Types of Irrigation Systems

Irrigation system analogously vary from large to small, and have different physical structures resulting from various combination and layouts of parts. COWARD (1980a:27)

9 The conditions he presumes are more like those of Southeast Asia, where the water shortage is relative not absolute as in South Asia.

classified irrigation systems according to the 'take-over' of the management into three types. They may be community systems, operated and maintained by the water users themselves and /or their representatives; they may be bureaucratically managed systems, fully administered by an agency of the government; or they may be jointly managed systems, in which some functions are performed by the irrigation agency while others or the responsibility of one are more water-user communities. Similarly, addition to the size and property as a classifying factor, gravity flow irrigation systems¹⁰ could be classified, according to REDDY (1986:96-9 ) into:

− Individually Owned Irrigation Systems: in these systems, farmers manipulate and control the water on the farm. There is usually no interference from other farmers, and the farmer-owner can irrigate at his convenience. The supply of water is usually from a well.

− Community-Managed Irrigation Systems: in such systems, performance on the farm depends upon the farmers' ability to control the water on his farm and to share water with the other farmers in the command area. The water distribution system and the cooperation between the other farmers in that command area decides the project performance.

− Large-scale Irrigation Systems: A large-scale gravity flow system¹¹consists of three components, as shown in Figure 1.1: main system, unit command area (similar to community-managed system), and farm system (individual ownership), each with distinct properties.

Figure 1.1 Components of Irigation System

Source: REDDY 1986:96

10 Gravity flow is the most widely used irrigation method in the world.

11 like Gezira Scheme in the Sudan, the major projects in northwest Mexico, and the extensive systems of the Indian Subcontinent.

Main System extends from the dam to the various outlets which supply water to a group of farmers. The irrigation bureaucracy operates the system.

Unit Command Area refers to the piece of land commanded by an outlet. Usually, a group of farmers is supposed to share the water available at the outlet among themselves and apply the water to their fields. They have not any control of the flow rate, duration, or timing of water received at the outlet.

Farm System refers to the individual farm in the command of an outlet. The farmer operates and manages the farm system. The flow rate and its timing and duration at an individual farm are influenced by the operation of the main system and the system below the outlet.

The performance of large-scale Irrigation Systems depends upon the integrated effort of the irrigation bureaucracy and the farmers in the command area, and the rules and tools provided for operation of the irrigation system. The overall performance of any irrigation system depends upon the performance of individual components (fields, unit command area, and the main system). The relative magnitude of performance of the three components varies from irrigation project to irrigation project, and for increased agricultural production good water control and management of all three components of the irrigation system is necessary.

It is supposed to be easy to associate irrigation development with large-scale activities¹². The size of those projects requires the involvement of large-scale public agencies that are able to recruit the technical personnel required to plan and manage complex undertakings and to obtain the enormous financial resources required for construction (COWARD 1980a :24). Some have maintained a very elaborate administrative network that extends from the water source to the individual farmers' field. The extreme case has been the Gezira Scheme in the Sudan, where the farmers may have a kind of "invisible" involvement in actual system operations.

Often, the organizational patterns of large-scale irrigation systems may be characterized as joint. In such systems some management functions are the responsibility of the agency and others are lodged with farmer groups within the command area. The irrigation system under such organization has integrative character which links virtually many farming communities into a unified national water grid that irrigates large scales of farmland.

UPHOFF (1991:32-37) also found that variables like size and organization are more suitable for classifying irrigation systems than their structures and technologies. This is

12 It is of important also to be noted that the small-scale irrigation systems can play a basic role in leading successful agricultural development. COWARD (1980b) discusses a number of examples of "silent success" traditional, usually small-scale systems. These systems offer important insights regarding the solution of organizational problems, particularly at the level of the unit. Two interesting examples are found in the cases of Philippines and Indonesia. The so-called BISA Program (Bario irrigation Service Association) is largely oriented toward the installation of pump systems to service small command areas (usually several hundred hectares) in the Philippine. The government assistance provide significant improvements to critical elements of the physical infrastructure. Approximately the same, Indonesia's Sederhana Program is aimed at developing command areas of 2000 hectares or less with the use of physical structures that are simple to design and construct.

partly because the physical structure of irrigation system is relatively similar across variations in size and technology. He noted that "the main difference found in the layout of systems is in the number of level of operation and organization they have.“ This is defined by the hierarchy of points at which water can be divided and controlled as shown in Figure 1.2. Number of levels correlates with size, but it does not translate directly into size, or vice versa. Gravity flow and groundwater systems, when one controls for size, are similarly configured as in Figure 1.2. All have a water source with main and subsidiary channels that carry, divide and spread the supply.

Figure 1.2 Irrigation System Structures By Number of Levels

Source: UPHOFF 1991:32

Alternative modes of organization do diverge across large and small sizes of irrigation systems, at least to some extent, and provide a basis for classifying it. The principal options for operating an irrigation system according to differences in organization are: management by agency personnel, or management by water users. Differences in structure, that means, the number of levels sketched in figure 1.2, interact with the variable of organization and classified three scales of irrigation systems ¹³ as follows:

( a ) small-scale systems have one or two levels of operation and one or a few point of water control. These systems usually serve less than 100 acres or only several hundreds of acres.

( b ) medium-scale systems: have three or four levels of operation at which water flow can be reduced and/or divided by control structures. Range from about 1000 acres upward

13 The reason for making these distinctions is that management tasks differ considerably in such scale terms.

to several tens of thousands of acres; the maximum is in the range 50,000 to 100,000 acres¹⁴.

( c ) large-scale systems: have five or more levels, with command areas from 50,000 to 100,000 acres or more, ranging up to a million or more in some countries.

UPHOFF et al. (1991) has subdivided these three size categories again by mode of organization into five types of irrigation systems as shown in Figure 1.3. Types (B, C and D) encompass the large majority of irrigation systems and the largest share of irrigated acreage. Type (A) for gravity flow systems is infrequent and the costs of its management are too great. Agencies sometimes undertake tasks for pump systems where the technology is unfamiliar to farmers and problems of maintenance and fuel supply must be overcome.

The one type not found is large-scale, user-managed system with more than four levels of operation and organization, a hypothetical type (F).

Figure 1.3: Types of Irrigation Systems, by Size and Organization

Smal-Scale (1-2 Levels)

Medium-Scale (3-4 Levels)

Large-Scale (5 + Levels)

Agency-Managed A B C

User-Managed D E F

Source: UPHOFF et al. (1991) p.36.

It now remains to say that, apart from the size, the management of any irrigation systems entails the provision of an operational framework which makes it possible for farmers to combine the water input with other required inputs in order to achieve their goals.

1.2 Irrigation Institutions and Organizations