Watershed Delineation with MAPWINDOW Tutorial Tutorial for watershed delineation using MAPWINDOW 4.8 R3. Edited 2011 Comments to:
[email protected]
Watershed Delineation with MAPWINDOW 2011
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Watershed Delineation with MAPWINDOW 2011 Contents Introduction ............................................................................................................................................ 4 Watershed delineation ........................................................................................................................... 5 How to delineate a watershed in MAPWINDOWS step by step? ....................................................... 5 Delineating watersheds performing all steps at once. ..................................................................... 22 Works Cited........................................................................................................................................... 22 Comments to: ....................................................................................................................................... 22
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Watershed Delineation with MAPWINDOW 2011
Table of figures Figure 1 some advantages of MAPWINDOW compared to ESRI’s GIS ................................................... 4 Figure 2 MAPWINDOW website main screen ......................................................................................... 5 Figure 3 Select DEM ................................................................................................................................ 5 Figure 4 Fill pits screen............................................................................................................................ 6 Figure 5 DEM with pits filled ................................................................................................................... 6 Figure 6 Flow direction screen ................................................................................................................ 7 Figure 7 Slopes grid ................................................................................................................................. 7 Figure 8 Flow direction grid .................................................................................................................... 7 Figure 9 Dinf Flow Direction screen ........................................................................................................ 8 Figure 10 Flow direction grid .................................................................................................................. 8 Figure 11 contributing area screen ......................................................................................................... 9 Figure 12 Contributing areas DEM .......................................................................................................... 9 Figure 13 creating a shape file .............................................................................................................. 10 Figure 14 Zoom to the selected area and click in the desired outlet cell ............................................. 10 Figure 15 Creating contributing area .................................................................................................... 11 Figure 16 Contributing area of the selected outlet .............................................................................. 11 Figure 17 Dinfinity Contributing Area screen ....................................................................................... 12 Figure 18 Contributing area .................................................................................................................. 12 Figure 19 Grid network screen.............................................................................................................. 13 Figure 20 River network classified according to Strahler ..................................................................... 13 Figure 21 Longest upslope length ......................................................................................................... 14 Figure 22 Total upslope length ............................................................................................................. 14 Figure 23 Peuker Douglas input screen ................................................................................................ 15 Figure 24Stream source grid for the specific area ................................................................................ 15 Figure 25 Extreme upslope screen........................................................................................................ 16 Figure 26 Extreme upslope grid ............................................................................................................ 16 Figure 27 Slope Area screen.................................................................................................................. 17 Figure 28 Slope area grid ...................................................................................................................... 17 Figure 29 Length area stream input window ........................................................................................ 18 Figure 30 Grid indicator ........................................................................................................................ 18 Figure 31 Stream and Watershed input screen .................................................................................... 19 Figure 32 Stream order grid with main rivers up to Strahler’s order 4 ................................................ 19 Figure 33 Watershed grid ..................................................................................................................... 20 Figure 34 Stream reach shape file ........................................................................................................ 20 Figure 35 Watershed Grid to Shape file input screen ........................................................................... 21 Figure 36 Delineated watershed with the main rivers ......................................................................... 21 Figure 37 Watershed............................................................................................................................. 21
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Watershed Delineation with MAPWINDOW 2011
Introduction Nowadays there is a wide variety of GIS software providers such as MAPWINDOW, ESRI, GRASS, Quantum, SAGA, ILWIS, IDRISI and more. ESRI’s ESRI product ArcGIS is by far the most popular and complete one with many applications already developed. developed However, one negative side of ESRI is that is heavy software that requires lot of computational power. MAPWINDOWS is very light GIS software with the most most used applications, and new applications being developed that can easily run even in small and light portable notebooks. It allows working with files created by other software’s such as ESRI’s shape file. Moreover, it is FREE and with a friendly interface to develop new applications. Since it is a light application, it does not require much computational power and processing is much faster than ESRI ArcGIS; as Google states: “Every millisecond counts” [1]. MapWindow is an open source “Programmable Geographic Information System” that supports manipulation, analysis, and viewing of geospatial data and associated attribute data in several standard GIS data formats. MapWindow is a mapping tool, a GIS modelling system, and a GIS application programming interface (API) ( ) all in one convenient redistributable open source form [1]. While most of the freeware GIS software can’t work with ESRI’s shape files,, MAPWINDOW does. Its popularity is growing and some agencies already accepted its benefits; for instance, the t United States Environmental Protection Agency (US EPA) decided to use it as the GIS platform for its Better Assessment Science Integrating point and Nonpoint Nonpoin Sources (BASSINS) which is a multipurpose environmental analysis system [2 2].
