Khuzestan, a south‐western province of Iran with a hot climate, long growing season and lots of water, is the main region of subsurface drainage. Sugar cane is the major artificially drained crop.In the past, drainage rates had been chosen based on highest water‐consuming crop in the cropping pattern. This approach neglects crops with less water demands, natural drainage and direct flow towards perforated collectors or open deep drains, and soil water reservoirs. The drains are installed deeply which bring more saline drainage water out of the underlying strata into the environment.The environmental problems are due to the high volume of very poor quality drainage water. The low irrigation efficiency results in a high volume of drainage water. Deeper drains are also responsible for over‐drainage because they usually work longer and bring mined salt water out of the deeper strata.This paper attempts to show that in arid areas with a long irrigation season and/or high deep percolation one does not have to expect secondary salinization provided that the leaching requirement is met. Maintaining higher irrigation efficiency, installation of shallower drains and the application of controlled drainage are measures to reduce salt removal, and hence reduce environmental hazards. Copyright © 2013 John Wiley & Sons, Ltd.
Sustainable agriculture can contribute to food security in arid and semi‐arid regions if soil salinity in the root zone is kept under control. Recently, experts have been concentrating their research towrds alternative and environmentally friendly solutions. In this study, dry drainage was evaluated as a sustainable and cost‐effective alternative technique, by means of both field experiments and a numeric approach based on the HYDRUS‐2D modelling environment. Results showed that soil salinity in the cropped area increased from the soil surface to the bottom, and soil salinity movement (transport direction) was from the cropped to uncropped area. Increasing the ratio of cropped to uncropped width led to an increase in soil salinity of the cropped root zone and lack of stabilization of salinity concentration. Results of modelling showed that there are no significant differences between observed and modelled data, even though HYDRUS‐2D simulated soil water content better than soil salinity. Averages of performance indices for simulated soil water content (SE = 0.08, NRMSE = 0.133) were better in comparison with simulated soil salinity (SE = 0.28, NRMSE = 0.262). Soil surface salinity in the cropped area increased 2.7 times (from 2.1 to 5.7 dS m−1) during the experiment for equal cropped to uncropped width (1 (cropped): 1 (uncropped)), and by increasing cropped width (2 (cropped): 1 (uncropped)) it increased 7.5 times (from 2.3 to 17.3 dS m−1). Copyright © 2017 John Wiley & Sons, Ltd.
This study was conducted to evaluate the performance of subsurface drainage and a rice husk envelope in Behshahr, a coastal region in the northern part of Iran. The subsurface drainage system was monitored in the rainfall seasons of 2006 and 2007 (22 November to 19 March). Various parameters such as daily groundwater table fluctuations and drain discharge rate were measured. To evaluate the drainage envelope, the gradation curve, bulk density and natural durability of rice husk and also the head loss of the groundwater table in the vicinity of the drain were measured. The large difference between the approach-flow head and entrance-flow head could be related to clogging of the external part of the rice husk envelope. The overall conclusion of this study was that subsurface drainage system performance was not satisfactory due to poor control of groundwater table depth, which could be related to clogging of the rice husk drain envelope. Hooghoudt's equation is not recommended to be used for evaluation of design parameters in this case. The basic uncertainty in application of a rice husk envelope was its durability, which was found to be very variable and depended on soil environmental conditions.
Historically, drainage systems have been considered as tools for removing excess water. In the past two decades, however, a more comprehensive and inclusive approach has been developed that considers drainage as only one of the central elements of an integrated and comprehensive water management scheme. Since its invention, the science and technology of agricultural drainage have undergone development in the formulation of design, materials and methods. Recently, more concern has been focused on the environmental consequences of adoption of drainage systems. Now, environmental conservation is the greatest challenge for drainage globally. The 13th International ICID Drainage Workshop, held from 4 to 7 March 2017 in Ahwaz City, Iran, was entitled Drainage and Environmental Sustainability, to address these challenges. Of the presentations, a number focused on the new outlook and technologies that have recently been adopted. In this paper, these presentations have been used to provide a brief history of the invention and development of materials and methods in agricultural drainage. Under the notion of ‘beyond modern drainage’, the latest innovations in materials and management of agricultural water, in general, and drainage systems in particular, are presented. © 2018 John Wiley & Sons, Ltd.
Abadan date palm plantations have long been irrigated by rivers under the tidal effects of the Persian Gulf. During high tides, river water makes subirrigation possible while during low tides the same ditches drain out the plant root zone. Recently parts of the plantation have been under traditional drainage and surprisingly failed to work efficiently. In order to find the cause, the hydraulic conductivity of the soil layers was measured using parallel drains which show that the topsoil up to 70 cm is very permeable, but then up to 95 cm it is impermeable. Piezometric measurements also show that the soil between 70 and 130 cm is impermeable. The ratio of contribution (RC) of the soil layers to the total flow in the soil profile decreases with depth. Values of the RC for the first 60 and 70 cm soil depths are about 91 and 98% respectively. Although soil texture in the first layer has been classified as clay, biological activities, mostly live roots, have changed both the magnitude and size of the pores. It was concluded that in tidal subirrigation, only the upper part of the soil which has been under the root spread can be assumed to be permeable. Copyright © 2018 John Wiley & Sons, Ltd.
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