'Wa'ter use efficiency in irrigated agriculture
The proportion of water absorbed by a crop and transpired by its leaves is called, in irrigated agriculture, the productive water use. This is the water that serves for crop growth resulting in yields. Therefore, the higher the productively used portion of water, the higher is its water use efficiency.
Content
Background
Water Use Efficiency – The Debate
Project example: Bolivia
Project example: Jordan
References
Background
Generally, in simple irrigation systems the efficiently used proportion of water adds up to less than 50%; frequently it ranges only between 30-40%. This low water use efficiency of ordinary irrigation systems has long been criticized by experts, with demands for improvements.
An increase of efficiency can be achieved by the following measures:
- Applying water saving technologies like drop irrigation
- Optimizing management of the irrigation intervals
- Balancing of seasonal fluctuations of water availability by construction of water storage facilities on the farm or regional level
- Reducing the amount of evaporation by irrigation at night, sub-surface irrigation or mulching
- Cultivation of less water demanding crops, or cultivation of crops adapted to marginal quality
These measures may sound simple, yet they are not easy to implement. In many cases, the above measures do not even make sense, as they may imply other unforeseen disadvantages or require untenable preconditions. Particularly in the least developed countries, the following obstacles for implementation exist:
- Efficient technical systems are associated with high investment costs. Hence, they might be too expensive for individual farmers and small scale operating companies.
- Needs-based irrigation management requires know-how regarding the water demand of specific crops. Conditions of the respective varieties and of crop locations must be identified.
- In surface irrigation, a certain amount of over-irrigation makes sense in order to avoid salinization (leaching requirement).
- The diminution of evaporation losses, as via optimal timing or irrigation at night, may collide with other exigencies. Especially in African countries, these measures can be dangerous due to roaming wild animals like elephants, hippos and snakes.
- Crops with a low water need usually have a low market price. Crop rotation not only depends on water consumption, but on various conditions of location and marketing.
As long as water is free of charge - as in most developing countries - the economic incentives to save water are too few to justify investment into new technologies or in advanced training.
In addition, there are some general aspects to be considered when the conservation of the water resources, and not only the profitability of a single farm or scheme, is in the focus. The conventional perception of water use efficiency focuses on the individual farm where, quite often, savings of irrigation water lead to an extension of the land irrigated on the farm. In the final analysis, more water may be used despite, or even due to, water saving technologies. Therefore, in developing countries with weak institutional structures, it is only in exceptional cases that the use of these technologies can contribute to a general reduction in the use of water resources across farms.
Water Use Efficiency - The Debate
For some years, Keller/Keller/Seckler (1996) and then later Giordano/Rijsberman/Saleth (eds.) (2006) from IWMI (International Water Management Institute) have called attention to the fact that improved water use efficiency on the farm level is not necessarily leading towards the conservation of water resources in general. Rather, improved efficiency of individual farms may even pander to a disparate distribution of water on the upper and lower course of a river if it is not combined with a reduction of water withdrawal by the same user.
Irrigation plants are open systems, from where water returns into the catchment area and can be used by the downstream resident. Therefore, improved water use efficiency upstream can abate the availability of water downstream if the upstream resident extracts as much water as previously. This is a frequent scenario, as it makes economic sense to the upstream user to take advantage of the already existing concessions or pumping capacities. When the operator is able to extend his irrigated area, the extension of irrigation is economically reasonable.
If the conservation of the water resources and the equitable distribution of water upstream and downstream are all in the focus of interest, the level of water abstraction of each farm must be considered and included into the strategies to improve the water use efficiency of the entire system through coordination of the users.
Single inefficient units at a water course may have a highly efficient use in total, if the return flow water is reused to a large extent. Such highly efficient systems do exist. For example, in Egypt many small scale farmers make use of the waters of the Nile in a very inefficient way; yet via the complete recirculation of the water, the water use efficiency of the whole user community is very high. Hence, the water productivity of the entire irrigation system, or what Keller calls the total effective efficiency, is excellent (see Keller et al., 1996: 5).
In order to elaborate effective strategies encompassing the effective efficiency of the entire water course, the following questions have to be answered:
- Is the backflow into the water course complete or are there losses in sinks, where the water cannot be regained?
- How is the use of water upstream and downstream adjusted? Can coordination be improved?
- How often can the return flow water be reused without too much contamination by residues of pesticides and fertilizer? Can the application of those inputs be reduced?
Irrigation policies and a good watershed management must have an eye on both the increase of water use efficiency on farm-level and on the whole watershed. Licensed amounts of water abstraction for each user, taking into consideration the backflow of water, can be a very efficient instrument for regulation.
The stronger a water course is in use, the more important the coordination among users and the conservation of the water quality becomes. Furthermore, a prior condition for the sustainable use of water resources is regulation by local or regional authorities and institutions, who can act effectively for the whole water catchment area.
