HRUweb Tutorial

Revision as of 06:11, 12 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 GRASS-GIS algorithms.

Fragen:

• Bezeichnung der 2. Unterteilung: Procedure, Workflow oder Parameter Settings?
• Legend description am Anfang?

Starting WebHRU Tool

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

Do user login:

Structure of 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 (set visibility, zoom in or remove -> see section "Legend")
2. Legend (description)
3. Processing step description and manual input/settings. Buttons for 'Run' and 'Next'.
4. Download browser (provides data layer as raster or shape file)
5. Server processing log: shows the uploading process

Step 0: Data Preparations

First of all, 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: Uploading Input Data

Aim: Define base map and upload input data.

Procedure:

At first, decide which map source should be used as the base layer (default: OpenStreetMap):

Then, upload the required input data (required data described in Step 0).

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

For starting the uploading process, click 'Run'.

Results:

The overlays 'Upload' and 'Gauges' are created.

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

They can be downloaded from data browser.

File:Databrowser step1.png

When finished, click 'Next'.

Step 2: Data Setup

Aim: Define area of interest for delineating HRUs.

Procedure:

To zoom into the area of interest, right-click on the 'Upload' layer and choose 'Zoom to layer extend' or use the magnifier to do so.

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

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

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 GRASS-HRU MAP menu.

By clicking on the symbol, another overlay layer called 'Region' is created and the automatically set 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 into 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.

Results:

A 'Hillshade' overlay is created.

The hillshade layer can be downloaded from data browser.

File:Databrowser step2.png

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), if the sinks should be filled or "No filling", if they should not be filled.

Results:

A DEM with filled sinks is created.

File:Overlays step3.png

File:Filled dem.png

Single maps of sinkless elevation, slope and aspect can be downloaded from data browser.

//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

Result:

The reclassified layers 'aspect' and 'slope' are created.

The reclassified maps of slope and aspect can be downloaded from data browser 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.

File:Eingabe der pixelzahl.png

• example 10.000

Results:

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

You can download a zip file of stream network + subbasin layer from data browser

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 (legend no. X).

Order the layer of gauges on top, followed by the layer of river network.

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: 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

Results: - watershed overlay? - watershed map

Step 7: Dataoverlay & Generalization

Results: - HRU overlay - HRU map

Legend

The layers can be edited in overview in the top left. By right-clicking on the overlays, the layers can either be zoomed or removed. By using drag and drop in the overlay list, the order of layer visibility can be changed.

== How to choose the best settings for ranges, HRU size+amount ==