ArcGIS
MAPWINDOW
Figure 1 some advantages of MAPWINDOW compared to ESRI’s GIS
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Watershed Delineation with MAPWINDOW 2011
MAPWINDOW can be downloaded at: http://www.mapwindow.org/
Figure 2 MAPWINDOW website main screen
Watershed delineation One of the most useful GIS applications is the delineation of watersheds. A watershed (or water decide) is the line that divides two basins [3]. In a mountainous area it can be easily defined by the mountain peaks, while in a flat area it is invisible. invisible MAPWINDOWS provides the “Watershed delineation” plugin to delineate watersheds. This plugin is part of the Terrain Analysis Using Digital Elevation Models (TauDEM) by David Tarboton and his students and collaborators [4] [5]. [ The delineation process may be performed by simple steps or automatically.
How to delineate a watershed in MAPWINDOWS step by step? Watershed can be easily delineated with some simple steps contained in: Watershed Delineation ->> Advanced TauDEm Functions •
Select the DEM. Go to Watershed Delineation ->> Advanced TauDEm Functions -> Select DEM.. There navigate to the folder and the selected DEM
Figure 3 Select DEM
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Watershed Delineation with MAPWINDOW 2011 •
Fill the pits. Go to Watershed Delineation ->> Advanced TauDEm Functions -> DEM Processing Functions ->> Fill Pits
Pits are cells surrounded by higher elevation cells that may interfere with the routing process. Such pits are identified and removed by raising its elevation to the the lowest one around its edge.
Figure 4 Fill pits screen
Figure 5 DEM with pits filled
•
Get the flow directions D8. D8 Go to Watershed Delineation ->> Advanced TauDEm Functions -> DEM Processing Functions -> D8 Flow Direction
This process creates 2 grids. One is the slope in the steepest descent direction, and the other contains the flow direction from each grid cell to one of its adjacent or diagonal neighbours, calculated using the direction of steepest descent. d The flow direction is obtained by checking the elevation difference with the 8 neighbouring cells
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Figure 6 Flow direction screen
Figure 7 Slopes grid
Figure 8 Flow direction grid
•
Get the flow directions Dinf. Go to Watershed Delineation ->> Advanced TauDEm Functions > DEM Processing Functions -> Dinf Flow Direction
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Watershed Delineation with MAPWINDOW 2011 This process assigns a flow direction based on the D-infinity D infinity flow method using the steepest slope slop of a triangular facet [6].. Flow direction is defined as steepest downward slope on planar triangular facets on a block centred grid.
Figure 9 Dinf Flow Direction screen
Figure 10 Flow direction grid
•
Get the contributing area. area. This step requires an outlet specified by a point shape file. In case it was not created, it can be easily created in MAPWOINDOWS with the Shape file editor plugin.
Create an outlet. First, a general contributing area has to be created. Go to Watershed Delineation ->> Advanced TauDEm Functions ->> DEM Processing Functions -> D8 Contributing Area
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Figure 11 contributing area screen
Figure 12 Contributing areas DEM
Then, verify that the shape file editor is selected (Pug-ins -> Shape file editor), select elect new to create a new shape file and click in the cell that will be the outlet. This shape file has to be a point.
