A Methodology to Estimate Climate Effects on Monthly Stream Runoff

This report is includes the effect of projected climate change on water resources. We would like to answer questions such as:"If due to a doubling of carbon dioxide in the atmosphere the air temperature increases by 4 °C, what will happen to the water resources, specifically the streams and lakes of a specific region? How much of the volume of its lakes will be lost? What will happen to the surface runoff of the region? Will flooding increase or decrease? What will happen to the available stream flow of a region? Will it decrease or increase and to what extent? Answers to these questions are related to the hydrologic cycle. Therefore, looking at the world water budget may give a perspective, Table 1 shows that longterm global precipitation is equal to global evaporation. Any global temperature increase will cause more evaporation and consequently more precipitation. What is important, perhaps is the distribution of precipitation and evaporation. If so, on the global scale, there is no change, but locally significant changes may occur, e.g. more rain may fall on oceans, and drier summers may occur over the lands. To develop answers regarding hydrologic responses to climate change, we will use the water budget theory to study the dependence of all its variables on. atmospheric parameters, particularly on air temperature.National Agricultural Water Quality Laboratory, US Department of Agricultur