Alongside the management and technical issues, the scheme or resource-oriented political and institutional aspects have to be included to enable higher water use efficiency to happen. But these political and institutional facets will only improve the situation if they are in the interests of the main stakeholders. Unfortunately, this is frequently not the case. Inadequate transparency with regard to water allocation and use, and the associated inefficiencies, often pave the way for officials to make money illegally through preferential allocation of water (petty corruption). Hence, increasing transparency and accountability in the management of irrigation can yield significant efficiency gains and water savings.
Project example: Sahel
Water-spreading weirs for the development of degraded dry river valleys
A very successful example for an activity in a whole region was the construction of water-spreading weirs in degraded dry river valleys in the Sahel. It took place for a period of twelve years in Niger, Burkina Faso and Chad. The Cooperating Partners of German Development Cooperation were GIZ and KfW.
The water-spreading weirs are constructed in a way that they span the entire valley. They consist of a spillway in the riverbed and lateral abutments and wings. Floodwaters are spread above the weir and will at a certain state overflow the wings and slowly flow to the riverbed behind the weir. Thus the basic runoff and sedimentation process in the site is changed. Erosion will be reduced; sedimentation and infiltration of the water into the ground will be increased. In most cases the groundwater table rises within a few years.
Furthermore agricultural production may be expanded and diversified. In many cases a second or even third crop cycle in the year becomes possible.
The implementation is undertaken in synchronized steps:
- Identification of geographically suitable sites
- Information of the respective villages, technical services and authorities
- Submission of a written request by interested communities
- Intermediate examination
- Feasibility study
- Final approval of the construction
- Technical study
- Construction performed with intensive manual labor
- Training of local craftsmen for maintenance
- Handing over to a local committee or administrative structure
An intensive participation by the communities is the principle of the project in order to transfer the responsibility as soon as possible. To ensure that the management committee or a local structure is able to function after the end of the project is crucial for the success and the sustainability.
Project example: Bolivia
Title of the Project: SIRIC (Subprograma de Inversiónes en Riego Intercomunal)
Overall objectives:
- Plan and implement medium-sized irrigation projects in the regions of Chuquisaca, Cochabamba Santa Cruz and Tarija
- Raise income of small-scale farmers in the region
Project time: 2005-2015
Cooperating Partners: KfW/ GIZ
Approach
The participating farmers are closely involved in the planning and construction of the irrigation systems, and then trained in how to use these systems. This takes the form of cooperation in some case, in others of a financial contribution. Altogether, five to six individual projects can support nearly 2,000 families (corresponding to some 8,500 people) on an area of about 3,000 hectares. The approach consists of:
- Assuring the financing, planning and implementation of the individual projects,
- Supporting training for participating farmers, e.g. trainings in technical detail planning and quality control for irrigation projects. In this way, the available local know-how gained from practical work is sustainably enhanced,
- Advising the Bolivia's Ministry of the Environment and Water on elaborating general guidelines for the irrigation sector, and on planning and implementing water catchment protection measures.
Project example: Jordan
Brackish Water Project (BWP), Jordan Valley
The objective of the agricultural component of the project was the improvement of management and practices when brackish water is used for irrigation. Guidelines have been compiled to serve farmers and agricultural extension agents as a source of appropriate know-how that can be applied in the field.
The project was executed in a period of four years (2000 – 2003). The cooperating Partners were the Jordan Valley Authority (JVA), individual farmers and the GIZ.
The following activities have been carried out:
- Monitoring and recording of irrigation practices along the Jordan river,
- Interviews and discussions with selected farmers and extension agents,
- Measurements by project staff (water and soil quality, yields etc.),
- Creation of a data bank,
- Identification and evaluation of local experiences and successful practices,
- Continuous scientific update and reviewing by researchers,
- Elaboration of guidelines,
- Promotion and distribution of the guidelines.
References
BMZ, Federal Ministry for Economic Cooperation and Development
Water-spreading weirs for the development of degraded dry river valleys
Experience from the Sahel, published by GIZ and KfW
GIZ (2010): Water Saving Irrigation. Briefing Note. Division of Rural Development
GTZ (2003): Brackish Water Project – Guidelines for Brackish Water Irrigation in the Jordan Valley
GIZ/VAG Armaturen GmbH/Institute for Ecopreneurship/ Institute for water and river
basin management: Guidelines for Water Loss Reduction: A Focus on Pressure Management
Keller, Andrew/ Jack Keller/ David Seckler (1996): Integrated Resource Systems: Theory and Policy Implications, Research Report 3. International Irrigation Management Institute (IIMI), Colombo
Giordano, Meredith A., Frank Rijsberman, R. Maria Saleth (2006) (eds.): “More Crop per Drop”: Revisting a Research Paradigm. Results and Synthesis of IWMI’s Research: 1996-2005, IWMI, Sri Lanka, Colombo, ISBN: 1843391120
www.waterlossreduction.com
