Page 73 - Soil Degradation, Conservation and Remediation

2.4 Lowering of Groundwater Table 59

through the pervious soils will not be able to go deep and, hence, quickly results in
waterlogging. In the absence of satisfactory natural drainage, well-planned artifi cial
drainage systems are needed to be installed. Often, drainage systems do not work

satisfactorily, neither they are sufficiently deep, nor they are adequately frequent.

2.3.2 Effect of Waterlogging

Waterlogging reduces aeration. After some days of flooding, the oxygen content in
soil may completely deplete. Growth of crop plants and yield are reduced by altered
physiological processes due to low oxygen and reduced root respiration in water-
logged soils. Often, waterlogging is responsible for crop failures. In addition, water-

logging does not allow following a definite crop calendar. The normal cultivation
operations, such as tilling and plowing, cannot be easily carried out in wet soils.
Plowing, sowing, and planting are delayed by waterlogging. Waterlogging converts
many croplands into wastelands. Rising water table brings dissolved salts in ground-
water to the surface soil. Water continuously evaporates leaving the salts in soil.

Thus, a high water table creates soil salinity, which is difficult to reclaim. Soil salin-
ity reduces productivity. Many soils have become saline and out of cropping due to
faulty irrigation in different countries, including Pakistan.

2.3.3 Control of Waterlogging

Waterlogging can be controlled only if the passage and quantity of water into the sub-
soil is reduced; the rising of the groundwater table is prevented, and the drainage of
excess water is improved. The infl ow of water into the underground reservoir may be

reduced by reducing the intensity of irrigation. The outflow of water may be increased
by deep and frequent interceptor and field drains. The groundwater table must be main-

tained well below the root zone. Generally, keeping the water table at least about 3 m
below the ground surface is desirable. This can be achieved by different drainage
systems. Seepage water can be prevented by interceptor drains. Stagnant water can be
removed by field drains, surface or subsurface. The drains must be regularly monitored.

Many soils become waterlogged by flooding from canals and rivers. Small- and large-
scale embankment has been successfully employed in different regions.

2.4 Lowering of Groundwater Table

Water that is located beneath the earth’s surface in pores and fractures in soil and
rock is called the groundwater. The highest level of this underground water is known
as the groundwater table. The water table is actually the boundary between the