WHY?
The iMOD RO-tool is based on the ArcGIS WaterNOOD-application (“WaterNOOD”approach: “Watersysteemgericht NOrmeren, Ontwerpen en Dimensioneren”) by Stichting Toegepast Onderzoek Waterbeheer ( STOWA).
The WaterNOOD-application provides water managers with information on hydrological requirements of farm crops and vegetation types, and helps them to predict the effects of water management measures on crop-yields and vegetation. The application is used in the water management of nature conservation areas and surrounding agricultural or urban areas.
The iMOD RO-tool (like the ArcGIS WaterNOOD-application) incorporates two knowledge/database/ model-based tools, that are widely used in the Netherlands to determine productivity of farm-crops and potential for development of groundwater dependent vegetation types under various abiotic conditions (soil type and soil-hydrology):
• “HELP2005-tabellen”for calculating farm crop productivity. (see also: http://help200x.alterra.nl/HELP2005.pdf and http://help200x.alterra.nl/)
• “WATERNOOD - Hydrologische randvoorwaarden natuur”for calculating potential for development of groundwater dependent vegetation types.(see also: http://www.synbiosys.alterra.nl/waternood/ and
http://waterwijzer.stowa.nl/upload/publicatie2014/STOWA%202015%2022_Webversie%20LR.pdf)
Note: Because this is a Dutch spatial planning tool, based on a Dutch policy-makers’approach for optimizing groundwater regimes for agriculture and nature restoration, Dutch remarks are included.
WHAT?
Abiotic conditions determine productivity of farm-crops and potential for development of groundwater dependent vegetation types. The tool calculates productivity of farm-crops and potential for development of groundwater dependent vegetation types, as a function of abiotic conditions (soil type, seasonal groundwatertables).
Agriculture: actual crop-yield, compared to crop-yield under optimal conditions. The RO-tool calculates the actual crop-yield (relative to crop-yield under optimal abiotic conditions) and decrease of crop-yield due to moisture-stress (“natschade landbouw”) or respiration-stress (“droogteschade landbouw”), given the actual, site specific abiotic conditions (soil type, seasonal groundwatertables). Decrease of crop-yield is calculated in % and/or Euros. doelrealisaties (= 1 –[opbrengstreductiepercentage t.o.v. optimale condities]/100)
Natural vegetation: potential for development of groundwater dependent vegetation types. The RO-tool calculates the potential for development of pre-defined groundwater dependent vegetation types. The potential is expressed as a percentage, relative to the potential for development under optimal abiotic conditions. doelrealisaties (= 1 –[actuele ontwikkeling vegetatie/ontwikkeling vegetaties onder optimale condities]
Urban area: suitability for urban development, as a function of groundwatertable-depth. The RO-tool calculates the suitability for urban development, based on a range of drainage-level, defined in a lookup-table. Groundwatertable above the upper range results in a 0% suitability for building, groundwatertable between upper and lower range results in a 50% suitability for building, and groundwatertable below the lower range results in a 100% suitability for building.
HOW?
The RO-tool is a post-processing scenario-tool. The user can use pre-defined maps of soil types, landuse (crop types) and vegetation types and pre-defined tables of hydrological requirements for vegetation and/or habitat types. All these maps and tables can also be modified by the user, to meet special interests. Input for the hydrological conditions are the Dutch groundwater-table-depth statistics maps (“GHG, GLG, GVG”). They are the result of a groundwate rmodel simulation. The user can run the RO-tool for different groundwater model scenarios.
Explanation of the Dutch groundwatertable-depth statistics (“GHG, GLG, GVG”): The groundwater-table-depth statistics (Mean Highest, Mean Lowest or Mean Spring Watertable depth). The Mean Highest Watertable (MHW or GHG) is defined as the mean value of the three shallowest groundwater depths measured in one year (in meter beneath soil surface), averaged over a period of 8 years with bi-weekly measurements or simulation-results. The Mean Lowest Watertable (MLW or GLG) is defined likewise, with the deepest groundwater depths. The groundwater depths measured at three dates nearest to April 1, are used for calculation of the Mean Spring Watertable (MSW or GVG). The period to calculate MHW is defined between October 1st and April 1st.
