HRUweb Tutorial

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.

Contents 1 Starting WebHRU Tool 2 Step 0: Data Preparations 3 Step 1: Uploading Input Data 4 Step 2: Data Setup 5 Step 3: Data Preparation 6 Step 4: Reclassification 7 Step 5: Waterflow 8 Step 6: Outlets 9 Legend

Starting WebHRU Tool

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

Do user login:

Description of user interface:

• map window
• table of layers (set visibility, zoom in or remove -> see section "Legend") [set link to legend]
• process log
• download browser (provides data layer as raster or shape file)
• processing step description and manual input/settings

The uploading process is always shown in the Server Processing Log:

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.

Input data	Description	Format
DEM	Raster of Digital Elevation Model	Tiff (.tif) or .zip-file	mandatory
Gauges	Layer of gauging stations	.zip-file	mandatory
Landuse	Raster of landuse	Tiff (.tif) or .zip-file	optional
Soil	Raster of soil	Tiff (.tif) or .zip-file	optional
Geology	Raster of geology	Tiff (.tif) or .zip-file	optional

Step 1: Uploading Input Data

Aim: Define base map and upload input data

Parameter Settings/ Workflow:

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.

File:Layers step1.png

//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

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.

Parameter Settings/Workflow:

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.

When finished, click 'Next'.

Step 3: Data Preparation

Aim: Preprocess the DEM

Now it has to be decided whether sinks in the DEM should be filled or not.

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.

Parameter Settings/ Workflow:

Choose "Filling" (default) or "No filling"

File:Layer step3.png

Results:

A DEM with filled sinks is created.

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

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

Parameter Settings/ Workflow:

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.

//Note: By using drag and drop in the overlay list, the order of layer visibility can be changed.

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

Parameter Settings/ Workflow: the number of cells (pixels) for the smallest size of a delineated subbasin has to be specified.

File:Eingabe der pixelzahl.png

• example 10.000

Results:

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

File:Layer Ansicht.png

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

File:Data browser layer.png

When finished, click 'Next'.

Step 6: Outlets

Relocate gauges: drag+drop gauge layer -> top;

(zoom)

click on and locate gauges on the right stream segment

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.

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