Agricultural drainage controls the water level in the soil. Engineering science has long recognized that there should be no irrigation without drainage in order to avoid water logging and other negative impacts on productivity and soils; but this has mostly not been put into practice. Although the concept of Integrated Water Resources Management (IWRM) has been intensively discussed by the international water community and irrigation system management has undergone significant change during the last 15 years, drainage needs are very often not even considered. Drainage is a technique, but foremost it is a service provided to clients. The way in which drainage is carried out has an essential influence on whether irrigated agriculture is sustainable – either for subsistence or for commercial agriculture.
Background: seven reasons for drainage
Data on land with high salinity levels, land removed from production, yield depressions, and waterlogged and flooded land all suggest that unmet drainage needs have created problems in at least 10-15 million hectares in developing countries. In monetary terms, this lack of proper drainage accumulates losses or costs of around US$ 900 million per year. In view of competing demands for financial resources, it can be difficult for policy makers to direct limited resources towards drainage. But there are at least seven important reasons why governments should mobilize resources. According to Scheumann/Freisem (2001: chapter 1) these seven reasons are:
1. Drainage protects the resource base for food production
Reports indicate that close to 0.5 to 1.0 million hectares of irrigated land are lost annually due to soil deterioration caused by waterlogging and salinity. In many countries, 10 to 30 per cent of the irrigated land is affected by salinity. Drainage would help to avoid salinization, and at much lower costs than would arise when soils are reclaimed or taken out of production.
2. Drainage sustains and increases yields and rural incomes
Salinity and water logging result in significant yield depressions; it severely limits crop choice, diversification, and intensification; adversely affects crop germination and yields; and can make soils difficult to work. Consequently, these losses can lead to income losses of up to 40-60 percent, and have negative effects on the overall food production.
3. Drainage protects irrigation investments
Irrigation has been the largest recipient of public agricultural investment in the developing world. Yet between 1990 and 2005 investments in irrigation decreased, largely because of limited water resources and degraded soils; but due to climate change and increased food demand, the investments have risen again during the past five years. These new investments in irrigation can only be sustainable when they are protected by adequate drainage measures.
4. Drainage infrastructure serves rural and urban residents as well as industry
In many countries, off-farm drainage infrastructure is also used by rural settlements, cities, and industries to dispose of wastewater. This benefit is rarely considered in planning drainage projects.
5. Drainage protects human lives and assets against flooding and high groundwater levels
Well-drained areas and properly functioning drainage infrastructure provide a buffer for torrential rainfall. Monsoon flooding and waterlogging are part of natural conditions in the humid tropics, but in other parts of the world such events are also becoming more frequent secondary to climate change. Since irrigation alters the hydrology of the soil, irrigated land no longer has the capacity to cope with highly intense rainfall. Tremendous loss of human lives and damage to assets increasingly occur through uncontrolled floods, as seen not only in India and Bangladesh, but also in Africa and other semi-arid regions.
6. Drainage services improve health conditions
Around five million people die annually from water-related diseases: i.e. vector-borne diseases (malaria etc.), diarrhea caused by fecal matter, as well as diseases related to the transmission of pesticides. Stagnant water found in inadequately drained and poorly maintained land contributes to the transmission of diseases and escalates their occurrence. With properly designed drains, disease vectors could be controlled. Sanitary conditions are improved when stagnant water is reduced, and pit latrines may work properly if the surrounding area has lower water tables.
7. Drainage protects the water quality
Irrigated agriculture produces emissions, such as pesticide residues and nitrates, which can contaminate groundwater. Properly designed and maintained drainage facilities contribute towards controlling effluents from agricultural lands.
Challenges: designing and financing the maintenance of drainage
Unlike irrigation infrastructure, which provides immediate benefits, drainage is a more difficult task. The biggest challenge is the public-good characteristics of drainage infrastructure, which makes it difficult to enforce any cost-sharing (Huppert, 1991). In this section, a bundle of strategies are suggested to overcome these difficulties. Financing maintenance means introducing the right incentives to the various actors so that they will ensure a continued functioning of the infrastructure at the agreed level of service. These incentives are to be incorporated in the management arrangements between farmers, irrigation and drainage authorities and government. These strategies include:
1. The payment for service should be outweighed by the benefits obtained in the form of increased productivity, farm income, and improved livelihood.
2. A direct link should be established between the provision of services and payment.
3. This direct link should establish a mutual dependency between the service provider and its clients.
4. These links can only be established effectively if the irrigation and drainage authority is financially and organizationally autonomous.
5. Enforcement of arrangements is fundamental to sustain service provision.
6. Deviations from the principle payment for service, i.e. service for payment, should be embedded in subsidy arrangements between the government and service provider.
Aside from consideration of the financing challenges, the main message of re-engaging in the irrigation and drainage sector, according to the World Bank (2006), should be to integrate such programs and projects into a broader perspective, one that embraces the objectives of productivity growth, poverty reduction, natural resources management and environmental protection.
Project example and impact evaluation - Egypt: National Drainage Programme (NDP)
One early example of the successful support of a national drainage program is located in Egypt, where the German Development Cooperation and other donors assisted the Egyptian Public Authority for Drainage Projects in planning, implementation and monitoring of this program (http://www.kfw-entwicklungsbank.de/ebank/EN_Home/Evaluation/Ex-post_evaluation_reports/PDF-Dokumente_E-K/egypt_ndp.pdf).
