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EARTHS WATER
By: Kamiya J. Avery W.
LaMarcus J. and JaMarcus W.
SURFACE WATER
Surface Water Basics
Lakes and reservoirs
Rivers
Rivers and the landscape
Sediment in rivers
Rivers of the world
Use of streamflow information
Seasonal streamflow patterns
Sea level and climate
Glaciers and icecaps
Watersheds
RIVERS AND STREAMS
Most of the water you see flowing in rivers comes from
precipitation runoff from the land surface alongside the river. Of
course, not all runoff ends up in rivers. Some of it evaporates on
the journey downslope, can be diverted and used by people for
their uses, and can even be lapped up by thirsty animals. Rivers
flow through valleys in the landscape with ridges of higher land
separating the valleys. The area of land between ridges that
collects precipitation is a watershed or drainage basin. Most, but
not all, precipitation that falls in a watershed runs off directly
into rivers - part of it soaks into the ground to recharge
groundwater aquifers, some of which can then seep back into
riverbeds.
The Chattahoochee River, Atlanta, Georgia, USA. The river
serves many purposes, from drinking water to wildlife
habitat to a recreation spot for the whole city.
Credit: National Park Service.
LAKES AND RESERVOIRS
A lake really is just another component of Earth's surface
water. A lake is where surface-water runoff (and maybe
some groundwater seepage) have accumulated in a low
spot, relative to the surrounding countryside. It's not that
the water that forms lakes get trapped, but that the water
entering a lake comes in faster than it can escape, either
via outflow in a river, seepage into the ground, or by
evaporation. And if humans live nearby, then water levels
can be affected by water withdrawals for human needs.
Hidden Lake, Glacier National Park, Montana, is
nestled in the high mountains, and runoff from the
steep slopes of surrounding landscape helps to keep
the lake full.
Credit: Lisa McKeon, USGS
GROUNDWATER
Some water underlies the Earth's surface almost everywhere, beneath hills, mountains, plains, and deserts. It is not always accessible,
or fresh enough for use without treatment, and it's sometimes difficult to locate or to measure and describe. This water may occur
close to the land surface, as in a marsh, or it may lie many hundreds of feet below the surface, as in some arid areas of the West.
Water at very shallow depths might be just a few hours old; at moderate depth, it may be 100 years old; and at great depth or
after having flowed long distances from places of entry, water may be several thousands of years old.
Groundwater occurs only close to the Earth's surface. There must be space between the rock particles for groundwater to occur, and
the Earth's material becomes denser with more depth. Essentially, the weight of the rocks above condense the rocks below and
squeeze out the open pore spaces deeper in the Earth. That is why groundwater can only be found within a few miles of the Earth's
surface.
Groundwater is an important part of the water cycle. Groundwater is the part of precipitation that seeps down through the soil until
it reaches rock material that is saturated with water. Water in the ground is stored in the spaces between rock particles (no, there
are no underground rivers or lakes). Groundwater slowly moves underground, generally at a downward angle (because of gravity),
and may eventually seep into streams, lakes, and oceans.
AQUIFERS
WELLS
Dug wells
Hacking at the ground with a pick and shovel is one way to dig a well. If the ground is soft and the water table is shallow,then dug wells can work. Historically, dug wells
were excavated by hand shovel to below the water table until incoming water exceeded the digger's bailing rate . The well was lined with stones, brick, tile, or other
material to prevent collapse, and was covered with a cap of wood, stone, or concrete. They cannot be dug much deeper than the water table -- just as you cannot dig a
hole very deep when you are at the beach... it keeps filling up with water!
Driven wells
Driven wells are still common today. They are built by driving a small-diameter pipe into soft earth, such as sand or gravel. A screen is usually attached to the bottom of
the pipe to filter out sand and other particles. Problems? They can only tap shallow water, and because the source of the water is so close to the surface, contamination
from surface pollutants can occur.
Drilled wells
Most modern wells are drilled, which requires a fairly complicated and expensive drill rig. Drill rigs are often mounted on big trucks. They use rotary drill bits that chew
away at the rock, percussion bits that smash the rock, or, if the ground is soft,large auger bits. Drilled wells can be drilled more than 1,000 feet deep. Often a pump is
placed at the bottom to push water up to the surface.
THE END
KAMRYN AVERY JAMARCUS
LAMARCUS