INCA-P New Papers

Modelling instream P and ecology

Jill Crossman and colleagues have just published a paper describing INCA-PEco, the Integrated Catchments model for Phosphorus Ecology. This new model is a major upgrade to the INCA-P model.

INCA-PEco integrates in-stream phosphorus (P), dissolved oxygen (DO), biological oxygen demand (BOD) and phytoplankton processes. The model simulates dissolved and particulate P transport and includes a new, more physically based streamflow submodel.

The team applied the new model to two eutrophied mesoscale catchments with differing climatic regime (continental vs. maritime) and phosphorus sources (point vs. diffuse). They used Generalised Sensitivity Analysis (GSA) to assess the effects of regional differences in climate, land use and P sources on parameter importance during calibration. In their analysis, they successfully reproduced in-stream total phosphorus (TP), suspended sediment, DO, BOD and chlorophyll-a (chl-a) concentrations across a range of temporal scales, land uses and climate regimes. While INCA-PEco is highly parameterized, they showed that model uncertainty, can be significantly reduced by focusing calibration and monitoring efforts on just 18 parameter, most of which are related to streamflow (i.e., base flow, Manning’s n and river depth). However, in catchments dominated by diffuse nutrient inputs, e.g., in agricultural areas, detailed data on crop growth and nutrient uptake rates are also important. The remaining parameters provide flexibility to the user, broaden model applicability, and maximize its functionality under a changing climate.

All model equations are exhaustively documented in the supplementary information.