Water Resources Adaptation Strategy in an Uncertain Environment Abstract Z. Kaczmarek and 1. Napiorkowski Institute of Environmental Protention Climate Protection Center Kolektorska 4, Warsaw, Poland Poland has an annual freshwater supply of only 1,500 m 3 per capita, resulting in a scarcity of water in much of the country. A recent impact analysis showed that, for some climate scenarios, the summer run-off from most of Poland's rivers, as well as the amount of soil moisture during the summer, may decrease. At the same time, irrigation water requirements may increase. This combination would increase water deficits in Central Poland. In the framework of the Country Studies Program, the Warta River basin was selected for analysis of possible adaptive measures to cope with adverse effects of climate change. Several alter- natives were investigated: (1) reducing economic activities in regions particu- larly scarce in water, (2) investing in water storage, (3) transferring water among river basins, and (4) establishing a policy aimed at more rational water use. Taking into account the highly uncertain climatic future, the "minimum regret" approach is advocated in formulating a national water-resources strategy, which means that alternative 4 merits priority. Large new investments should be un- dertaken only when absolutely necessary, that is, when other measures prove insufficient. Introduction During an average year, Poland's rainfall and snowfall yield about 197 km 3 of water. Of this amount, 142 km 3 returns to the atmosphere via evaporation, and 55 km 3 feeds the Baltic Sea through the river systems. The spatial distribution of surface run-off is presented in Figure 1. Variations in the run-off from 1951 to 1990 are shown in Figure 2, where the values range between a low of 34.4 km 3 in 1954 and a high of 79.5 km 3 in 1981. An additional 5 km 3 of flow enters Po- land from neighboring countries. The annual per capita freshwater supply is about 1,500 m 3 , the lowest value in Europe. Because of the inter- and intra- J. B. Smith et al. (eds.), Adapting to Climate Change © Springer-Verlag New York, Inc. 1996