A nitrogen model for European catchments: INCA, new model structure and equations

Abstract

A new version of the Integrated Nitrogen in Catchments model (INCA) was developed and tested using flow and streamwater nitrate concentration data collected from the River Kennet during 1998. INCA is a process-based model of the nitrogen cycle in the plant/soil and instream systems. The model simulates the nitrogen export from different land-use types within a river system, and the in-stream nitrate and ammonium concentrations at a daily time-step. The structure of the new version differs from the original, in that soil-water retention volumes have been added and the interface adapted to permit multiple crop and vegetation growth periods and fertiliser applications. The process equations are now written in terms of loads rather than concentrations allowing a more robust tracking of mass conservation when using numerical integration. The new version is able to reproduce the seasonal dynamics observed in the streamwater nitrogen concentration data, and the loads associated with plant/soil system nitrogen processes reported in the literature. As such, the model results suggest that the new structure is appropriate for the simulation of nitrogen in the River Kennet and an improvement on the original model. The utility of the INCA model is discussed in terms of improving scientific understanding and catchment management.

A cost-effectiveness analysis of water security and water quality: impacts of climate and land-use change on the River Thames system

“…A comprehensive process-based dynamic model INCA [25][26][27][28] has been set up for the whole of the Thames catchment, so that we can investigate effects of changes in land use and climate on flow, water quality and ecology. Jin et al [20] applied the nitrogen version of INCA to the whole Thames system and evaluated the effects of climate change on flow and water quality.…”

Modelling flow and inorganic nitrogen dynamics on the Hampshire Avon: Linking upstream processes to downstream water quality

“…One other aspect that needs to be considered in any modelling study is that of model uncertainty. INCA-N has been the subject of many uncertainty investigations, including Whitehead et al, 1998b, Wade et al, 2002, and McIntyre et al, 2005. All these studies demonstrate that process based models are difficult to calibrate and there is always some degree of equifinality occurring, whereby processes can duplicate behaviours making it difficult to find truly unique parameter sets.…”

“…A major issue with modelling is how to calibrate models and the nitrate removal rates are crucial parameters as emphasized by Whitehead et al (2011) and Wade et al (2002). The advantage of having a set of process experiments is that it is possible to use the measured nitrate loss rates for the measured tributaries to extrapolate to un-monitored river reaches, or to create a weighted average to use in the modelling.…”

“…The Integrated Catchment model for Nitrogen (INCA-N) was first developed by Whitehead et al in 1998 to simulate flow, nitrate and ammonium concentrations in soil, streams and groundwater (Whitehead et al, 1998 a, b) and later modified by Wade et al (2002). The process-based INCA model tracks the movement, stores and fluxes of water, nitrate and ammonium in both the land and in-stream components of a river system.…”

Applying profile- and catchment-based mathematical models for evaluating the run-off from a Nordic catchment

“…Flows from the soil and groundwater zones are controlled by residence times in the reservoirs. The Base Flow Index is used to split between the volume of water stored in the soil and the groundwater (Wade et al, 2002). Calculation of river flow is based on mass balance of flow and on a multi-reach description of the river system (Whitehead et al, 1998).…”