Groundwater Assessment for Agricultural Irrigation in Toshka Area, Western Desert, Egypt

Abstract

Toshka area is located southeastern of the Western Desert. In 1997, Egypt established a development project to irrigate 216,000 ha (540 feddan) by 2017 through pumping surface water from High Dam Lake as a part of the mega project “Developing Southern Egypt.” Currently, the Egyptian government plans to extend the project by about 100,000 feddan depending on surface water irrigation and 25,000 feddan depending on groundwater (through 102 wells) as a part of the recent mega project called “1.5 Million Feddan Project.” Egypt is now fully utilizing its annual share of the Nile waters 55.5 km3 from the Nile, and it has a shortage of water estimated at 20 km3. The present chapter aims to evaluate the groundwater conditions to determine the sustainability of the groundwater resource, the expected changes in groundwater levels, the amount of recharge and the suitable discharge from the groundwater for irrigation of 25,500 feddan through 100 years, and the changes in water quality. The hydrochemical analysis was carried out using 38 productive wells and 1 surface sample from Aswan High Dam Lake (AHDL) for major ions. The present study was carried out in Toshka using 102 groundwater wells located west of AHDL using static, dynamic water levels, well depth, discharge, and pumping tests to determine the hydraulic parameters of the aquifer system in the study area and building the groundwater model. Visual MODFLOW 2011.1 software was used to estimate the expected drawdown in the groundwater levels using four different scenarios. A conceptual model was constructed to simulate water flow system of the Nubian Sandstone Aquifer through 100 years. The safe water use of groundwater for 100 years is 1,007 m3/day from each well working 8.4 h/day at 120 m3/h, to provide 1,500 m3/feddan/year for a total of 25,000 feddan. The expected lowering in the groundwater level after 100 years is 15 m. The salinity ranges from 480 to 1,200 ppm with an average of 648.5 ppm. It increases with increasing distance from AHDL.