Namibia - CountryWatch

Global Environmental Concepts Environmental Overview
and large-scale irrigation. The supply of freshwater is inherently limited, and moreover distributed
unevenly across the earth's landmasses. Moreover, not just demand for freshwater but activities certain
to degrade it are becoming more pervasive. By contrast, the oceans form a sort of "last wilderness,"
still little explored and in large part not seriously affected by human activity. However, coastal environments
- the biologically richest part of the marine ecosystem-are experiencing major depletion due
to human encroachment and over-exploitation.
Freshwater:
In various regions, for instance the Colorado River in the western United States, current withdrawals
of river water for irrigation, domestic, and industrial use consume the entire streamflow so that almost
no water flows into the sea at the river's mouth. Yet development is ongoing in many such places,
implying continually rising demand for water. In some areas reliant on groundwater, aquifers are being
depleted at a markedly faster rate than they are being replenished. An example is the San Joaquin Valley
in California, where decades of high water withdrawals for agriculture have caused land subsidence
of ten meters or more in some spots. Naturally, the uncertainty of future water supplies is
particularly acute in arid and semi-arid regions. Speculation that the phenomenon of global warming
will alter geographic and seasonal rainfall patterns adds further uncertainty.
Water conservation measures have great potential to alleviate supply shortages. Some city water systems
are so old and beset with leaking pipes that they lose as much water as they meter. Broad-scale
irrigation could be replaced by drip-type irrigation, actually enhancing the sustainability of agriculture.
In many areas where heavy irrigation has been used for decades, the result is deposition of salts and
other chemicals in the soil such that the land becomes unproductive for farming and must be abandoned.
Farming is a major source of water pollution. Whereas restrictions on industrial effluents and other
"point sources" are relatively easy to implement, comparable measures to reform hydraulic practices at
farms and other "nonpoint sources" pose a significantly knottier challenge. Farm-caused water pollution
takes the following main forms:
- Nitrate pollution found in wells in intensive farming areas as a consequence of heavy fertilizer use is
a threat to human health. The most serious danger is to infants, who by ingesting high-nitrate water can
contract methemoglobinemia, sometimes called "blue baby syndrome," a potentially fatal condition.
- Fertilizer runoff into rivers and lakes imparts unwanted nutrients that cause algae growth and eventual
loss of oxygen in the body of water, degrading its ability to support fish and other desirable aquatic
life.
- Toxic agricultural chemicals - insecticides, herbicides, and fungicides - are detectable in some aquifers
and waterways.
205 Namibia Review 2013