Journal of Water Resource and Protection, 2013, 5, 377-394 doi:10.4236/jwarp.2013.54038 Published Online April 2013 (http://www.scirp.org/journal/jwarp) Laboratory Validation of an Integrated Surface Water— Groundwater Model T. D. Sparks, B. N. Bockelmann-Evans, R. A. Falconer Hydro-Environmental Research Centre, Cardiff School of Engineering, Cardiff University, Cardiff, UK Email: Bockelmann-Evans@cf.ac.uk, FalconerRA@cf.ac.uk Received November 29, 2012; revised January 5, 2013; accepted January 20, 2013 Copyright © 2013 T. D. Sparks, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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 Hy- draulics Laboratory at Cardiff University has a large tidal basin that was adapted to simulate a surface water—ground- water 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 nu- merical 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. Keywords: Integrated Surface Water Groundwater Modelling; Laboratory Experiments; Open Cell Foam 1. Introduction Surface water and groundwater—two different resources —require careful management and protection. Computer modelling of both resources has long been used as an aid to the management of water resources. Historically, groundwater and surface water flows have been modelled separately, as their behaviour is represented by different mathematical equations and over very different time scales. However, these flow processes are a linked re- source; 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. Usually it requires little or no treatment before it is drinkable. However, if contaminated, these resources are expensive and difficult to restore, so groundwater needs to be protected. Surface water in rivers, lakes, es- tuaries and coastal systems is more visibly abundant, but no less important—its behaviour affects our everyday lives through flooding, leisure activities, transport, drink- ing water etc. These two resources are integral; the base- flow in streams and rivers comes from the contributing groundwater; agricultural chemicals may seep into ground- water, which subsequently may flow into streams. Accu- rate modelling of surface water flows needs to include contributions from groundwater resources, which can contribute significantly to the behaviour of free surface flows. Historically, both open channel and groundwater flows have been considered for solution by numerical methods. Where the two “zones” meet, the problem has usually been approached by calculating the response of the groundwater system to changes in the river elevation [1,2]. [3] developed a model describing infiltration and overland flow based on the soil moisture properties. [4] took this approach a stage further and described numeri- cal solutions to the coupled boundary problems repre- senting 3-D, transient, saturated-unsaturated subsurface flow, and 1-D, gradually varied, unsteady channel flow. Copyright © 2013 SciRes. JWARP