Because of the increasing concentration of greenhouse gases (GHG's) in the atmosphere, a GHG-forced climate change would supposedly manifest itself in the latter half of this century.

This paper focuses on the impacts of a GHG climate change on crop water use and irrigation requirements in Southern Quebec. For a selection of C4 (corn, sorghum, C3 ( barley, oats, wheat) leguminous (soybean, phaseolous beans), vegetable ( onions, tomatoes, cabbage), oleaginous (canola, sunflower)and other (potato, tobacco) crops, water requirements are determined for current and future climate conditions so as to gauge changes in irrigation requirements.

Crop water use is to be determined through evapotranspiration (ET) rates as determined by crop models (DSSAT) and irrigation requirements and applications using the AISSUM methodology.

Weather data (solar radiation, air temperature and humidity, precipitation, wind speed) for current (1961-90)and future (2035-65)time frames will be derived from two GCM ( HadCM3 and CGCM1) scenarios of GHG climate change.

Based on the preceeding results, adaptation recommendations relating to costs, water allocation and crop selection, are discussed.