Conclusions

It is clear that for Walawe Basin in Sri Lanka climate change will have an impact on water resources and therefore on food security and environmental quality. Precipitation will be higher, temperatures will increase, evapotranspiration demands will be higher and potential crop growth will rise due to elevated CO2 levels. The overall impact of these factors is that long-term average yields and production will increase, but at the same time extremes will occur more frequently.

Socio-economic issues in Walawe Basin are expected to undergo major changes. The current agriculture-oriented society is likely to change to a more industrialized and service-oriented one, having impacts on water resources, food and the environment. On top of this will be the impact of climate change and changes in climate variability. In this research a comprehensive framework was developed to evaluate adaptation strategies for alleviating impacts by climate change. The framework uses current data, identifies relevant water resources issues, quantifies future trends, generates climate change projections and integrates model results to support water managers in strategic decision-making.

Overall, the threat on water resources issues in the basin as a result of these internal and external factors appears to be small. The expected increase in water required for industry, urban and service-oriented activities of about 100 X 106 m3 is about 10% of the overall water consumption by irrigated agriculture. Crop production will increase as a result of the small increase in precipitation, but mainly as a result of the positive impact of enhanced CO2 levels on plant growth. The major concern is the increased variation in climate. The basin has experienced some consecutive dry years over the last decade, and according to our analysis this will happen again in the future. Policy should therefore be directed to this and some possible options are mentioned in this document. A summary of these options is presented in the effect table (Table 10.2), and more details can be extracted from Figs 10.6 and 10.7. Obviously, more extensive details can be obtained by using the modelling framework as developed under this study.

The analysis framework strongly emphasizes the main issues related to water-food-environment in the context of Walawe Basin: rice production and irrigation. The physically based field-scale SWAP model provides detailed soil-water-plant processes, and the basin-scale WSBM assesses water allocation. The coupling of the two models ensures linkages between food production and the environment.

This study could be considered an implementation of the Initial National Communication (INC) as initiated by the Ministry of Forestry and Environment under the United Nations Framework Convention on Climate Change (UNFCCC). The INC provides the general structure and is the first step towards climate change policy in Sri Lanka.

Outstanding issues are adaptation options related to rainfall harvesting, rainfall-runoff processes, and, most importantly, hydropower generation. Indirectly, it has been shown that more water will become available in the future, but at the same time the variation will be greater, putting more pressure on the vulnerable energy situation in the country.

Another important factor is the dominant influence of CO2 on potential crop production. Although the complex interactions between crop production and enhanced CO2 levels are still not fully understood, the literature and experiments provide sufficient proof that yields could increase substantially.

Finally, the presentation of the output of this study is attractive for policy makers and water resources managers. More options can be assessed by looking at the detailed output, or by using the framework presented in this study for analysing other adaptation strategies.

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