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Abstract
Keywords:Irrigation Technology; Sprinkler System; Drip System; Furrow Bed; Climate Change; Small Farmers; Water Use Efficiency
Introduction
The Indus Basin of Pakistan is comprised of one of the largest contiguous canal irrigation systems in the world that lies at the downstream of HKH, thus prone to frequent climatic disasters [5]. For instance, the recent 2010 floods, originated in HKH region, drowned around one fifth of Pakistan, affected ~20 million people and caused more than US $43 billion impact on the country’s economy [6]. Irrigated agriculture produces around 90% of crop production in Pakistan and contributes more than 21% in the country’s GDP. Moreover, production in Pakistan has global implications, thus may impact on global food security. For instance, Pakistan produces wheat crop greater than the whole Africa and nearly equal to South America. Therefore, agriculture needs to be more wisely managed and traditional farming and irrigation methods needs to be modified according to the changing climatic conditions. This paper reviews some of the salient features of agriculture in Pakistan, its vulnerability to climate change and few promising irrigation technologies capable of improving farming system resilience to climate change.
Salient Features of Pakistan’s Agriculture and their Vulnerability to Climate Change
Land use in Pakistan
The province wise land use is presented in Table 1. The total area of Pakistan is 79.61 million hectares (mha) with 23.40 mha cropped area. The current cultivated area is concentrated in Punjab province with 12.46 mha, which is ~50 % of the total cropped area of Pakistan followed by Sindh Province at ~8 % of country’s cropped area. However, there is 7.82 mha culturable waste area that is largely concentrated in least developed provinces of Khyber Pakhtunkhwa (KP) and Baluchistan, which can be brought under cultivation to enhance food security. The province wise culturable waste areas are 12%, 23%, 64% and 190% of current cultivated lands in Punjab, Sindh, KP and Baluchistan respectively. Therefore, the agro based economies of KP and Baluchistan has greater potential for improvement by cultivating their culturable waste lands.
Table 1: Land use in Pakistan.
The irrigated cropped area in Pakistan is around 18.84 mha
(Table 2) according to Agriculture Statistics of Pakistan 2006-07.
This includes: wheat 7.34 mha (36.3 % of total); rice 2.58 mha
(12.8 % of total); cotton 3.01 mha (15.2 % of total); sugarcane
1.03 mha (5.1 % of total); and fodders 2.00 mha (9.9 % of total).
These five crops cover 16.03 mha of total irrigated area in Pakistan,
which is 79.32% of the total irrigated area. Therefore, improving
water productivity of these five major crops would have major
impacts on productivity of irrigated agriculture in Pakistan. Other
crops cover 4.17 mha; which constitute around 21.68 % of total
irrigated area in Pakistan. The climate change induced floods and
droughts significantly impact on crop production, especially during
Kharif (summer) season, from both irrigated and rain-fed areas
of Pakistan. The current land use methods tend to exacerbate the
soil and water degradation and reduce land productivity potential.
Similarly damage to standing crops due to lodging caused by heavy
winds, water logging and salinity and frequent water stresses at
crop critical growth stages causes production losses. Therefore, the
traditional farming techniques need to be modified to control crop
damage due to climate change induced threats, which is essential
for sustainable agriculture in the country.
Table 2: Irrigated cropped area of major crops in Pakistan.
Temporal Water Availability During Rabi and Kharif Seasons In Pakistan
Temporal surface water availability and deficiency during rabi (winter) and kharif (summer) seasons in Pakistan is shown in Figure 1. Temporal changes indicated up to 23% increase and down to 16% decrease in total annual available surface water since 2001 until 2007. However, the variability in total annual available surface water diminished below 5% since 2009 onward. Interestingly a major flood occurred during 2010, but data show insignificant impact on the total water availability (Figure 1). Thus, climate change cannot be judged from the total water availability. However, the frequency, intensity and distribution of rainfall are important parameters to be considered. Similarly, the average deficiency remained around 6.4% during Kharif (summer season) and around 24% during Rabi (winter season) with an average annual water deficiency of around 13% during the last twelve years.
Figure 1: Temporal surface water availability and deficiency during rabi (winter) and kharif (summer) seasons in Pakistan.
Increased Use of Groundwater in Pakistan
Canal water fluctuation and unreliability due to climate change has increased farming community dependence on groundwater during the last decade. The changing trend of water availability is presented in Table 3. The statistics of canal and tube well irrigated area in provinces from 1993-94 to 2010-2011 (Table 3) indicate a decrease of 19% and 26 % in canal irrigated areas and an increase of 26 % and 157% in tube well irrigated areas in Punjab and Sindh provinces respectively. The overall tendency from 1993-94 to 2010- 11 indicated a decrease of 17.5 % in the canal irrigated areas and an increase of 33.5 % in groundwater irrigated areas in Pakistan. The overexploitation of groundwater is coupled with saline water up-coning and disposing of deep brackish groundwater into the soil surface thus causing fertile lands barren in Pakistan. It is therefore essential to reduce groundwater usage by utilizing surface water more efficiently for fulfilling irrigation demands of larger areas. Thus, the traditional irrigation methods need to be modified to more efficient methods to reduce groundwater usage.
