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It might be offensively simple for me to start by reminding everyone
that water is a liquid, and liquids conform to their shape. But, as you
can see, I decided to start that way anyway. It’s important to
remember the basic properties of water determine where it flows.
I’m no member of the River Police (or any other such group), but I’d
like to cover the fundamentals of waterways below.
RIVER PHYSICS:
Law #1: A river will always enter the sea (or lake) in one location. A
delta is considered to be one location due to how it forms, but you
won’t find a river that dumps into the sea and continues on down the
coast. The water will follow the most natural path to the lowest location.
Older rivers will have carved out that path.
Law #2: You’d be hard pressed to find a major river that doesn’t have
tributaries. This is something cartographers on the site are consistently
talking about, from what I can see. Tributaries, like the main river,
are coming down from high-elevation places and merge. All tributaries
will merge in the same direction and will widen the river when merging
(most likely).
Law #3: A river grows deeper or wider the closer it gets to the sea.
Rivers will also form big arcs (meandering old rivers, slower current)
or rapids (possibly newer rivers with more active currents). Most
obviously, rivers flow downhill, so it’s important to know your terrain
and slopes.
Law #4: While rivers can come together, as previously mentioned, it’s
very very rare to see one break apart. The water will always take the
steepest (downwards) route and there can only be one. Rivers may
indeed split when the first route simply cannot move that much water
quick enough. Splits are generally very short-lived; the river will
reconnect somewhere down the line.
LAKES:
How does a Lake Form? A lake can form many ways. Most notably,
lakes form when a river leads into an area where the surrounding
slope is all upwards. The water will fill this valley and create a lake.
Other lakes could be formed by human-built structures, volcanoes,
melting ice, etc... A lake must be constantly filled or else it will dry up.
Outgoing Water: The river that empties a lake is unique in that it is the
only river emptying the lake. The water exits the lake all via the same
river in most cases, and so it’s not realistic to see a river that’s splitting
off into many different branches and emptying via many small rivers.
You’d have to have very flat terrain and a lot of other factors.
More: I’m basing some of the information here off of Redrobes (I thought
I’d give him credit) In his words “a lake is a bit like a very fat bit of
river.” Also, check out a movie from his thread that shows water drainage
post five <here>. Very cool.
IRRIGATION
Given that farming was such a big deal for medieval culture, and is also
pretty important now, moving water to crops has been important. Irrigation
techniques and such helped farmers supply populations with enough to eat.
There are different levels of irrigation systems based on the technology of
the times and the requirements of the area.
One of the simplest forms of an irrigation system is a maze of ditches; water
(often filled with waste) is filtered through the fields and out. Since plants
aren’t harmed by waste, and are actually benefitting from it, this can be
effective. It’s also the sign of a very undeveloped farm. These sorts of
techniques were used in the very earliest of civilizations.
An early piece of technology that improved irrigation was called a “sakia”. It’s
also used today in India. It’s essentially a hollow wheel used to transport water.
It’s largely dependent upon current and floods. Some civilizations built artificial
containers to hold and channel water. These could be underground or
above-ground. These are used today of course - perhaps you know of one nearby.
With the motors and technology we have today, much of advanced irrigation is
done by pumps and machines. It’s undeniably more effective because it provides
a steady amount of water. I’ll expand on this when I get into agriculture next post!
Additional Resources:
World Map of Water Usage for Agriculture This map shows each country’s water
usage for agriculture for the year 2001.
[Attachment] The animation shows natural water drainage. Courtesy of Redrobes.
Read more here.
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If you’re using this for a project, please check my research with some of
your own. There’s a chance I jumbled something up here. Let me know
if I did; I’ll edit it.
If you have a further question or such, ask it! Send me information and
I might edit it into this post. The goal of this thread is to be a hub of
resources for the making of scientifically accurate maps.
MOVIE of Waterways
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