The Soil and Water Assessment Tool
The Blue Nile Catchment
Ann van Griensven
Senior Lecturer of Environmental Hydroinformatics, UNESCO-IHE
0. Before getting started
0.1 Set your data together
The Blue Nile model is only by means of global and freely available information.
The collection of the data was followed by an accurate compilation and analysis of the
quality and integrity.
(i) Digital elevation model (DEM)
- DEM-HYDRO1k: the U.S. Geological Survey’s (USGS) public domain geographic
database HYDRO1k (http://edc.usgs.gov/products/elevation/gtopo30/hydro/index.html),
which is derived from their 30 arc-second digital elevation model of the world
GTOPO30. HYDRO1k has a consistent coverage of topography at a resolution of 1
kilometer.
(ii) Digital stream network (DSN):
- DSN-HYDRO1k: The USGS’ HYDRO1k stream network database is derived from the
flow accumulation layer for areas with an upstream drainage area greater than 1000 km2.
(iii) Soil map:
-SOIL-FAO: Food and Agriculture Organization of the United Nations (FAO, 1995)
provides almost 5000 soil types at a spatial resolution of 10 kilometres with soil
properties for two layers (0-30 cm and 30-100 cm depth). Further soil properties (e.g.
particle-size distribution, bulk density, organic carbon content, available water capacity,
and saturated hydraulic conductivity) were obtained from Reynolds et al. (1999) or by
using pedotransfer functions implemented in the model Rosetta
(http://www.ars.usda.gov/Services/docs.htm?docid=8953).
(iv) Landuse map
- LANDUSE-GLCC: the USGS Global Land Cover Characterization (GLCC) database
(http://edcsns17.cr.usgs.gov/glcc/glcc.html) has a spatial resolution of 1 kilometre and 24
classes of landuse representation. The parameterization of the landuse classes (e.g. leaf
area index, maximum stomatal conductance, maximum root depth, optimal and minimum
temperature for plant growth) is based on the available SWAT landuse classes and
literature research.
(v) Weather data:
-WEATHER-CRU/dGen: The Climatic Research Unit (CRU,
http://www.cru.uea.ac.uk/cru/data/hrg.htm) data-sets TS 1.0 (wet days per month; New et
al., 2000) and TS 2.0 provides precipitation and average minimum and maximum
temperature per month (Mitchell et al., 2004). These monthly climate grids have a
resolution of 0.5°. Daily weather values for each sub-basin were generated based on CRU
data using the semi-automated daily weather generator algorithm dGen (Schuol and
Abbaspour, 2007). To make use of the climate grid in SWAT, dGen changed the grid
data into synthetic station data by overlaying the climate grids with SWAT subbasins
shape-file and then aggregating into point data. This program creates Thiessen polygons
around each value point representing the center of the grid cell, overlays and intersects
the subbasin layer with the climate grids and finally computes the area-weighted average
which is then assigned to each subbasin centroid.
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Spatial data
Check the following data:
Resolution
DEM
Land Use map
Soil Map
FAO
Projection
Projection
known?
Y/N (should
be YES)
Projection
same as
DEM ?
Y/N (should
be YES)
Projection
same as
DEM ?
Y/N (should
be YES)
Database
-
Other crops than mentioned in
crop.dat?
Y/N
../AVSWATX/AvSwatDB/crop.dat
Database or update usercrop.dbf
If outside US, update/replace the
../AVSWATX/AvSwatDB/
usersoil.dat database
How to change projection (geographic to projected)?
1.
2.
3.
4.
5.
6.
7.
8.
You make a table in *.xls
Save it as txt or dbf
Go to Arview, to tables and add the table
Go to a view, go to Theme menu and choose “add theme event” where you select
the table and the X/Y fields
GO to View properties and give map units (meters) and distance (km)
You select projection, select costum projection and give the properties.
Go to theme and convert to shapefile (save as location.shp).
You can now load it in your SWAT view or watershed.
For the Blue Nile case, we use the following data:
DEM
Resolution
1 km
Land Use map
1 km
Soil Map
10 km
Projection
Projection
known
Projection
same as
DEM ?
Yes
Projection
same as
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Database
Other crops than mentioned in
crop.dat?
Yes
../AVSWATX/AvSwatDB/crop.dat
database
update the
../AVSWATX/AvSwatDB/
DEM ?
Yes
usersoil.dat database
Climate/weather data
Weather Generator Files
You need a table with LOCATIONS and NAMES of stations with weather generation
info located in your data directory.
