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Water conservation and drip irrigation
An international seminar on water conservation and drip irrigation by D-8 countries was held recently in Islamabad . The major emphasis in this seminar was that due to increasing population and declining water resources for agricultural ,industrial , drinking ,sanitation purposes there is great need for water conservation to meet the future challenges in the new millennium .Various representatives of D-8 countries such as Turkey , Nigeria ,Malaysia , Iran ,Indonesia ,Egypt ,Bangladesh and Pakistan made commendable suggestions for conservation of surface , ground and rain water on the basis of their respective country experience .They were rightly of the view that besides increasing irrigation efficiency of surface and groundwater major emphasis should also be laid on rain water harvesting and drip irrigation .
The scribe wrote in the national press in eighties about the immediate need of water conservation technologies including sprinkler ,drip and pitcher irrigation in our arid ,semi-arid and desert regions to meet the future national water crisis .The present Defence Minister Rao Sikander Iqbal who was than Federal Agricultural Minister responded positively to my suggestions saying that these will be included in the new agricultural development policy of the then Government .But unfortunately that government was removed and my suggestions on water conservation strategies could not be considered .Again ,while assisting in the preparation of draft report of agriculture and water sectors of Eighth Five year Plan(1993-98) ,I prepared and included plan to develop water conservation strategies keeping in view the impending water shortage problems in the new millennium .But again ,my suggestions were ignored by the successive governments due to their poor governance .
One of the reason of this indifference by previous policy makers could be that they thought that Pakistan has a largest single contiguous gravity flow irrigation system in the world fed by the mighty River Indus and its tributaries .Consequently , the nation has a rich source of water and hence water conservation technologies like viafro and sprinkler irrigations ,low energy precision applications ,drip irrigation .pitcher irrigation and rain water harvesting were treated as orphans .
The FAO reported in 2002 ,that due to declining water resources deserts have already expanded in over 100 countries and due to increasing drought ,poverty and creaping deserts there are 1.1 billion people who lack access even to potable water .As a result with the passage of time , increasing water demand for drinking ,agricultural ,industrial , sanitation and hydropower purposes ,there is now awareness in the country that there is need for adopting water conservation strategies .Of the various water conservation techniques , drip irrigation is one of the efficient technique .It consists of a network of porous or perforated piping usually installed on the surface or below ground that delivers water directly to the root zone of crops. This irrigation system keeps evaporation losses low at the efficiency rate of 95 % and cut water use by 40-60 % as compared to the conventional gravity flow system .
It is now extensively used world wise .For instance in Israel who initiated this technology in 1960 ,it is now used on 50% of their irrigated area making them self sufficient in most of their agricultural crops .As a result this technology spread on large areas in USA ,Australia ,Newzealand , Spain ,Mexico ,South and North Africa and is now extending to middle east .For instance , nearly 32389 hectares have been brought under drip irrigation in UAE which has become self sufficient in vegetables and date palm . Similarly , in Iran the area under drip irrigation increased from 800 hectares in 1990 to 170,000 hectares in 2004 ,where this irrigation system is extensively used for fruits ,vegetables , row and ornamental crops .However ,in some economically poor countries dip irrigation using sophisticated imported equipment may be unaffordable ,especially by small farmers .Therefore the equipment may be locally manufacture or modified .For instance ,poor farmers in Indonesia are using locally developed bamboo dripirrigation ,disposed plastic bottles with ceramic emitters and plastic pipe drip irrigation methods .
