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|03-18-2010, 06:02 AM||#1 (permalink)|
Need And Importance Of Irrigation
Need And Importance Of Irrigation
1.Most of the plain areas of Pakistan have been built by alluvial soil brought by the River Indus and its tributaries.But due to deficient rainfall ,agricultural activities cannot be performed without adopting some artificial means of irrigation.So the areas lying between the rivers have provided irrigation facilities through canals and various types of crops are grown in these areas.
2.The Rivers of our country used to take millions of gallons of water into the Arabian Sea.That water is being used for canal irrigation and a number of dry desert areas have become fertile and productive regions of our country.
3.The supply of water in our rivers remains irregular during the year.To regulate the water supply throughout the year the year the water is stored by constructing barrages,dams and weirs etc.
4.The slope of our country lies from north east towards south.This helps in the construction of canals and water can easily be distributed through canals from higher regions to lower areas.
5.All the rivers of our country come from snow-covered mountainous areas,having abundance of rainfall in summer ,in those rivers a huge amount of water comes due to heavy rainfall and the melting of snow during summer.Thus we store this surplus water in huge dams which is used for irrigation purposes in dry season.
6.The upper and lower areas of Indus plain have soft soil,where digging of canals is easier,and cheap labour is available in abundance.That reduces the cost of construction.That is why canal irrigation is preferred in our country.
7.Canal water adds to the fertility of the soil by bringing a number of organic and in-organic matters with it,while the water of tube -wells lacks all these matters,so people prefer canal irrigation.
8.Canal irrigation is the cheapest and easiest means by which vast areas can be commanded and made productive.
Means Of Irrigation In Pakistan
The following means of irrigation are practiced in various areas of our country:
1.Wells or Tube-wells:
This is one of the oldest methods of irrigation which is being used from ancient times in our country.Well irrigation is quite common in pledmont areas of North Eastern mountains and in the vicinity of rivers where the water-table is high.They are found all over the plain where canal water is not available and water table is high enough for their construction.Many shallow wells are dug by hand the areas where the water table is not far below the surface of the earth .The water is then lifted by "Charas" or "Persian wheels" driven by oxen or camels.
In areas where the water table is low and cheap electric power is available ,tube wells are used;due to shortage of canal irrigation water ,government is encouraging the farmers to dig more and more tube wells.
Irrigation from rivers is an ancient practice.It was being carried before the birth of christ in various areas of our country,but the modern system of large perennial canals was introduced by the Britishers.The first modern canal in Punjab was opened in 1859;it was taken out from river Ravi at madhopur (Gurdaspur district,India).After that a number of canals have been taken out from various rivers and our country has got one of the most excellent systems of irrigation in the world.The canals found in our country may be divided into the following types:
Those canals which supply water to their commanded areas throughout the year are known as perennial canals.To regulate the supply dams and barrages have been built.Most of the canals of our country are of this type.
(b)Non Perennial Canals:
Such canals runs only during the summer and the rainy season .They are closed down during winter months when there is not enough water in the rivers.Some of the canals from Sutlej ,the Sidhnal canals from Ravi and Haveli canals from Chenab are of this type.Only one crop can be harvested in the commanded areas of such types of canals.
(c) Inundation or Flood Canals:
These canals work only during the rainy season,when the rivers have a plenty of water .Because no dam or barrage is built at their head ,their construction cost being low,they also help in reducing the flood water and save the area from many dangers.Many old canals from the Indus and Chenab are of this type.
In Baluchistan short underground canals called Karez have been built to carry the water which soaks into the ground at the foot of the mountains to the fields and villages .As the canals are underground no water is wasted by evaporation.In Queta and Pashin districts this system is very popular and a large area of this region is irrigated by the Karez system.
The irrigated area is served by more than 40 major canal commands.Main canals start from a barrage or dam or weir on a river.A barrage feeds one or more main or link canals.A number of minor tributaries feed out of the main canal and these in turn,serve a number of outlets to the farmers water-courses each of which irrigates between 60 and 240 hectares.
There are three major groups of canal system :
(i) Canals on upper Indus Tributaries
(ii) Systems on the Indus
(iii) Systems west of the Indus.
(i) Systems On Upper-Indus Tributaries
The principal canal systems are:from the Jhelum,(a) Upper Jhelum canal,which starts from Mangla,joins the Chenab at Khanki to give its surplus water to the lower Chenab canal,and (b) the Lower Jhelum canal which starts from Rasul:from the Chenab (a) the upper Chenab canal starting from marala and joining the Ravi near Ballokin to supplement the water supply of the Lower Bari Doab canal,(b) the lower Chenab canal from Khanki,and (c) the Haveli system of canals from the Trimu weir below the junction of the Chenab and the Jhelum;from the Ravi,(a) the upper Bari Doab canal,which begins in Madhopur (India),irrigating mainly the Indian Punjab,with only its Lahore branch reaching Pakistan,(b)the Lower Bari Doab canal from Balakot and (c) the Sidhanaj Canals from the left bank of the Ravi at Sidhnal ;from the Sutlej,the Sutlej valley project,in which canals depart from the river Gandas in Ghwala,Sulaimanke,Islam and below the juction of the Sutlej with the Chenab at Panjnad.
The upper Jhelum,the upper Chenab,and the lower Bari Doab canals together form The Triple Project ,which was designed to carry surplus water from the Jhelum to the Chenab ,and from the Chenab to the Ravi.
