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NAME

m.swim.substats.py - Soil and Water Integrated Model (SWIM) preprocessor: subbasin statistics

KEYWORDS

SYNOPSIS

m.swim.substats.py --help

DESCRIPTION

The m.swim.substats module creates the SWIM subbasin statistics input files (.sub, .rte, .gw) and the file.cio file. All parameters maybe given as either default value for all subbasins or as a raster map for which subbasin average values are found and written to the files. By using the drainage, accumulation and mainstreams maps produced by the m.swim.subbasins and m.swim.routing modules, it can also compute the main channel length, slope, depth and width. These four parameters are computed as follows:

• Channel length: The length is approximated from the mainstreams and drainage map and constrained to be at least one cell size long and not greater as the subbasins perimeter (this constraint allows for uncertainties in the mainstreams map).
• Channel slope: The slope is calculated from the elevation raster and then averaged over the mainstreams cells and reported for each subbasin.
• Channel width: Approximated using the drainage area calculated from the accumulation map through this empirical relationship (with an upper limit of 3000m):
• width[m] = 1.29 * darea[km2] ^ 0.6
• : Approximated using the drainage area calculated from the accumulation map through this empirical relationship (with an upper limit of 50m):
• depth[m] = 0.13 * darea[km2] ^ 0.4

Raster maps with subbasin mean values are created implicitly and the values are uploaded to the subbasin table with the following names: mainChannelLength, mainChannelSlope, channelDepth, channelWidth This allows a faster recalculation by setting the arguments chl, chs, chd, chw to these names.

For all other parameters default values are given that apply to all subbasins, except for the USLE slope length and steepness, for which the output of the m.swim.subbasins or r.watershed is used to calculate average values for each subbasin.

NOTES

All parameter arguments are the same as their variable names in the SWIM code.

Although this module has been tested, it is still in beta mode and hasn't been extensively error coded. Please report unexplained errors to the author (see below).

EXAMPLE

Setting up a SWIM project in the North Carolina (basic) testing location:

Create a new mapset and set region:

g.mapset -c mapset=subbasins
g.region rast=elevation@PERMANENT

Stations

Create a stations point vector map:

echo "640579|215607|outlet|0.1
640388|216617|headwater|0.05" > stations.dat
v.in.ascii input=stations.dat out=stations x=1 y=2 columns='x int, y int, name varchar(20), subbsize double'

Subbasins

Make subbasins (default output arguments):

m.swim.subbasins elevation=elevation@PERMANENT stations=stations upthresh=0.1 subbasins=subbasins slopesteepness=slopesteepness slopelength=slopelength

In addition to the subbasins vector and raster map, this also produces catchment raster and vector maps, accumulation, drainage, streams, slopesteepness and slopelength rasters (as needed by the subsequent m.swim.* modules) by default.

Routing

Calculate the routing structure, routing network and mainstreams (the output defaults are: mainstreams=mainstreams, routingnet=routingnetwork, outlets=subbasinoutlets, inlets=subbasininlets; which can also be set explicitly):

m.swim.routing subbasins=subbasins accumulation=accumulation mainstreams=mainstreams

Subbasin statistics

Create the subbasin statistics files in a Sub folder and the file.cio in the projectpath with all default input (mainstreams, drainage, accumulation,  stp and sl also have default values but included here to emphasise that they are needed as input):

m.swim.substats subbasins=subbasins projectname=mypro projectpath=. elevation=elevation@PERMANENT \
                mainstreams=mainstreams drainage=drainage accumulation=accumulation stp=slopesteepness sl=slopelength

When recalculating or changing parameters, the calculation can be accelerated by setting chl, chs, chd, chw explicitly:

m.swim.substats subbasins=subbasins projectname=mypro projectpath=. elevation=elevation@PERMANENT \
                delay=geology@PERMANENT chl=mainChannelLength chs=mainChannelSlope chd=channelDepth chw=channelWidth

SEE ALSO

m.swim.subbasins, r.watershed, m.swim.hydrotopes, m.swim.routing

Documentation [external]: m.swim

AUTHORS

Michel Wortmann, Potsdam Institute for Climate Impact Research (wortmann@pik-potsdam.de)

Last updated (docs/code): Mon Dec 2 15:41:04 2019 +0100 / Wed Jan 19 23:04:38 2022 +0000