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- Catchment name: unique name (max. 30 characters)
- Major River Basin: Major basin (max. 30 characters)
- River name: river draining the catchment (max. 30 characters)
- Tributary of: name of main river of which the catchment river is a tributary (max. 30 characters)
- At km: chainage along main river at which the tributary enters
- Left or Right bank: side of river at which the tributary enters (L or R)
- Area (km2): catchment area (is computed from the boundary)
- Length (km): length of river
- Slope ('-): average slope of the river (*10^10-3^ 3 )
- Latitude: geographical co-ordinates of the outlet (origin) of the catchment
- Longitude: geographical co-ordinates of the outlet (origin) of the catchment
- Local X Outlet: X co-ordinate of the outlet (origin) of the catchment in a local co-ordinate system (meters)
- Local Y Outlet: Y co-ordinate of the outlet (origin) of the catchment in a local co-ordinate system (meters)
- Stream order: stream order (1-9) of catchment river, see also note below
- Remarks: extra information on the catchment,no restriction on the layout or contents of the remarks text.
Besides these characteristic data you can also enter catchment boundaries. All catchment boundary data are entered in km relative to an origin or catchment outlet point. The origin or outlet point of the catchment is stored in the database. This origin is to be given in geographical co-ordinates or in local co-ordinates at the very first time you add a catchment to the database. The boundary data are in km west/east (east = positive x-co-ordinate) and km north/south (north = positive y-co-ordinate) of the origin. If no values are entered for the origin, HYMOS will take a value of "0.0" in a meter co-ordinate system as the origin of the catchment.
Note
When boundary co-ordinates are entered for a catchment, they are referenced to the co-ordinates of the Outlet point. After editing the local origin of the (sub-)catchments, the boundary co-ordinates in km are automatically referenced to this new origin!!!.
You can enter the catchment boundaries by: - importing a GIS ASCII (*.BNA) file with a polygon representing the catchment, or
- entering the co-ordinates with your keyboard.
If you import a boundary file you have to choose the co-ordinate system the co-ordinates of this file are in. When entering the co-ordinates with your keyboard you must give the co-ordinates in KM relative to a origin. Press the <Co-ordinates> button to import or edit the co-ordinates, you will then be presented with a spreadsheet where co-ordinates can be entered. If you have a file with co-ordinates, select the <Import Co-ordinates> option and the appropriate co-ordinate system from the 'File' menu.
You can also export the co-ordinates to a GIS layer by selecting the <Export Co-ordinates> option and the appropriate co-ordinate system from the 'File' menu.
The spreadsheet of the 'Co-ordinates' form supports the options of copying and pasting to and from the Windows Clipboard.
Notes - All data except for the <Catchment ID> can be edited.
- For stream ordering different systems are in use:
- Strahler's definition the smallest channels, most upstream, constitute the first-order streams; a second-order stream is formed by the junction of any two first-order streams and so on; the order of the stream only increases when two streams of the same order join;
- the other system counts from the river mouth, giving the most downÂstream section order 1, its tributaries order 2, etc.
Which system is to be used, is to be decided upon by the user, but only one system should be followed in a particular database! The stream order does not have any consequences for further processing activities. - To be able to describe catchment boundaries on a kilometre-grid, it is necessary to define the local origin for this grid in geographical or local (meter) co-ordinates.
Atlas Boundary File Description (BNA)
This is an ASCII format file used to store geographic information including areas, curves, ellipses and points. In HYMOS we will use it for storing catchment boundaries. The format of the file is:
"ID", "Name", length
x1,y1
x2,y2
...
xn,yn
ID is the name of the ID of the catchment, and name is the name of the catchment (not used in HYMOS). The length is an integer which identifies the object as an area, curve, ellipse or point. Following the length are the actual X,Y co-ordinate pairs that make up the catchment polygon. The co-ordinates can be integers or real numbers, and are stored 1 pair per line.