University of Twente Student Theses


Groundwater Fluxes in Konya Closed Basin, Turkey

Naing, Zizawar Win (2011) Groundwater Fluxes in Konya Closed Basin, Turkey.

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Abstract:Konya Closed Basin (KCB) is located in central Anatolia (Turkey). KCB includes Konya sub-basin in the north and Tuz Lake sub-basin in the south. The very productive karstic Neogene aquifer, reaches the maximum elevation of not more than 1150m a.s.l, with an the areal extend 51,250 km2 in KCB. It outcrops in almost all of the two sub-basin areas such that groundwater can easily be accessed almost anywhere in KCB. The objective of this study is to quantify groundwater fluxes in KCB. Moreover, to estimate accurately groundwater fluxes in a spatially distributed manner, MODFLOW-96 (Harbaugh and McDonald (1996) was applied in the karst aquifer model with a grid resolution of 5km. The map inputs include the following: recharge map based on wet season orographic rainfall, evapotranspiration map, mountain runoff. Geometry of the Neogene aquifer system was constructed in two layers according to the same hydrostratigraphic properties. The model was constructed with the target to balance the total discharge amount from the Neogne aquifer towards the Lake according to the discharge of 0.6MCM/day. In this regard, it was assumed in the model setting that all of the groundwater flow in the Neogene aquifer terminates in the Tuz Lake. Steady-state calibration of the hydraulic conductivities was carried out to obtain spatially distributed hydraulic heads. Measured hydraulic heads from hydrogeologic map (1966) were used to evaluate the steady state model calibration because the aquifer was almost at pristine state in the late 1960. By detailed analysis of the discrepancies between the measured heads and the simulated heads, an artesian area was observed since the hydraulic head was higher than the ground surface during calibration. By comparing the present time hydraulic head of Timras Sinkhole (Obruk), which is 1006 m that represents average head in 2002, the hydraulic head became 16 m lower during last 36 years. According to the groundwater budget results provided by numerical model, a total recharge of 2.2 MCM/day was found as the upper limit in steady state simulation. The model failed in quasi-transient mode due to unbalanced huge abstraction rate of 5.2 MCM/day that was adopted from two major irrigation zones: Konya Curma area and Sultanhani-Obruk-Karapina area. The recharge of 2.2 MCM/day, which is the result of a balanced model, could not support the huge abstraction rate of 5.2 MCM/day. It was also found out that the Neogene aquifer does not balance the high evapotranspiration outflux of 7791.5 MCM/year, and the low precipitation influx with an upper limit of 2133 MCM/year. Therefore, the assumption that groundwater flow through Neogene aquifer terminates only at the Tuz Lake is not correct and there has to be other groundwater inflow/outflow components to/from the aquifer system. If the result of head changes was possible to fit in quasi-transient mode to predict future, the head changes could represent hydrogeological environments such as lakes, wetlands and springs etc. related to the Neogene aquifer and environmental impacts could be estimated. If the head decline rate could be determined, the available groundwater reserve could be calculated and it could be estimated how long the aquifer could yield water applying the same rate of abstraction as now. Then, further calibrating the aquifer storage capacity, the ecological groundwater demand of KCB could be estimated. Therefore, the numerical groundwater modelling was found to be an important tool to estimate the spatio-temporal distribution of groundwater fluxes.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geo-informatics MSc (60031)
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