In order to meet this deficit, ESCWA member countries can manage their existing water resources more efficiently through demand side management tools or by increasing their supply of freshwater through the development of conventional and non-conventional water resources. A combination of both water supply and demand side options is often pursued in order to fill the gap in the water balance. The renewable amount of freshwater is the volume of water that is replenished on a yearly basis, and of both surface water and groundwater that is recharged. Non-renewable sources of water include non-renewable groundwater (fossil aquifers) and groundwater that is withdrawn at rates faster than recharge (overdraft).