jalal Behzadi - Department of Agriculture and Natural Resources, Lahijan Branch, Islamic Azad University, P.O. ۱۶۱۶, Lahijan, Iran

Climate has always been changing during the lifetime of the earth, and has appeared in the form of the ice age, hurricanes, severe and sudden temperature changes, precipitation and other climatic elements, and has dramatically influenced the environment, and in some cases has caused severe changes and even destructions. Some of the most important aspects of climate changes can be found in precipitation types of different regions in the world and especially Guilan, which is influenced by drastic land conversions and greenhouse gases. Also, agriculture division, industrial activities and unnecessary land conversions are thought to have a huge influence on climate change. Climate change is a result of an abnormality of meteorological parameters. Generally, the element of precipitation is somehow included in most theories about climate change. In the present study, climate change and precipitation abnormalities and their impacts on water balance in Guilan Province have been studied. The stations possessing climate change were determined and ranked. The GIS software was used to present the distribution and severity of climate changes in the province as a map. In the next step, the water balance of five stations was estimated using the Thornthwaite method. To do so, the mean data of thirty years, precipitation elements, temperature, and evaporation were used first, and the second time, the estimation was done using the data of the critical year (climate change in the drought trend). The charts related to the mean and critical years were compared. The highest and most severe climate change in drought trend was observed in Lahijan, and therefore this station was introduced as the sample of climate change. These results can be used in planning and identifying the effects of these changes on the environment.in the study station rankings have been determined based on the significance level in drought trend. The intensity of climate change in drought trend is observable in this ranking.

Climate Change, GIS, Guilan, Water balance