Groundwater and Surface Water Interaction

Groundwater-surface water (GW-SW) interaction affects the physical, chemical, and biological attributes of both subsurface and surface ecosystems linked by exchange flows. Hydrologists and ecologists studying streams have led the way in pursuit of understanding GW-SW interactions, with particular focus on hyporheic zones, groundwater environments with bidirectional hydrologic connectivity to stream channels. This chapter emphasizes hyporheic GW-SW exchange but also reviews the importance of GW-SW exchange for other inland waters. GW-SW exchange is promoted by geomorphic features that interact with the flow of water. Such features range in size and character from bed forms to gravel bars to meanders and valley floor configurations, and—in general—the residence times for water (i.e., amount of time spent in flows linking surface and subsurface environments) increase with the spatial dimensions of flowpaths involved. A range of field methods exist to assess GW-SW exchange, which are tied to spatiotemporal scales of assessment. Recent advances in computer modeling of stream systems integrate ideas from hydrology, engineering, and ecology to increase understanding and predictive ability associated with GW-SW and its implications, particularly for water quality. Continued advancement of theoretical frameworks, computer models, and field studies addressing GW-SW interaction are critical for addressing the management and stewardship of water resources in times of environmental change.