Aquatic weed control within an integrated water management framework

E.P. Querner

    Research output: Thesisexternal PhD, WU

    Abstract

    <p>Aquatic weed control, carried out by the water boards in the Netherlands, is required to maintain sufficient discharge capacity of the surface water system. Weed control affects the conditions of both surface water and groundwater. The physically based model MOGROW was developed to simulate the flow of water in the unsaturated zone, the saturated zone and the water courses in an integrated manner. The model was verified with field data on groundwater levels, discharges, moisture storage in the root zone and evapotranspiration in the Hupselse Beek catchment.<p>The time and frequency of weed control during summer were determined using data on weed growth, flow resistance and discharges. This study was carried out in the Poelsbeek and Bolscherbeek catchments located in the east of the Netherlands. Weed obstruction was measured in nine water courses of these catchments. The boundary roughness coefficient κ <sub><font size="-2">M</font></sub><em></em> was calculated from field data and laboratory experiments. The κ <sub><font size="-2">M</font></sub><em></em> varied for the unobstructed part of the cross-section between 30-34 m <sup><font size="-2">1/3</font><strong>.</strong></SUP>s <sup><font size="-2">-1</font></SUP>. A numerical model was used to determine the velocity distribution in a cross-section of a water course. This calculated velocity distribution resulted also in κ <sub><font size="-2">M</font></sub><em></em> values of the same order. The minimally required weed control was estimated using the data on weed obstruction, flow resistance and estimates of expected discharges. These expected discharges for the summer period were calculated for three water table fluctuation classes, using a one-dimensional groundwater model. Comparing the expected discharges and the permissible flow rates for a water course, gives the required periods of weed control.<p>Weed control strategies were evaluated for the Poelsbeek and Bolscherbeek area using the model MOGROW. Results of the modelling experiments are the occurrence of high surface water levels, high groundwater levels and high stream flow velocities. In a cost-benefit analysis the cost of weed control and the damage for pasture (in terms of financial losses) were considered. Seven simulation years with varying wet conditions in summer were selected. The financial loss resulting from one clearing at the end of summer, was too high for only one of these years. The multi-objective decision method ELECTRE II enabled the ecological impact to be incorporated in the evaluation. The method identified weed control strategies that are most favourable for agriculture or nature conservation.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • Feddes, R.A., Promotor, External person
    • Bogardi, J.J., Promotor, External person
    Award date9 Jun 1993
    Place of PublicationS.l.
    Publisher
    Print ISBNs9789054851226
    Publication statusPublished - 1993

    Keywords

    • ditches
    • maintenance
    • rivers
    • streams
    • canals
    • water
    • discharge
    • hydrodynamics
    • liquids
    • fluids
    • flow
    • channels
    • weed control
    • waterways
    • aquatic weeds
    • groundwater
    • surface water
    • water table
    • hydrology
    • models
    • analogues
    • research
    • Netherlands
    • water use

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