Using of Climatic Water Balance to Assess The Reality of Groundwater Recharge in Baiji – Tikrit Sub Basin North West of Iraq

The Annual and monthly averages of rainfall and temperature of the tow tikrit and baiji meteorological stations showed that the general annual rainfall is (185) mm. The maximum rainfall is 35.5 mm in January and the minimum is (0.0) mm in august while the general monthly averages of temperature ranging between (8.7 C° in January - 36.5 C° in july ). After calculating the potential evapotranspiration values PE by thornthwait method then derive the values of water surplus WS in order to determined the amount of water that permeates to the groundwater level for each zone in the basin. After the main elements was selected depending by equations that has been developed for each zone as follows : 26 % of rainfall permeates to replenish the groundwater in the basin when the zone A lack o opportunity to allow infiltration of rainfall to the groundwater level for both A and B zones are based on monthly averages of whole surveillance period ( 1989 – 2009 ). The soil moisture amount (SM) is 25 mm for the zone A and 75 mm for each of A and B zones. When we search in the years that exceeds the general annual averages of rainfall ( 185 ) mm , founded that there are (9) years beyond the mentioned averages and account for about (43 %) of surveillance period where the general annual average equal to (242.39) mm and maximum monthly average of the rainfall is ( 41.86) mm in march and lowest average is (0.0) mm in july and august. Depending on these years mentioned, the water surplus for both zones C and B , showed that an increase about ( 29.93) mm from the average of annual rainfall equal to (242.39) mm and (12.34 %) from the rainfall permeates to fed the groundwater in B zone. 7 % adopted as a surface runoff from the rainfall equal to (16.96) mm and the ratio groundwater recharge in C zone is equal to (12.97 ) mm. The variation in groundwater values of recharge along the basin ( A,B and C ) is only a reflection for the type and texture of the deposits on the hand and varying depths, simple differences in topography and evolution of surface water drainage especially in the western part of C zone on the other hand . while the demonstrating convergence of inventories renewed values for the three zones although they have different area and water depths pervasive in all of them but the justification for this approach the increase in area of zones A , B and C, accompanied by decreasing values of deep water permeates for each zone must be noted here that the opportunity to renew stocks of ground water for both B and C amounting to 42 % of the prospect for renewed stocks of water in the zone A as well as the presence of large quantities of leaked water from the liquefaction and sewage water in zone A .