Keywords

model reduction, ensemble runs, catchment, nitrogen, retention

Start Date

1-7-2004 12:00 AM

Description

Process-oriented models of the retention of nitrogen in catchments are by necessity rathercomplex. We introduced several types of ensemble runs that can provide informative summaries ofmeteorologically normalised model outputs and also clarify the extent to which such outputs are related tovarious model parameters. Thereafter we employed this technique to examine policy-relevant outputs of thecatchment model INCA-N. In particular, we examined how long it will take for changes in the application offertilisers on cultivated land to affect the predicted riverine loads of nitrogen. The results showed that themagnitude of the total intervention effect was influenced mainly by the parameters governing the turnover ofnitrogen in soil, whereas the temporal distribution of the water quality response was determined primarily bythe hydromechanical model parameters. This raises the question of whether the soil nitrogen processesincluded in the model are elaborate enough to correctly explain the widespread observations of slow waterquality responses to changes in agricultural practices.

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Jul 1st, 12:00 AM

Reduced Models of the Retention of Nitrogen in Catchments

Process-oriented models of the retention of nitrogen in catchments are by necessity rathercomplex. We introduced several types of ensemble runs that can provide informative summaries ofmeteorologically normalised model outputs and also clarify the extent to which such outputs are related tovarious model parameters. Thereafter we employed this technique to examine policy-relevant outputs of thecatchment model INCA-N. In particular, we examined how long it will take for changes in the application offertilisers on cultivated land to affect the predicted riverine loads of nitrogen. The results showed that themagnitude of the total intervention effect was influenced mainly by the parameters governing the turnover ofnitrogen in soil, whereas the temporal distribution of the water quality response was determined primarily bythe hydromechanical model parameters. This raises the question of whether the soil nitrogen processesincluded in the model are elaborate enough to correctly explain the widespread observations of slow waterquality responses to changes in agricultural practices.