What is water-logging?

What is water-logging?

 An artificial land is said to be water-logged when its productively gets affected by the high water table. The productivity of land may become affected when the root zone of plants gets flooded with water, and thus become ill- aerated.
                           Oxygen present in the air is not only needed bu human being but is also needed by plants. The life of plants depends upon the nutrients like nitrate. The form in which nitrate s are consumed by the plants is produced by the bacteria, under a process called nitrification. These bacteria need oxygen for their survival. The supply of oxygen gets cut off when the land becomes water-logged, resulting in the death of these bacteria and fall in production of plants food (i.e. nitrate) and consequent reduction in plants growth and hence, crop yields are reduced.

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Effects of Water-logging 

Apart from ill-aeration of plants, many other problems are created by water-logging such as

1. The normal cultivation operations such as tilting, ploughing etc cannot be easily carried out in wet soils. In extreme cases, free water may rise above the surface of the land, making the cultivation operations impossible. In ordinary languages, such land is called swampy land.

2. Certain water-loving plants like grass, weeds etc. grow profusely and luxuriantly in water-logging lands, thus affecting and interfering with the growth of the crops.

3. The presence of excessive moistures lowers the temperature of the soil, which retard the bacterial activity of the plants, thus reducing crop yields.

4. Water-logging leads to salinity.

Causes of Water-logging

Water-logging is the rise of the water table, which may happen due to various factors such as

1. Over and Intensive Irrigation - When a policy of intensive is adopted, then the maximum irrigable area of the certain region is irrigated. This leads too much irrigation, resulting in heavy percolation and the subsequent rise of the water table. For this reason, to avoid water-logging, a policy of extensive irrigation(i.e., irrigation, spread over wider regions) should supersede the policy of intensive irrigation.

2. Seepage of water from the adjoining high lands - Water from the adjoining high lands may seep into the sub-soil of the affected land and may raise the water table.

3. Seepage of water through the canals - Water may seep through the bed and side of the adjoining canals, reservoir etc, situated at a higher level than the affected land, resulting in the high water table. This seepage is excessive, when the soil at the site of canals, reservoir etc, is very previous.

4. Impervious Obstruction - Water seeping below the soil, moves horizontally(i.e laterally) but may find an impervious obstruction, causing the rise of water table on the upstream side of an obstruction, similarly, an impervious stratum may occur below the top layer of pervious soils. In such cases, water seeping through the previous soil will not be able to go deep hence, quickly resulting in high water-table.

5. Inadequate natural drainage - Soil having less permeable substratum(such as clay)  below the top layer of pervious soil, will not be able to drain the water deep into the ground and hence resulting in high water level in the affected soil.

6. Inadequate surface drainage -  Stormwater falling over the land and excess irrigation water should be removed and should not be allowed to percolate below. If proper drainage is not provided, the water will constantly percolate and will raise the level of the underground reservoir.

7. Excessive rain - Excessive rainfall create temporary water-logging and in the absence of good drainage, it may lead to continued water-logging.

8. Submergence due to floods - If the land is continuously submerged by floods, water-loving plants like grass, weeds etc. may grow, which obstruct the natural surface drainage of the soil and thus increasing the chance of water-logging.

9. Irregular or flat topography - In steep terrain, the water drained out quickly. On flat or irregular terrain having depression etc. the drainage is very poor. All these factors lead to greater detention of water on land and hence, more percolation and increased the water table.

How to Prevent Water-logging

it is evident that water-logging can be controlled only if the quantity of water into the soil below is checked and reduced. To achieve this, the inflow of water into the underground reservoir should be reduced and the outflow from this reservoir should be increased. The various measures adopted for controlling water-logging are enumerated below:

1. lining of canals and watercourses - Attempts should be made to reduce the seepage of water from the canals and watercourses. This can be achieved by lining them.  It is a very effective preventive method to control waterlogging.

2. Reducing the intensity of irrigation - In areas where there is the possibility of water-logging, intensity of irrigation should be considerably reduced. Only a small portion of irrigable land should receive canal water in one particular season. The remaining areas can receive water in the next season by rotation.

3. By introducing crop-rotation - Certain crops require more water and others requires less water. If a field is always shown with a crop requiring more water, the chance of waterlogging is more. In order to avoid this, high water requiring crop should be followed by one requiring less water, and then by one requiring almost no water. Rice may be followed by wheat and wheat may be followed by dry crop such as cotton.

4. Optimum use of water - We know that earlier that only a certain amount of water gives the best results. Less than that or more than that reduces the yield. But most of our cultivators are unaware of these technicalities and they feel that by using more water they can increase there yield. Therefore they try to use more water and more water. This can be checked by educating the cultivators by proper propaganda. moreover, revenue should not be charged on the basis of the irrigated area but should be charged on the basis of the quantity of water utilized. A strict watch should be kept at the outlet in order to stop undue tapping.

5. Providing intercepting drain - Intercepting drains along the canals should be constructed, wherever necessary. These drains can prevent the subsoil water from reaching the area likely to be waterlogged.

6. Provision of an efficient drainage system - An efficient drainage system should be provided in order to drain away from the stormwater and the excess irrigation water. A good drainage system consists of surface drains as well as subsurface drains.

7. Improving the natural drainage of the area - To reduce percolation, it is necessary that water is not allowed to stand for a longer period. Some relief in this reduction can be obtained by removing the obstructions in the path of the natural flow. This can be achieved by removing bushes, jungles, forests etc. and improving the slopes of natural drainage lines.

8. Introduction of lift drainage system - lift irrigation utilises the underground water for irrigation. It, therefore, helps in lowering the water-table through tubewells etc. Canal irrigation may, therefore, be substituted by lift irrigation, in areas which are likely to be water-logging. It is an efficient remedial measure for controlling water-logging.

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