Important Note: Despite the fact that the iMOD RO-tool is based on version 2 of the “WaterNOOD”application, it is possible to implement tables with hydrological requirements for user defined vegetation/habitat-types, created with “WaterNOOD”version 3. The tables can be created with and exported from the “WaterNOOD”application, version 3. To download “WaterNOOD”version 3 go to: http://www.synbiosys.alterra.nl/waternood/ and follow the instructions in the manual to export the user created tables for later use in iMOD RO-tool.
Before starting the RO-tool, the desired settings need to be defined in the Preference file (see section 9.1). The preference tab at the RO-tool window is filled with these settings. The keywords in the preference file are linked to the required input files of the RO-tool. section 7.12.2 contains a list and description of these files. In section 7.12.3 the operational setup of the RO-tool is explained and in section 7.12.4 a list of output files and a short explanation can be found. To start the RO-tool window, select the Toolbox option from the main menu and then choose RO-tool from the bottom of the menu-list.
In this section an explanation is given about each tab on the RO-tool window. General settings on the RO-tool window are:
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Compute... |
Click on this button to start the scenario based map calculation with the given settings. |
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Help… |
Click on this button to search for relevant information in the iMOD-manual if the directory of the file is defined in the PRF-file (see section 9.1). |
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Cancel |
Click on this button to Quit the RO tool without saving or computing anything. |
After all settings are selected the user can click on the Compute... button to start the scenario computation. Directly after starting the calculation iMOD checks continuously which input files and lookup-tables are needed. The computation is performed per selected subtype. In case one scenario is chosen in combination with a reference situation, iMOD creates, additionally to the reference/scenario related result maps, a map with the difference between reference results and scenario results. Result-files are immediately loaded in the iMOD Manager.
Compute Settings tab:
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Select type |
Choose the preferred group of investigation questions. (Note: at this moment only the RO (flood related) type is available.) |
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Subtype |
Depending on the selected type a list of scenario related subtypes appears. Selecting 1 or more subtypes enables the Scenario Input tab. |
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Compare with reference situation |
Check this option if it is preferred to compare the selected scenario with a reference (or other) situation. Checking this option enables the Reference Input tab. |
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Sprinkling on |
This option is only available in drought related scenarios. Check this option if re-wetting through sprinkling during a period of drought is wished. By applying this option, respiration-stress of farm crops is eliminated. |
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Output directory |
Enter the name of the output directory where iMOD stores the scenario results. Default: TMP-folder in the USER directory. |
Scenario Input tab:
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GHG |
Enter the directory and name of the GHG-file to be used in the scenario. |
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GLG |
Enter the directory and name of the GLG-file to be used in the scenario. |
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LUSE (Optional) |
Enter the directory and name of the landuse type related file to be used in the scenario (Note: only available if at least an Agriculture-subtype is chosen, or a combination of Agriculture- and Nature-subtypes; not available if only a Nature-subtype is chosen). |
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NDT (Optional) |
Enter the directory and name of the file with the vegetation type(s),"natuurdoeltype kaart" (Note: only available if a Nature-subtype is chosen, or in a combination with a Nature-subtype and Agriculture-subtype). |
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Result |
Enter the directory and name of the result file (Note: not available if more than 1 subtype is selected). On default the Output Folder is selected and the name of the results file equals the chosen subtype description *.idf, e.g. subtype="natschade_landbouw" the name of the file is "natschade_landbouw_SCEN.IDF". |
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Legend |
Enter the directory and name of the legend file (Note: not available if more than 1 subtype is selected). |
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Reference Input tab:
Only available if option Compare with reference situation on tab Compute Settings is checked.
