5 - Assessment of the impacts of climate variability and change on the hydrology of Europe

Summary

INTRODUCTION

The droughts of 1988–92 and the floods of 1994 and 1995, both of which affected many parts of Europe, served as a reminder that climatic and hydrological variability still have significant economic and social impacts, despite decades of investment in a wide variety of water and river management schemes. Inevitably, the question of whether these ‘extreme’ events were signs of global warming has frequently been raised. It is, of course, too early to draw any definitive conclusions, but the recent floods and droughts have shown the sensitivity of water resources in Europe to change.

There have been several studies into the potential effects of climate change on hydrological characteristics in Europe, using unfortunately a wide range of scenarios and different methods of analysis. This chapter reviews many of these studies and summarizes some of the experiments that have been undertaken in Europe to explore the processes relating climatic variability to hydrological behaviour. First, however, it is necessary to summarize European hydrological regimes.

HYDROLOGICAL REGIMES IN EUROPE AND THEIR VARIABILITY OVER TIME

In the most general terms, hydrological regimes in Europe can be divided into two types: regimes dominated by rainfall, and regimes dominated by snowmelt. Rainfall-dominated regimes, with maxima in the winter and minima in late summer, occur in the west and south, whereas snow-dominated regimes, with maxima in spring and minima in summer or winter, are found in the north and east. In practice, of course, the picture is considerably more complicated than this (Krasovskaia et al., 1994).