Jafar Naji - Assistant professor at PWIT

Water resources includes surface and subsurface or underground Waters. The underground water exists in a geological structures named aquifers. ' These aquifers can be alluvial and/or karst ones; Underground water of an aquifer mostly runs offshore into oceans, seas and l&. Such cases in Iran includes Persian Gulf Caspian and Oman Seas and interior leak such as Oromia. Running off coastal UG fresh water causes sometime inconvenient conditions to the valley and/or shortages in it's water demand and supply or at least losses of good h s h water without use into salt water. Therefore, measurements were taken to prevent such losses of fiesh water into offshore. Among such measurements or methods is to construct dams in underground to prevent water run off h m coastal aquifer into ofhhore. Materials needed, techniques and application to construct such dams are to be indicated . Experiences done in some countries of the world , which were done successfully would be briefly mentioned.