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Groundwater - river interaction in a chalk catchment: the River Lambourn, UK

Grapes, Timothy Rupert (2004)
Ph.D. thesis, University of Birmingham.

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Abstract

Chalk streams are of high ecological value and are dependent upon groundwater discharge to support flows. This study investigates chalk stream-aquifer interaction, focusing on a near-natural catchment; the River Lambourn of the West Berkshire Downs. The topographic catchment of the Lambourn is 234km$$^2$$, principally underlain by Upper Chalk. The river has a perennial length of c.16km, and a 7.5km seasonal section.

Temporal dynamics of the recharge-storage-discharge sequence are investigated using linear regression techniques to identify the lag between recharge and discharge. The effective maximum duration of groundwater flow is 9.1 months, which is used with regional hydraulic gradients to calculate a bulk (interfluve) hydraulic conductivity of 114m/d (using Sy=1%), suggesting that interfluve permeability has been historically underestimated.

Spatial flow accretion on the Lambourn is defined from 12 reaches (each 1-2km long), exhibiting mean accretion rates between -0.019 and 0.211 cumecs/km. The accretion rate profile approximates a sinusoidal pattern $$(\lambda$$=12km) suggesting a catchment scale litho-structural control. However, local topography and lithology also exert influence. High accretion rate reaches are associated with major dry valley intersections and elevated valley floor permeability, whilst the presence of Chalk Rock at shallow depths restricts local accretion.

Type of Work: Ph.D. thesis. Bradley, Christopher and Petts, Geoff and Bradford, Richard B Schools (1998 to 2008) > School of Geography, Earth & Environmental Sciences School of Geography, Earth and Environmental Sciences groundwater, river, interaction, surface water, chalk stream, chalk aquifer, permeable catchment, berkshire downs GB Physical geography University of Birmingham 4036
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