Assessment of temperature and precipitation trends in Kashan Namak lake basin during the last half-century

Temperature and precipitation are basic constituent components of the climate of a region. For this reason، the assessment of present and future trends of these elements have been considered by different scientists such as natural resources or environmental experts. In this study، Namak lake basin was divided in to six sub-basins and then monthly precipitation and temperature data were collected and reconstructed from 1956 to 2005. Average precipitation، maximum and minimum temperatures of sextuple sub-basins of the lake were calculated using Thiessen method in Arch Map software. In order to evaluate the precipitation trend، Standard Precipitation Index (SPI) was used. The trend of climatic factors (temperature and precipitation) was studied by linear regression and Mann-Kendall test. No significant trend was observed in standardized precipitation of the Namak Lake and in its sub-basins except in the sub-basin of Arak in which the trend of precipitation change was decreasing and significant. According to the study of monthly precipitation، strong droughts have been observed in sub-basins of Arak، Roodshoor and Karaj during the last 50 years. The trends of maximum and minimum temperature change were increasing and significant in most basins. Increasing the temperature of the Namak lake basin may be caused by several factors، including increasing greenhouse gases especially in big cities such as Tehran، Qom، Arak، Kashan، Hamadan، and Qazvin.