Groundwater-Surface Water Interactions

Surface water and groundwater are linked components of watersheds, and finding effective solutions to water quality problems often requires an understanding of both, as well as the interactions between them.  Surface water bodies such as ponds or lagoons can affect groundwater quality down-gradient, especially when drinking water wells are actively pumping.  Conversely, groundwater can be an important source of the contaminants that are of concern in surface water, and efforts to remediate surface water must take into account the importance of the groundwater pathway.  For example, efforts to reduce contamination in surface water by reduction of direct point sources (for example, in response to a TMDL) may be impeded due to ongoing transport from contaminated groundwater.  Even uncontaminated groundwater water can be important, because groundwater flows enhance the flux of contaminants from sediments to overlying water.  Finally, the localized impacts of contaminants at the interface between groundwater and surface water can be significant and in some cases may drive regulatory decisions that are based on ecological or human health risk assessments. 

Typical groundwater evaluations may treat surface water interactions simplistically, or neglect them altogether, because the area of the interface between the two is typically small relative to the spatial scale of the groundwater system being evaluated.  Conversely, surface water evaluations often disregard exchanges with the local groundwater system because the amount of water that flows across the interface is usually small relative to that which originates from other routes (e.g., tributary streams and precipitation runoff).   However, there are many instances in which the groundwater/surface water interaction must be considered to develop the most appropriate remedial plan.  QEA's approach to problems that involve both groundwater and surface water components involves a strong focus on solving the important management questions with the appropriate level of analysis, whatever the media.  Studies can range from relatively simple field programs to measure groundwater flows, to mass balance estimates of contaminant fluxes between ground and surface water, to quantitative modeling of groundwater and surface water flows and contaminant fate and transport.

QEA has extensive experience in evaluating both surface water and groundwater contamination problems, including field data collection, data analysis and mathematical modeling.  This experience, coupled with our knowledge of groundwater hydraulics, hydrogeology, surface water hydrology, chemistry, and biology, allows QEA to provide the comprehensive evaluation that is required to formulate cost-effective management solutions for sites where both groundwater and surface water are significant components.