Irrigation Automation
As we approach a new millennium, there are growing concerns and periodic warnings that we are moving into an era of water scarcity. With increasing demand for food and competing use within the water sector, the pressure is on irrigation professionals to manage water efficiently. The rallying cry is "more crop per drop". In response to this, strategic decisions and interventions need to be made on a continuous basis. These decisions should cover the full spectrum of the irrigation water supply system, from diversion and distribution to on-farm application down to the crop root zone.
In many parts of the world, irrigation systems are performing well below their potential. The problem of poor irrigation performance has stimulated the interest of a whole range of development professionals. There is unanimous agreement among them for the need to improve the operation of irrigation systems in order to increase productivity. In most countries great importance is now placed on programmes for rehabilitation, operation and maintenance of existing projects. However, works included in these programmes are often limited to canal lining, land levelling, construction of additional control structures, rehabilitation of existing control structures, improvement of access roads and to non-physical components such as staff training, improvement of cost recovery systems and so on. Too often, not enough attention is paid to alternative approaches to irrigation management, system operation and design.
One weakness of conventional operation is the inevitable discrepancy between forecast and actual delivery flows. In addition, there will be always inaccuracies in checking the flow and the amount of water stored in the canal pools. Since the canal system is not operated to react to actual demand, any such errors are transferred downstream. The sum of all operational errors will accumulate at the far end of the canal. Tail-end water users will often suffer from too much or too little water. To prevent shortages of water at the downstream end, excess water must be supplied at the headwork. Most of the time, this excess ends up being wasted near the downstream end of the system. The typical wastage in a conventionally operated canal system is about 5 to 10 percent of the total flow.
The overall water use efficiency of a manually operated system, exclusive of the use of any return flow, seldom exceeds 40 percent. It is reasonable to expect an increase of the overall efficiency of about 10 percent or more for a system with some automation. The advantages of automation are not limited to savings in operation cost and in water. It also alleviates the risk of waterlogging and salinization. A further advantage is that it increases the reliability and accuracy of water distribution. This contributes to the establishment of a climate of confidence between the operating authority and the farmers, which in turn contributes to the effective organization of water user groups and their participation in operation and maintenance activities. With automation, it may also be possible to accurately know the volume of water delivered to individuals or groups of farmers. This makes possible the introduction of volumetric water charges, combined or not with a system of annual volumetric allocation. This approach is a useful tool for encouraging farmers to optimize the use of limited water allocations and to increase productivity.
The flexible, high-quality operation of a canal system will yield many benefits, some of which are:
Most of these benefits result in obvious economic savings and some of them represent intangible benefits to which it is difficult to assign a monetary value. Regardless, they all result in a better and more cost-effective water resource project.
In many parts of the world, irrigation systems are performing well below their potential. The problem of poor irrigation performance has stimulated the interest of a whole range of development professionals. There is unanimous agreement among them for the need to improve the operation of irrigation systems in order to increase productivity. In most countries great importance is now placed on programmes for rehabilitation, operation and maintenance of existing projects. However, works included in these programmes are often limited to canal lining, land levelling, construction of additional control structures, rehabilitation of existing control structures, improvement of access roads and to non-physical components such as staff training, improvement of cost recovery systems and so on. Too often, not enough attention is paid to alternative approaches to irrigation management, system operation and design.
One weakness of conventional operation is the inevitable discrepancy between forecast and actual delivery flows. In addition, there will be always inaccuracies in checking the flow and the amount of water stored in the canal pools. Since the canal system is not operated to react to actual demand, any such errors are transferred downstream. The sum of all operational errors will accumulate at the far end of the canal. Tail-end water users will often suffer from too much or too little water. To prevent shortages of water at the downstream end, excess water must be supplied at the headwork. Most of the time, this excess ends up being wasted near the downstream end of the system. The typical wastage in a conventionally operated canal system is about 5 to 10 percent of the total flow.
The overall water use efficiency of a manually operated system, exclusive of the use of any return flow, seldom exceeds 40 percent. It is reasonable to expect an increase of the overall efficiency of about 10 percent or more for a system with some automation. The advantages of automation are not limited to savings in operation cost and in water. It also alleviates the risk of waterlogging and salinization. A further advantage is that it increases the reliability and accuracy of water distribution. This contributes to the establishment of a climate of confidence between the operating authority and the farmers, which in turn contributes to the effective organization of water user groups and their participation in operation and maintenance activities. With automation, it may also be possible to accurately know the volume of water delivered to individuals or groups of farmers. This makes possible the introduction of volumetric water charges, combined or not with a system of annual volumetric allocation. This approach is a useful tool for encouraging farmers to optimize the use of limited water allocations and to increase productivity.
The flexible, high-quality operation of a canal system will yield many benefits, some of which are:
- increased crop production,
- reduced water use,
- better service to the water users,
- increased power generation,
- decreased power consumption,
- labour savings,
- less water wasted,
- easier management of the water system,
- improved protection of the conveyance facilities,
- reduced maintenance requirements,
- more accurate and equitable distribution of water,
- fish and wildlife enhancement,
- decreased flood damage,
- less need for subsurface drainage,
- better response to emergencies,
- social benefits (user's satisfaction, less conflict),
- environmental protection, and
- improved co-ordination with power operations.
Most of these benefits result in obvious economic savings and some of them represent intangible benefits to which it is difficult to assign a monetary value. Regardless, they all result in a better and more cost-effective water resource project.