The Chalk unsaturated zone is crucial in controlling the delivery of nitrate to Chalk streams and groundwater abstraction wells. In this paper, results from a dual-permeability numerical model of the Chalk unsaturated zone are used to illustrate the relative roles of matrix and fracture flow. A major challenge arises in representing the Chalk unsaturated zone within catchment-scale models for nutrient management. These have generally been based on simple conceptual reservoirs or compartments to represent soils and groundwater. A more appropriate conceptualization has recently been developed and applied to the Lambourn catchment within a catchment-scale nutrient model (INCA-Chalk). Preliminary results from this work are discussed, which clearly illustrate the decadal time scales that need to be considered in the context of nutrient management and the Water Framework Directive.

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