Groundwater is a major factor affecting water quantity, chemistry and ecology of surface water bodies such as streams, lakes and wetlands. Understanding of these interactions is needed in efficient management of water resources due to increasing pressures from land use, water abstraction, and climate change. More research is especially needed to better establish the link between groundwater bodies and surface water ecosystems or terrestrial ecosystems directly dependent on groundwater.
In this work groundwater – surface water interaction at Rokua esker aquifer is studied using a fully integrated groundwater flow model the HydroGeoSphere. The code allows water to flow and partition into different components overland and stream flow, evaporation, infiltration, recharge and subsurface discharge into surface water features in a physically-based way, which is needed in simulating groundwater surface water interaction in a complex aquifer system. The constructed model is validated with innovative field observations of groundwater surface water interaction. The model performance in transient simulations is first examined using measured time series data for lake and groundwater levels and stream discharge. Secondly, locations of groundwater discharge to lakes at Rokua area is mapped with areal infrared imaging, and the spatial patters of observed discharge are compared to simulated discharge locations. Finally groundwater component in the lake water balance is estimated using lake water isotopic composition (H2 and O18), and the estimate is compared with simulated values.
The novelty of work is in identifying and quantifying groundwater-surface water interaction in esker aquifer using several field based methods and state of the art modeling approach. The study provides new information flow processes and water fluxes at GW-SW interfaces, which are needed in integrated management of water resources and related ecosystems in esker aquifers.