Hi, 2012/7/19 Vishal Mehta <[email protected]>: > Thanks Soren, > for your script. > > i'm using r.gwflow in v6.5svn, which does not have the budget parameter > option. do you know how i can get the 7 version to work in my 6.5 version?
Unfortunately the grass7 version of r.gwflow does not run in grass6.5 and i have no plans o back port the budget feature. So maybe you would like to switch to grass7 to compute the budget? > also, i'd like to know how all th rest if it is set up - the river_bed > parameters etc. do you have complete documentation of it? i'm trying to You need three parameters to model the river: 1.) The water table of the river in [m], mostly derived from a river vector map and converted into a raster map 2.) The bed of the river in [m], mostly derived from the river water table: r.mapcalc "river_bed = river_table - 2" 3.) The leakage coefficient of the river bed in [1/s] River table, river bed and leakage are occupying the same pixels. Simple and stupid example: # River with a water table of 20m and the bed at 18m with a # leakage coefficient of 0.0001 1/s # First convert the stream network into a raster map v.to.rast input=streams output=streams type=line # Then compute the water table of the river at 20m # and the height of the bed that is 2m lower than # the water table of the river r.mapcalc "river_head = if(isnull(streams), null(), 20)" r.mapcalc "river_bed = river_head - 2" # The river leakage coefficient can be computed from the hydraulic conductivity # of the river bed (0.0001m/s) and the thickness of the river bed (1m) r.mapcalc "river_leakage = if(isnull(streams), null(), 0.0001/1)" > model the coupled water supply-extraction and groundwater system of a city, > so more complex real world examples of the use of r.gwflow would be really, > really useful. have you used it in a ocomplex setting perhaps for your > dissertation? The only documentation that is available is the r.gwflow manual page and my diploma thesis [1] (in German) that describes the mathematical details. I never utilized r.gwflow to compute large complex real world problems. Best regards Soeren [1] http://www.hydrogeologie.tu-berlin.de/fileadmin/fg66/_hydro/Diplomarbeiten/2007_Diplomarbeit_Soeren_Gebbert.pdf > > thanks again, > Vishal > > > On Wed, Jul 18, 2012 at 2:47 PM, Sören Gebbert > <[email protected]> wrote: >> >> Hi Vishal, >> >> 2012/7/18 Vishal Mehta <[email protected]>: >> > hi Soren, >> > >> > my constan head boundary conditions on the edges are causing water >> > tables to >> > build up everywhere else. so i estimated a constant flux 0f 0.0019 m3/s >> > that >> > i want to apply for edge cells. this is what i am trying in order to >> > impose >> > a constant flux on the edges >> > >> > r.mapcalc "sink.init=if(row()==1 || row()==444 ||col()==1 >> > ||col==477,-0.0019,null()) >> > >> > #sink.init is the constant flux on edges >> > # my r.gwflow script runs at monthly time step- ihave a loop >> > $month-here's >> > the r.gwflow snippet >> > >> > r.gwflow --o -s solver=cg top=top bottom=bottom status=bc2 hc_x=k.1 >> > hc_y=k.1 >> > s=s.1 type=unconfined dt=2592000 error=0.05 phead=sim.$((prevmonth)) >> > r=gwnaturalms.$((month)) q=sink.init output=sim.$((month)) >> > >> > my boundary condition map (bc2) has contant head in strea pixels. all >> > else >> > are calculated. >> > >> > do you think the above implementation will correctly impose the constant >> > flux on the edges? it seems though that since this is not a boundary >> > condition, how can it ensure a constant flux at edges? >> >> Your script looks reasonable, except that the error term is much to large. >> You may need to use a smaller number like 10⁻7, >> otherwise your results my be wrong. >> >> I have attached a small r.gwflow example to show you how to estimate >> the constant flux at >> a western boundary using the budget computation. Since the flow will >> be specified >> as a source term, it will be constant the whole computational time. >> >> Maybe you can apply this method to estimate the boundary flux in your >> area? >> >> JFYI i am using r.gwflow of GRASS 7. >> >> Best regards >> Soeren >> >> > >> > Thanks for any help you can provide, >> > Vishal >> > >> > On Mon, Jul 16, 2012 at 1:46 PM, Vishal Mehta <[email protected]> >> > wrote: >> >> >> >> Thanks Soren, >> >> From you response, can you please tell me how to do the following two >> >> tasks (which i dont find in the online manual for r.gwflow): the >> >> remainder >> >> of your comments i have figured out. >> >> >> >> - How can i compute the flux in [m^3/s] for each cell with r.mapcalc? >> >> and >> >> >> >> - i have set the bc of the edges and stream cells at constant head for >> >> now- how can i get the budget raster maps you mention? >> >> >> >> thanks again, >> >> Vishal >> >> >> >> >> >> On Sat, Jul 14, 2012 at 12:05 PM, Sören Gebbert >> >> <[email protected]> wrote: >> >>> >> >>> Hi, >> >>> sorry for the delay. >> >>> >> >>> 2012/7/11 Vishal Mehta <[email protected]>: >> >>> > Thanks Soren, >> >>> > That explains some of the results i'm getting, with water piling up >> >>> > above >> >>> > the surface in the edges in low-lying areas. >> >>> > >> >>> > Can you please tell me how i can change that to constant flux or >> >>> > constant >> >>> > head? If constant flux, should that be in m/s units? >> >>> >> >>> Constant flux can currently only be defined using sources/sinks with >> >>> unit [m^3/s], that is option q. >> >>> But i can add two new options (fn, fe) that defines the flux in >> >>> northern or eastern direction using the unit [m/s] >> >>> that will be multiplied internally with the northern or eastern face >> >>> area of the cell? >> >>> >> >>> Otherwise you need to compute the flux in [m^3/s] for each cell with >> >>> r.mapcalc. >> >>> >> >>> > >> >>> > My problem though is that i dont know what a constant flux or head >> >>> > at >> >>> > the >> >>> > edges should be set to. For now the only bc i have put in there >> >>> > deliberately >> >>> > (beyond the default you mention) is that i have set constant head in >> >>> > stream >> >>> > pixels. I'll have to let flow through at the edges but i have no >> >>> > idea >> >>> > what >> >>> >> >>> You can use the river boundary condition to specify the flux in stream >> >>> pixel. >> >>> >> >>> > that flow should be. Are there some ways of setting the edge >> >>> > conditions >> >>> > such >> >>> > that the gw evolution in the central areas of interest are not >> >>> > highly >> >>> > influenced? >> >>> >> >>> You can set the boundary of interest to constant head pixel and >> >>> compute the flow throw the boundary pixel using the budget option. >> >>> The resulting budget raster map shows the flow from active cell into >> >>> sources, sinks and constant heads in [m^3/s]. >> >>> >> >>> Best regards >> >>> Soeren >> >> >> >> >> >> >> >> >> >> -- >> >> Vishal K. Mehta, PhD >> >> Scientist >> >> Stockholm Environment Institute - US >> >> 133 D St Suite F >> >> Davis CA 95616 >> >> www.sei-us.org >> > >> > >> > >> > >> > -- >> > Vishal K. Mehta, PhD >> > Scientist >> > Stockholm Environment Institute - US >> > 133 D St Suite F >> > Davis CA 95616 >> > www.sei-us.org > > > > > -- > Vishal K. Mehta, PhD > Scientist > Stockholm Environment Institute - US > 133 D St Suite F > Davis CA 95616 > www.sei-us.org _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
