Session FT 4.03
Drain for Gain
- Egyptian National Committee on Irrigation and Drainage (ENCID)
- The Arab Water Council(AWC)
- International Commission on Irrigation and Drainage (ICID)
Irrigation induced salinity is a global threat to agricultural productivity and cause of land degradation in arid and semi-arid regions. About one third of irrigated lands are suffering from salinity problems. The world loses about 0.5-1.0 million ha of productive land annually due to salinization. Agricultural drainage is practiced as a mean of control and defence against water logging and salinization. In recent years, reuse of drainage water in irrigation is increasingly important for augmenting scarce resource and reducing environmental problems in the downstream reaches of river basins.
Agricultural drainage proved to be extremely useful in enhancing crop productivity, increasing farm income, and improving the livelihood in rural areas where majority of the poor live. It could also contribute significantly to the national income of countries. However, drainage has many effects and impacts on other functions of the resource system and could involve many stakeholders other than farmers. These effects and impacts could be positive or negative, within and outside the drainage area.
- Practical experience provided many lessons and success stories from Australia, Egypt, and Mexico where drainage and drainage water reuse were practiced in different physical, social and economical contexts. Among these lessons are:
- Implementing land drainage for sustainable development requires a vision and long-term commitment at the policy and decision making levels. Government commitment and support proved essential to initiate and maintain sustainable drainage programs. This support could include soft loans recovered over extended period of time and subsidies for improvement of irrigation practices, installation of surface and subsurface drainage and education and training programs for irrigators.
- Because of their multiple effects and impacts, within and outside the drained area, drainage and drainage water reuse should be planned and managed from an integrated perspective to achieve an optimal mix of economic and social benefits while safeguarding key ecological functions. A basin or sub-basin level of planning is necessary in the case of land drainage. Involvement of farmers and other stakeholders from early stage a key for successful development.
- An institutional setup with a first order mandate towards drainage which addresses the multifunctional aspects of drainage and involves all stakeholders in planning and management is a key to achieve the goals of integrated resource management.
- Continuous capacity building and training of government and contractor's staff as well as relevant water users on the different functions of drainage is necessary to cope with the developments in technology and management. National scale subsurface drainage projects require local industry for producing drainage materials and capacity to implement and maintain drainage systems. Private sector could be instrumental in taking this role.
- Financial sustainability of drainage projects requires an affordable and easy to implement cost recovery system. Formal plans for implementing on-farm drainage proved are important for sustainable development. A fair arrangement for crop damage compensation encourages farmers to come forward and evenly share the cost of damages.
- Reuse of drainage water can close the gap between escalating water demand and available water resources for irrigated agriculture. It also helps reducing contamination of the lower reaches of rivers. Monitoring programs, standards, and guidelines have to be developed as well as the supporting institutional and legal frameworks to ensure sustainability should be in place and effectively implemented.
- Applied and adaptive research provide strong base for drainage development and drainage water reuse on technically effective and economically sound basis. Technical assistance and technology transfer help building local capacity in countries lacking experience in land drainage.
- Drainage is an indispensable component of the hydrological cycle and helps to maintain favorable water and salt balance in irrigated lands, thus increasing productivity and conserving important land resources.
- Down stream reaches, estuaries and deltas of the river basins are fragile productive ecosystem; therefore, drainage should be carefully planned to minimize negative impacts on their production and environmental functions.
- Drainage, as a management tool for a multifunctional resource system, needs to be viewed and handled from an integrated perspective. Its ultimate goal is to improve the quality of life for people through fair sharing of the economic and social benefits, while safeguarding key ecological functions.