Executing agency: Egyptian Public Authority for Drainage Projects: (EPADP)
Supporting Partners: World Bank (lead), German FC (KfW), Dutch DC
Period of implementation 1993-1998, 1993-2001
Objectives of the project
- Stabilization and increase of agricultural yields (10-20% for the main crops) by improving the drainage systems in a production area of approximately 310,000 ha
- Strengthening of the Egypt Public Authority for Drainage Projects (EPADP)
- Installation / renewal of underground drainage systems and open drainage ditches
- Supply of equipment / spare parts
- Measures to strengthen the executing agency
- Complementary measures, including the introduction of an (M&E) system at the project-executing agency designed to establish the effects of drainage
Year-round irrigation along the Nile, which became possible due to the Aswan Dam, produced constantly rising groundwater levels and led to related water logging and soil salinization. When these side-effects became clearly visible from the mid-1970s, the Egyptian government started to implement extensive drainage programs. Under these programs field drainage pipes were installed in the soil of the drainage areas. The water collected in the drainage pipes is diverted, by force of gravity, in underground pipes (collectors) into a system of open drainage canals (receiving waters), and finally all surplus water collected in these canals is channeled via the River Nile into the Mediterranean Sea. Pumping stations are used where the water cannot be diverted by means of gravitation. The extensive drainage programs, of which the above mentioned project was a part, were very successful in preventing a rise in the groundwater level and the further salinization of the soil. They thus contribute substantially to improving the conditions for higher agricultural yields.
The following measures were implemented:
- (a) initial drainage of roughly 248,000 ha;
- (b) rehabilitation of roughly 63,000 ha of field drainage;
- (c) extension of about 1344 km of existing receiving waters which cover a drainage area of 214,200 ha;
- (d) Financing of electro-mechanical equipment and spare parts for drainage pumping stations and of vehicles;
- (e) financing of equipment for the installation and maintenance of drainage pipes and systems for the production of pipes.
Measures (a), (b), (c) and (e) were part of the original project design concluded between the Egyptian Government and the World Bank. Since pumping stations are indispensable for the functioning of the system, the later modification in the course of the project implementation to include the financing of measure (d) to the amount of USD 37.8 million was factually justified. The construction work was provided by Egyptian firms with a good quality outcome. The selection of areas, the planning of drainage measures, and the implementation of the measures were all conducted properly.
Key Results of the Impact Evaluation
(Analysis conducted by Euroconsult & Darwish Consulting Engineers, 2004)
The results of the investment measures implemented are the establishment of functioning field drainage systems with proper diversion of the water collected into open receiving waters, and the installation of the pumps required to further channel the water collected. Overall, the project measures were appropriate to eliminate the bottlenecks in the drainage systems that had been identified in the project appraisal. The achievement of the overall and project objectives can be summarized as follows:
- Yield and income increase
The yield targets for wheat, maize, cotton were achieved, and even partly exceeded. The forecast yield increases for most of the other crops were also largely achieved. The income produced from drained fields was compared with the income produced from un-drained fields. Income increases attributable to the project were 30% and 38%. Thus, the overall objective was clearly exceeded.
The maintenance condition of the areas drained to date with underground drainage systems is good, but the maintenance of open drainage canals (receiving waters) is more problematic. Another problem is the low cost-participation of the users, who currently only repay the investment costs (without interest) over a period of 20 years. The users do not contribute to covering the operating costs, even though they are in the position to bear additional costs. At present, EPADP receives sufficient public funds to ensure the functioning of the drainage systems. However, in the long run, the Egyptian state will not be able to bear the main brunt of the investment costs and the ongoing costs of the water supply and drainage systems. Thus, a legal framework has to be established in order to ask the users to bear a larger share of the operating costs.
References and further reading
- ↑ 1.0 1.1 Scheumann, Waltina/ Claudia Freisem (2001): The Forgotten Factor: Drainage – Its’ Role for Sustainable Agriculture. Expert Statement written on behalf of Ministry for Economic Cooperation and Development (BMZ), German Development Institute (DIE), Bonn, Germany.
- ↑ Huppert, W./ M. Svendsen/ D.L.Vermillion (1991): Governing maintenance provision in irrigation: A guide to institutionally valuable maintenance strategies, GTZ GmbH. Eschborn, Germany.
- ↑ Hofwegen, Paul J.M. van (2000): Incentives for Financing the Maintenance of Irrigation and Drainage Systems, Thematic Paper, No. 12, Division Rural Development, GTZ Eschborn, Germany.
- ↑ Worldbank (2006): Reengaging in Agricultural Water Management. ISBN: 9780821364987.fckLR
Hofwegen, Paul J.M. van (2000): Incentives for Financing the Maintenance of Irrigation and Drainage Systems, Thematic Paper, No. 12, Division Rural Development, GTZ Eschborn, Germany.
Huppert, W./ M. Svendsen/ D.L.Vermillion (2001): Governing maintenance provision in irrigation: A guide to institutionally valuable maintenance strategies, GTZ GmbH. Eschborn, Germany.
Petermann, Thomas (1993): Irrigation and the Environment: A Review of Environmental Issues, GTZ Eschborn, Germany.
Scheumann, Waltina (1997): Managing salinization. Springer Berlin, Heidelberg, New York.
H.P. Ritzema (Ed.) (1994): Drainage Principles and Applications. International Institute for Land Reclamation and Improvement (ILRI), Publication 16, Wageningen, the Netherlands. ISBN 90 70754 3 39.