Moving Beyond the Banks: Hyporheic Restoration Is Fundamental to Restoring Ecological Services and Functions of Streams

摘要

Hyporheic zones are aquifers beneath and adjacent to stream and river channels through which surface water exchanges and mixes with groundwater (Figure 1) (1). Hyporheic zones are intimately connected to the water column and benthic zones (Figure 2), and underpin stream ecosystem function through important contributions to biogeochemical cycling and biological habitat. Specifically, the movement of stream-water into the subsurface provides a vector for dissolved constituents (oxygen, nutrients, and pollutants) to come into direct contact with entrained carbon sources, microbial communities occupying the extensive surface area of sediment grains, and a unique array of biogeochemical conditions (e.g., both oxidative and highly reducing zones). Additionally, hyporheic exchange of water buffers surface water temperatures by facilitating heat exchange with relatively constant temperature groundwater. Thus the hyporheic zone contains gradients of physical, chemical, and thermal conditions; the water column and deeper groundwater are end members (Figure 2).