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Some experiences on modernization in irrigation system rehabilitation in Sri Lanka

Dr G.G.A. Godaliyadda1, K.R.P.M. Mullegamgoda2, A.M.U.B. Alahakoon3


The history of irrigation in Sri Lanka goes back more than two thousand years and over time many irrigation systems were abandoned due to various reasons. During the British colonial rule many of the irrigation systems were renovated to promote irrigated agriculture. After Independence the main emphasis of the government of Sri Lanka was on agricultural development through the renovation of ancient irrigation works and resettlement of the landless population in the dry zone. The main objectives of the development were:

However, the renovated irrigation systems deteriorated within a couple of decades due mainly to poor maintenance and flows being carried over the designed capacities of the canals to cater to the excessive use of water by farmers. This has led to serious operational problems in many irrigation systems, the worse being the inability to irrigate the planned area. During the last two decades, many irrigation systems have been rehabilitated mainly to bring back land under cultivation as originally planned and to assure more reliable water supplies to farm lands. However, many rehabilitation projects have not contributed much to increase water delivery and water use efficiency through management innovations. Of course, physical rehabilitation has contributed to some extent to increase efficiency. At the same time, it is not correct to say that there have been no modernization efforts on physical structures or management to improve irrigation system operations in Sri Lanka.

Rehabilitation projects

The main rehabilitation projects implemented in Sri Lanka during the last few decades can be listed as follows:


The Tank Irrigation Modernization project



The Gal Oya Rehabilitation project



The Major Irrigation Rehabilitation project



The Irrigation System Management project



The National Irrigation Rehabilitation project


The Tank Irrigation Modernization project

This was the first modernization project implemented in five main irrigation systems in North Central Sri Lanka and North Sri Lanka under World Bank funding. Even though this was the first project of this nature, it had several innovative efforts of physical modernization to improve the operational aspects in irrigation water delivery. The project was criticized by many as drastic changes were brought in the technological designs without any consultation of the beneficiaries. If the objectives of the project had been known to the beneficiaries before implementation, it might have been more successful. In this project much weight was given to modernization design proposals for rotational water distribution within field (tertiary) canals feeding a turnout area of about 40 acres. The distributary (secondary) canals were split into several segments to facilitate the water distribution to head and tail farms. Separate control gates for each canal segment were provided at the head end. The segments were continued until the tail-end field canals to get them isolated from the branching-off canals. In the main canal cross realtors with gates and in distributary canals duckbill weirs with regulators were introduced to regulate the flow. A flow measuring device at the sluice (Parshall flume) and many measuring weirs were installed at every off-take to improve the operational capabilities of the systems

The improved water management programme

Subsequently, using the above improved physical facilities, water management programmes were implemented in many systems. In the Mahakanadarawa irrigation system where water management was implemented successfully, it was possible to irrigate the entire service area with rotational water distribution within turnout areas with the co-operation of the farmers. For some reason, though, the programme was not continued, and the success of such innovative modernization efforts was short-lived.

The pilot project on on-demand delivery

In one of the systems, i.e. Mahakanadarawa, under the direction of the World Bank a pilot project on on-demand delivery was introduced in a distributary canal service area. Starting from the outlet of the main canal up to the farm outlet, underground concrete pipelines were laid and each farm was provided with a valve to get water as and when required. Even though the project intended farmers to use water on demand, they continued to take water as in a conventional system.

Simultaneously, a similar project was implemented in the 150ha service area of a distributary in Area H of the Mahaweli scheme. This automated supply system consists of a reservoir, a downstream level-control gate, level top canal, and low pressure concrete pipes supplying individual turnout valves. The principal objective was to compare demand irrigation to conventional agency-controlled rotational irrigation. The project operated for six seasons (three years) and interesting useful results were achieved. As in the previous case, a few years after the study period the project reverted to conventional rotation irrigation, as did the rest of Area H. There were no follow-up attempts to replicate such interventions even though the farmers responded positively to such methods (Plusquellec, 1996).

Technical assessment area and dry land preparation

Under the tank irrigation modernization project, there was a very close link between the Irrigation and Agriculture Departments from the inception. The Agriculture Department was involved in planning the cropping pattern and calendar and applying other agronomic inputs. A technical assessment area was set up to demonstrate various techniques in crop cultivation. Even the preparation of land with initial moisture in the soil without using irrigation water was demonstrated. This too had been considered in the design of the tank irrigation modernization project.

The Gal Oya Rehabilitation project

The Gal Oya irrigation system, the largest system operated and managed by the Irrigation Department of Sri Lanka, was rehabilitated under USAID funding in the early 1980s. There was no innovative design procedure before the implementation of the project. The rehabilitation requirements at secondary and tertiary organizations were defined by staffers known as institutional organizers. The entire system was rehabilitated by providing the necessary structures for better control and delivery of water. Different flow measuring devices were introduced in Gal Oya where farmers did not feel that the devices were obstructing the flow.

