centre Coupled Model, version 3.

General circulation model is a model using atmospheric conditions like temperature, wind circulation etc.

When fed with these data the model automatically develop future estimations. “It was not available in Sri Lanka at the time I was doing my study but I got the chance to carry out my research while studying in Cranfield University on a Commonwealth scholarship,” she explained.

“The HadCM3 projections are available for only three time scales – i.e. 2020s, 2050s and the 2080s. And in this study the 2050 projections were used for predictions,” she explained. The study used all the data of Sri Lanka spreading over thirty years (1961 – 1990) and the ten years since 1999 – 2008 available with the Meteorological Department.

Based on a special report done by the Intergovernmental Panel on Climate Change (IPCC) the climate change effects are divided into several scenarios. One extreme end is named as A1. This considers a more integrated world where there is a rapid economic growth, a global population that reaches 9 billion by 2050 and then gradually decline thereafter and with quick spread of new and efficient technologies. It is a world where income and way of life converge between regions with an extensive social and cultural interactions across the globe. The other extreme end describes a more divided and ecologically friendly world. This includes a continuously increasing population but at a slower rate than in A2, world where there is an emphasis on local rather than global solutions to economic, social and environmental stability, intermediate levels of economic development and less rapid and more fragmented technological change.

According to IPCC the environmental consequences of the A2 scenario predicts that the population will reach 15.1 billion and the global annual mean temperature change will be by 3.09 degrees Celsius.

According to the study three areas with high risk for drying up is identified – i.e. Anuradhapura, Trincomalee and Batticaloa. “The actual rainfall decrease of these three areas have exceeded the predicted rainfall decrease according to the HadCM3 model,” she explained. According to the predictions there will be 7 percent decrease in the rainfall by the 2050 in Anuradhapura. “According to the data available for 1999 – 2008 the northeast monsoon has already decreased by 6 p.c.. And in Trincomalee it is predicted as a 32 p.c. decrease according to the A2 scenario as mentioned above. Yet according to the 1999-2008 data, the rainfall in Trincomalee has already decreased by 14 p.c.

The bright story is that overall as a country the average annual rainfall is predicted to increase by 14 p.c. The research also predicts temperature increases with concurrent decrease in rainfall in the dry zone. Possibly it would create drought problems which would affect agricultural activities. It was revealed in another Sri Lankan study done in 1996 that temperature increase in the wet zone areas of the country will have an impact on low country tea cultivation and rubber yields. According to Professor Shanthi de Silva's study predictions for 2050 indicates increasing temperatures mainly in the north, northeastern regions of the country.

The study done indicates, according to the A2 scenario, a possible increase of temperature by 1.6 degrees Celsius. And even under a milder conditions of the B2 scenario the predicted increase in temperature is around 1.2 degrees Celsius. As per scientific calculations the changes will also decrease the run off water too. According to Prof. de Silva the decrease in annual run off will have a serious impact on the storage of water in the existing village tanks ('wewas') and subsequently will affect agricultural activities in the dry zone. The climatic factor described as Potential Soil Moisture Deficit (PSMD) can predict the demand for irrigation water for a particular area. This is the difference between field capacity and the actual soil water content in the root zone. Soil Moisture Deficit (SMD) is the amount of water needed to bring the soil moisture content back to field capacity, which is the amount of water the soil can hold against gravity. It does sound very technical but this actually helps agriculturists and scientists to understand the demand for irrigation water in a particular area.

Dry Zone areas such as Jaffna, Batticaloa and Trincomalee could be demarcated as high stress zones because these regions will experience high drying up of soil due to the predicted decrease in the north-east monsoon rainfall and high irrigation water requirements. Prof. de Silva analysed Sri Lanka's dry and intermediate zones to understand the impact of climate change on dry zone agriculture. Accordingly areas with highest potential SMD are located in the Northern and Eastern parts of Sri Lanka notably in Jaffna, Mannar, Vavuniya, Trincomalee, Anuradhapura and Batticaloa – covering a major area of our dry zone.

“These corresponds to parts of the country where agricultural activities are intensive and where the availability or water resources are under severe pressure,” the Professor said. The areas with lower potential SMDs extend to Colombo, Galle, Ratnapura, Nuwara Eliya and has a comparatively low demand for irrigation. Climatic factors such as temperature, wind speed, radiation and humidity changes with the climatic change scenario. The higher the numbers higher the need for irrigation waters.

According to scientific studies, the ground water recharge across the country is predicted to increase 38 p.c. by 2050, according to the prediction methods. Soil recharges with water when the water seeps downward from surface water to groundwater.

Groundwater is recharged naturally by rain and snow melt and to a smaller extent by surface water (rivers and lakes). The major recharging period for aquifers in the dry and intermediate zones of Sri Lanka is from October to March due to the Maha season rains which is the second inter monsoon and the north east monsoon. Recharge can be estimated using numerical methods.

Although the figures show an increase for the country, certain dry zone areas' total potential recharge is predicted to decrease and it will affect agricultural activities which depend on groundwater. However substantial increases is predicted for Hambantota, Puttalam and Mannar that will be beneficial for groundwater based agricultural activities.

The wet zone areas of Kandy show the highest percentage increase 74 p.c. in potential groundwater recharge in A2 scenario in 2050. Potential recharge is predicted to increase in Nuwara Eliya, Ratnapura, Colombo and Galle by 23 p.c. (in A2 scenario).

In order to safeguard ourselves we are not late to take precautionary methods, according to the researcher. “We need to give attention to cultivate crops such as Maize and other drought resistance crops where irrigation water is not available. And should make farmers aware on how to cultivate paddy with less water,” she explained. In order to be ready to have enough clean fresh drinking water, which will be a problem according to the predictions, Prof. de Silva explained that adequate awareness and education must be given to people on proper way of collection, storage, maintenance and usage of water.

For the high stress areas – i.e., Anuradhapura, Batticaloa, Vavuniya and Trincomalee the 'wewas' (tanks) need to be renovated and remove silt in order to deepen it as mush as close to original depth of the tank. Prof. de Silva also suggests diverting water or augment reservoirs of Mahaweli Ganga project to provide more irrigation water for these areas. “It is best if we can adopt new trends in cultivation. For example cultivating varieties of paddy that gives harvest in three to three and a half months so that farmers will avoid the rainless period during Maha season.

And commence paddy cultivation in early October to avoid rainless period during critical stages of paddy.” she explained.

For low stress areas Jaffna, Puttalam and Mannar she suggests to increase the storage capacity of Giant Tank in Mannar and Iranamadu Tank in Jaffna to increase the volume of irrigation water, encourage other field crops and vegetable with drip and sprinkler irrigation systems and provide rainwater harvesting systems for domestic purposes and encourage runoff collection tanks for agricultural activities in highlands of the area.

“For beneficial area which is Hambantota, the researcher suggests to encourage two season paddy cultivation as rains are predicted to increase by considerable percentage. Farmers need to be encouraged to cultivate high yielding paddy varieties with good management practices to increase the paddy yield per hectare,” she explained.

“This study shows the possible effects of climate change in 2050s. Even though predictions are not always accurate, they cannot be ignored if we want to minimize the disasters,” Prof. de Silva said.