Drip irrigation system has a great potential in the arid and semi-arid regions of Pakistan which comprises of 70 million hectares of the total geographic area of 79.6 million hectares of the country .Although 18.04 million hectares have been brought under irrigated agriculture but nearly 52 million hectares still comprises of arid and semi arid lands where arid agriculture is practiced on cultivated areas due to limited availability of irrigation water as well as mismanagement of available irrigation water .For instance , in Balochistan ,the largest arid and semi-arid province of Pakistan , due to indiscriminate expansion of authorized and unauthorized tubewells and over irrigation to orchards and vegetables has lead to over-mining of groundwater acquifer and its consequent lowering by over 2 meter annually .As a result there is now little to no groundwater potential in
Quetta , Pishin ,Mustung ,Mangochar and Pishin Lora basins and sub-basins ,while Zhob ,Qilla-Sufaid ,Nari River ,Hamun-e-Lora and Kachhi plains have limited groundwater potential . If water conservation techniques such as drip irrigation are not immediately adopted and over-mining of groundwater is not properly managed then the Province of Balochistan will seriously face water shortage by the next 15 years .
Over a decade of research on drip irrigation in Balochistan by FAO , it has already been established that drip irrigation not only saves 40-60 % of irrigation water but also increases yield of orchards up to 20 % per hectare .So Mir Zafarullh Khan Jamali Prime Minister of Pakistan should take serious cognizance of this situation of his Province and should immediately implement drip irrigation ,especially outside the canal command areas of his Province and Pakistan .The use of ground water should be legally adjusted strictly in a manner that use of ground water should not exceed 70% of the total annual recharge rate for sustainability of groundwater acquifer .
Although ,the completion of Mirani Dam ,Sabakzai Dam and Kachhi canal projects in the next few years will increase the canal irrigated area by 405809 hectares, thus increasing the total canal irrigated area of 0.5million hectare to0.91 million hectares .
But still large areas outside the canal commands will be facing severe water shortage due to over-mining of groundwater by over 25734 electric and diesel tubewells resulting in further drying of orchards and leaving their homes by the villagers Therefore , the Government should also give top priority to drip irrigation as the system may result in significant conservation of water in the province .
Similarly , drip irrigation has great potential in our desert regions of Thal, Cholistan ,Thar ,Chagai-Khran and Derajat .These deserts though have some sweet water lenses but most of the ground water varies from slightly to highly saline .Drip irrigation can use both sweet and saline water on sandy desert soils .Low and medium salinity water can be used for irrigation on most of the soils where certain amount of leaching occurs .Whereas ,high salinity water can be used on soils with good drainage .Sandy soils provide excellent strata for quick percolation .
The salt tolerant field and horticulture crops and forest tree plants growing on such sandy soils may be well aerated as sand provides more space between its particles . Chlorides of sodium and magnesium components of saline water ,are easily washed down to deeper layers without effecting the selective root system of salt tolerant plants . The harmful sodium ions are not absorbed on sand particles as compared to clay and silt particles .Chemical amendments further improve prospects of saline agriculture in the sandy deserts .India has already successfully grown salt tolerant fruits and vegetable crops by irrigating with saline water having EC between 5-15 dSm in their adjoining Rajisthan Desert .
Since water is a limiting factor in our sandy deserts ,it should not be applied by flood irrigation as most of it will percolate down the root system through sandy soils .It should be applied by drip irrigation using local PVC pipes . Alternately discarded plastic infusion/drip sets from hospitals can be used .Each drip set be filled with water through slit made at the closed end of the bag and tied to a pole fixed near the pit of the planted fruit sapling .Each pole may have one to three suspended infusion sets depending upon the availability of water , age of plant and season of irrigation ,Each morning water should be poured into the bags and flow through emitters be properly regulated . Keeping the pits/basins covered with plastic sheets may further minimize water losses through evaporation . Pitcher irrigation has also been found as an effective water conservation method for sandy and arid areas .
It has been announced sometime back by the Federal Minister of Agriculture that the Government may allot Rs200 million for the development of drip irrigation in the country which is urgently needed in Balochistan ,major parts of Sindh such as Nara canal belt ,arid and semi-arid belts of NWFP and Punjab ,especially those outside the canal commands.
The Government should prepare an efficient water consevation plan and monitor its effective implementation at the field level for the survival of the nation and our future generations .
sardar Riaz A. Khan
Courtesy The Nation |
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