Local Actions presented
Salinity control in irrigated lands and river flows, Australia
In the late 1980’s water tables in the irrigated areas in the Murray Darling Basin were less than 2m deep over about 70% of the area. There were already severe outbreaks of salinization and waterlogging and this was predicted to spread over 30-40% of the entire irrigated area. Each irrigated region started to undertake planning and implementation measures to improve irrigation application and to provide surface and subsurface drainage to control water tables and reclaim salinized land. The drainage waters from these activities were to be directed to the Murray River system. Causing increased salinity in the lower reaches and impacts were being felt by water users in the lower reaches. This led to the development of Salinity, Land and Water Management Plans (SLWMP) funded by the State governments of the states of South Australia. The plan development was managed by committees made up of irrigators, water supply companies, and urban councils, State agency personnel. The plans included activities and subsidies for improvement of irrigation practices, installation of surface and subsurface drainage and education and training programs for irrigators.
Concurrently the Murray Darling Basin Commission (MDBC) was developing the Salinity and Drainage Strategy (SDS) to improve the water quality in the Murray River. The implementation of SLWMP’s has been successful due to the irrigator and community involvement from early stage and the availability of government funds to assist irrigators and irrigation companies in implementing works. However, due to the voluntary nature of these plans the on-farm works have not been undertaken by all irrigators. Problems in the implementation of SDS were related primarily to monitoring and evaluation of salt levels and calculation of salt loads. Funding of Salt Interceptor Schemes has been difficult. The results of the SLWMP’s have been to control waterlogging and salinity to levels where only small areas that have problematic hydrogeology are now at risk. The SDS has been effective in controlling salinity levels in the Murray River. Water efficiency schemes as part of the Living Murray are under construction.
National Drainage and Drainage Water Reuse Programs, Egypt
In Egypt, food security of a fast growing population required measures to intensify crop production within the existing irrigated area. The construction of the Aswan High Dam (AHD) allowed perennial irrigation in the Nile Delta and Valley. This put the limited fertile land at risk of water logging and salinity. Provision of effective drainage systems was an obvious mitigation measure in 1970, a program that covers all the irrigated lands (about 6 million acres at that time) with drainage infrastructure has been launched.
Water logging and salinity have been controlled in all areas provided by drainage infrastructure. This enhanced crop productivity and increased yields of wheat, rice yields and corn, significantly. Implementation of such large scale program imposed huge financial, institutional and technical challenges. Institutional capacity has been developed at the national and local level to operate and maintain a complex on-farm and main drainage infrastructure. To date an area of about 5.2 million acres are provided with subsurface drainage. Implementation of drainage improved health conditions, sanitation, and safety of buildings in the drained areas. However, the environmental impacts of drainage on environment were mixed. While, land degradation was reversed or avoided, polluted drainage water is a problem.
The drainage infrastructure provided means for maximizing water use efficiency through reuse of drainage water for irrigation in downstream areas. Criteria and guidelines for reuse were developed through applied research. At present, 5 billion cubic meters of drainage water are annually reused. Sustainable development called for an integrated approach to address drainage needs and drainage water reuse from an IWRM perspective at basin level including stakeholder participation from within and outside the agricultural sectors. Implementation of such large scale program imposed huge financial, institutional and technical challenges. The historical development of drainage in Egypt provides many lessons that can be shared with the global community.
Subsoil Parceling Drainage in Mexico
Problems on salinity or shallow subsurface water levels in agricultural areas under irrigation are of a great importance, due to negative impacts associated to the production processes, as well as for the extensive areas in which such problems are presented. This important issue stands out even more when considering that in these areas under irrigation, a high percentage of the world’s agricultural production is obtained, and also, because huge investments have been made within these areas in order to build up the whole infrastructure required for irrigation systems.
With the purpose of solving the aforementioned problems on saline contamination in agricultural soils, the National Water Commission of Mexico (CONAGUA) and the Mexican Institute on Water Technology (IMTA), began a joint project in 1994, which consisted in an experimental program within the Irrigation District 076 Carrizo Valley, located at the state of Sinaloa (on the northwest part of the country), aimed to demonstrate the recovery of soils through subsoil parceling drainage, and to provide a feasible technical and economic alternative to the problem outlined by the farmers on irrigation areas where their parcels yielded low productivity or were abandoned due to the presence of salinity and high phreatic levels, problems that were present mainly in irrigation areas of the northwest of Mexico.