The difficulties of deducing the possible effects of climate change on hydrological regimes stem from attempts to adapt the essentially large-scale climatic predictions derived from General Circulation Models to the smaller catchment scales appropriate to hydrological modelling; from errors in the climatic and hydrological data; and from converting climatic inputs into hydrological responses.
The climatic change predicted by current modelling may be expected to lead to:
1. A more vigorous world hydrological cycle.
2. More severe droughts and/or floods in some places and less severe ones in others.
3. An increase in precipitation intensities withpossibly more extreme rainfall events.
4. Greater hydrological effects of climate change in drier areas than in wetter ones.
5. An increase in overall potential evapotranspiration.
6. An increase in the variabilityof river discharges along with that of rainfall.
7. A shift of runoff peak times from spring to winter in continental and mountain areas if snowfall decreases.
8. The greatest falls in lake water levels in dry regions with high evaporation.
The implication that the hydrological impacts of climate change will be greatest in currently arid or semi-arid regions may well mean that the more severe runoff events there will be particularly destructive in terms of soil erosion.