If the inland areas of the northern hemisphere are expected to receive less moisture, then it follows that lake and river levels will be lower. Some reports predict the level of the Great Lakes will drop between 2 and 8 feet from historical levels.
River flows in the western US may be very vulnerable to increased temperatures expected as result of the greenhouse effect. A study by Stockton and Boggess, from the Army Coastal Engineering Research Center, looked at the greenhouse scenario of a 3.6 degree F temperature rise, coupled with only a 10% decrease in precipitation.[Geohydrological implications of climate change on water resource development, 1979] The study identified 7 areas in the western US, where river flows would be cut by 40 to 76 percent under the above scenario. A partial listing of results for the Missouri, Rio Grande, Lower Colorado rivers, as well as a composite figure for rivers in California, is given in the graph on the right. These results were obtained using empirical (derived from actual data) relationships found to exist between historic river flows, seasonal average temperatures, and seasonal average precipitation levels. Apparently, the historic relationships show that in relatively dry areas, river runoff is much more sensitive to temperature than to precipitation levels. ***
