| The off-line version of the Goddard Institute for Space Studies (GISS) land-surface hydrological model over-predicted run-off from the karstic Rio Cobre watershed in Jamaica. To assess possible climate change impacts on runoff from the watershed, the model's simulation of observed runoff was improved by adding to it a karst component that has pipe flow features. The improved model was tested on two other karstic watersheds (Yangtze - China and Rio Grande - USA) and the results were encouraging. The impacts that possible climate change may have on the three karstic watersheds were then assessed. The assessment indicates that in a doubled carbon dioxide climate, the Rio Cobre and the Rio Grande may experience decreases in runoff, especially in low flow periods. The Yangtze, on the other hand, may not experience decreases in total runoff, but its peak flow which now occurs in July may be attenuated and shifted to September.; The results of the study also show that climate feedbacks convolute climate change assessments and that different results can be obtained from the same climate change scenario depending on the choice of the modeling methodology--that is, on whether the models are coupled or uncoupled. |
