Geography Reference
In-Depth Information
to the quality of the watershed that feeds it. Watershed management concerns a wide
rage of efforts that monitor and ensure the quality of watersheds and, thusly, the receiv-
ing bodies. This is a significant environmental undertaking in any case, but especially so
when municipal or regional drinking water is at stake.
Various geographical techniques are routinely applied to this endeavor. The Global Posi-
tioning System (see Chapter 4), for example, is used in field surveys to pinpoint and map
pollution sources. Aerial photography and satellite imagery may be used to assess the
health of vegetation that anchors watershed soils. But perhaps the most intriguing tech-
nology is
digital terrain modeling,
in which the lay of the land in exacting detail is stored in
computer memory, allowing managers to simulate all kinds of eventualities. Want to see
what will happen if a small pollution source becomes a big one? Or if acid rain should
reduce forest cover by 55 percent (or any other percentage)? Or if 2 inches of rain should
fall anywhere or everywhere in 25 minutes? This computer technology facilitates simula-
tion of all kinds of scenarios, the goal being watershed management that promotes and
preserves the quality of drinking water.
The geographical dimension
To some extent, acid rain happens everywhere, but its intensity is very uneven (Figure 18-5). In gen-
eral, the world's principal industrial regions tend to the major source areas. That includes the south-
eastern Great Lakes region, Western Europe in general, plus the Ukraine and southwestern Russia,
EasternChina,andJapan.Acidraintendstobegreatest intheseimmediate regionsplusthosedirectly
downwind. Given the general west-to-east movement of the atmosphere at mid latitudes, the typical
result is an elongated impact area that tails off easterly from the source region.
Thus, in North America, relatively pristine areas in northern New York, New England, and Canada's
Maritime Provinces have been hard hit. Forests are dying over large areas and numerous lakes, es-
pecially small ones, are becoming lifeless. The situation is similar in Europe, where the Black Forest
and similar tracts are being affected.
Sometimes a state or country finds itself on the receiving end of pollution that originates in another
state or country. This is called
trans-boundary pollution
. Thus, the nitrates that cause algae blooms
that kill fish and hurt the economy in Maryland's portion of the Chesapeake Bay may have their
origin in fertilizers that were spread on agricultural fields in Pennsylvania. Similarly, acid rain that
kills forests in eastern Canada may have their origins in power plants in the United States.
