This final report of the Working Group of UNESCO's IHPIV project H-2.1 provides an overview of ongoing activities in the ‘trans-science’ domain that is the concern of hydrologists, water resource engineers, climatologists and meteorologists. The members of the first two communities need inputs from the latter two, but climate change and variability is in turn determined by changes in hydrological conditions. The interaction between climate and hydrological conditions is also affected, either directly or indirectly, by other factors such as population pressure and changes in land use.

This chapter presents the final conclusions of the Working Group, and their recommendations for research and measures in the future. It is hoped that the implementation of these recommendations will help to improve the practical utility of the results of large-scale modelling at the catchment scale for water resource managers and policy makers.

CONCLUSIONS

The conclusions of the Working Group are discussed under the following headings:

1. (a) the use of paleoclimate scenarios;

2. (b) the use of GCM scenarios;

3. (c) hydrological models and climate change;

4. (d) the uncertainties associated with GCMs and hydrological models;

5. (e) field experiments to improve GCMs;

6. (f) climate change and water resources management; and

7. (g) the outcomes of the IPCC process.

The use of paleoclimate scenarios

Paleoclimate scenarios are used to provide analogues of changes in climate that have actually occurred in the past, even though the causal factors may not be known and therefore can not be easily incorporated into GCMs.