Study on Geotechnical and Agricultural Properties of Sediment Deposited in Tungabhadra Dam (Munirabad Lake)

Based on the comprehensive geotechnical and agricultural characterisation of sediment deposited in TB Dam (Munirabad Lake), the following conclusions are drawn:   • The sediment is classified as sandy silt (SM), with fine sand and silt fractions dominating the grain size distribution. Only 3.6% of particles are finer than 0.075 mm. • The natural water content (33.18%), specific gravity (2.41–2.53), liquid limit (31%), plastic limit (18%), plasticity index (13%), and shrinkage limit (7.21%) are characteristic of medium-plasticity silt of low to intermediate compressibility. • The optimum moisture content is 10.16%, indicating adequate compaction characteristics for potential use as fill or agricultural topsoil. • Agricultural analysis confirms that the sediment satisfies permissible ranges for all fourteen parameters tested, including pH, electrical conductivity, macronutrients (N, P, K), and trace metals. • The sediment is enriched in available nitrogen (340.6 kg/ha) and potassium (485.6 kg/ha), making it a valuable soil amendment for improving crop yields in the agricultural lands surrounding the TB Dam command area. • Lead contamination is absent (nil), and all other trace metals are within safe agricultural limits, confirming that the sediment poses no heavy metal toxicity risk to crops or soils. • The study demonstrates that TB Dam sediment can be profitably utilised for agricultural purposes. Planned desilting operations would simultaneously restore reservoir storage capacity (currently reduced by approximately 33 TMC due to sedimentation) and generate nutrient-rich soil amendment material, providing a dual environmental and agricultural benefit.

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