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Watershed Delineation with MAPWINDOW 2011 Create a new shape file
Figure 13 creating a shape file
It will appear a warning that am empty shapefile was created. Just accceot and press ok. Now zoom to the where the outlet is to be created, press to add new shapefile, and click in the outlet cell.
Figure 14 Zoom to the selected area and click in the desired outlet cell
•
Contributing area.. Go to Watershed Delineation ->> Advanced TauDEm Functions -> DEM Processing Functions ->> D8 Contributing Area. Area Check the box Upstream of nodes and navigate to the folder and file of the created outlet. It may appear the warning that the shape file has no ID and it will be created automatically, just accept.
It gets the contributing area as the outlet’s own contribution plus the upslope cells that drain in to it.
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Figure 15 Creating contributing area
Figure 16 Contributing area of the selected outlet
•
Get the catchment area.. Go to Watershed Delineation -> Advanced TauDEm Functions -> DEM Processing Functions -> Dinf Contributing Area
It calculates a grid of the specific catchment area which is the contributing area per unit contour length. It uses the so called D--infinity infinity approach which is the steepest downward slope on planar triangular facets on a block centred grid. The contributing area of each grid cell is then t taken as its own contribution plus the contribution from upslope neighbours that have some fraction draining to it according to the D-infinity infinity flow model.
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Figure 17 Dinfinity Contributing Area screen
Figure 18 Contributing area
•
Get the river hierarchy.. MAPWINDOW allows to easily creating layers where the network is classified according to a hierarchy. Go to Watershed Delineation ->> Advanced TauDEm Functions ->> DEM Processing Functions -> Grid Networkss Order and Flow Path Lengths
It will create 3 grids contain for each grid cell 3 attributes [4]: 1. The longest upslope path which is the length of the flow path from the furthest cell that drains to each cell.
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Watershed Delineation with MAPWINDOW 2011 2. The total path which is the length of the entire grid network upslope of each grid cell. Lengths are measured between cell centres taking into account cell size and whether the direction is adjacent or diagonal. 3. The Strahler order number defined by the D8 Flow Direction grid. grid. These values are derived from the network defined by the D8 flow model. Source flow paths have a Strahler order number of one. When two flow paths of different order join the order of the downstream, flow path is the order of the highest incoming flow path. When two flow paths of equal order join, the downstream flow path order is increased by 1. When more than two flow paths join, the downstream flow path order is calculated as the maximum of the highest incoming flow path order or the second highest incoming flow path order + 1.
Figure 19 Grid network screen
Figure 20 River network classified according to Strahler
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Figure 21 Longest upslope length
Figure 22 Total upslope length
Usually the user needs the basin and river networks as shape files,, since some attributes such as area, length or river order are required to further analysis. MAPWINDOW provides prov a Stream Network Analysis toolset with tools for creating and analysing stream networks.. Peuker Douglas Indicator. Go to Watershed Delineation -> > Advanced TauDEm Functions -> Network and Watershed Processing Function -> Peuker Douglas. Thhis tool generates a stream source grid. It creates an indicator grid (1,0) of upward curved grid cells according to the Peuker and Douglas algorithm. In the inputs a pit filled grid has to be specified. The program by default will load the whole grid. For a specific ic analysis, it is possible to specify just a delimited grid such as the contributing area grid
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Figure 23 Peuker Douglas input screen
Figure 24Stream source grid for the specific area
Extreme upslope value. Go to Watershed Delineation -> > Advanced TauDEm Functions -> Network and Watershed Processing Function -> > D8 extreme upslope value. This tool Evaluates the extreme (either maximum or minimum) upslope value from the grid based on the D8 D flow model. This is useful for use in stream raster generation to identify a threshold of the slope times area product that results in an optimum stream network. The program by default will perform the task the whole grid. For a specific analysis, it is possible to specify just a delimited area, by checking the outlet upstream box and selecting the outlet shape file
