there can also be important economic externalities which result in use costs eg subsidence and salination as well as damages to nonuse values such as the lifesupport function of water figure cl in middle east and north africa mena countries the estimated economic cost foregone extractive uses of full groundwater depletion is in the range of to of gdp see below between and global economic losses were estimated at usd billion per year for floods and usd billion per year for droughts oecd damage from floods in the united states is now estimated to be usd billion each year brody et al