Geography Reference
In-Depth Information
Infiltration
No, I didn't forget to write something. Instead, each deserves a separate heading because, no matter
where you live, one or both is responsible for your water supply.
Run-off: Going with the flow
Some of the water that falls to earth collects on the surface and begins a down-slope journey
to the sea — there to complete the water cycle. Trickles join to form babbling brooks (why do
brooks babble, anyway?), which join to form rivers. Basically, it's fresh water on the move,
and every last drop of it is potentially available to people.
Rivers have long served as water supply systems for cities and towns. But rivers that bring drinkable
water can also take away sewage and waste. That's great unless you happen to live downstream —
there to discover your drinking water is no longer drinkable thanks to your upstream neighbors. And
most people live down stream from somebody else, so problems afloat.
To solve the problem, many towns and municipalities have gotten into the business of capturing
drinkable run-off by building dams that create reservoirs that store water that can be transferred to
where people need it. These public works tend to get located in not-yet-contaminated headwaters.
Some-times, however, these headwaters are far from the people who will consume them, and there-
fore require construction of aqueducts to resolve the geographic difference between supply and de-
mand.Someofthewater that supplies NewYorkCity,forexample, comes fromareservoir morethan
a hundred miles away.
Infiltration: Out of sight, not out of mind
Some of the water that falls to earth
infiltrates
the soil. That is, it seeps into the ground. Because
nature has been at this for a long, long time, some lands are underlain by substantial
aquifers
— sub-
terranean accumulations of water. Better to think of these not as underground lakes but as areas of
super-saturated soil or porous rock (yes, rock!) with a high water content. If your water supply comes
from a well, then you live on water that has infiltrated. Well water can be suitable to drink as is, or
it may require minimal treatment. But infiltrated water has two potential problems — contamination
and depletion.
