Groundwater is considered as an important source of water supply in Iraq, so it is need replenishing by any way of recharging. The most important way for recharging the groundwater is by rainwater harvesting. The part of rainfall which losses as surface runoff can be store during the monsoon in collecting reservoirs (such as ponds or tanks) and use it when required. This study deals with the way of harvesting rainwater that falls on the land for the replenishment the groundwater and use it in the dry seasons.
According to availability of recommended potential for successful artificial recharge projects, a site was selected in the Jolak basin north of Karkuk city, north of Iraq. The area is about 400 km2. Since the occurrence of rainfall in the north of Iraq is mostly limited to about five or six months in a year, so the recharge to ground water reservoir is restricted to this period only. The surplus rainwater is assumed to be collected in the several suggested collecting rectangular ponds to catch monsoon rains (storing a fraction of runoff). This water can then be diverted to the aquifer through recharge wells (which already exist in the study area) and replenish falling groundwater table by pumping the stored water. Ponds need to be lined to stop water from seeping out. Plastic lining has proved to be appropriate mainly because of low cost and reliability of the material , so it is suggested to be use in the lining of the ponds. Also the ponds are suggested to be cover during groundwater recharging in order to stop water from being lost into the air by evaporation. A computer software known as Groundwater Molding System (GMS) has been used in the present study to simulate the water conveyance from the collecting ponds to the underground reservoirs by wells. Results indicated that movement of surface water into the groundwater was predominantly an effective process. It can be shown also, that collecting ponds were a key driver of surface water into the subsurface along the study area.