--- In
BoundaryPoint@yahoogroups.com, "adamnvillani" <avillani@u...>
wrote:
> --- In BoundaryPoint@yahoogroups.com, "Lowell G. McManus"
> <mcmanus71496@m...> wrote:
> > The current 1970 MXUS treaty says that the international boundary
> in both the
> > Colorado River and the Rio Grande "shall run along the middle of
> the channel
>
> Thanks! That should be a fairly easy point to estimate.
yes but it stands a good chance of being incorrect
for why please see below
>
>
> > The juncture of the two mentioned river would be the ghost
> tripoint; however,
> > both rivers show evidence of having been highly braided and
> meandering
> > streamcourses in their relevant reaches. I doubt that it would
be
> humanly
> > possible to ascertain the precise point.
yes this was my point too for what i took to be the relevant years of
your quest for this ghost
namely its birth in 1848 & death in 1853
but your primary quest point mxn just happens to be the essentially
exact position of the confluence in 1849
the year of the first mxus survey
which began expressly & precisely at the middle of the gila colorado
confluence as determined by &or at the time of this survey anyway
so your first quest point is also your very best bet for your second
quest point
hahahahaha
talk about finding 2 needles in the same desert or something
you dont need to go to the library because you probably cant beat
that position anyway
>
> One idea is that perhaps I could swing by a library in Yuma
Saturday
> morning to see if they had any historical maps of the region.
> Checking the city's website, I see that Fort Yuma was built on the
> U.S. side in 1853, and the Gadsden Purchase was made one year
later.
> If I'm in luck, they might have a map from the time that the fort
was
> founded. It depends on how much time I have; I'll be travelling
with
> a buddy who has to catch a plane at LAX on Saturday night.
>
> The Colorado River used to have a lot more water in it before so
much
> got siphoned off to quench the thirst of Southern California and
> various agricultural areas. So it's possible that with a higher
flow,
> the river was less braided back in the days before irrigation. The
> confluence has probably changed pretty drastically since 1854,
though.
yes as you can see it has moved over a dozen miles upstream since 1849
but your point about these rivers formerly having more water in them
is most telling in deciding the question of midline or thalweg
because they certainly were at least seasonally navigable in the
relevant years of the treaties
& indeed still are
so it seems to me the presumption of thalweg is much stronger than
that of midpoint between the veggies
however until you can project the mxus monument line thru the veggies
you still wont know what cross section of the river to find the
middle or thalweg of
that will be the primary & main task
in actual practice you may find the difference between the middle &
thalweg quite negligible since the bed is fairly narrow here
& not even worth deliberating
but if you are serious about being as punctilious as possible here
i can tell you that azcas at least is a documented geodetic point
in fact the position where the midchannel line crossed the mxus
survey line in 1963
yet if the living rio grand & rio colorado thalwegs are what the 1970
mxus treaty says or means mxus follows
as i believe it does
then azcas is irrelevant for finding mxn
because mxn must fall on the living thalweg
aha
& a tripointing stitch must be administered after all
for if the thalweg has moved east since 1963
a micrometer or many meters
then mxn falls that distance east or slightly ene of azcas
& there needs to be an extra stitch of azbc added between these 2
points along the geodetic prolonation of bcca
separating baja california from alta arizona if you will
& if the thalweg has moved any distance west since 1963
then mxn falls that distance west or wsw of legal azcas
in which case a totally extralegal as well as logically impossible
extra stitch of azca has to be added wsw from azcas to mxn
yikes
because baja cant extend east of the living thalweg
so azca must continue wsw from azcas to mxn
& actually terminate at a point more southerly than its own legally
southernmost point
so this has the potential of keeping us in stitches indefinitely
depending on where the living thalweg happens to be on the day of
anyones visit
but there is one new thought to be gained from this 1963 azca survey
which btw is given in full in usgs technical bulletin 27
you may remember from my report last month that azcanv is indirectly
demarcated by a pair of 1963 riverbank markers resembling cowflops &
numbered 1a & lb
each triangulated with a pair of supporting pointer markers
well that same survey ends not surprisingly at azcas with a similarly
indirect demarcation by a probably identical pair of riverbank
markers
numbered in this case 34a & 34b
given the placements of cowflops 1a & 1b along the canv line & its
prolongation into az
i think it highly likely that 34a & 34b will be found along the bcca
line & its prolongation into az
so if you can find any of these 6 markers
& if so then you ought to be able to find them all
most probably down near but just above the riverbed
& if you can confirm even just by best guessing that their alignment
runs along the mxus bcca survey line as i believe
then you may not have to clear a sight line to the mxus monuments
after all
for these cowflops will be your surrogate mxus markers
so i would say if you are very lucky you may just need to look for
the point where the thread of the stream passes between the cowflops
>
> Adam