Soil salinity processes under drainwater reuse in the Nile delta, Egypt
In many parts of the world agricultural drainage water is reused for irrigation. Although the practice can bring significant benefits to watershort areas, it can also lead to the accumulation of salts and toxins in soils, with detrimental consequences to agricultural production. The report presents the findings of a project which studied the processes of salt accumulation and movement under drainwater reuse in the Nile delta, Egypt.
Background
The use of marginal quality water for irrigation is becoming more widespread across the world. The reuse of drainage water for irrigation involves the application of water that is inherently of lower quality than fresh water. Water that has passed through the agricultural system may contain increased levels of salts, toxic ions, heavy metals and organic residues. The entry of these pollutants into watercourses and accumulation in soils poses a threat to agricultural production and the environment.

In order to implement appropriate management techniques to control soil salinity and toxic ion build-up, it is necessary to have an understanding of processes of salt accumulation under drainwater reuse and be able to make predictions about likely accumulation over time. The aims of the study were thus:

  • To investigate the processes occurring in an agricultural field, representative of the Nile Delta where drainwater is reused for irrigation.
  • To provide data and information to develop and test a predictive procedure for salt accumulation under drainwater reuse over time.

The report
The report presents the results from a micro-study, which monitored salt and water movement in a typical farmer's field on the Nubariya Scheme in the Western Nile Delta, which had been reusing saline drainwater for irrigation for over ten years. The main fieldwork from the project provided quantitative evidence that the reuse of agricultural drainage water (both directly and after blending with fresh Nile water) has led to increased salinity levels in the fields of the Nile Delta

What it covers
The report presents the results of analysis of salt leaching and diffusion processes occurring within the

 

study area over a one-year period. It demonstrates how very saline drainwater can be successfully used for agricultural production provided appropriate management methods are adopted.

The report contains a useful summary of the methods available for predicting salinity accumulation:

  • Rhoades and Merril Relation
  • Ayers and Westcot Relation
  • Rhoades Relation
  • Hoffman and Van Genuchten Equation
  • Computer models
The results of testing these different predictive procedures against the field observations on are presented.

Contributors
HR Wallingford Ltd, UK; Water Management Research Institute, National Water Research Centre, Egypt.

Intended Users
The report can be used to develop and improve predictions of salinity build-up under drainwater reuse in similar areas. It will therefore be of use to researchers and planners concerned with drainwater reuse in developing countries.

The information in this report has also contributed to the development of practical guidelines on the safe use of drainage water for irrigation (HR Wallingford report, OD 134)

Abbott, CL and EL Quosy, DED, 1996. Soil Salinity Processes under Drainwater Reuse in the Nile Delta, Egypt. HR Wallingford, UK. Report no. OD 133.

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