The hydrogeological investigation of karst springs located at the northeast of Erbil (northern part of Iraq)

The aim of this study is to investigate the hydrogeology of the Haudian, Mergasur-1, Kani Shakir, Khardin karstic springs. The study area lying throughout the mountainous region of northern Iraq, is located in Diana – Mergasur Sub-Basin. The age of geological formations ranges from Lower Cretaceous to Pliocene. The discharge rates of the karstic springs were measured periodically (twice a month during one year) using the specific volume method and other suitable flow values such as a current meter, rectangular/v-notch. Groundwater levels were monthly measured during one year for two wells (Haudian-2 and Shivazyarat) in the study area using an electrical sounder, which started in January 2021. The fractured-karstic limestones of Bekhme and Govanda formations are the aquifers for karstic springs. The investigated wells in the present study recharge from Bekhme and Shiranish Formation. According to the Jacob method calculation, no meaningful difference is determined in the average hydraulic conductivity (1.03*10-6 m/s) of marly limestone belong to Shiranish Formation and average hydraulic conductivity (1.15*10-6 m/s) of both marly limestones (belong to Shiranish Formation) and dolomitic limestones (belong to Bekhme Formation) in the study area. Maillet formula is used to calculate the recession coefficient and water storage capacity above the discharge level of karstic springs in their real regimes. The storage capacity (V0) of Haudian Spring above the discharge level in the real regime between 12.04.2021 and 16.10.2021 is calculated 461218 m3. According to the Iraqi Standard data, the average amount of drinking and domestic usage per person is 392 L/day. Around 1500 local residents utilize Haudian spring for drinking and domestic purposes. If just this spring alone is used for drinking and domestic purposes by a population of 1500, the period of this spring, in the real regime, was calculated as 785 days. The recession coefficients (α) for Haudian Spring were calculated as α1= 0,01 day -1 and α2= 0,0025 day -1. The real regime period of the Kani Shakir spring was between 12.04.2021 and 16.10.2021, and the water storage capacity of the spring (V0) was calculated as 13133 m3, two flow regimes are determined for Kani Shakir springs in the real regime. The first recession coefficient = 0,01 day-1, whereas the second recession coefficient = 0,005 day-1. The real regime period of the Khardin spring is between 29.03.2021 and 16.10.2021, and the water storage capacity of the spring (V0) is 44280 m3. The real regime period of the Mergasur-1 spring was between 12.04.2021 and 16.10.2021. The water storage capacity of the spring (V0) in the real regime was calculated as 50594 m3. The calculated recession coefficient for Khardin and Mergasur-1 springs in the real regimes was 0.012 day-1. In order to get better efficiency from the karstic springs in dry periods, it is necessary to protect the recharge areas, to license the wells to be drilled in the study area in a controlled manner and not to draw too much water from these wells.