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This project is co-financed by the European Regional Development Fund through the Interreg Alpine Space programme

This project is co-financed by the European Regional Development Fund through the Interreg Alpine Space programme

This project is co-financed by the European Regional Development Fund through the Interreg Alpine Space programme

wiki:nitrogen_removal_2

Filtration of surface water by ecosystem types - Flow

General description

InVEST “Nutrient Delivery Ratio (NDR)” model, specifically focusing on nitrogen. The model uses a mass balance approach, which describes the movement of a mass of nutrients through space. Unlike more sophisticated nutrient models, the present approach does not represent the details of the nutrient cycle but rather represents the long-term, steady-state flow of nutrients through empirical relationships. A detailed description of the model can be found at://data.naturalcapitalproject.org/nightly-build/invest-users-guide/html/ndr.html

Input Data

  • Land use map
  • Biophysical table with data on specific coefficients regarding Land cover/land use (LULC) type, nutrients and water (listed in Table 1 of this document).
  • Nutrient runoff proxy, a raster dataset with the yearly average amount of precipitation
  • LAU2 boundaries

Calculation process

(1) Prepare Input data for InVEST NDR model

To run the model both raster and shapefile data are required. To avoid errors, it is advised to harmonize the data using the same projection, linear units, and cell size and then snapping the rasters to the DEM.

To obtain the results at the municipal level the Eurogeographics LAU2 Boundary Map was used instead of a watershed shapefile.

(2) Calculate the parameters required in the biophysical table

The biophysical table is a .csv table with information on LULC classes and specific nutrient and water coefficients used in the model. For some land uses these parameters have been refined using specific values (either modelled or based on a literature review) for the different regions in the Alpine Space, while for other coefficients the default values provided by InVEST have been used (See Table 1).

Table 1: default and recalculated parameters used in the Biophysical table


Parameter

Field name

Used value

Nutrient load for each land use

load_n

Recalculated for agricultural areas

The maximum retention efficiency for each LULC class, varying between zero and 1

eff_n

Default

The distance after which it is assumed that a patch of LULC retains nutrient at its maximum capacity (in meters)

crit_len_n

Default

The proportion of dissolved nutrients over the total amount of nutrients, expressed as ratio between 0 and 1

proportion_subsurface_n

Default

For the agricultural areas in the LULC map, the N input for the dedicated field of the biophysical table is calculated in kg/ha/year by summing up inputs from the following data sources:

  • Manure fertilization: values calculated using zonal statistics on the basis of the data from JRC (JRC, 2012).*
  • Wet and dry deposition: values calculated using zonal statistics on the basis of the data from the Norwegian Meteorological Institute (Norwegian Meteorological Institute, 2016).
  • Biological nitrogen fixation: proxy value taken from (Vries et al., 2011).

For all other LULC classes (i.e. urban fabric, forests…) the default values provided by InVEST were used.

(3) Set the other watershed parameters and Run InVEST NDR model

By running the NDR model, choosing the “Calculate Nitrogen Retention” option, the N load and N export per municipality are calculated. The model requires additional parameters that can be set before starting the calculation.

We used the following thresholds:

Table 2: Additional parameters required by the model


Parameter

Threshold

Subsurface Maximum Retention Efficiency

0.8

Subsurface Critical Length

150

Threshold Flow Accumulation

1000

Borselli k parameter

2

(4) Calculate the amount of filtered nutrients per municipality

The amount of nitrogen that is filtered in a municipality can be calculated from the outputs of the Nutrient Delivery Ratio model by subtracting the nitrogen exported per municipality from the total nitrogen load in the same area.

20181807water_filtration_flow.jpg

test_legens.jpg

Bibliography:

JRC (2012). Nitrogen load gridded dataset for Europe on HSMU level. http://afoludata.jrc.ec.europa.eu/dataset/nutrient-load-n-and-p-europe-basis-hsmu ;
accessed: 2017-12-07.

Natural Capital Project (2017). Invest documentation.http://data.naturalcapitalproject.org/nightly-build/invest-users-guide/html/ndr.html; accessed: 2017-12-07.

Norwegian Meteorological Institute (2016). Nitrogen deposition gridded dataset for years 2000-2015.http://www.emep.int/mscw/; accessed: 2017-12-07.

Vries, W. d., Leip, A., Reinds, G., Kros, J., Lesschen, J., and Bouwman, A. (2011). Comparison of land nitrogen budgets for european agriculture by various modeling approaches. Environmental Pollution, 159:3254–3268.


wiki/nitrogen_removal_2.txt · Last modified: 2018/07/18 11:41 by eurac