Water stress occurs when the demand for water exceeds the available amount during a certain period or when poor quality restricts its use. Water stress causes deterioration of fresh water resources in terms of quantity (aquifer over-exploitation, dry rivers, etc.) . Climate change, such as altered weather-patterns (including droughts or floods), deforestation, increased pollution, green house gases, and wasteful use of water can cause insufficient supply. ... All causes of water scarcity are related to human interference with the water cycle. Plants experience water stress either when the water supply to their roots becomes , or when the transpiration rate becomes intense. Water stress is primarily caused by a water deficit, such as a drought or high soil salinity.