Evaluating the performances of surface drainage efficiency in left bank outfall drain (LBOD) at Sanghar component, Sindh

Rahim Bux Vistro, Munir Ahmed Mangrio, Abdul Ghafoor Siyal, Abdul Qudoos Abbasi, Aijiz Ali Ahpun and Rajesh Kumar Soothar

ABSTRACT    This study was conducted at Sanghar component of left bank outfall drain (LBOD) project for evaluating the efficiency of drainage system in terms of operation and maintenance. Makhi Branch Drain and Sanghar-1R drain were selected and their allied tubewells along with disposal channels for the system evaluation. The results showed that the operational efficiency of drainage tubewells was found very poor. The average operational efficiency was calculated as 24%, whereas the value of coefficient of variation of tubewell operational efficiency is greater than 0.30 and leads up to 0.90, which shows high variability in operation. The disposal channels are 88% efficient in terms of carrying the tubewell discharge into the main drain. This percentage is considered high in relation to the shorter length. Therefore, the losses from these channels under study were estimated as 2.5 million m3 of drainage effluent which directly diverts to the adjacent land and builds up upper surface salinity. The drainage efficiency of surface drains was observed to be very poor. Despite of being drained out from the study area, the drains were contributing a considerable amount of drainage effluent to the groundwater. However, thick vegetation in main and branch drains has proved the strong factor to retard the velocity of flow in the drain. Due to high vegetation the main and branch drains have been inefficient. The operational efficiency of tubewells should be increased by operating them at the design hours in order to drain out the recommended magnitude of water to lower down the water table. There is a severe need to maintain disposal channels by providing design slope and cross-section to prevent drainage water from overtopping into the agricultural lands. This channel is the first that directly harms the adjacent land. Moreover the longitudinal slope may be checked to maintain the regime of flow. © 2021 Department of Agricultural Sciences, AIOU

Keywords: Wheat productivity, Weeds, Weed dynamics, Yield

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