TY - JOUR

T1 - A multi-technique approach to determine temporal and spatial variability of groundwater-stream water exchange

AU - Koruk, Kasimcan

AU - Binley, Andrew

AU - Yilmaz, Koray

AU - Akyurek, Zuhal

N1 - This is the peer reviewed version of the following article: Koruk, K, Yilmaz, KK, Akyurek, Z, Binley, A. A multi‐technique approach to determine temporal and spatial variability of groundwater–stream water exchange. Hydrological Processes. 2020; 34: 2612– 2627. https://doi.org/10.1002/hyp.13754 which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1002/hyp.13754 This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.

PY - 2020/5/30

Y1 - 2020/5/30

N2 - Characterizing the spatio-temporal distribution of groundwater-surface water exchange fluxes is of paramount importance in understanding catchment behavior. A wide range of field-based techniques are available for such characterization. The objective of this study is to quantify the spatio-temporal distribution of the exchange fluxes along the Çakıt stream (Nigde, 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 catchment scale to determine key areas for reach-scale focus. Second, electromagnetic induction (EMI) surveys were conducted along the reach to pinpoint potential groundwater upwelling locations. EMI anomalies guided our focus to a 665 meter-long reach of the stream. Along this selected reach, a fiber-optic distributed temperature sensing (FO-DTS) system was utilized to investigate streambed-temperature profiles at fine spatial and temporal scales. Furthermore, vertical hydraulic gradients and exchange fluxes were investigated using nested piezometers and vertical temperature profiles, respectively, at two potential upwelling locations and a potential downwelling location identified by previous surveys. The results of the study reveal heterogeneity of vertical water-flow components with seasonal variability. The EMI survey was successful in identifying a localized groundwater upwelling location. FO-DTS measurements revealed a warm temperature anomaly during cold air temperature and low streamflow conditions at the same upwelling site. Our point-based methods, namely vertical temperature profiles and vertical hydraulic gradient estimates, however, did not always provide consistent results with each other and with EMI and DTS measurements. This study, therefore, highlights the opportunities and challenges in incorporating multi-scale observations in a hierarchical manner in characterization of the groundwater-surface water exchange processes that are known to be highly heterogeneous in time and space. Overall, a combination of different methods helps to overcome the limitations of each single method and increases confidence in the obtained results.

AB - Characterizing the spatio-temporal distribution of groundwater-surface water exchange fluxes is of paramount importance in understanding catchment behavior. A wide range of field-based techniques are available for such characterization. The objective of this study is to quantify the spatio-temporal distribution of the exchange fluxes along the Çakıt stream (Nigde, 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 catchment scale to determine key areas for reach-scale focus. Second, electromagnetic induction (EMI) surveys were conducted along the reach to pinpoint potential groundwater upwelling locations. EMI anomalies guided our focus to a 665 meter-long reach of the stream. Along this selected reach, a fiber-optic distributed temperature sensing (FO-DTS) system was utilized to investigate streambed-temperature profiles at fine spatial and temporal scales. Furthermore, vertical hydraulic gradients and exchange fluxes were investigated using nested piezometers and vertical temperature profiles, respectively, at two potential upwelling locations and a potential downwelling location identified by previous surveys. The results of the study reveal heterogeneity of vertical water-flow components with seasonal variability. The EMI survey was successful in identifying a localized groundwater upwelling location. FO-DTS measurements revealed a warm temperature anomaly during cold air temperature and low streamflow conditions at the same upwelling site. Our point-based methods, namely vertical temperature profiles and vertical hydraulic gradient estimates, however, did not always provide consistent results with each other and with EMI and DTS measurements. This study, therefore, highlights the opportunities and challenges in incorporating multi-scale observations in a hierarchical manner in characterization of the groundwater-surface water exchange processes that are known to be highly heterogeneous in time and space. Overall, a combination of different methods helps to overcome the limitations of each single method and increases confidence in the obtained results.

KW - distributed temperature sensing

KW - electromagnetic induction

KW - exchange processes

KW - groundwater–surface water interaction

KW - hierarchical approach

KW - hydrogeophysics

KW - streambed temperature profile

KW - thermochrons

M3 - Journal article

VL - 34

SP - 2612

EP - 2627

JO - Hydrological Processes

JF - Hydrological Processes

SN - 0885-6087

IS - 11

ER -