The project has indicated that significant benefits can be attained using controlled drainage - both to the farmer (in terms of increased yields) and to the wider community (in terms of water saving). Controlled drainage has been field-tested by the project, although farmer-managed trials are an essential next step. Guidelines and tools have been developed that allow the technique to be taken forward and implemented.

To save water and protect resources through integrated irrigation and drainage management strategies incorporating controlled drainage.

1. Predictive tool to assess water saving, resource protection and crop production under controlled drainage.
2. Practical guidelines for integrated irrigation and drainage incorporating controlled drainage.
3. Guidelines for uptake and dissemination of controlled drainage.
4. Report on potential for controlled drainage around the world.

Output 1:

The simulation model CDWaSim has been developed to allow formulation of controlled drainage strategies for different crops in different situations. CDWaSim was field-tested using data from the field trials carried out in Egypt. Demonstration applications indicate that significant water savings can be attained - 20-40% of rotational water application.

Output 2:

Guidelines for controlled drainage have been produced and are available as a draft report (with software tools included on CD), currently being circulated for review. These guidelines are intended to assist planners and water resource managers in irrigated (or rainfed) areas in developing countries, who wish to assess the benefits and requirements of controlled drainage. Other potential users include extension services wishing to advise farmers on management of controlled drainage, irrigation and drainage engineers designing controlled drainage systems, and research institutes and universities who may find the guidelines and accompanying software useful as educational tools.

The guidelines enable users to:

• Gain an understanding of the concepts involved in controlled drainage.
• Assess the benefits and issues involved in implementing controlled drainage at a particular location.
• Use the simulation tool CDWaSim to develop site-specific controlled drainage strategies to maximise water saving and crop yield improvement, whilst minimising negative impacts.
• Carry out an economic assessment of the costs and benefits of controlled drainage at the farm and system level.

Output 3:
Following review of the discussion document "Outline Uptake and Dissemination Plan for Controlled Drainage", the guideline has been finalised. The proposed uptake and dissemination path is based on information obtained in expert missions to Egypt and India, and consultation with agencies, government bodies and extension workers in the field. There are 4 key steps:

• Awareness creation among policy/decision makers.
• Field testing and study of farmer management of controlled drainage.
• Enhancing the skills and knowledge of front line staff.
• Simple guidance leaflets for farmers.

Output 4:
A review of the potential for controlled drainage around the world has been completed. Based on a series of pre-requisites for successful introduction and uptake of the technique, countries of potential application were identified. The countries where controlled drainage is most applicable and could offer greatest benefit were identified as: North Africa - Algeria, Egypt. Middle East - Israel, Syria, Iraq, Bahrain. Central Asia - India (Punjab, Haryana, Rajasthan), Pakistan, Northern China, Uzbekistan, Tajikistan, Turkmenistan.

An exploratory mission was conducted to India, where experimental work has indicated that controlled drainage can offer significant benefits to farmers and the wider community. Although the current lack of widespread drainage provision constrains the immediate uptake of controlled drainage, there is certainly scope for the technique in the states of Punjab, Haryana and Rajasthan. These states have sufficient irrigation and drainage infrastructure in place and would benefit from the water saving aspects of the technique, and crop yield improvements that can be achieved in areas where yield is constrained by periodic water shortage.

Overall results

The main benefits of controlled drainage are as follows:

• Significant water savings can be achieved at field and basin level.
• Improvements in crop yield.
• Controlling soil water through-flow rates to ensure that nitrate and phosphate levels are maintained, and that soil fertility is not degraded in high irrigation or high rainfall areas.
• Reduced nitrate and phosphate losses to downstream water bodies, reducing eutrophication and ecological damage.
• Conservation of wetlands and water-sensitive regions.

It is particularly beneficial in areas where farmers experience periodic water shortages, which limit crop production, or where increased availability of water has direct farmer benefits. In terms of the basin water balance, the benefits are greatest where rice forms a significant part of the crop rotation, and also in areas where reused water is of poor quality.

Field trials of controlled drainage were carried out at an experimental station in the Nile Delta, Egypt over 2 crop seasons. A weir device was developed to control drainage flows from the controlled drainage plot, whilst conventional irrigation and drainage management was applied to the conventional plot. Drainage flow was significantly reduced from the controlled drainage plot without detriment to the crop, indicating that significant reductions in irrigation application can be achieved.

The simulation model CDWaSim has been developed to allow formulation of controlled drainage strategies for different crops in different situations. CDWaSim was field-tested using data from the field trials carried out in Egypt. Demonstration applications indicate that significant water savings can be attained - 20-40% of rotational water application.

A spreadsheet tool was developed for economic appraisal of controlled drainage. In situations where water does not limit production, the benefits to farmers of controlled drainage are usually modest. There will be savings in labour, water delivery costs and fertiliser requirements, but in most cases these will not be sufficient incentive to invest in the technique. For society to reap the benefits in terms of the basin water balance, it is likely that farmers will require support in terms of financial incentives to adopt the technique.

The method becomes really attractive to farmers where yield increases can be achieved (ie areas where a periodic water shortage threatens crop production) and in areas where saved water has a direct benefit to farmers - ie allows additional crops to be grown, or allows a shift to a more profitable cropping pattern.

Areas of potential application include North Africa - Algeria, Egypt. Middle East - Israel, Syria, Iraq, Bahrain. Central Asia - India (Punjab, Haryana, Rajasthan), Pakistan, Northern China, Uzbekistan, Tajikistan, Turkmenistan.

Further Information

Publications:

Integrated Irrigation and Drainage to Save Water - Phase 1. (1999) Abbott, C. L., Abdel-Gawad, S., Wahba, M. S., Counsell, C. J. HR Wallingford Technical Report ODTN96, Wallingford, Oxon, OX10 8BA, UK.

Field testing of Controlled Drainage and Verification of the WaSim Simulation Model. (2001) Abbott, C. L., Abdel-Gawad, S., Wahba, M. S., Lo Cascio, A. HR Wallingford Technical Report ODTN102, Wallingford, Oxon, OX10 8BA, UK.

Review of the Potential for Controlled Drainage Around the World. (2002) Abbott, C. L., Lawrence, P., Pearce, G.R. and Abdel-Gawad, S. HR Wallingford Report OD146, Wallingford, Oxon, OX10 8BA, UK.

Guidelines for Controlled Drainage. (2002). Abbott, C. L., Lo Cascio, A., Abdel-Gawad, S., Morris, J. and Hess, T. HR Wallingford Report OD147, Wallingford, Oxon, OX10 8BA, UK.

Controlled Drainage - A path for uptake and dissemination (2002). Brabben, T.E. and Abbott, C.L. HR Wallingford Report OD148, Wallingford, Oxon, OX10 8BA, UK.

Collaborating Organisations

Tel: +44 1491 835381
Fax: +44 1491 826352
Email: dfid-kar-water@hrwallingford.co.uk

Project Manager
Catherine Abbot
Email: cla@hrwallingford.co.uk