Table 3: Temporal change in irrigated area under surface and groundwater in Pakistan.
Climate Resilient Interventions for Improving Food Security in HKH Region
Furrow Bed (Raised Bed) Irrigation Systems
Furrow bed irrigation system is one of the commonly used form of surface irrigation throughout the world (Figure 2) and is generally considered a more water-efficient system compared with the traditional flat basin because of (i) the speed with which water is conveyed to the low end of a field [7]; and (ii) the relatively small proportion of the soil surface is in contact with the flowing water during irrigation than the basin [8]. Furrow bed irrigation system is important in the current climate change scenario of
Figure 2: Advantages of furrow bed over flat basin [11].
Pakistan agriculture in particular and Himalaya region in
general due to the following reasons:a) Furrow bed can save up to 50% irrigation water in comparison with traditional flat basin thus can reduce impact of limited water availability on crops in drought prone areas;
b) Furrows can quickly drain excess floodwater thus can reduce crop damage in flood prone areas;
c) Furrow beds reduce crops lodging by providing safe path and exit to speedy wind currents and greater reinforcement due to strong roots and soil grip;
d) Furrow beds laid perpendicular to slope can increase soil infiltration and ground water recharge by delaying runoff down slope and providing larger surface water storage capacity in furrows;
e) Conservation agricultural practices including minimum tillage, ground cover/mulching etc can be conveniently adopted on furrow beds which reduce soil erosion and soil and water degradation;
f) Furrow beds support mechanized farming thus can increase crop production and can be adapted to technological progress.
The Climate, Energy and Water Research Institute (CEWRI) of Pakistan Agricultural Research Council (PARC) has played a pioneer role in evaluation of furrow beds in Pakistan. Research conducted has shown that furrow beds is effective in improving yield of wheat by 20%, cotton 19%, Maize 58%, rice 26% compared with flat basin or ridge irrigation systems [9,10]. Similarly, crop yield per unit area increases by increasing the bed width. For instance, crop yield of maize showed up to 15% increase while wheat crop showed 26% increase on 180 cm bed size compared with flat basin [11], which was the largest increase noted when compared with other bed sizes given in Figure 2. Water saving of up to 50% in wheat, 30% in maize, 40% in cotton, 29% in rice were reported by N Ahmad et al. [9], Gill et al. [10], Hassan et al. [12]. Increase in water saving by increasing bed has been demonstrated in Figure 2 [9], which shows up to 40% and 36% increase in water saving by adopting 180cm bed size for maize and wheat crops respectively. Furrow bed increase crop yield and reduce irrigation application thus consequently crop water productivity is increased. For instance, an increase in water productivity of up to 70% in maize and up to 43% in wheat were reported by Hassan et al. [12] and Akbar et al. [13]. Impact of bed width on water productivity is illustrated in Figure 2, which shows up to 70% and 43% increase in water productivity for maize and wheat crops respectively compared with flat basin [13].
The CEWRI-PARC in collaboration with Australian Centre for International Agricultural Research (ACIAR) played a pioneer role in adopting furrow bed irrigation system in Maize wheat system of Pakistan. Conservation agricultural practices involving minimum soil disturbance were introduced in the form of permanent raised bed (PRB) farming system. Different bed width and furrow sizes were evaluated and demonstrated at farmer fields. Raised bed machinery imported from Australia was indigenously produced. The furrow bed farming system was disseminated by giving incentive to the farmers in the form of giving subsidies in purchasing raised bed machinery, training and demonstrations in the country. Although there are still issues in the machinery, especially for adopting PRB farming system, but the furrow bed system has been adopted widely for maize, cotton, sugar beat and vegetables crops throughout the country.
Sprinkler Irrigation Systems
In sprinkle irrigation method water is spayed into the air at 70-700 kpa (10-100 psi) pressure that fall on the ground or crop canopy like rainfall [14]. Using sprinkle irrigation system, the crop requirement can be accurately fulfilled through a combination of measures involving careful selection of sprinkle nozzle size, operating pressure and sprinkle spacing, thus adjusting sprinkle application rate to suit the soil infiltration rate. Sprinkle irrigation systems have increased importance for HKH region in the current climate change scenario due to the following reasons:a) Use limited available water more efficiently as the application efficiency of a well-designed sprinkle system can vary from 60-80% thus can increase crop production and irrigated lands;
b) No land leveling required thus reduce operation cost and protect environment by avoiding cutting and filling of cultivated lands;
c) Irrigation of steep and rolling topography without producing runoff or erosion;
d) Greater potential to increase agricultural production by bringing extra undulating and sloppy HKH terrain under irrigation;
e) Light shower can avoid crop damage due to temperature extremes year around;
f) Timely irrigation of few centimeter using sprinkler irrigation system can double crop yield at critical crop growth stages, especially during wheat germination in HKH region;
g) The pre-sowing irrigation (Rouni) can be applied with sprinkler system for timely planting of crops.
