Water, Environment and Development

pointdepressedMécanique

22 févr. 2014 (il y a 2 années et 9 mois)

49 vue(s)

Water, Environment and Development


Part 1: Introduction

What You Need to Know About Water


Segment 1D:
Land Degradation and Water Resource Degradation


This unit

examine
s

the relationship between
various forms of basic land use and their
impact on water
resources and water

quality.
The capacity of natural systems to recharge water
resources can be diminished by

deforestation and overgrazing
. The results
include

erosion and
desertification.

In
gen
eral

terms, deforestation is suffered by tree stands, i.e., forests, while overgrazing is
suffered by grasslands and scrublands that are susceptible to
excessive
foraging
by
livestock

herds
.
Deforestation can result from conversion of forest to farmland o
r by intensive gathering
of wood for fuel. Overgrazing is the negative damaging outcome of a natural process, that of
animals eating plants. Notice the terms: “excessive”
and

“over.



They point to a condition in
wh
ich natural growth and natural process
es are overwhelmed by some form of use or
exploitation that exceeds the natural capacity for regeneration. A common result
of deforestation
and overgrazing
is e
rosion
, which

is the water
-

or wind
-
driven removal of soil
. When water
-
driven it results in
gullies, runnels, and ditches; when wind
-
driven it takes

the form of sheet
erosion
, which is simply dry and unprotected topsoil being blown away by wind
.
The former
occurs when

soil is insufficiently protected from rapid
ly flowing water by natural
plant
c
anopies
or
“umbrella
s
” and
is
inadequately held in place by interwoven plant roots.
The latter occurs
when soils is inadequately secured by roots and nothing

such as forests or wind breaks


prevent it from being blown long distances. In dry climates, th
e result of deterioration of plant
cover is known as “d
esertification
.”

The effects of these processes on water resources
can be seen
as

the reverse of the
benefits of intact plant cover on ground water and stream recharge. In the absence of plant
cover,
precipitation hits the ground with greater force, loosening soil particles and washing them
away. In addition to washing away topsoil and possibly creating gullies,
both water
-

and wind
-
driven
erosion causes sedimentation of streams and turbidity of strea
m

water.
The quality of
w
ater quality
is diminished for both habitat and
household
uses
.

Given the great impact that poor water quality has on quality of life in households at the
subsistence level, it is especially sad that the root of the problem is so
often the efforts of poor
people to
subsist
, to merely have
barely enough
.
T
he a
ttempt
of poor people to obtain
just
enough fuel, or just a few more goats or cattle, for example
,
is the reason for overgrazing or the
overharvesting of fuel wood. In fact,
these are the legitimate efforts of people who have no other
means of livelihood.

At first glance, it appears that such people are trapped
in the
unfortunate
dilemma of either preserving their natural surroundings but doing without the necessities of life
,
or of securing their necessities by means that damage their natural environment. The solution is
to utilize techniques that increase the production of necessities while enhancing the value of what
has been called “natural capital”

those resources and na
tural systems on which human systems
of production rest: soil fertility and retention

and

water purification
.