They usually seem to be pointed up into the sky (towards some
satellite); is there information available about these satellites,
their downlink frequencies, format of the data, etc.?



There are a zillion remote weather stations all over the country.
Many are for specific purpose such as providing info for Fire weather,
snow pack levels, and as you have seen, stream flow guages for water
management and flood control. Some of the remote weather stations
(RAWS) can be seen listed at:

http://raws.boi.noaa.gov/rawsidx.html

Do a Google search on "RAWS" weather data. Also, stream flow
stations and remote snow pack stations can often be found on your local
State's water management department.

Bottom line answer to your question, YES, the data you probably
would like to see is available on the Internet.


Ed K7AAT