All these factors increase sprinkle irrigation system suitability to the HKH region in the current climate change scenario. However, there are few drawbacks. For instance, these systems are affected by wind and, depending on the size of droplets and the spray trajectory, uniform distribution may be limited. Sprinkle systems have high initial costs and maintenance requirements. They also use high operating pressures, which has large energy requirement. The cost of portable and semi portable system is less but difficult to operate due to movement of laterals. The CEWRI-PARC in collaboration with local industries developed a complete range of rain gun sprinkler irrigation systems, including diesel, electric and PTO-driven pumping systems, couplers, other fittings and joints. To keep the systems portable, the pumping unit along with power unit (diesel engine, electric motor and solar panels) was mounted on a trolley. These systems have been used in the Khanpur Dam area where the rain gun sprinkler irrigation system is being used for establishment of orchards, efficient irrigation of fruits and vegetables, washing of Lychi and citrus, and for cooling and frost control in orchards. Initial investment requirements and unreliable electricity are restricting wider adoption of this technology.
These rain gun sprinkler irrigation systems have been installed in various parts of Pakistan for demonstration and introduction of the technology. In rain fed areas, these systems are being used for supplemental and life-saving irrigations to fruits, vegetables and field crops. The research conducted by CEWRI-PARC resulted in local fabrication of Poly Ethylene (PE) based irrigation system components, sprinklers and high-pressure pumps. Based on research findings and success of pilot-scale installations, the Government of Pakistan launched a National Program entitled “Water Conservation and Productivity Enhancement through High Efficiency Irrigation Systems in Pakistan” during 2007-12. Drip and sprinkler irrigation systems were installed on an area of 6852 acres in all provinces (PARC 2010). The major area was in Punjab and followed by KP. There were 255 farmers benefitted from the project. There were 80 % sprinkler irrigation systems and 20 % were drip system during the period (Table 4).
Table 4: Drip and sprinkler irrigation systems in provinces,
installed under the national project (from 2007-2012).
Drip Irrigation Systems
Drip irrigation system applies water close to each plant and the application uniformity depends on the uniformity of discharge from the emitters [14]. It generally comprises of a pumping station, control head, main and sub main lines, lateral lines, emitters, valves and fittings. The drip irrigation system has special agronomical, agro technical and economic advantages that make it a suitable option of irrigation in the HKH and adjoining region. These advantages are as under:a) Drip irrigation can conveniently and efficiently supply water directly to the individual crop rows or plants, thus can effectively utilize small continuous streams of water in the HKH region;
b) It reduces water requirement by saving up to 50% irrigation water to a young orchard as compared to sprinkle or surface irrigation methods thus can enhance community resilience to drought;
c) It requires less labor, as a well-regulated system can effectively utilize a continuous stream of water, a norm in HKH region, with less farmer supervision thus can increase production;
d) It discourages weeds growth and offers greater control over fertilizer placement and timing thus can save farmer resources;
e) Drip irrigation can be designed for any topography even if the area is rocky with steep slopes and plants are with irregular spacing, which increase its importance for HKH region.
Drip irrigation systems have shown yield gains of up to 100%, water savings of up to 40–80%, and associated fertilizer, pesticide, and labor savings over conventional irrigation systems [15]. The low rate of water application reduces deep percolation losses. The systems have lower energy requirements than sprinkler systems because of lower operating pressure requirement. The water application uniformity of locally developed drip irrigation system was above 85 % [16]. Evaluation of drip systems at CEWRIPARC showed lowest coefficient of variation of locally developed microtube emitters [17] with application uniformity above 85 per cent [16]. This shows that trickle irrigation systems have potential to use scarce water resource more efficiently if designed properly. The evaluations by Ahmad MM et al. [18] indicated that drip system with micro tube emitters can be operated at low pressure head (3.5 m) with an insignificant loss in uniformity as compared to operating at high pressure head (10 m), which can save energy cost, as given in Table 5. This low head drip system is being used for small scale vegetable production in Pakistan.
Table 5: Microtube emitter discharge and water application uniformity at various pressure heads and distances Ahmad et al. [9].
These research outcomes are currently being disseminated
through training and demonstration in provinces. The provincial
governments are adopting drip/sprinkler systems evidenced
through various programs, indicating government commitment
for accelerating drip/sprinkler system adoption. By successful
adoption of these technologies, more water can be saved or
efficiently used along with an increase in yield. The saved water
will automatically reduce over exploitation of groundwater and
consequently mitigating the secondary salinity by improving
overall water use efficiency of the irrigation system. This shows
that the system has potential to use scarce water resource more
efficiently if designed properly.Conclusion and Recommendations
b) The 51% area of Pakistan falls in HKH region, thus was considered as a representative case example for analyzing their agricultural production system, growing food security and climate change issues and promising climate resilient interventions mainly adopted in downstream leveled irrigated areas of HKH region;
c) Furrow bed, sprinkler and drip irrigation systems has been shown efficient irrigation methods with multiple advantages thus can be instrumental for improving community resilience to climate change by conserving the declining and uncertain available water resources in the hill ecology of HKH region;
d) However, adoption of these technologies is equally important for improving climate change resilience, food security and livelihood of the hill ecology of HKH region.
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