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GHG |
Enter the directory and name of the GHG-file to be used in the scenario. |
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GLG |
Enter the directory and name of the GLG-file to be used in the scenario. |
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LUSE (Optional) |
Enter the directory and name of the landuse type related map to be used in the scenario (Note: only available if at least an Agriculture-subtype is chosen, or a combination of Agriculture- and Nature-subtypes; not available if only a Nature-subtype is chosen). |
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NDT (Optional) |
Enter the directory and name of the file with the vegetation type(s), "natuurdoeltype kaart" (Note: only available if a Nature-subtype is chosen, or in a combination with a Nature-subtype and Agriculture-subtype). |
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Result |
Enter the directory and name of the result file (Note: not available if more than 1 subtype is selected). On default the Output Folder is selected and the name of the results file equals the chosen subtype description *.idf, e.g. subtype="natschade_landbouw" the name of the file is "natschade_landbouw_SCEN.IDF". |
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Legend |
Enter the directory and name of the legend file (Note: not available if more than 1 subtype is selected). |
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|
Click on this button to search for the needed file. |
On the Scenario Input tab and Reference Input tab, it is not necessary to fill in the fields for LUSE ("landgebruik") and NDT ("natuurdoeltype"). When empty, iMOD uses the defined file as given in the Preference file; defined with keyword LANDUSE in case of LUSE and keyword NDT in case of NDT. As mentioned, it is not possible to fill in the fields for Result and Legend whenever more than 1 scenario objective is chosen.
Input Preferences tab:
This tab contains all information as defined in the Preference file (section 9.1), including cross reference tables, lookup tables and basic files. Files may be placed in any directory and/or different directories on user’s harddisk(s).
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Item |
List of the preference keywords. |
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Assigned file |
Name and directory of a file referring to Item. |
The needed input files to be prepared:
• Two IDF-files, one containing the GHG and one with GLG information in meters relative to surface level (positive values = below surface level). A minimum of 1 set is required for the scenario situation.
• A landuse map (IDF-format) according to the LGN5 encoding.
• A soil map (IDF-format) with HELP soil units and RFC soil units (explained later in more detail). This conversion from the 1:50.000 soil map to HELP soils and to RFC soils is done by Deltares, using a conversion table.
• A map of vegetation types (NDT, natuurdoeltypenkaart), with encoding matching the lookup-tables NDT_LUT and ABIOT_LUT.
• So called “HELP”-tables, with HELP2005-database, containing relations between crop - soiltype - GHG/GLG -respiration/moisture-stress.
As mentioned in section 7.12 “WHY?”, actual crop-yield, decrease of crop-yield and potential for development of selected vegetation types are determined by use of the two knowledge/database/ model-based tools:
• “HELP2005-tabellen”for calculating farm crop productivity.
• “WATERNOOD - Hydrologische randvoorwaarden natuur”for calculating potential for development of groundwater dependent vegetation types.
The RO-tool requires maps, tables and binary files that represent the above mentioned knowledge/database/ model-based tools.
To calculate Agriculture-subtypes, these files from “HELP2005-tabellen”are required:
• HLP_DRY.DAT HELP2005-database: crop|soiltype|GHG/GLG|respiration-stress.
• HLP_WET.DAT HELP2005-database: crop|soiltype|GHG/GLG|moisture-stress.
• HLP_SOIL.IDF Raster file: 1:50.000 soil map reclassified for HELP2005 (using bod2hlp.lut).
• LUSE\LGN5.IDF Raster file with land use types in LGN5-codes.
• CROP_COSTS.LUT Lookup table with crops (in LGN5-codes) and crop-yields (Euro/ha/year).
To calculate Nature-subtypes, these files from “WATERNOOD - Hydrologische randvoorwaarden natuur”are required:
• RFC_SOIL.IDF Raster file: 1:50.000 soil map reclassified to RFC-soils (using bod2rep.lut).
• RFC_LUT.LUT Lookup table with RFC(reprofunction)-characteristics.
• NDT.IDF Raster file with vegetation types to calculate potential development for.
• NDT_LUT.LUT Lookup table with option to aggregate vegetation types.
• ABIOT_LUT.LUT Lookup table: hydrologic requirements for vegetation types (NDT’s).
