IMPROVING SUBSURFACE DRAINAGE DESIGN USING GEOSTATISTICAL ANALYSIS OF THE HYDRAULIC CONDUCTIVITY IN THE NILE DELTA

Abstract

The agricultural subsurface drainage system is a system which almost all the Nile Delta of Egypt uses to drain excess water from the soil to enhance crop production and to ensure irrigated agriculture sustainability. The design spacing between lateral drains is playing an important role in determining the efficiency of the subsurface drainage system and its cost. The main input for design is the value of the saturated hydraulic conductivity of the soil. The current practice in Egypt for economical and practical considerations requires dividing the drainage area into blocks and using a single spacing in this block. The selection of the value of the hydraulic conductivity that can be used in the design for this block is challenging due to the high spatial variability of the hydraulic conductivity. Currently, the design practice involves dividing the drainage block into a grid of 500 m X 500 m and the hydraulic conductivity is measured at each point of the grid using the auger-hole method. After conducting the field measurements, an average value of the measured hydraulic conductivities is obtained and used in the design. These practices have been applied for years and are applied for every new subsurface drainage project.