Main question

Food security to sustain the growing world population is one of the key challenges for mankind. According to a recent FAO study about 800 million people in the developing world do not have enough to eat.

Climate change will gradually change temperatures and precipitation but, more importantly, is expected to increase extremes as well. Especially these extremes are very difficult to cope with in the context of food production. For the Walawe Basin in Southern Sri Lanka, a framework based on modeling at different scales was developed to evaluate the impact of climate change on future water resources, food production and the environment, and to explore adaptation strategies. The framework was developed to assist water managers and policy makers in their responsibilities to make sound decisions.


Climate projections from the Hadley General Circulation Model HadCM3 were used to assess impact and to analyze adaptation strategies for the basin. Projections based on the most recent IPCC SRES A2 emission scenario projections have been used. Special emphasis was put on downscaling of the HadCM3 projections to local conditions using an absolute adjustment for temperature and relative for precipitation. The field scale model SWAP (Soil-Water-Atmosphere-Plant) and the basin scale model WSBM (Water-Salinity-Basin-Model) were setup for Walawe Basin to analyze and understand current water resources issues, to analyze the impact of climate change and, most importantly, to evaluate adaptation strategies.

Result and conclusions

Climate change will have an impact on water resources in the Walawe Basin and therefore on food security and environmental quality. The HadCM3 projections show a clear trend that precipitation and temperatures will increase, and variation will increase as well. This change in variation is not only a gradual change, but includes more consecutive years of extremes.

Figure 1. Number of years with low yields, defined as a year where total rice production is lower than the 5 years moving average.

Potential crop growth will rise due to elevated CO2 levels, but also temperature and potential evapotranspiration. Total impact of these factors, combined with the somewhat higher precipitation, is that long term average yields and production will increase, but at the same time extremes will occur more frequently.

Overall, the impact of climate change on Walawe will have more positive than negative aspects. However, some aspects have not been fully included in our analysis. It is likely that increased temperatures have a negative impact on the number of pests and diseases and thus on yields. The expected rise in sea level might induce salt water intrusion, which will also have a negative impact on yields. Finally, these analyses are so far based on one GCM and one climate change scenario. Further analysis should reveal whether other projections will show the same trends.

As indicated earlier the adaptation strategy that will be selected is a decision by policy makers, but the results from the approach presented here is a tool to evaluate the consequences of a certain adaptation strategy selected.

Figure 2. Example of results from the integrated framework as applied for the Walawe Basin in Sri Lanka presented in a policy maker oriented way. Results show what the impact and adaptation options are for food quantity (upper left), food security (lower left), environmental quantity (upper right), and environmental security (lower right). Presented results are for the HadCM3 A2 forcing for the period 2010-2039.

To ensure food security it might be wise to increase the cropped area by 10 to 20% and keep the irrigation applications at the 100% levels. Since irrigation levels are in reality somewhat higher at the moment than 100%, this means a small reduction in irrigation depths. Although this will decrease the reliability in yields, total production will benefit from this.

Please feel free to contact the Project Leader of this project for more information.