Fresh water resources of Pakistan are being used to fulfill the food requirements and to improve
the living standards of the population of Pakistan. But due to increasing onslaught of human
population, these resources continue to dwindle and are becoming scare. The country onceconsidered as a water surplus has emerged into a water deficit one. Despite having the world’s largest contiguous irrigation system, it is facing the dilemma of water shortage and situation will even exacerbate in the near future. The seepage losses in the irrigation network, mismanagement in distribution system and over application at farm level have created the problems of water logging and salinity. Thousands of hectares of farmland are lost annually due to rising water tables. It is an established fact that almost 20% of water is lost due to traditional surface irrigation methods at farmers’ field. If this water is saved and consumptively used, additional arable and fertile lands essential for modern agriculture could be brought under cultivation which otherwise are lying barren due to water shortage. In order to achieve the comparable crop yields to that of other countries, to save land from water logging and salinity, to feed ever increasing population of the country, and to bring agriculturally potential land under cultivation, the potential of limited water resources must be utilized to its full extent. Since, new sources of water supply are becoming scare and are unlikely to be constructed in the near future due to geo-political reasons, the emphasis must be given on the methods that can salvage the supplies already being lost within the present irrigation system. Though the existing water resources of the country are not sufficient to meet the crops’ water requirement, yet they are not properly managed and efficiently used. The gap between the potential yields and actual yields could be narrowed down by the efficient use of available resources.
Distribution system at outlet
The coordination between water users and the irrigation department has remained a major problem since the existence of irrigation network that has resulted mismanagement, poor maintenance, inequitable and unreliable distribution. Under prevailing rotational (warabandi) irrigation system, the distribution of water to the outlets is inequitable. The outlets located at the head and middle reaches of distributaries draw 3 to 6 times more than the actual allocated share, whereas outlets at the tail reaches draw less than the actual allocated share, hence, the poor tail-enders are always faced with shortage of water. Those who draw greater shares apply more water than the crop’s water requirement resulting in excessive wet stresses to crops and excessive leaching of nutrients, whereas, the tail ender apply less water than the crop’s water requirement resulting in dry stresses to crops. Under both stresses, not only crop yields exaggerate but the water use efficiency significantly reduces. Some tail-enders compensate the inadequate supply with poor quality groundwater and their fertile lands become prone to secondary salinization due lack of proper knowledge on conjunctive use of such water. All this suggests proper management and adoption of scientific approaches to utilize the water available at the outlet. This could be done at the farm level either by improving the present application methods or by introducing highly efficient irrigation methods.
Improvement in traditional methods
In fact, the farmers use traditional flood irrigation methods without consideration of land slope
and soil texture. Thus, more than 20% water is lost at the field level through deep percolation. Similarly, furrows are prepared without proper knowledge on slope consideration. The farmers need proper training on the application of furrow, border and basin irrigation methods. These
methods would still give high production if they are properly designed and applied according to
soil and water conditions. One of the factors identified for inefficient use of irrigation water through these methods is poor leveling. The unleveled lands are characterized with nonuniform
distribution of irrigation water and deep percolation which requires excessive application that in turn affects application efficiency. A properly leveled field with an appropriate layout and size reduces application losses, ensures uniform distribution, and increases crop yields.
Potential of modern irrigation methods
Efficient irrigation methods like trickle, sprinkler, pitcher, and sub-irrigation are required to beintroduced at the tail reaches with water shortage problem. These methods are proven to be efficient in terms of water saving but are considered expensive thus farmers are reluctant to use them. However, the acceptance of these methods depends upon their success in terms of maximum yield returns associated with minimum water required. Since these techniques have potential to save lot of water, hence, more land could be brought under cultivation with small amounts of water available, particularly, at the tail reaches of the conveyance systems. The irrigation methods so introduced must be acceptable as well as economically affordable by the farmers; hence government should take initiative and install demonstration plots at farmers’ fields to introduce them. Once, the farmers will realize the benefits of water saved and returns achieved, they will install such systems from their own resources.
Among the new methods mentioned, trickle irrigation has been reported one of the efficient methods of water application than any of the conventional surface irrigation methods. It provides prescribed amount of water, achieves high field application efficiency, offers better uniformity, saves water, and ensures better yields. Also, the water is applied to plants in a precise quantity thus their immediate water requirements are met.
Water storage ponds
The concept of water storage ponds at the farm level is quite new and needs research on how to
make it economically and physically viable. Their use is a premeditated management tool to harvest water when it is in excess and utilize when needed. The storage capacity depends on the
size of the pond and availability of water to be harnessed. For example, a 40 m long, 20 m wide, and 2 m deep pond will store 1600 m3. If an irrigator applies 5 cm irrigation depth then the stored volume can irrigate at least 3.2 hectares. It is farmer’s choice to properly manage and efficiently use the stored water as needed.
Dr. Shakeel Ahmad Anjum, Muhamamd Umair, Dr. Imran Khan, Ali Zohaib
Agro-biology Laboratory, Department of Agronomy, University of Agriculture, Faisalabad 38040, Pakistan