DYNAMIC SURFACE WATER-GROUNDWATER EXCHANGE IN TIDAL FRESHWATER ZONES: INSIGHTS FROM THE CHRISTINA RIVER BASIN (DELAWARE, USA)

摘要: OF THESIS DYNAMIC SURFACE WATER-GROUNDWATER EXCHANGE IN TIDAL FRESHWATER ZONES: INSIGHTS FROM THE CHRISTINA RIVER BASIN (DELAWARE, USA) In coastal rivers, tides can propagate for tens to hundreds of kilometers inland beyond the saltwater line. Yet influence on river-aquifer connectivity and solute transport in tidal freshwater zones (TFZs) is largely unknown. We estimate that along TFZ White Clay Creek (Delaware, USA), more than 17% river water exchanges through hyporheic riparian storage due pumping alone. Additional processes such as flow bedforms likely contribute even exchange. The turnover length associated with process 39 km, similar lengths all exchange non-tidal rivers size. Based measurements at a transect piezometers located 17 km from coast, 0.44 m3 across bank 0.49 bed per unit length. Exchange fluxes range -0.81 1.68 m d-1 -0.84 1.88 bed. During rising tide, infiltrates into aquifer, downstream rate channel low (1.45 s-1). falling stored groundwater released river, increases by 380%. Tidal may remove nutrients or other contaminants attenuate nutrient loads coasts. Alternating expansion contraction aerobic aquifer contaminant removal paths. A clear need exists understand ecosystem services TFZs adopt best management practices promote these services.