Efficient use of water in agriculture
Loss during storage, conveyance, application and irrigation are causes of 65 per cent wastage out of the total 105 MAF available at canal heads.
Irrigation has a larger impact on reducing poverty than rural literacy. Increase in the adoption of high yielding varieties (HYV)) and the use of fertilizers too, help in reducing poverty but their influence is lower than the impact of irrigation and rural literacy.
When irrigation water is enough, the cultivation of high yielding varieties and fertilizers is also high. An astute irrigation is the first prerequisite of high productivity.
Our farmers are bereft of optimum quantity of water for irrigation due to two major problems; lack of storage reservoirs and a major part of available water is lost during conveyance from canal heads to fields.
Storage efficiency may be increased by improved management while the lack of capacity of reservoirs to regulate variations in incoming flows results in low storage. Thus, the storage efficiency of dams would be increased when the capacity is increased.
Conveyance, water use in irrigation and on farm application efficiencies should be looked into. Huge quantity is lost during conveyance from canal heads to fields via minors and water channels.
Conveyance efficiency is defined as the net amount of water delivered to a farm as a ratio of the amount taken from some source. The difference between the two amounts represents the seepage, management and evaporative losses incurred en route from source to field. Conveyance efficiency is the possible loss of water quality through pollution such as that caused by wading animals or by human use of the canal water for washing and waste disposal. Water quality is really affected in Pakistan by pollution.
Conveyance losses may be subdivided according to the cause into seepage; evaporation; leaks in structures in poor condition; and poor water management in the distribution network.
Irrigation efficiency may be defined in various ways depending on the nature of inputs and outputs. An economic criterion might be the financial return. Costs and prices fluctuate every year and vary from place to place. Some costs and benefits cannot easily be quantified, especially where a market economy is not yet fully developed. Only short-term costs and immediate benefits are seen.
How to assess the economic value of saving the population of a region from the potential effects of a drought, if the probability or severity of future drought events is not known? To some degree, it is necessary to operate in a state of uncertainty. In Pakistan water use efficiency is very low because we lack conservation practices and enhancement of crop growth.
The term on-farm or field application efficiency refers to the fraction of water volume applied to a farm or a field that is “consumed” by a crop, relative to the amount applied. Crop consumption is the amount of water absorbed by the crop. Here on farm efficiency is low as farmers use conventional methods, fields are not levelled and soil texture fayed by the intensive use of chemicals.
Due to above reasons the overall efficiency is 35.5 per cent. Irrigation efficiency is a compound of three i.e., canal-head, watercourse and on farm efficiency.
Problems like water shortage, theft, seepage and leakage, silting, erosion of canal lines, conflicts, cutting of trees from canal banks and many other pilfering activities have not been stopped. If delayed further it may ruin our agriculture.
The idea of Nehri Punchayat System has been introduced in some areas of Punjab, according to which farmers will participate in irrigation management and decision-making. Let’s see which way the wind blows. Can farmers’ community stop water losses in conveyance and irrigation? Farmers have expectations from this system but the government fears that the farmers will unnecessary intervene in policy matters. That was why the government was dallying full implementation of this system.
Implementation of the system will increase the productivity to an optimum level. Water requirement for high yielding varieties is more than for native. Fertilizer application further increases the use of water because metabolic activities in plants and microbial activities in soil increase significantly.
If water shortage fear is eliminated from the mind of a farmer, he will cultivate varieties of high productivity targets. Farmers must be given a chance to resolve the water problem.
For maximum efficiency, the idea of HELPFUL Irrigation is ideal. It produces more than 90 per cent efficiency but is difficult to manage. It is like a dream as astute irrigation management enhances production. During the study it was observed that moving from head to middle reach and middle to tail reach decreases the production of crops because this overall move from head to tail decreases the chances of availability of water for cultivation.
In the canal head areas silting is lesser than that of middle and tail reaches. Moreover, huge amount of water is lost or spoiled by seepage, leakage, percolation, evaporation, theft, animals, pollution and many pilfering activities while flowing from head to middle and tail.
So, farmers at middle and tail reaches have to face more risks of shortage and quality. Estimated production of farmers living at tail reaches is more than the left areas because they have no fear of shortage and loss.
Silting of canals and watercourses, paucity (water is not available on time when available not in adequate quantity), theft, unlined watercourses and canals, damages done by animals to watercourses and canal lines, leakage, seepage, high percolation rates and pollutants are major problems farmers face as far as our irrigation system and its management are concerned.
Farmers also claim that they are not provided with their authorized quantity of water but pay full charges. Fields are also unlevelled and conventional irrigation methods are applied (surface irrigation/flood irrigation). Still, modern methods should be applied to manage the limited volumes of water.
Sprinkle, drip irrigations, subsurface exuders, sub-irrigation are costly methods but once established there is no need to spend every year on it. Small fruit orchards and vegetables can be cultivated and irrigated by these methods.
In field, farmers should conserve water whatsoever its quantity is. Conveyance losses should be decreased by lining channels or, preferably, by using closed conduits. Runoff and percolation losses must be avoided due to over-irrigation because these losses are the right of others.
Evaporation from the bare soil should be reduced by mulching and by keeping the inter-row strips dry. By doing this limited available water can be conserved. In fields transpiration by weeds should be decreased by keeping the inter-row strips dry and applying weed control measures where needed. For efficient use of irrigation water and high productivity all farmers should adopt the following:
Select most suitable and marketable crops for the region according to available water quantity.
Use optimal tillage (avoid excessive cultivation).
Apply manures and green manures where possible and fertilize effectively (preferably when the irrigation water is available).
Practise soil conservation for long-term sustainability.
Avoid progressive salination by monitoring water-table elevation and early signs of salt accumulation, and by appropriate drainage.
Irrigate at high frequency and in the exact amounts needed to prevent water deficits, taking account of weather conditions and crop growth stage. Over-irrigation must be avoided to save water for other fields where it is required in huge volume.