Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 27

Report describing development of new and existing water quality and ecological models

This report describes the structure and equations of two new catchment−scale models and the on−going development of existing approaches used within work package 6 (Task 6.2). As such, this deliverable provides more detail than given in the Year 1 Annual Report on model development. This report does not describe the applications of models to new sites.

To explore and quantify the effects of climate change and pollution inputs on freshwater ecosystems it is desirable to have mathematical models. In particular, such models (a) integrate measurements and process understanding in an attempt to provide a mathematical description of how freshwater ecosystems function and (b) provide quantitative estimates of the likely changes in freshwaters due to the impacts of climate, deposition and land−management change. As such, models will play a key role in developing the science in Euro−limpacs.

Specifically, this report details the new structure and equations of the Integrated Catchments Model of Carbon (INCA−C) and the Integrated Catchments Model of Sediment (INCA−Sed). The development of these two models takes environmental−science further by providing an ability to simulate carbon and sediment dynamics at a catchment−scale, with a daily time−step, in the soil, ground− and surface waters. This capability is important given the current uncertainties in the understanding of carbon loss from catchments and the feedbacks between carbon storage in soils and the atmosphere, and the simulation of pollutants transported in a particulate−form and the changes in the aquatic habitat caused by sediment transport.
The Integrated Catchments Models of Nitrogen and Phosphorus (INCA−N, INCA−P) have also been modified to better simulate the effects of longer−lying snow on soil temperatures and the dependency of soil−nitrogen processes on soil−temperature. ?Monte−Carlo? versions of the two models have been created that will be used to test the model structures in future work, and to investigate the relationship between pollutant inputs, outputs and the ecological impact under a broad range of climates. The TRANS model, which simulates flow, sediment, nitrogen and phosphorus delivery and in−stream dynamics, has been chained to a precipitation−runoff model (NAM), ecological sub−models and new equations have been added to describe denitrification on inundated floodplains. The Multi−year Lake simulation model (MyLAKE) has been developed to describe lake temperature variations, stratification, evolution of ice and snow cover and phosphorus−phytoplankton dynamics, thereby adding a capability to simulate lakes in northern Europe or at high altitudes.

Together these developments allow all the key pollutants central to Euro−limpacs to be simulated (i.e. sediment, nitrogen, phosphorus, carbon) except toxics; it is expected that the carbon and sediment models will form the basis for the development of a mercury−model in future phases of the project. The component models will provide the basis for model chains which will provide descriptions of linked river−lake−wetland systems, and for single−models of more than one pollutant to compliment the TRANS model. Some of the developments have already been published in the scientific literature, whilst papers describing the remainder are currently in production.

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