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Determining Optimized Distance and Depth of Subsurface Drains under Unsteady Flow Conditions at Multiple Cropping Pattern

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  9th International Drainage Symposium held jointly with CIGR and CSBE/SCGAB Proceedings, 13-16 June 2010  IDS-CSBE-100055.(doi:10.13031/2013.32108)
Authors:   Farnood Vahdat, Amirpooya Sarraf, Ebrahim Pazira, H Sedghi
Keywords:   Subsurface drainage, Drain depth, Drain spacing, Unsteady drainage models, Land reclamation

The study area was located in central part of Khuzestan province, Iran. Soil survey and land classification conducted in the area indicated that from total area of 41,855 hectares, about 36,430 hectares (87.0%) was affected by water logging as well as poor internal drainage conditions. These problems were usually associated with shallow and saline to extremely saline groundwater tables. Also, about 14,100 hectares (33.7%) of the studied area was faced with soil Salinity and Alkalinity. The pre-request of soil desalinization and land reclamation of such problematic conditions, are subsurface drainage installation and soils salt leaching, by making use of suitable and available surface water resources of the area. The main objective of this study was to obtain the optimal subsurface drain spacing and depth, considering the new suggested idea for decreasing the installation depth. Calculation and optimizations were done with Dynamic Equilibrium Method, by making use of computer simulation technique, for unsteady drainage conditions. The obtained results indicated that the optimum tile drain spacing of 35-50 meters, together with 2.0 meter depth of installations, is the most effective, practical and economical alternative. The mentioned condition responds properly for application of 1.0 meter depth for leaching water in four 0.25 meter intervals intermittently. Also a cropping pattern with 100% intensity for irrigated crops production and with 53% irrigation efficiency is suggested to be practiced after soil desalinization in the same study area.

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