Climate change impacts on New York City's water supply system

It has been well established that the greenhouse gas loading of the atmosph ere has been increasing since the mid 19th century. Consequently, shifts in the earth's radiative balance are expected with accompanying alterations t o the earth's climate. With these anticipated, and perhaps already observab le, changes in both global and regional climate, managers of regional water resources seek insight to the possible impacts climate change may have on their present and future water supplies. The types and degrees of impacts t hat climate change may have on New York City's water supply system were ass essed in a study of a watershed at Allaben, New York. Hypothetical scenario s of future climate and climate change projections from three General Circu lation Models (GCMs) were used in conjunction with the WatBal hydrological model and the Palmer Drought Severity Index (PDSI) to ascertain how runoff and soil moisture from this watershed may change in a warmer climate. For t he worst case predictions, the results indicate that within the century of the 2000s, the watershed's air temperature may increase up to about 11 degr ees F, while its precipitation and runoff may decrease by about 13 and 30 p ercent, respectively. If this watershed is typical of the others within the New York City water supply system, the system's managers should consider i mplementing mitigation and adaptation strategies in preparation for the wor st of these possible future conditions.