Computer-aided irrigation system operation

One of the innovative efforts on system operation implemented in this project was the computer-aided water scheduling model with a two-way communication network for daily monitoring of the water deliveries throughout the system (Godaliyadda, 1987). The model computes the weekly irrigation requirements based on crop water requirements according to growth stages, soil percolation rate, rainfall with application and conveyance losses. The daily diversion requirement at major diversion points and branching-off points were monitored and gauge readings were transmitted to the central office through telephones. Similarly the instructions from the central office were transmitted to the field through the same arrangement.

The Major Irrigation Rehabilitation project

There was no significant difference in physical rehabilitation in relation to previous projects in systems selected under this project. Even though this project too was funded by the World Bank, many of the innovative design concepts in the tank irrigation modernization project were not fully adopted.

Under the direction of the World Bank, a pilot project was implemented in a distributory canal in the Rajangana system with two structural modifications: an automatic constant downstream level gate associated with modular distributors at the head of the distributory canal, and baffle distributors at the head of field canals. The pilot area of 150 ha was compared with the conventional gates system. It was found that there was no significant difference in terms of water use and crop yields. However, there are some doubts about the reliability of the data. The operational cost of the new design was 40-percent lower that the conventional design. The feeling of both the Irrigation Department and the farmers is that this kind of design provides greater facility in operation and possibility in checking the quantity of water delivered to the fields (Plusquellec, 1996).

The National Irrigation Rehabilitation project

This is the largest project of all those listed above which undertook many major systems for rehabilitation under World Bank funding. One of the features of this project was beneficiary participation on physical rehabilitation. According to the project agreement, a voluntary beneficiary contribution of 10 percent from the overall civil cost of the system rehabilitation was enforced.

Operation and maintenance manual

Even though there were no modernization efforts of physical rehabilitation, several improvements have been introduced for the operation and maintenance of irrigation systems, such as the preparation of an operation and maintenance manual for each irrigation system rehabilitated and the implementation of the after-care programme to fully achieve the objectives of the projects on operation and maintenance.

Proposed typological approach to the modernization of irrigation system operation

The basic assumption of this approach is that irrigation systems have a heterogeneous behaviour with respect to operation. The goal is to bridge the gap between generic recommendations and site-specific recommendations. Generic rules are often mandated at national or regional levels and do not incorporate site-specific constraints at present. Local managers integrate these constraints by rule of thumb (Godaliyadda, 1998).

The foreseen applications of the typology are twofold: at global, national and regional levels, as a grid for characterizing irrigation systems as a whole and for assessing the requirements for operation; at local level, as a grid of criteria to divide the irrigation system into more homogeneous units (subsystems) with respect to operation. At system level, subsystems appear to have different behaviours and thus managers should distribute efforts in a non-homogeneous way. For instance, a double-bank canal fed by a reservoir and having an intermediate reservoir is much easier to operate than a single-bank canal fed by river diversion and having inflows into the system. To reach the same level of performance, the second case should receive more attention and efforts.

Four main types of irrigation systems have been identified in Sri Lanka. Under the current practice of operation, very little improvement can be expected. Introducing new operation strategies to take into account the opportunities offered by physical features is more promising. On a more global perspective, it is expected that the typology will prove to be useful in resource allocations for the modernization of irrigation systems for improved operation (Godaliyadda, 1998).

Proposed pilot projects

Modernization operational techniques are programmed to be tested in the near future using the typological approach in the Minipe diversion system with a 74km-long single-bank main canal and in the Kirindi Oya reservoir system with a 20km-long double-bank main canal.


Godaliyadda, G.G.A. 1987. Computer application in irrigation system operation: case study from the Gay Oya project in Sri Lanka. Commemorative volume, Central Board of Irrigation and Power, CBIP Diamond Jubilee, New Delhi

Godaliyadda, G.G.A. 1998. Typology for irrigation system operation, generic approach and application in Sri Lanka, PhD dissertation. Cornell University, Ithaca, New York

Plusquellec, Hervé. 1996. Investments and opportunities for modernization projects in Asia: past and future needs, Proceedings of expert consultation on modernization of irrigation schemes: past experiences and future options, Bangkok

1 Deputy Director, Head of Sri Lanka Irrigation Training Institute, Irrigation Department

2 Deputy Director, Southern Region, Irrigation Department, Sri Lanka

3 Irrigation Engineer, Minipe Irrigation Scheme, Irrigation Department, Sri Lanka

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