Salinity can be controlled and lands reclaimed,
though not overnight and not easily or inexpensively
By Dr. S.M.
Alam NIA
Tando Jam
Dec 10 - 16 , 2001
Salinity has long been recognized as a major
problem in rural areas for agriculture and damaging of buildings, in
urban areas. However, it also affects deterioration of towns and
cities across the country. Evidence of salinity can sometimes be seen
in damaging building's foundation and roads, but damaged foundations
and underground services may be more difficult to detect. Urban
salinity, like salinity in rural areas, is caused mainly by rising
water tables, through excess and frequent watering and infiltration
from rain, bringing salts to surface, causing salinity and water
logging problems. Historically, the salinity has damaged or destroyed
many civilizations in the past. Water is the upper surface of
groundwater, below which the layers of rock, sand and gravel are
saturated with water. In a well-balanced system, the water table
usually remains many meters (1 meter = 3.28 feet) below the Earth's
surface. Any amount of water added to the garden, in excess of
evaporation and plant needs, filters down slowly through the soil,
thus adding to the groundwater and making the water table rise or high
near to the surface. A water table rising towards the surface, carries
with it dissolved salts that are normally locked in the soil and rock
profile.
The problem of salt in agriculture is not new, or
limited to the worldwide. FAO experts have estimated that salinity
affects productivity on about 80 million hectares or arable land just
about the total land area of a country like the size of Pakistan. The
problem arises, when salt is left behind in the soil as water passes
back into the atmosphere through the processes of evaporation and
plant transpiration. In areas, with good rainfall and effective
drainage systems, the soluble salts change in composition and
concentration as water carries them away, eventually to the seas. But,
in parts of the world having little rainfall and restricted drainage,
the salts can not easily be transported. They accumulate in lowlands
or in the groundwater below them. Natures own geographical and
geological processes are major contributors to salinity. Experts say
that more than 30 million hectares of salt-affected land arise from
natural causes, aridity, and high rates of phenomenal evaporation of
water from the soil surface.
More saline lands are in or near areas, where
irrigation is the backbone of farming, predominantly in developing
countries. Lack of good drainage is a major contributor to salinity.
So is seepage from irrigation systems and drainage fields, which can
lead to a loss of nearly half of the water. Gradually, the groundwater
table rises bringing salts to soil layers, where crops get nutrients.
As surface water evaporates, the fields become white encrusted,
salt-capped wastelands. Farmers abandon them and agricultural
economies suffer. Salinity can be controlled and lands reclaimed,
though not overnight and not easily or inexpensively. One approach is
constructing good irrigation systems that gradually improve soil
conditions and prevent formation of water logged and unproductive
fields. Unfortunately, poor irrigation practices often promote rather
than control salinity and engineered drainage systems extending over
large areas of and are financially out of reach for most countries.
Biosaline agriculture suiting salt-tolerant plants to soil and water
conditions may offer more affordable alternative, though not
necessarily an easier one.
These salts such as NaCl, Na2SO4, Na2CO3, CaSO4,
CaCl2, Ca(NO3)2, MgSO4, MgCl2, Mg(NO3)2, CaC03, etc. generally
accumulate at the surface, causing salinity problems in and around the
locations or on the spots. Other factors contribute to a rising water
table along with excess garden watering are: tree clearing or cutting
in urban areas, over-irrigation of public recreation areas, disruption
of natural drainage lines and over flow of septic tanks and sullage
pits. The effect of salinity on the environmental material is very
serious. Saline ground water kills grass, shrubs and trees, damages
roads and buildings, corrodes pipes, causes water logging, scalds
ground, destroys soil structure and damages septic tanks, cemeteries,
rubbish dumps and water supplies, lawns and shallowrooted, so can
utilize little water. Most water applied to lawn drains through beyond
their root systems.
Urban salinity is a complex process affected by
characteristics of the local and regional geology, so evidence of
salinity, and the damage it causes, may not occur throughout the whole
urban area and may take many years to become apparent. Even though a
house or a street may not feel the direct effects, poor water
management may aggravate the problem elsewhere. That is why, dealing
with the problem requires a committed and coordinated approach from
government and the community. The cost to the community is enormous.
For example, the reconstruction of just one street block of a roadway
cost an enormous amount. Similarly, the repairing the foundation of a
house or rebricking the lower course can cost substantial amount. The
major effects, which can be seen on the items of the locality are as:
Unhealthy or dead grass, shrubs and trees; greasy, boggy or water
logged ground; spread of salt tolerant species such as couch grass;
bare patches of ground, often with white crust on the surface; septic
tanks not working properly; deterioration and rising damp in bricks
and mortar; white crust of salt on brickwork, usually close to the
ground; cracked or collapsed pavements, roads and driveways; shifting
or sinking house foundations; corrosion of water, gas and sewage
pipes.
One should follow the following instructions as
precautionary measures: Avoid water wastage; don't over-water lawns
and gardens. Lawns are shallow-rooted so don't utilize much soil
water. Most water applied to lawns drains through beyond the reach of
their roots; group plants with similar water needs together and gives
water only, when there is almost necessary; plant deep-rooted plant
varieties and have small lawn areas; use mulch on garden beds;' keep
plants healthy by testing the pH value of the soil. Lime or fertilize
as appropriate; don't wash your car on the lawn unless the ground is
very dry; don't empty pool water onto the lawn; connect roof drainage
to the storage water system, not to sullage pits; join or start a
local urban land-care group.
Salt action is a strategy for joint action by the
government official and the community. Its aim is to manage and
control salinity levels within the land and water resources of the
State as an important part of Total Catchment Management. Salt action
recognizes that people are the key to tackling the State's urban
salinity problems.
Individual residents, community groups and
governments all have an important role to play. Researchers are
currently documenting the complex processes involved in urban
salinity: the movement and characteristics of ground water, and
regional or local geology, climate and land use. Community involvement
is essential to assist in the collection of data and to ensure that
urban salinity is given the attention it deserves.
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