Interaction between groundwater, the hyporheic zone and a Chalk stream: a case study from the River Lambourn, UK

Abstract

Understanding the processes controlling groundwater-surface water interaction is essential for effective resource management and for protecting sensitive ecosystems. Through intensive monitoring of Chalk groundwater, surface water, and shallow gravel groundwater along a river bank and below the river, using a combination of hydrochemical and hydrophysical techniques a complex pattern of interactions has been elucidated. The river is broadly in hydraulic contact with the river bed and adjacent gravels and sands (although with local variability), but these sediments are mainly hydraulically separate from the underlying Chalk at the site. The relationship between the river and underlying alluvium is variable, involving components of groundwater flow both parallel and transverse to the river and with both effluent and influent behaviour seen. The degree of groundwater-surface water interaction within the hyporheic zone at this site seems to be controlled by a number of factors including lithology, topography, and the local groundwater flow regime. While the gravel aquifer is significant in controlling groundwater-surface water interaction, its importance as a route for flow down the catchment is likely to be modest compared with river discharge.

Groundwater and Surface Water Interaction at the Regional-scale – A Review with Focus on Regional Integrated Models

“…Allen et al 2010;Banzhaf et al 2013;Boulton et al 1998;Krause et al 2009). Much less research has been carried out at the local or flood plain scale (Langhoff et al 2006, see also section 2.1.2).…”

Instream and riparian implications of weed cutting in a chalk river

“…This site is approximately 14 km from the ephemeral source of the River Lambourn and encompasses approximately 600 m of river and 10 ha of wetland. The Chalk bedrock at the observatory is overlain by river terrace deposits, which nearby have been demonstrated to comprise primarily coarse-grained gravels that are typically 3-4 m thick (Allen et al, 2010). These are in turn overlain by an assortment of alluvial deposits consisting of peat, clay, silt, sand and gravel.…”

Macronutrient status of UK groundwater: Nitrogen, phosphorus and organic carbon

“…A number of studies have found that natural attenuation at the groundwater-surface water interface is a significant control on observed river nitrate concentrations (Allen et al, 2010;Lapworth et al, 2011;Pretty et al, 2006;Smith et al, 2009). Lapworth et al (2011) showed that ecologically significant P concentrations (20-30 μg/L) are present in the hyporheic zone in dissolved and colloidal forms.…”