Drainage-water travel times as a key factor for surface water contamination

P. Groenendijk, G.A.P.H. van den Eertwegh

Research output: Chapter in Book/Report/Conference proceedingChapterAcademic


The importance of the unsaturated zone as an inextricable part of the hydrologic cycle has long been recognized. The root zone and the unsaturated sub-surface domain are chemically and biologically the most active zones. The interrelationships between soil, subsoil and surface waters make it unrealistic to treat the saturated and unsaturated zones and the discharge to surface waters separately. Point models describe vertical water flow in the saturated zone and possibly lateral flow by defining a sink term. To account for the influence of two- and three-dimensional water flow on the travel-time distribution a conceptualization of the flow field is required. A formulation for upscaling the groundwater flow field is presented which yields the average vertical flux as a key factor for describing the travel time implicitly. Analytical solutions are given for the upscaled description for the transport; they are applied to a simple model consisting of a cascade of reservoirs. The analytical approach given, which includes the main properties of the soil system as well as the drainage system, proves to be useful for the prediction of solute concentrations in exfiltrating groundwater. The use and significance of conceptual models is discussed as well as the opportunities of detailed mechanistic integrated models that treat the unsaturated/saturated zone, overland flow and surface water flow comprehensively. Some results of experimental field work on the assessment of drainage water quality impacts of agricultural land management are summarized. Strengths, weaknesses, opportunities and threats of different modeling approaches are discussed. The unsaturated zone is an essential link in the chain between land management practices and the ecological status of freshwaters.
Original languageEnglish
Title of host publicationUnsaturated-zone modeling: progress, challenges and applications
EditorsR.A. Feddes, G.H. de Rooij, J.C. van Dam
Place of PublicationDordrecht [etc.]
Number of pages364
Publication statusPublished - 2004
EventFrontis workshop on unsaturated-zone modeling -
Duration: 3 Oct 20045 Oct 2004

Publication series

NameWageningen UR Frontis Series


WorkshopFrontis workshop on unsaturated-zone modeling


  • groundwater flow
  • groundwater pollution
  • surface water
  • hydraulic conductivity
  • models

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