Powering Agriculture: Irrigation

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Agriculture is the backbone of the majority of developing and emerging countries. Therefore, access to reliable and affordable irrigation water for agriculture is a crucial factor for the economic development of the country.

Definition

Irrigation is the controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall. Crop irrigation is vital throughout the world in order to provide the world's ever-growing population with enough food. Irrigation can be defined as replenishment of soil water storage in plant root zone through methods other than natural precipitation.

Background

Irrigation water is brought to cultivated land through artificial means, such as pipes, hoses or ditches. The irrigated land usually contains crops, grass or vegetation which would not receive enough water from rainfall or other natural sources. Sometimes the reason to irrigate a portion of land is that it happens to be a dry season with less-than-average amounts of rainfall, or it might be necessary to do so because the land would never receive enough water on its own to be fertile. The water used for irrigation might be taken from nearby lakes, reservoirs, rivers or wells.

Manual lifting of irrigation water significantly reduces the scope of cultivation and the efficiency of irrigation – it does not, for example, allow for pressurized systems that are required for water saving drip or sprinkler irrigation techniques. In the absence of reliable electricity supply due to lack of grid connection or intermittent service, farmers in developing countries have hence to rely often on diesel-driven pumps for water abstraction and conveyance. These diesel-driven pumps create high operation costs and are prone to service gaps due to an insufficient fuel supply and technical defects. A reliable and cost-effective supply of irrigation water is therefore a core problem in many rural areas in developing and emerging countries.

The perspective of grid extension and the establishment of uninterrupted and affordable electricity supply into rural areas is a distant vision in many of these countries. Rural electrification in economically weak rural areas in Africa, Asia and Latin America will be largely based on investments into local off-grid solutions.

Sustainable Irrigation

What is sustainable irrigation and how can it be promoted? Around 93% of human water consumption is utilized for irrigation. Most of this water needs to be moved, often from below the ground. Yet, water distribution is often inefficient and requires significant amounts of energy, mostly supplied through diesel generators.

The ability to move water is critical for irrigated agriculture in most areas of the world. Both surface and underground water resources are commonly tapped for irrigation. Around 57% of current irrigation water demand is covered by the former, the remaining 43% by the latter source of water (World Bank, 2010).

In particular irrigation from underground sources requires an energy input. In off-grid areas of the world, this is currently covered to a large part through diesel generators. The disadvantages of this fossil energy supply are known. High operating costs and frequent maintenance, environmental damage through ground water soiling with fuels and lubricants or CO2 emissions are the most significant drawbacks of the status quo. Using renewable energy (RE) sources is an attractive alternative as they feature several economic, managerial and ecological advantages.


Types of Irrigation

There are various types of irrigation methods, each requiring an experienced farmer to determine the quantity of water to apply and the timing of the irrigation. The most commonly used modern irrigation methods are:

  • Surface irrigation. Subtypes:
    • Borders (strips of land are irrigated)
    • Furrows (water is fed into small channels)
    • Basin irrigation (entire field is flooded)


A number of factors determine the suitability of the various methods:

  • Natural conditions: soil type, slope, climate, water availability, water quality
  • Type of crop
  • Type of technology
  • Previous experience with irrigation
  • Required labour input
  • Capital requirements and availability
  • Costs and benefits

For further information on irrigation click here


Energy Sources for Irrigation: Water Pumping

Motor-driven water abstraction and conveyance requires a reliable energy source – or a reliable combination of energy sources. The vast majority of water pumping for irrigation purposes is to date done by diesel or petrol motors as well as by electric motors that fed from the grid or are run by diesel generators. The utilization of renewable energy sources is steadily increasing but still on the minority side.

The most commonly used energy sources for irrigation water pumping:

  • Petrol engine
  • Diesel engine
  • Natural gas engine
  • Electric engine: distinction has to be made according to the actual source of electricity
  • Network/grid-supplied electricity
  • Generator (diesel, petrol)-supplied electricity
  • PV-generated electricity
  • Electricity generated from other off-grid RE sources (biogas, biomass generators)
  • Wind powered pumps

Solar-powered Irrigation Systems

Among the renewables, solar Photovoltaic (PV) is often the most attractive option. It features a near-absence of running costs, little maintenance requirements and ease of use. In terms of CO2 emissions, an off-grid solar pumping system that replaces a typical diesel generator unit will save about 1 kg of CO2 per kilowatt-hour of output (GIZ, forthcoming). Due to falling costs for the components necessary for a PV pump, the renewable powered systems have become increasingly attractive from an economic perspective. However, many farmers in remote areas of the world do not know of these advantages of solar powered pumps, or if they do, non-technical barriers such as access to finance hinder an increased adoption of the systems.

Nevertheless, as prices for solar modules have fallen substantially in recent years, governments, extension services and technical cooperation are reconsidering PV water pumps to be employed in agricultural production and beyond. However, demand in this regard will have to be largely generated from the rural farm households themselves.

Barriers

  • Farmers and extension services are not aware of the variety of new technologies that may be appropriate for them
  • CES (clean energy technologies) are relatively new, therefore farmers have limited access to distributors for installation, parts, and service
  • Farmers often do not have the means to cover high capital costs associated with clean energy upgrades – and financing is seldom available

Further Information

►For further information on SPIS see the article Manual and Tools to promote Solar Powered Irrigation Systems.

Case Studies

Solar-Powered Pumps for Improved Irrigation in Honduras, Nepal and Zambia: iDE’s Clean Irrigation Solution (CIS) can compete with fossil fuel pumps both in terms of cost and enhancing agricultural productivity. CIS’s universal piston pump can run on a variety of power sources (solar steam power, photovoltaic power, and grid-connected alternating current (AC) where available). The system accesses groundwater from deeper depths than conventional pumps, and maintains a slow, steady discharge rate. iDE will work with local businesses to sell and service the CIS. Recently, field testing of pumps have been started in Nepal.

►Read more here.


Micro-Solar Utilities for Small-Scale Irrigation in Senegal: Earth Institute’s solution will enable a small group of farmers to use a central solar energy unit to power multiple AC pumps for irrigation. The proposed solution takes advantage of the benefits of solar without the high costs associated with DC-powered pumps and battery storage. This power will be accessed by farmers with prepaid electricity cards issued by a micro-utility, and sold through local vendors who will benefit from a small commission. Recognizing that a major obstacle to technology adoption is financing, a tariff-based financing model will allow customers to cover their appliance loans in small payments added into their micro-utility bills.

►Read more here.


Solar Powered Irrigation Systems in Egypt and the initiative "RaSeed": This initiative aims to promote the use of Photovoltaic (PV) systems in drip irrigation farming in order to support cost-effective and sustainable agriculture. Therefore, the aim is to introduce high capacity solar operated water pumps - of up to a pump size of 100kW - to the Egyptian agricultural sector. Furthermore, soil in the “New Lands” is mostly sandy, and water used for irrigation is ground water. Hence, it is crucial to use water efficient irrigation systems. RaSeed targets farm specific optimization of drip irrigation systems that enable maximum fuel savings and water efficiency by taking into account soil compositions and environmental conditions. In order to further the initiative, a Private Public Partnership (PPP) was established with a solar energy firm that is supported by the multi-donor initiative: ‘PoweringAgriculture - an Energy Grand Challenge for Development’. Together with its partners, RaSeed establishes a network, providing high quality solar energy technology and training in Egypt.

►Read more here.


Further Country Case Studies:


Further Case Studies

Further Information

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