Abstract
Process-based models are widely used to investigate nutrient dynamics for water management purposes. Simulating nutrient transport and transformation processes from agricultural land into water bodies at the catchment scale are particularly relevant and challenging tasks for water authorities. However, few practical methods guide inexperienced modelers in the selection process of an appropriate model. In particular, data availability is a key aspect in a model selection protocol, since a large number of models contain the functionalities to predict nutrient fate and transport, yet a smaller number is applicable to specific datasets. In our work, we aim at providing a model selection protocol fit for practical application with particular emphasis on data availability, cost-benefit analysis and user’s objectives. We select for illustrative purposes five process-based models with different complexity as “candidates” models: SWAT (Soil and Water Assessment Tool), SWIM (Soil and Water Integrated Model), GWLF (Generalized Watershed Loading Function), AnnAGNPS (Annualized Agricultural Non-Point Source Pollution model) and HSPF (Hydrological simulation program-FORTRAN). The models are described in terms of hydrological and chemical output and input requirements. The model selection protocol considers data availability, model characteristics and user’s objectives and it is applied to hypothetical scenarios. This selection method is particularly formulated to choose process-based models for nutrient modeling, but it can be generalized for other applications which are characterized by a similar degree of complexity.
Highlights
Nutrients, such as nitrogen and phosphorous, are a serious problem threatening water quality [1,2,3].Excessive nutrient loads cause water quality deterioration, including toxic algal blooms, oxygen deficiency, fish death and eutrophication of the river network and lakes [4,5,6,7]
Despite the uncertainty related to model predictions, a process-based modeling approach is necessary to simulate nutrient fate and transport at the catchment scale and to support water managers and decision makers
It models the changes in water, sediment, and nutrient amounts with a series of vertical storages
Summary
Nutrients, such as nitrogen and phosphorous, are a serious problem threatening water quality [1,2,3]. These methods are mainly driven by the necessity for a modeler to discuss with a wide non-specialist public, and by the need to guide the decision of inexperienced user with a simple multi-criteria analysis Such simplified schemes are relevant for policy makers and water authorities called to comply with regulations such as the WFD. A novel model selection protocol, calibrated to choose models predicting nutrient dynamics, was formulated and explained by considering five widely used process-based models (SWAT, SWIM, GWLF, AnnAGNPF and HPSF) These five models were selected among all available open source continuous models to describe nutrient transport for illustrative purposes and to cover a range of variation in (1) the degree of simplification in representing physical, chemical, and bio-chemical processes; and (2) the input data requirements for implementing the models. The protocol is used as an integrated assessment tool to take into consideration the potential objectives of user, model characteristics, data availability and a “cost and benefits” analysis
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