Laboratory Validation of an Integrated Surface Water— Groundwater Model

T D Sparks,R A Falconer,B N Bockelmann-Evans

doi:10.4236/jwarp.2013.54038

Abstract

The hydrodynamic surface water model DIVAST has been extended to include horizontally adjacent groundwater flows. This extended model is known as DIVAST-SG (Depth Integrated Velocities and Solute Transport with Surface Water and Groundwater). After development and analytical verification the model was tested against a novel laboratory set-up using open cell foam (60 pores per inch—ppi) as an idealised porous media representing a riverbank. The Hyder Hydraulics Laboratory at Cardiff University has a large tidal basin that was adapted to simulate a surface water—groundwater scenario using this foam, and used to validate the DIVAST-SG model. The properties of the laboratory set-up were measured and values were determined for hydraulic conductivity (permeability) and porosity, evaluated as 0.002 m/s and 75% respectively. Lessons learnt in this initial experimentation were used to modify the flume construction and improve the experimental procedure, with further experimentation being undertaken of both water level variations and tracer movement. Valuable data have been obtained from the laboratory experiments, allowing the validity of the numerical model to be assessed. Modifications to the input file to include representations of the joints between the foam blocks allowed a good fit between the observed and modelled water levels. Encouraging correlation was observed in tracer experiments using Rhodamine-WT dye between the observed exit points of the tracer from the foam, and the modelled exit points with time.

Highlights

Surface water and groundwater—two different resources —require careful management and protection
The properties of the laboratory set-up were measured and values were determined for hydraulic conductivity and porosity, evaluated as 0.002 m/s and 75% respectively
Useful data have been obtained from the laboratory experiments, allowing the validity of the numerical model to be assessed

Summary

Introduction

Surface water and groundwater—two different resources —require careful management and protection. Groundwater and surface water flows have been modelled separately, as their behaviour is represented by different mathematical equations and over very different time scales These flow processes are a linked resource; one depends upon and impacts on the other. Groundwater provides a third of the United Kingdom’s drinking water, and in some areas of southern England up to 80% of the drinking water comes from groundwater resources It requires little or no treatment before it is drinkable. Lakes, estuaries and coastal systems is more visibly abundant, but no less important—its behaviour affects our everyday lives through flooding, leisure activities, transport, drinking water etc These two resources are integral; the baseflow in streams and rivers comes from the contributing groundwater; agricultural chemicals may seep into groundwater, which subsequently may flow into streams. Accurate modelling of surface water flows needs to include contributions from groundwater resources, which can contribute significantly to the behaviour of free surface flows

Methods

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Discussion

Conclusion