Numerical and Experimental Assessment of Suspended Material Effects on Water Loss Reduction from Irrigation Channels

Abstract

In the past, seepage was the main problem in water conveyance in arid and semiarid areas. Adding soil to water and making it muddy was a common way to reduce seepage, especially in new construction earthen channels or qanats. However, this technique is used to convey water from Baladeh Qanat to farmland in eastern Iran while the large amount of its irrigation channels is lined. The present research was carried out to investigate the effects of suspended materials on water conveyance. Three channels used in experiments included a farmland channel, a hand-built channel and part of Baladeh irrigation channel. Experiments consisted of passing freshwater and muddy water while water losses were measured. This research confirmed the effect of suspended materials in earthen channels sealing. Seepage from hand-built channel decreased significantly by passing water with suspended particles. Because of high slope of the channel, no sedimentary layer was formed in this test. Seepage from the farmland channel was much more than the hand-built channel because of seepage from the places that water inter to the farmland. Seepage in an earthen part of Baladeh channel with several gates was 71 times less than one from farmland channel. Sediment laden flow for years deposited a layer of fine sediment in Baladeh channel platform. Also, it seals outflow gates by leaving sediment behind the gates. Nowadays, the main purpose of adding sediment in flow is reducing the seepage from flow gates.