Please replace the file
../AVSWATX/AvSwatDB/Userwgn.dbf with the
../data/ata\soil_landuse_wgn_database/ Userwgn.dbf file
Rainfall data
You need a table with LOCATIONS and NAMES of stations with daily rainfall data +
files with the data located in your data directory.
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Temperature data
You need a table with LOCATIONS and NAMES of stations with daily minimum and
maximum temperature data + files with the data located in your data directory.
0.2 Replace the databases with Nile-databases
You should put your databases in folder ../data/ata\soil_landuse_wgn_database/
- Crop.dat
- Crop.dbf
- Usersoil.dbf
- Userwgn.dbf
In ../AVSWATX/AvSwatDB/
You find these in the ..\Data\soil_landuse_wgn_database folder
0.3 Install AVSWAT-X (Using ArcView 3.x and Spatial Analysis)
You can find AVSWATX at:
ftp://ftp.brc.tamus.edu/pub/swat/pc/swatav/avswatx.zip
or
http://www.brc.tamus.edu/swat/downloads/pc/swatav/avswatx.zip
After unzippen, you should click on setup.apr. The installation will go from itself. If all
goes OK, you should be able to select the AVSWATX extension in ArcView. If you have
problems, you may need to choose ‘only for me’ option while installing AVSWATX.
0.4 Update swat2003.exe
After installing AVSWAT-X you have to put an update of swat2003.exe into
AVSWATX/AvSwatPr/
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I Getting started....
I.1 Activate AVSWATX as an extension
Open ArcView (in ESRI folder of the programmes listed in the start menu). Choose
Cancel for this window.
Open AVSWAT-X as an extension.
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PROBLEM: AVSWATX is not in the extension list. This means that AVSWAT-X was
not installed -> See step 0.3
PROBLEM: you can not run the extension: this might be due to authorisation issues. Try
to install AVSWATX with proper authorisation.
I.2 Open a new project
Make a directory (e.g. D:\\AVSWATX\NILE) and put your data directory there and put
all the data in that folder.
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.
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Open a new project, e.g. name NileModel in the Nile directory:
Make proper reference to the data directory:
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II DEM delineation
II.1: DEM Set-up
Load your DEM by clicking on the open folder symbol:
Choose “Load DEM grid from disk”.
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Select dem_af
You should provide the projection information for the DEM.
PROBLEM: you can not load the DEM (or other maps). This might be due to having
‘spaces’ in folder or file names. E.g. ‘Nile Model’ in stead of ‘NileModel’
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Load the mask and digitized streams network in the same way and push on ‘Apply’
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PROBLEM: Apply is not activated. This is probably because the projection has not been
specified.
You’ll get the following window:
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Answer ‘Yes’
II.2: Stream definition
Provide threshold area = 1 000 000 ha, then push on ‘Apply”.
Select manually the outlet of the Blue Nile (use the focus in ArcView).
II.3 Save your project
If the DEM processing was successfull, please SAVE your project
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III Definition of Land Use and Soil Themes
III.1 Define the Land Use data
Push on the open folder symbol and select a first “Load Land Use theme from Disk” and
hence “Grid”.
Open the folder for the Lookup data:
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Load the User table (named “\Lookup\landuse.dbf”)
Push on “Reclassify”
PROBLEM: Reclassify is not activated. This is probably because the lookup table was
not loaded.
III.2 Define the Soil data
The soil grid is loaded in the same way as the Land Use grid. A lookup table
“soil_af.dbf”has to be loaded (option “Name”).
PROBLEM: Reclassify is not activated. This is probably because the lookup table was
not loaded.
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III.3 Overlay Soil and Land Use map
Just by clicking on “overlay”.
PROBLEM: Overlay is not activated. This is probably because you should first push on
“reclassify” both Land Use as for the Soil data.
III.4 Save the project
IV Definition of Land Use/Soil distribution
IV.1 Define the Hydrological Response Units
Select: “Multiple Hydrologic Response Units”, and select the thresholds (5%/5% in this
example). Push “OK”
If all goes well, AVSWATX will automatically load the SWAT View
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You can switch between the views “SWAT View” and “Watershed” in the Windows
menu.