(ii) Systems On The Indus
The largest dam on the Indus has been built at Tarbela.Other barrages,in descending order along the river,are Jinnah barrage near Kalabagh,part of the Thal project;Taunsa Barrage 290 km.further downstream,which has 100,000 kw power station in addition to diversion works;Guddu Barrage,150 km.upstream from Sukkar;Sukkur or Liodyd Barrage,the oldest barrage on the river,and Ghulam Mohammad Barrage,near Kotri.
(iii) Systems West of The Indus
These include (a) the Swat Canals departing from the river at Malakand (upper Swat canal) and Abazal (Lower Swat Canal); (b) the warsak Multipupose Project on the Kabul River 30 kms.north west of Peshawar which includes a 160,000 KW power plant;and (c) the kurram Garhi Project on the kurram and barren rivers in Bannu tehsil.
In addition to these major projects.Some smaller dams have also been built by the Water and power Development Authority (WAPDA).These include reil Dam,Gomal Dam Multi-Purpose Project Khanpur Dam,and Hab Dam.The Agricultural Development Corporation has set up the small Dam Organization to construct dams of localized utility storing the flood water of hill stream.A number of such dams have been constructed in the dry sub-mountain areas of the north west.
Mangla And Tarbella Dam
The Mangla Dam
Under the Indus Basin Treaty,this is the second largest multi-purpose project designed to control and conserve the flood water of the Jhelum for use mainly as replacement irrigation supplies for the area which was served by the three eastern rivers.On the Jhelum river near the village of the Mangla,about two miles upstream from the regulator of the upper Jhelum Canal and about 20 miles from Jhelum town,a dam of the embankment type has been built.The dam has crest length of about 11,000 feet and its height is 380 feet.The reservoir created by the dam is about 40 miles long,having a storage capacity of 5.5 million acre feet.It is the second largest earth filled dam of our country.The project is providing 400,000 kilowatts of electricity and 88 lakh acre feet water for irrigation purposes.The design of the dam has a provision for future extension.Its height can also be increased about 99 feet and storage capacity can also be increased upto 9.6 million acre feet and electricity generated can also be increased from the present 400,000 k.w. to one million k.w. The Mangla lake has been developed as a fishing centre and a health and tourist resort.This project was completed in 1967.
The Tarbela Dam
This is one of the largest earth and rock filled dam in the world.This dam has been built on the river Indus at Tarbela,15 miles from maripur and 30 miles from Attock.This is also a multipurpose project .The dam has a gross storage capacity of 11.1 million acre feet.It is 9,000 feet long and 485 feet high.A 50 mile long lake has been built behind it.It will provide 21 lakh kilowatts of electricity and 93 lakh acre feet of water for irrigation when completed .It construction started in 1968 under the Indus Basin Treaty,and the dam was completed in 1974.The installation of 10 units of electricity has been completed in 1985.There is proposal of or the tarbela project that 2 large off-channel reservoirs will have to be built to increase storage and lengthen the life of the generating facilities,since silting is expected to reduce the life of main dam.Water from Tarbela will be used in the Haro and Soan Basins and for replacement the supplies will be diverted to the Chashma Jhelum link canal and thence to the Trimmu-Sidhnaj-Mailsi-Bahawal link system.This project will help other barrages to retain the supply of water.
According to Indus Basin Treaty five barrages have been built and various link canals have been taken out from these barages.
A barrage has been built on River Indus at Chashma .A link Canal has been taken out from the right bank of Chashma providing water to canals of jhelum and Chenab.The work of Chashma wast Bank is under progress.It is hoped that after completion,this canal will irrigate large area of barren land in Dera ismail Khan and dera Ghazi Khan districts.
The other Barrages from where the following link canals have been taken out are:
1. Rasul at Jhelum
2. Near Qadirabad on Chenab
3. Near Sighnaj on Ravi
4. Near Mailsi below the existing Islam headworks on the Sutlej.
All these Barrages have a total length of nearly 3 1/2 miles.These barrages are providing about 100,000 cusecs of water to their link canals.
1.The Rasul-Qadirabad :
A 30 miles long canal has been built linking Rasul with Qadirabad and 19,000 cusecs water has been brought from Jhelum to Chenab.
Qadirabad-Baloki link canal is supplying 18,600 cusec combine water of Jhelum and Chenab to Ravi at baloki.It is about miles long.
3.The Balloki Sulemanki Link:
This link canal is providing 6,500 cusec water of Ravi to the Sutlej canals ,e.g.Pakpattan and Depalpur canals.
4.The Chashma-Jhelum Link Canal:
This link canal is 63 miles long and it is supplying 21,700 cusecs water of Indus from Chashma to Jhelum so that the supply of water at Trimmu head works can be maintained.
5.Trmmu-Sidhnal Link Canal:
Trmmu-Sidhnal link canal is providing 11,000 cusec combined water of Indus ,Jhelum and chenab at Sidhnal on Ravi
6.The Sidhnal-Mailsi-Bahawal Link:
It is a sixty miles long canal,which is carrying the Indus,Jhelum and Chenab waters to the Islam headwrks canals from the Sutlej.
7.The Taunsa-Punjnad Link Canal:
This link canal is 38 miles long .It is carrying the Indus water for use at the Panjnad headworks.The link canals have a total length of 388 miles with a total capacity of about 100,000 cusec,but the present supply of water from the canal is insufficient for our requirements and a large amount of water is obtained from tube wells and other means.
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