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Since the second half of the 20th century, investments in irrigation have represented a considerable share of agriculture-related investments in developing countries. The recently renewed interest for water management in agriculture in support to rural development, agriculture modernization and rural poverty alleviation calls for further investments in irrigation infrastructure modernization, rehabilitation and expansion. Regional investment plans and strategies require a good assessment of costs and benefits related to irrigation infrastructure investments.
Understanding the factors influencing irrigation development costs helps shaping irrigation investment programmes. Costs vary with local conditions (including topography, soils, water resources, etc.), institutional and macroeconomic environment, scheme size, technology, or level of prior investments. These conditions determine regional trends and allow for the estimation of average regional unit costs, of particular interest to regional planning.
In 2003, FAO conducted a desk study collecting data on irrigation projects from various sources, with the FAO Investment Centre and the World Bank as the major data sources. Project appraisal reports, i.e. ex-ante cost estimates, represent the bulk of the sources of information of the study. Several hundreds of projects were studied and of these 248 projects were screened more in detail and investment costs were analysed and presented in a standard format.
In this database, a number of terminologies are used to describe different forms of irrigation investments and associated factors. These terminologies and related methodologies are described and defined below.Regions
The following five regions are used: Eastern Asia (EA); Southern Asia (SA); sub-Saharan Africa (SSA); Near East & North Africa (NENA); Latin America and the Caribbean (LAC). The database focuses on the developing regions of the world only.Governance
Dominant type of irrigation system governance. Private: schemes are managed by private entrepreneurs, including smallholders. Public: irrigation scheme management is mostly controlled by a public authority.Gravity or pumped
Dominant type of water supply to the scheme: either by gravity from dams or river diversion, or through pumping from rivers or groundwater sources.Irrigation technology
The AQUASTAT definitions of irrigation technologies are used. Surface irrigation: Surface irrigation systems are based on the principle of moving water over the land by simple gravity in order to wet it, either partially or completely, before infiltrating. They can be subdivided into furrow, borderstrip and basin irrigation (including submersion irrigation of rice). Sprinkler irrigation: A sprinkler irrigation system consists of a pipe network, through which water moves under pressure before being delivered to the crop via sprinkler nozzles. The system basically simulates rainfall in that water is applied through overhead spraying. These systems are also known as overhead irrigation systems. Localized irrigation: Localized irrigation is a system where the water is distributed under low pressure through a piped network, in a pre-determined pattern, and applied water as a small discharge to each plant or adjacent to it. There are three main categories: drip irrigation (where drip emitters are used to apply water slowly to the soil surface), spray or micro-sprinkler irrigation (where water is sprayed to the soil near individual plants or trees) and bubbler irrigation (where a small stream is applied to flood small basins or the soil adjacent to individual trees). The following other terms are also sometimes used to refer to localized irrigation: micro-irrigation, trickle irrigation, daily flow irrigation, drop-irrigation, sip irrigation, diurnal irrigation. Spate irrigation: Spate irrigation, also sometimes referred to as floodwater harvesting, is a method of random irrigation using the floodwaters of a normally dry water course or riverbed (wadi). These systems are in general characterized by a very large catchment upstream (200 ha - 50 km²) with a "catchment area : cultivated area" ratio of 100 : 1 to 10 000 : 1. There are two types of spate irrigation: 1) floodwater harvesting within streambeds, where turbulent channel flow is collected and spread through the wadi in which the crops are planted; cross-wadi dams are constructed with stones, earth, or both, often reinforced with gabions; 2) floodwater diversion, where the floods - or spates - from the seasonal rivers are diverted into adjacent embanked fields for direct application. A stone or concrete structure raises the water level within the wadi to be diverted to the nearby cropping areas.Year of project
The project year is defined as the year of appraisal or as the completion year in the case of completion reports.Type of investment
Irrigation investment costs are defined here as the costs specifically related to the irrigation project. This means that costs related to roads, bridges, dams, new agricultural technology, fertilizer, seeds, operation and maintenance, etc. are not included in the investment costs. However costs related to "irrigation software" - directly related to the specific irrigation project - are included. Irrigation software includes irrigation training for farmers, training for operation and maintenance people, organizational structure building, study tours, etc. Many irrigation projects are a combination of new development components as well as rehabilitation and/or modernization components, in these cases it is the largest component that defines the type of investment. New development: Development of areas that have not previously been irrigated. It should be noted, that in many cases the new development areas have previously been used for agricultural purposes, which means that preparatory measures such as land levelling and land clearing have already been taken care of. Rehabilitation: Restoration of an existing irrigation system into good/working condition. Modernization: Upgrading the system with more modern technologies and management. Note: In view of the difficulties in distinguishing between rehabilitation and modernization in the projects, the two categories have been merged as one under the heading "Rehabilitation/modernization".Costs in year 2000 US$ - current prices
To be able to compare the investment costs of projects carried out in various countries and various years, all cost data have first been converted (when needed) into US dollars (US$) using the official exchange rate effective at the time of the project. Then the US$ figure has been calculated into year 2000 US$ in order to make it possible to compare investment costs over time. The idea behind calculating the investment costs into current prices (in this case year 2000 US$) is to make prices comparable over time by removing the effect of inflation. In this database the inflation effect has been removed by using the American Consumer Price Index.
The Excel file containing the projects can be downloaded from here:
|Database on investment costs in irrigation|
Several hundred appraisal documents, project completion reports, working papers and articles have been reviewed during the research process, and a total of 248 irrigation projects have been recorded in this database. These projects where carried out in 33 different countries covering a total area of about 7.3 million hectares. Almost 40 percent of the data in the database (equal to 102 projects) is based on reports, documents and articles written after the project had been completed, the rest of the data is based on material written either while the project was being planned or while it was in its early stages. Data have been collected for the period from 1980 to 2003.
Data on a total of 57 irrigation projects in this database come from 13 countries in sub-Saharan Africa. These projects represent a total of 107 762 hectares of irrigated land only, which is less than 1.5 percent of the total area of 7.3 million ha. However, these 57 projects represent more than 22 percent of the total number of 248 projects studied and the 13 sub-Saharan countries represent more than 38 percent of all the 33 countries in this database.
The data used in this database come from various sources. The two by far most important sources of data are the FAO Investment Centre and the World Bank documentation unit. But besides these two sources data have also been collected from IFAD, the French Ministry of Foreign Affairs, AFD, articles written by FAO staff and research conducted by FAO staff.
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