Surface–groundwater interactions in hard rocks in Sardon Catchment of western Spain: An integrated modeling approach

• Published in: Journal of hydrology (Amsterdam) 2014-09, Vol.517, p.390-410
• Main Authors: Hassan, S.M. Tanvir, Lubczynski, Maciek W., Niswonger, Richard G., Su, Zhongbo
• Format: Article
• Language: English
• Subjects: Catchments; Dynamical systems; Earth sciences; Earth, ocean, space; Exact sciences and technology; Freshwater; Ground-water flow; Groundwater; Groundwater evapotranspiration; GSFLOW integrated hydrologic model; Hard rock aquifer; Hydrogeology; Hydrology; Hydrology. Hydrogeology; Mathematical models; Networks; Recharge; Surface water; Surface–groundwater interactions; Water balance; Water resources
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2014.05.026

•We calibrated and post-audited transient GSFLOW model of hard rocks.•Surface–groundwater interactions and detail water balances were investigated.•Groundwater flow was surprisingly small as compared to overland and interflow.•18-year simulation indicated decline of groundwater storage, groundwater outflow and baseflow. The structural and hydrological complexity of hard rock systems (HRSs) affects dynamics of surface–groundwater interactions. These complexities are not well described or understood by hydrogeologists because simplified analyses typically are used to study HRSs. A transient, integrated hydrologic model (IHM) GSFLOW (Groundwater and Surface water FLOW) was calibrated and post-audited using 18years of daily groundwater head and stream discharge data to evaluate the surface–groundwater interactions in semi-arid, ∼80km2 granitic Sardon hilly catchment in Spain characterized by shallow water table conditions, relatively low storage, dense drainage networks and frequent, high intensity rainfall. The following hydrological observations for the Sardon Catchment, and more generally for HRSs were made: (i) significant bi-directional vertical flows occur between surface water and groundwater throughout the HRSs; (ii) relatively large groundwater recharge represents 16% of precipitation (P, 562mm.y−1) and large groundwater exfiltration (∼11% of P) results in short groundwater flow paths due to a dense network of streams, low permeability and hilly topographic relief; deep, long groundwater flow paths constitute a smaller component of the water budget (∼1% of P); quite high groundwater evapotranspiration (∼5% of P and ∼7% of total evapotranspiration); low permeability and shallow soils are the main reasons for relatively large components of Hortonian flow and interflow (15% and 11% of P, respectively); (iii) the majority of drainage from the catchment leaves as surface water; (iv) declining 18years trend (4.44mm.y−1) of groundwater storage; and (v) large spatio-temporal variability of water fluxes. This IHM study of HRSs provides greater understanding of these relatively unknown hydrologic systems that are widespread throughout the world and are important for water resources in many regions.