HRUweb Tutorial

Revision as of 13:06, 19 April 2017

The WebHRU is a web tool which was developed to derivate hydrological response units (HRU) online. It was implemented in Python and calculates HRUs according to opensource GRASS-GIS algorithms.

After every processing step, the results are provided as raster or shape data which are all compatible with established GIS formats.

For this tutorial, sample data from Rio de Janeiro in Brazil were used.

Starting WebHRU Tool

Link to HRU Tool: http://intecral.uni-jena.de/hruweb

Structure of HRUWeb user interface

The map window is located in the centre. By using the arrow buttons or the +/- tool bar in the top left, the view can be set manually. The remaining items are located around the map:

1. Table of Layers
   1. Change order of layer visibility by using drag and drop
   2. Select a layer by clicking on it. Now the layer can be edited by using the Map Legend.
2. Map Legend (→ section Map Legend Description see below)
3. Wizard: Processing step description and manual input/settings. Includes the buttons for 'Run' and 'Next'.
4. Server Log and Results: Shows the uploading process & provides the result layer as raster or shape file. (→ click on to reveal the item and to hide it again)

Map Legend Description

1. Remove layer
2. Zoom to map extend: restores smallest possible scale of the map
3. Zoom in the map () or zoom out of the map ()
4. Zoom to previous map extend (backward forward)
5. Create bounding box of interest (→ section Step 2)
6. Relocate gauge (→ section Step 6)
7. User login (→ NEXT STEP)

Step 0: Check Your Data

First of all: Do user login!

Otherwise, your work will not be saved!

Check your input data!

Then, open your input data in a GIS and check them for:

• completeness: At least DEM and gauges are required for delineating HRUs. The rasters of landuse, soil and geology are optional input.
• projection: The coordinate system has to be metric (like e.g. UTM) in order to enable distance calculations.
• layer extend: The layers should have at least the size of the catchment. A base map could be helpful.

The following sections describe the single substeps in the WebHRUTool. Each substep is divided into the subsections Aim, Procedure and Results.

Step 1: Define Data Sources

Aim: Upload input data or choose data via catalog.

Procedure:

The required input data are described in Step 0.

You have two options to define the dem input data:

• Upload your own local input data

or

• Use input data via catalog: choose the DEM you need by clicking on 'add'.

Note:The chosen DEM is listed in the Table of Layers as a new layer. You can edit it by clicking on the layer and using the Map Legend.

→

The projection of the map will be set automatically on the basis of the input data.

For starting the uploading process, click 'Run' in the Wizard.

Results:

The overlays 'Upload' and 'Gauges' are created in the Map View as well as the Table of Layers.

Zoom into your area of interest.

The gauges are shown in light blue dots. The area of the gauges is marked automatically in a red bounding box.

//Note: If the 'Upload' or the 'Gauges' layer are removed, the whole uploading procedure has to be done again by reloading the page.

When finished, click 'Next'.

Step 2: Data Setup

Aim: Define area of interest for delineating HRUs.

Procedure:

In this step, you can specify your region of interest.

The red box marks the maximum extend. Data outside of this extend are not delineated.

//Note: If the red bounding box does already represent your region of interest, you can skip the next step and click 'Run'.

If you want to specify your region of interest, click on the box symbol in the Map Legend.

By clicking on the symbol, another overlay layer called 'Region' is created.

The automatically set red bounding box is now covered by a blue box.

This blue box represents the area that should be used for delineating HRUs later on. Due to computational reasons, its extend should

be fitted to the gauges' positions.

Fit it by clicking on the outline of the blue box and move it at the blue crosses : .

In order to shift the whole box, drag&drop it by the blue cross in the centre.

In order to resize the box, use the cross at the side.

//Note: The 'Region' layer can be removed without problems. To do so, right-click on the layer and choose "remove".

By clicking on , the region layer can be restored again.

//Note: If the extend of the blue box is chosen too small, important parts for delineating HRUs could be left out which makes the results unusable.

For starting the process, click 'Run'.

Results:

A 'Hillshade' overlay is created in the Table of Layers and showed in the Map.

When finished, click 'Next'.

Step 3: Data Preparation

Aim: Preprocess the DEM by filling its sinks.

If the DEM was already preprocessed that way, no sink filling is necessary.

Otherwise, it is recommended to do so in order to prevent lack of data.

Procedure:

Choose "Filling" (default) in the Wizard window, if the sinks should be filled or "No filling", if they should not be filled.

For starting the process, click 'Run'.

Results:

A DEM with filled sinks is created.

Single maps of sinkless elevation, slope and aspect can be downloaded from Server Log.

//Note: If filling fails, no maps for slope and aspect are available.

When finished, click 'Next'.

Step 4: Reclassification

Aim: Reclassify terrain attributes.

Procedure:

In this step, the class ranges of slope and aspect can be reclassified and renamed.

In order to change table entries, click in the concerning field and type in the desired value.

"Old": lists all existing class ranges

"New": assigns IDs to classes

For starting the process, click 'Run'.

Result:

The reclassified layers 'aspect' and 'slope' are listed in The Table of Layers.

Aspect and slope are also shown as maps.

The reclassified maps of slope and aspect can be downloaded from Server Log as well.

When finished, click 'Next'.

Step 5: Waterflow

Aim: Define resolution of the stream network/ river system.

Procedure:

With each subbasin, one river segment is created. In this step, the maximum number of cells (pixels) for a subbasin of the smallest size has to be specified.

In this tutorial, the cellsize was defined by 10.000 pixels.

For starting the process, click 'Run'.

Results:

The layers 'Streams' and 'Subbasins' are created.

You can download a map of the subbasins in raster and shape format and a vector zip file of stream network from Server Log.

When finished, click 'Next'.

Step 6: Outlets

Aim: Check the gauges' position and decide which gauges should be considered.

While creating the subbasins, the gauges' position can differ from the stream network.

Procedure:

First of all, use the drag and drop mechanism to change the visibility of the layers in the layer view (→ section Starting the Webtool).

Order the layer of gauges on top, followed by the layer of streams and the subbasins.

Open Google Earth and zoom in to the gauges. Now use the gauges' position in Google Earth

as a reference and relocate the gauges in the map of your results.

Now the tool for relocating gauges had to be activated. Click on in the legend to activate it.

In order to relocate a gauge, click on a gauge and drag it to the proper river segment.

//Note: For every gauge on a river segment, a catchment is created. If a gauge should not be considered in the further delineation of HRUs, just drag it out of the blue bounding box.

File:OutOfBB.png

For starting the process, click 'Run'.

Results:

The layer 'Watershed' is created.

A map of the watersheds can be downloaded from data browser

When finished, click 'Next'.

Step 7: Dataoverlay & Generalization

Aim: Computing HRUs.

Procedure:

In this step, all data layer are calculated to one HRU layer by the WebTool.

No user activity is required here.

Results:

The layer 'HRU' is created in the layer overview.

A map of the created HRUs is provided in the data browser

When finished, click 'Next'.

Step 8

Results:

- Statistics per HRU

Help Section

How to ...

• Step 4: choose the best settings for ranges of values of slope and aspect
• Step 5: choose the best settings for number of pixels for the smallest subbasin

• Step 6: decide, if a gauge should be considered or not?

---> in farbig hinterlegten Kästchen?

Fragen:

• Hilfe Abschnitte auf die Schritte aufteilen oder einen ganzen Abschnitt für alle?