WATER LOGGING PROBLEMS DUE TO THE CONSTRUCTION OF DAMS , CANYON AND RESERVOIRS

CONTENTS ;

INTRODUCTION WATERLOGGING and SALINITY CAUSES PROBLEMS DUE TO WATERLOGGINGTYPES OF WATERLOGGINGWATERLOGGING BY DAMS WATERLOGGING BY RESERVOIRS CONTROLS OF WATERLOGGING CONCLUSIONS 04/05/17

INTRODUCTION

Water-logging refers to the saturation of soil With water. Soil may be regarded as waterlogged when the water table of the groundwater is too high to conveniently permit an anticipated activity, like agriculture.

In agriculture, various crops need air (specifically, oxygen) to a greater or lesser depth in the soil. Water-logging of the soil stops air getting in. How near the water table must be to the surface for the ground to be classed as waterlogged, varies with the purpose in view. A crop's demand for freedom from water-logging may vary between seasons of the year, as with the growing of rice (Oryza sativa).

In irrigated agricultural land, water-logging is often accompanied by soil salinity as waterlogged soils prevent leaching of the salts imported by the irrigated water.

From a gardening point of view, water-logging is the process whereby the soil blocks off all water and is so hard it stops air getting in and it stops oxygen from getting in.

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Water Logging and Salinity ;

As a result, the lands become uncultivable. In some cases, the underground water does not reach the upper level of lands but remains slightly lower and the land salts gather near the roots of the plants such situation is called Salinity. In this case, the sufficient amount of water is not available for irrigation, hence the salts are not absorbed in the land after having mixed.

These salts gather in the form of a layer in the upper level of land. Thus due to water logging and salinity the water retains itself on the surface of land and salts gather themselves in the zones of roots of plants. This leads to decrease the efficiency and productivity of lands and finally lands become uncultivable.

CAUSES

Over irrigation. Canal irrigation in areas adjoining agricultural lands where

subsoil water table steadily rises. Inadequate drainage. Surface flooding. Construction of dams and reservoirs. Presence of high water table. During monsoon & soon after some areas remains totally

submerged by the discharge of the rivers & accumulation of runoff from the surrounding catchment.

Water logging conditions are also caused in depressions along roads, canals & railway sides during rainy season.

Sea water comes to a particular area during high tidal surges.

PROBLEMS DUE TO WATER LOGGING

· It creates anaerobic condition in soils for which microbial activity is hampered.

· The availability of nutrient elements in soil is reduced & leaching loss is higher.

· Increases soil pH in coastal & dry area which leads salinity & alkalinity.

· Pollutes soil water & favors excessive weed growth.

TYPES OF WATER LOGGING 1) Water logging due to permanent submersion of

land. Such as ponds, rivers, etc. 2) Water logging from periodical submersion such as

coastal & estuarine land inundation by soil water or runoff of freshwater over lands etc.

3) Temporary water logging by stagnation of water as a result of heavy rainfall.

4) Water logging by coming out of water table to the surface & swampy areas in valleys are mostly caused by the phenomenon.

5) Water logging from artificial irrigation of agricultural lands in polders areas.

Dams, Reservoir's and canyons

Water logging caused by constructions of dams ;

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Water logging:

Rich soils in the states of Punjab and Haryana have been robbed for their use because of water logging. The Indian Institute of science estimates that 40 percent of the command area for Sardar Sarovar Dam will become waterlogged. This area contains black cotton soils which are particularly prove to water logging under perennial irrigation due to high water retention capacity. Soils become water logged and crop yields fall.

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Effects by Reservoirs ;

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MEASURES TO REDUCE IT

· Construction of dams & embankments along the coast to restrict saline to enter the agricultural lands. Could be an effective measure of reducing the water logging.

· Providing adequate number of bridges & culverts, along the roads, railroads, highways, across the canal etc could be a handy measure against water logging.

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REFFERENCE ;

Keller E A – Environmental Sciences Pages : 84 – 91 , 121-125.

Santra S C - Environmental Science

Wikipedia.com

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