Water Needs of Cotton Plants under Climate Change in Syria During the Period 1970-2020

This research aims to study the reality of changes in the climatic water balance and its impact on the water needs of cotton plants in Syria during the period from 1970 to 2020. It evaluates drought in the study area using the NDMI (Normalized Difference Moisture Index) based on 20 cloud-free Landsat satellite images with a spatial resolution of 30m over the study area during the studied period (1970-2020). Additionally, the research analyzes climatic water balance elements such as precipitation and potential evapotranspiration (PET) at annual, seasonal, and monthly levels, while identifying the general trend throughout the study period. It also aims to determine the changes in actual evapotranspiration (AET), which reflects the actual water needs for cotton plants in the main cultivation areas in Syria (Hama, Aleppo, Raqqa, Deir Al-Zor) during the growing season and at each of its four growth stages, within the context of current climate changes. Simple linear regression models were used to identify the trend for precipitation, potential evapotranspiration (PET), actual evapotranspiration (AET), and the climatic water balance. The results indicated a statistically significant general trend (P < 0.05) for both potential and actual evapotranspiration during the studied period, while showing a statistically significant decreasing trend for precipitation (P < 0.05) at the selected climate stations, along with the existence of a climatic water deficit in the cotton-growing regions of Syria throughout the studied period.