To calculate Urban area:
• URBAN_RANGE.LUT Lookup table with range of drainage-level (upper- and lower value in meter below surface)
Realization of the RFC soil map
A soil map containing 1:50000 soil codes is needed for this realization as well as a field with an assimilation of the fields "VOOR", "LETTER", "CIJFER", and "KALK". In case a new field needs to be added, ArcView3.x can be used by fill in the following line in the Field calculator:
[VOOR]+[LETTER]+[CIJFER].ASSTRING+[KALK]. The associations are not included in the conversion table and therefore the value of the field "EERSTE_BOD" can be used as a replacement. In the soil map, the codes related to excavated soils starting with a "|"-character are represented in the conversion table with the first two characters of the soil code (RFC-value = 99). All codes starting with a "|"-character can be selected by making use of a query function (in ArcView3.x), e.g. ([fieldname]).contains("|"). Via the calculator the specific field can be filled with the first 2 characters by making use of
[CODE].LEFT(2). Similar functions are available in ArcGis. A final step in the preparation of a RFC soil map is joining the soil map with the table RFCCODES.DBF.
Realization of the HELP soil map
The same soil map (1:50000 soil codes) as was used for the realization of the RFC soil map, is needed for realization of the HELP soil map. Only now an additional field is needed, containing the groundwater tables. Accordingly, a compilation of the following fields is included in the map: "VOOR", "LETTER", "CIJFER", "KALK", and "GWT". This field is available in most of the soil maps labeled as "CODE". Next, the "BOD50_2_HLP.DBF" table needs to be joined to the "GWT"-field and converted to a raster format on field "HELPID".
To start the computation of the RO-tool, it is necessary to define at least a GHG- and/or a GLG-file (depending on chosen subtype) on the scenario tab. If iMOD cannot find all needed files, an explanatory error is raised. In case a scenario has to be compared with a reference situation, computation is only possible if all required files are defined in the Scenario Input and Reference Input tabs. At the moment everything is correctly defined, clicking on Compute... executes the computation.
In case of comparing a scenario with a reference situation, the output contains:
1. For both scenario and reference:
(a) For Agriculture-subtypes: an IDF and table with actual crop-yield (relative to crop-yield under optimal abiotic conditions), and/or an IDF and table with decrease of crop-yield due to moisture-stress (“natschade landbouw”) or respiration-stress (“droogteschade landbouw”).
(b) For Nature-subtypes: an IDF and table with the potential for development of chosen vegetation types, expressed as a percentage, relative to the potential for development under optimal abiotic conditions.
(c) An IDF and table with the difference between the scenario results and the reference situation results for chosen Agriculture and Nature subtypes (difference = reference - scenario).
In case the computation is limited to 1 situation (either scenario, or reference), the output only contains one IDF and table with either actual crop-yield, decrease of crop-yield, or potential for development of chosen vegetation types, depending on the chosen subtype(s).
Calculation of subtype “Urban Area” returns an IDF and table with suitability for urban development (values 0, 50 and 100). A range for drainage-level is defined in a lookup-table. Groundwatertable above the upper range results in a 0% suitability for building, groundwatertable between upper and lower range results in a 50% suitability for building, and groundwatertable below the lower range results in a 100% suitability for building.
The output of the computation contains:
1. IDF-files (raster files) containing:
• Agriculture: decrease of crop-yield due to moisture-stress and respiration-stress (“natschade landbouw”, “droogteschade landbouw”).
• Agriculture: actual crop-yield, relative to crop-yield under optimal abiotic conditions (“doelrealisatie landbouw”).
• Nature: potential for development of pre-defined groundwater dependent vegetation types, expressed as a percentage, relative to the potential for development under optimal abiotic conditions (“doelrealisatie natuur”).
• Urban Area: suitability for urban development (“doelrealisatie stedelijk”).
2. A table with:
• Total crop-yield for all crops in scenario and reference situation (if applicable).
• Total yield per area.
• Average decrease in crop-yield, for both decrease of crop-yield due to moisture-stress and respiration-stress.
• Computed area of total extent with pro-/regression per subtype (crop-yield, vegetation type, urban class).
The output per subtype is managed over the surface area for which the computation was performed. Cells within the area but lacking any information (nodata values), are not taken into account and therefore these cells are not visible in the output totals.