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Figure 25 Extreme upslope screen
Figure 26 Extreme upslope grid
Slope area combination. Watershed Delineation -> > Advanced TauDEm Functions -> Network and Watershed Processing Function -> > Slope Area Combination. This tool Creates a grid of slope-area area values based on slope and specific catchment area grid inputs, i and parameters m and n. It is useful for use as part of the slope-area area stream raster delineation method
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Figure 27 Slope Area screen
Figure 28 Slope area grid
Length Area Stream. Watershed Delineation -> Advanced TauDEm Functions -> Network and Watershed Processing Function -> > Length Area Stream Source. This tool creates an indicator grid (1,0) which indicates likely stream source grid cells. It uses a method based in Hack's law which states that for streams L ~ A^0.6. However for hill slopes with parallel flow L ~ A, a transition from hill slopes to streams may be represented by L ~ A^0.8
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Figure 29 Length area stream input window
Figure 30 Grid indicator
Stream reach and watershed.. Go to Watershed Delineation -> > Advanced TauDEm Functions -> Network and Watershed Processing Function -> > Stream Reach and Watershed. This tool creates a vector network and shape file from the stream raster grid. The flow direction grid is used to connect flow paths along the stream raster. The Strahler order of each stream segment is computed. The sub watershed draining to each stream segment (reach) is also delineated and labelled with th the value identifier that corresponds to the WSNO (watershed number) attribute in the Stream Reach Shape file.. In the final shape file the stream network is ordered according to the already explained Strahler ordering system. It creates the stream order grid. grid Then creates the watershed grid.. Finally, it creates the stream reach shape file.. In this file the rivers are already a shape file with several attributes such as length, order, magnitude, slope, drop and others [4].
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Watershed Delineation with MAPWINDOW 2011
Figure 31 Stream and Watershed input screen
Figure 32 Stream order grid with main rivers up to Strahler’s order 4
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Watershed Delineation with MAPWINDOW 2011
Figure 33 Watershed grid
Figure 34 Stream reach shape file
Watershed to shape file. Go to Watershed Delineation ->> Advanced TauDEm Functions -> Network and Watershed Processing Function -> Watershed Grid to Shape file. This tool converts the grid watershed representation into a polygon shape file.. Each shape in the Watershed Shape file will be assigned an identifier.
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Figure 35 Watershed Grid to Shape file input screen
Figure 36 Delineated watershed with the main rivers
The watershed is now a polygon shape file. It is also possible to define different colouring schemes according the preference
Figure 37 Watershed
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Watershed Delineation with MAPWINDOW 2011 Delineating watersheds performing all steps at once. Some users might be used to the ESRI procedure where all the catchments for the whole grid are delineated automatically and deciding where which will be the outlets. MAPWINDOS also allows delineating the entire watershed with just one click, avoiding the previous steps. Personally I don’t like this method since the software decides everything according its own criteria, and sometimes it may be suggested to give more detail to some specific area according the specific project needs. To perform all the steps at once, just go to: Watershed Delineation -> Advanced TauDEM Functions -> Do All Network and Watershed Steps.
Works Cited 1 Google. Google user experience. [Internet]. [cited 2011]. Available from: http://www.google.com/about/corporate/company/ux.html. 2 MAPWINDOW. MAPWINDOW Project Overview. [Internet]. [cited 2011]. Available from: http://www.mapwindow.org/apps/wiki/doku.php?id=project_overview. 3 US EPA. US EPA BASINS. [Internet]. Available from: http://water.epa.gov/scitech/datait/models/basins/index.cfm. 4 Maidment D. Handbook of Hydrology. Mc Graw Hill; 1992. 5 MAPWINDOW. TauDEM Help. Utah State University; 2005. 6 Andrade E. Geoprocessamento para Linux. [Internet]. [cited 2011]. Available from: http://geoparalinux.wordpress.com/2011/04/03/delimitacao-automatica-de-bacia-hidrograficausando-mapwindow-gis/. 7 Tarboton D. A New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models. Water Resources Research. 33(2).
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