IV.2 Save your project
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V load the weather data
V.1 Open “Input” menu and select “Weather Stations”
V.2 load the rainfall data
Select “Raingages” and load the file pcpnile.dbf
V.3 load the temperature data
Select “Climate stations” and load the file tmpnile.dbf
V.4 load the weather simulation data
Select “Custom database” and load the file wgnnile.dbf
V.5 Push OK
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VI Build the input data
VI.1 select “Input” menu and select “Build all defaults”
The following windows will get open. All types of input files will be created one by one.
VI.2 Create Watershed Configuration File (.fig)
Just push on ‘Continue’
VI.3. Create Soil Input (.sol)
In case of error:
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Please update the ../AVSWATX/AvSwatDb/usersoil.dbf file (step 0.2) for the Nile data
set
VI.4 Create Weather Generator Input (.wgn)
In case of error
Please update the ../AVSWATX/AvSwatDb/userwgn.dbf file (step 0.2) for the Nile data
set.
VI.5 Create Subbasin General Input (.sub)
Select ‘No’
VI.6 Create HRU General Input (.hru)
VI.7 Create the Main Channel Input (.rte)
Select ‘No’
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VI.8 Create Groundwater Input (.gw)
VI.9 Create Water Use Input (.wus)
VI.10 Create Management Input (.mgt)
Select ‘Yes’
In case of the error:
Please update the ../AVSWATX/AvSwatDb/crop.dbf file and
.../AVSWATX/AvSwatDb/crop.dat (step 0.2) for the Nile data set.
VI.11 Create Soil Chemical Input (.chm)
VI.12 Create Pond Input (.pnd)
VI.13 Stream Water Quality Input (.swq)
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VII Run SWAT
Select in menu “Simulation” the option “Run SWAT”
The following window will open:
Push first on “Setup SWAT RUN”
Select “No”
Push on “Run SWAT”
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In case of the error:
Please update the swat2003.exe in ../AVSWATX/AvSwatPr/swat2003.exe (replace the
file) as described in step 0.4 or you should update cr../AVSWATX/AvSwatDb/crop.dat
in step 0.2
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VIII Reading the outputs
If SWAT ran successfully, you get this window. Push on ‘Yes’.
Go to the SWAT view. You can look at the results by using “MapChart’ Option in the
reports menu.
Select a simulation:
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You can select a subbasin (in case you want to see a basin wide map, it does not matter),
a variable (see SWAT manual) and a time period. SWAT will calculate a Chart (time
series) and a basin-wide map then for the variable. You can find the map in the SWATView.
The Chart corresponds to the selection in the table. If you select more lines (use the shift),
you will get more results in the chart. You can export the table (only the selections) and
the map towards a *.jpg (View -> Layout; File -> export
)
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You can find other results in the Report -> show list (e.g. basin wide statistics in the .std
file). You can also find output tables in
Or find the actual input and output files in the txtinout folder.
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IX Manually changing the input files
You can change the inputs in the EDIT INPUT menu (SWAT view). If you chose
‘subbasin parameters’ you get the following window. You can select a subbasin, a land
use and a soil type and an input file extension (see SWAT manual).
e.g You can add operations in the management file.
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After you have done the change, you can copy these to other HRU’s in the following
window
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Another way of changing parameters is to edit de dbf in the default/tablesin/ folder.
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To have these changes activated in your model, you should do the following
Open the SWAT simulation window, push on ‘setup SWAT run’ select Ýes
After you have done this, you should rewrite the input files of the changed dbf’s:
Your simulations will be stored in a separate folder
(sim#+1).
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X Running the sensitivty and auto-calibration tools
X.1 Activating the sensitivity and auto-calibration tools
These tools can be activated in the SWAT View by choosing “AVSWATX extensions”
in the “Tools” menu. Please activate AVSWATX Sens-Auto-Unc. When done
successfully, you will find options “sensitivity analysis” and “auto-calibration and
uncertainty” in the “Tools” menu.
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X.2 The sensitivity analysis
X.2.1 Running the sensitivity analysis
The sensitivity analysis is started at “tools menu”. First, a window appears where you can
select the scenario and the simulation. Next, a the following window will appear. You
can choose here between an analysis for flow only, flow and suspended sediments or also
for Water Quality. For the sediments and other water quality variables, you can choose
between an analysis on the loads or the concentrations.
A sensitivity analysis will be carried out by default on the change of the mean value of
the output variables of interest (e.g. mean flow during the entire simulation time). In
addition, you can also do a sensitivity analysis on the objective function that is of interest
for calibration. This is only possible in case you load an observation file with the
observations of the variable of interest. In that way, the objective function (by default
equal to the sum of the squared errors between the observations and the simulations) will
be calculated during each run. The effect of a change of a parameter value on this
objective function will then be calculated.
