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A Multi-technique approach to determine temporal and spatial variability of groundwater-stream water exchange in Çakit stream, Niğde/Turkey

Koruk, Kasımcan.
Characterizing the spatio-temporal distribution of groundwater-surface water exchange fluxes are of paramount importance in understanding catchment behavior. The objective of this study is to quantify the spatio-temporal distribution of the exchange fluxes along the Çakıt Stream (Niğde, Turkey) through coupling a set of geophysical techniques and in-stream measurements in a hierarchical manner. First, geological and water quality information were combined at the regional scale to determine the focus area at the reach-scale. Second, Electromagnetic Induction (EMI) surveys were conducted over the determined reach of stream to pinpoint potential groundwater upwelling locations along the streambed. EMI anomalies guided our focus to a 600 meter-long reach of the stream. Along this selected reach, Fiber-Optic Distributed Temperature Sensing System (FO-DTS) was utilized to investigate top-of-the-streambed-temperature profiles at fine spatial and temporal scales. Furthermore, vertical hydraulic gradients and exchange fluxes were investigated at three potential locations using nested piezometers and vertical temperature profiles, respectively. Water quality parameters were also measured along the reach in surface water and in the piezometers. Results of these studies indicated that study reach has heterogeneities in terms of vertical water-flow components with seasonal transitions. EMI survey was successful in identifying a groundwater upwelling location with relatively high anomaly. FO-DTS measurements also indicated high temperature anomaly during cold air temperature and low flow conditions at the same upwelling site. Finally, point-based traditional methods supported the observations of EMI and FO-DTS quantitatively.