r.mapcalc question

[Jim Klein]

I am trying to identify any lands that drain from private land to public 
land.  In this case the public land is mostly a ridgetop, but there are 
areas of private land that do drain into public land.  

Does anybody have any suggestions as to how to do this.

First I found all the watershed subbasins that are on the edge of the 
public land.

Now I want to be able to find the lowest elevation point *in each 
subbasin* so that I could use that point to determine the 
more specific catchment area (using the old r.watershed3.0, 
i presume).  I am tyring to think of a way to mask the elevation file 
with the public land boundary, and then use r.mapcalc to find the minimum 
elevation value in each subbasin *at that boundary*

Any suggestions, or alternatives would be greatly appreciated.
Thanks

Jim Klein
lkla at netcom.com
703-739-0972