Variations in Water and Deposited Sediment Qualities in the Tidal River Basins of Bangladesh and Their Implications for TRM Success

Abstract

The tidal river management (TRM) in coastal areas of Bangladesh has been successful in varying degrees. Though there are many studies on the social, institutional, hydrological and hydraulic factors in relation to TRM, there is no study that investigated the relationship between the water and soil qualities and the TRM success. This paper investigates the variations of water and deposited sediment qualities vis-à-vis the TRM success in selected tidal basins in the southwest coastal delta of Bangladesh. The basins were selected based on the level of success in TRM operation: Beel Bhaina (a successful TRM), East Beel Khuksia (a partially successful TRM), and Beel Pakhimara (an unsuccessful TRM). The level of success in TRM was decided from the local community’s perception and how the TRM operation reduced the drainage congestion and increased the sedimentation depth inside a tidal basin. Fifteen water quality parameters with seven indices and eight soil quality parameters were analyzed to evaluate their suitability for agricultural purposes. The analysis reveals that the water of Beel Bhaina and East Beel Khuksia has high salinity, TDS, TSS, SAR and Na% than that of Beel Pakhimara due to the presence of an active tidal current. The most dominant cation is Na+ in almost all the water samples due to the seawater influence. The most dominant anion is Cl− in Beel Bhaina and East Beel Khuksia, and HCO3− in Beel Pakhimara. The deposited sediment quality parameters are worse in the dry season than in the monsoon, except for organic matter. The soil EC of Beel Bhaina and East Beel Khuksia is low, which may be one of the reasons for good yield in these basins. The average yields of boro rice were 7.2, 7.7 and 6.4 ton/ha in Beel Bhaina, East Beel Khuksia and Beel Pakhimara, respectively, which might be related to the quality of the deposited sediment in the tidal basins and also to the level of TRM success.