Water table dynamics and groundwater–surface water interaction during filling and draining of a large fluvial island due to dam‐induced river stage fluctuations

Abstract

[1] Dam-controlled river stage fluctuations alter groundwater-surface water interaction between persistent bars and islands and the rivers bounding them by rapidly changing hydraulic gradients and expanding hyporheic zones. A 300-m long and 80-m wide sandgravel island with established vegetation located on the Colorado River (Austin, Texas, USA) is subjected to >1 m daily river stage variations due to upstream dam operations. Piezometer nests with probes monitored the evolution of the water table and groundwater flow paths through several cycles of dam-induced stage fluctuations. Results show that hydraulic head and the water table within the island closely track the river stage associated with dam release. Water table mounds and depressions which overlap in time were mapped through the course of one storage-release cycle over which >4,000 m 3 of water moved in and out of the island. Dam operations have drastically altered groundwater-surface water connectivity between the Colorado River and the fluvial island aquifer by pumping substantial amounts of water in and out of the aquifer during dam release and storage cycles.

9.13 Geomorphic Controls on Hyporheic Exchange Across Scales: Watersheds to Particles

“…However, we expect that the surface water elevations in channels bounding the island create boundary conditions for total head and control HEF through islands as is generally indicated by the available literature (Dent et al, 2007;Francis et al, 2010). The hyporheic hydrology of islands has not been extensively studied.…”

Abundance and dimensions of naturally occurring macropores along stream channels and the effects of artificially constructed large macropores on transient storage

“…Thus, such macropores have potential to enhance bank storage when rapid reversals of head gradients at stream margins push water into and out of the banks (Sawyer et al 2009). This concept also applies to water-level fluctuations caused by daily snowmelt, evapotranspiration, hydropeaking, and tidal fluctuations (Peterson and Connelly 2001, Westbrook et al 2005, Arntzen et al 2006, Loheide and Lundquist 2009, Sawyer et al 2009, Francis et al 2010, Wondzell et al 2010. Bank storage can have significant effects on temperature and biogeochemistry of the stream and the floodplain ground water (Chen and Chen 2003, McCallum et al 2010, Anderson et al 2011, Gu et al 2012.…”

Flux dynamics at the groundwater-surface water interface in a tropical catchment

“…Human activities such as groundwater abstraction and dam operation have been shown to have effects on water exchange between rivers and nearby sediments (Francis et al, 2010;Nyholm et al, 2003). In the case of the La Vi River, the dam operation at S1 downstream caused an increase of river stage, which reduced the hydraulic gradient resulting in a decrease of outflow to the river during the dry period.…”