"There were some small effects on stream flow in rural areas, but nowhere near what we see in urban areas," says De Walle. "In general, there is some decrease in stream flow with increase in temperature in urban areas, but in the Northeast, this does not seem terribly important."
Increases in stream flow boost the potential for flooding and in the Northeast at least, the areas of most increase -- the most developed -- are those areas that stand to lose the most in property and human life if flooding occurs.
"If the greenhouse effect causes global warming, everyone is pretty confident that temperatures will increase, but how much precipitation will change is hotly debated," says De Walle. "We are interested in the effects of precipitation because it is the least reliable of the two variables in the climate models."
The global climate models can provide regional predictions, so De Walle will dedicate the final year of this two-year project, funded by the U.S. Environmental Protection Agency, to the other three regions and to comparing how climate change will effect stream flow in all four regions.