|Evett, Steven - Steve|
Submitted to: International Journal of Phytoremediation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2010
Publication Date: 8/3/2011
Citation: Evett, S.R., Kandil, N.F., Soriano, C., Stanturf, J.A., Zalesny, R.S. 2011. Opportunities for woody crop production using treated wastewater in Egypt. II. Irrigation strategies. International Journal of Phytoremediation. 13(S1):122-139. Interpretive Summary: As part of the Middle East peace process, the United States has worked closely with Egypt to improve agricultural production for food self-sufficiency and to increase crop water productivity. A USDA team composed of Forest Service personnel and an irrigation scientist with the ARS Soil and Water Management Research Unit, Bushland, Texas, worked with Ministry of Agriculture personnel to evaluate the potential for tree plantations using treated waste waters. The team developed guidelines for tree species selection and irrigation system design to control deep percolation losses. Successful tree plantations in Egypt will make use of a water source, primary treated waste water, that cannot be used for food production, while providing wood and oil products for a region that imports nearly all wood requirements. The preferred irrigation application method is drip irrigation because it applies water more uniformly than does flood or furrow irrigation on the sandy soils that will be planted. Uniform application helps avoid deep percolation, which would allow waste water to reach aquifers below the plantations. Even with drip irrigation, the system must be carefully designed not to apply more water at one time than the sandy soil can hold within the tree root zone. The paper provides design guidelines and equations for estimating tree water use, irrigation depth and frequency, and dripper surface distribution so that deep percolation can be avoided and tree water use requirements met. Recommendations for directed research are also given, aimed at filling knowledge gaps about tree rooting depth in local soils, tree water use under Egyptian conditions, and the performance of drip irrigation systems on the sandy desert soils where trees will be planted.
Technical Abstract: Egypt's share of Nile waters is allocated according to international treaty obligations and is fixed at 55.5 billion cubic meters annually. As a result, Egypt will not be able to meet increasing water demand using freshwater from the Nile and has been developing non-conventional wastewater reuse strategies to meet future demands. The yearly volume of available wastewater is expected to increase from 2.3 billion cubic meters in 2000 to 3.0 billion cubic meters by 2017. Since 2004, Egypt's Ministry of Water Resources and Irrigation has promoted strategies for water reuse through its Integrated Water Resources Management Project with the United States Agency for International Development (USAID) Mission in Cairo. Guidelines for safe and direct reuse of treated wastewater for agricultural purposes were approved in 2005 (Egyptian Code 501/2005). The government of Egypt (Ministry of Agriculture and Land Reclamation and Ministry of State for Environmental Affairs) has established 24 man-made forests through the National Program for the Safe Use of Waste Water for Afforestation, some forests of which have been useful for assessing the efficacy of using treated wastewater (TWW) for afforestation. The National Program targets an annual reuse of 2.4 billion cubic meters of treated wastewaters to irrigate 84,000 hectares. At present, approximately 4,340 hectares are under irrigation with treated wastewater. The irrigation takes place across governorates in areas close to wastewater treatment plants that are adjacent to the desert. A joint USDA Forest Service – Agricultural Research Service technical assistance team evaluated the feasibility of scaling up such afforestation efforts throughout Egypt. In this paper, 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.).