After pushing on the “start” bottom, 340 simulations will be started.
X.2..2 Looking at the input files
C:\AVSWATX\swatdemo2\scenarios\default\sim1\txtinout\sensitivity\
The main sensitivity input file is sensin.dat
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Some files have been changed:
- file.cio
- basins.fig
Other input files (general) are:
- changepar.dat
- objmet.dat
- responsmet.dat
X.2.3 Looking at the results
By clicking on the “REPORT” bottom, the following window will appear: This gives a
list of the parameters ranking. Each line corresponds to a result. The results for OF1 refer
to the results for the Objective Function (Sum Squared Errors) for flow while OF2 refers
to the sediment loads (this will not make much sense, since no data where provided for
the sediment loads). OUT1 refers to the sensitivity analysis results for the average flow
output, while OUT2 provides a ranking for the average sediment load output. You can
see that for all the outputs, the Curve number is the most sensitive (it gets rank 1).
Parameters that are not sensitive at all, get the rank 35 = number of parameter +1.
More
details
can
be
found
at
sensout.out,
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sensobjf.out,
sensrespons.out.
X.3. The auto-calibration
X.3..1 Running the auto-calibration
An auto-calibration can be started by clicking on the “auto-calibration and uncertainty”
option of the menu “Tools”. After selecting a scenario and a simulation, the following
winding will appear:
First, you should select parameters (as example, select “Sol_K”, “Cn2”, “Alpha_Bf”, and
“Surlag”). You can change default settings for the parameters by dubbelclicking on the
parameter names. Please do so for CN2, where the update method and ranges were
changes according to:
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Next, you can select a watershed outlet, and providing an observation file for that node
by dubbelclicking on the number of the outlet. In this example case, the outlet of the
entire basin corresponds to outlet number “3”. For an auto-calibration, you should first
make an observation file. We did not provide this for this exercise.
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X.3.2 Looking at the input files
The ParaSol input file that has been created is called ParaSol.in. It contains the control
parameters for the SCE-UA algorithm and some statistics for the uncertainty analysis.
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X.3.3.3 Looking at the results
The best start is to open the report “detailed output for each optimisation loop”, what
corresponds to the “parasolout.out” file.
The first part of the files gives an summery of the inputs: the parameters are listed (these
are also listed in “changepar.dat”, followed by a list of objective functions, also listed in
“objmet.dat”(only one in our case), and the outputs of interest (however, not used in
calibration) that are listed in “responsmet.dat”. The general control settings for the SCEUA optimisation method, given in parasolin.dat, are listed below.
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Below, intermediate results for each loop will be given. You can manually interrupt the
calibration process. In that case, the results of the last loops can be used for further
processing. During the loops, we see that the Nash-Sutcliffe efficiency improved from
-8.21 to 0.31.
If ParaSol itself ends the optimisation, you will find the following below the
parasolout.out file, with some statistical results on uncertainty:
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The best parameter sets are printed in bestpar.out
0.99912E+02
Sol_K
0.00000E+00
Surlag
0.95914E+02
CN2
0.10000E+01
Alpha_Bf
Unfortunately, here stops the automated part of the auto-calibration. To actually run the
best parameter sets, you have the following options:
-
you manually change the parameters through the interface. In that way, you can
further use the interface for further changes, output data processing etc. The
quickest way is probable to update the tables
C:\AVSWATX\swatdemo2\scenarios\default\tablesin
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For instance, you will find the CN2 values in the file mgt1.dbf. For rerunning
SWAT, you should choose the option for “YES” in window below and rewrite the
corresponding files (when updating mgt1: this is mgt).
-
you run your model outside the interface, but that is much less user friendly. To
do so, you should copy C:\AVSWATX\AvSwatPr\swat2003.exe to
C:\AVSWATX\swatdemo2\scenarios\default\sim1\txtinout\autocalibration and change
ICAL=4 in File.cio.
Reference:
Tessema R., Agricultural Drought Assessment for Upper Blue Nile Basin,Ethiopia using
SWAT, MSc Thesis, Master of Water Science and Engineering, UNESCO-IHE,
2007.
Schuol, J., Abbaspour, K.C., 2007. Using monthly weather statistics to generate daily
data in a SWAT model application to West Africa. Ecol. Model. 201, 301-311.
SWAT manuals that can be found at http://www.brc.tamus.edu/swat/
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