Opportunities for Woody Crop Production Using Treated Wastewater in Egypt. II. Irrigation Strategies

Abstract

An Egyptian national program targets annual reuse of 2.4 billion m³ of treated wastewater (TWW) to irrigate 84,000 ha of manmade forests in areas close to treatment plants and in the desert. To evaluate the feasibility of such afforestation efforts, we describe information about TWW irrigation strategies based on (1) water use of different tree species, (2) weather conditions in different climate zones of Egypt, (3) soil types and available irrigation systems, and (4) the requirement to avoid deep percolation losses that could lead to groundwater contamination. We conclude that drip irrigation systems are preferred, that they should in most cases use multiple emitters per tree in order to increase wetted area and decrease depth of water penetration, that deep rooting should be encouraged, and that in most situations irrigation system automation is desirable to achieve several small irrigations per day in order to avoid deep percolation losses. We describe directed research necessary to fill knowledge gaps about depth of rooting of different species in sandy Egyptian soils and environments, tree crop coefficients needed for rational irrigation scheduling, and depth of water penetration under different irrigation system designs. A companion paper addresses recommendations for afforestation strategies (see Zalesny et al. 2011, this issue).

KEY WORDS:

• irrigation management
• phytoremediation
• phytotechnologies
• water quality
• deep percolation
• irrigation systems

ACKNOWLEDGMENTS

R.S. Zalesny Jr. presented this information at the Sixth International Phytotechnologies Conference; 2–4 December 2009; St. Louis, MO, USA. We thank Engineer Wafaa Faltaous (Cognizant Technical Officer, USAID Cairo), Professor Hamdy Khalifa (Director of SWERI), and Dr. Taha El-Maghraby for collaborations and help during our technical assistance mission in Egypt. We appreciate review of earlier versions of the manuscript from: David Coyle, Eric Gustafson, Freddie Lamm, Mick O’Neill, Tom Schmidt, Clint Shock, and Jill Zalesny.