Investigation of hydrogeology and hydrogeochemistry of the Çubuk Plain (Ankara)

In this thesis, it is aimed to establish the management plans of the groundwater resources of the basin with detailed hydrogeological, hydrogeochemical studies on the current and prospective groundwater potential, quality and quality of the Çubuk Basin and to reveal the sustainability of the groundwater reserve and quality. For this purpose, current and future use of groundwater, operating reserve in period recession, storage volume and recession coefficients and the effects of climate changes on springs have been revealed by discharge rate and groundwater level measurements. At the same time, chemical composition, physical properties, relationship with lithology, origin, feeding area and altitude of groundwater were determined by hydrogeochemical and isotope studies. The geology of the study area generally consists of Permo-Triassic, Keçikaya Formation limestones, Middle Eocene aged volcanic units, Miocene aged sedimentary and volcanic units, Pliocene and Quaternary aged units. The discharge of springs fed from Pliocene aged units (K-1, K-3, K-4, K-5, K-6, K-24 and K-25) are between 0.008 and 2.22 l/sn in 2019 discharge measurements made in springs using the specific volume method. It has been determined that the operating reserve volume of these springs in the period recession is higher than the springs fed from other lithological units. The recession coefficients of the springs examined by the Maillet method were calculated and it was determined that the groundwaters moved in laminar flow in Pliocene aged units and turbulent flow in Permo-Triassic and Miocene aged units. These springs can be used to renew their basins and provide potable water with package treatment systems when needed in the future. Al, As, Pb, Mn and Ni concentrations in the metal element contents of the groundwaters gave high values in some water samples. While the Pb concentration in all water samples was above the TS 266 (2005) and WHO (2017) standards in the dry period (October-2019), it remained below the standards in the rainy period (May-2020). The decrease in Pb concentration was associated with the fact that the rainy season sampling was in the Covid-19 pandemic period and the anthropogenic activities, fertilization in agricultural areas and the emission of aircraft/vehicle exhaust gases at Ankara-Esenboğa Airport due to the restrictions that came with the process. The waters examined according to the isotope analyzes of the groundwater are of meteoric origin and according to the δ18O contents of the 1963-2016 Ankara precipitations and the discharge-precipitation graphs of the springs examined, the groundwater is fed from the precipitations in February, January, December and March, respectively. Groundwater recharge heights according to δ18O and δ2H isotope data; It lies between 1078-1591 m and originates from Yiğitkıran Hill just outside the drainage area of the K-17 well. Due to the low deuterium excess value (-8.16 and -8.9‰) and <1TU 3H value of the well water Ç-18, means that it is fed by precipitation in colder climatic conditions compared to today's climatic conditions that supports the existence of paleo water.