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?
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 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? 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
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