Sediment particles, a product of erosion in the catchment are transported along the river with flowing water. The construction of Weir, barrage or a dam causes obstruction to the flow resulting in reduction of velocity. The reduced velocity causes sedimentation resulting in reduction of storage capacity which affects the overall life of the reservoir. The sediment deposition in the reservoir is a continuous and complex process which affects the useful life of a reservoir. The quantification of sediment deposition in a reservoir is necessary for effective reservoir and river basin management. The present study has been carried out to assess sediment deposition in Koyna Reservoir which is located in the Western Maharashtra, India. In India most of the rainfall is caused due to the southwest monsoon during the period from June to September, massive convective thunderstorms dominate the weather. In the present study analytical methods are used for estimation of sediment deposited in the Koyna reservoir. For the prediction annual inflow data is used. The storage capacity of Koyna reservoir is calculated considering the loss of storage due to sediment deposition for a period from 1961 to 2375. The results obtained indicated a loss of reservoir capacity by the year 2004, as 267.25 Mm 3 (9.55%). The physical measurement indicated that the Koyna reservoir had lost 293.09 Mm 3 (10.48%) of its capacity by the year 2004. The results obtained by analytical method have 8.82% error compared with the actual measurements.

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Watershed development and management plans are very important for surface and groundwater conservation. To prepare a watershed development plan, it becomes important to know the topography, lithology, erosional status and drainage pattern of the area. In the present investigation various morphometric parameters of the Bhogavati river basin are outlined. The Bhogavati river basin is 5th order and shows dendritic to sub-dendritic type drainage pattern. The elongation and circulatory ratio reveals that the Bhogavati river basin is highly elongated and flood flows are easier to manage than that of circulatory basins. The bifurcation ratio reveals that the basin is not having any structural control. The highest number (69) and longest length (99.8 km) of lineament is oriented in NWW-SEE sector while lowest number (32) in NE-SW sector and shortest length (32.6 km) of lineament oriented in NNE-SSW sector. The hypsometric curves suggest that basin is in late youth to early mature stage of the fluvial geomorphic cycle.

In southern part of India, most of the precipitation occurs due to south-west monsoon during the months of June to September. Storage reservoirs are constructed to store the run-off volume and utilize it for long term requirements in the command such as irrigation, power generation, domestic water supply etc. The sediment deposition in the reservoir is a continuous and complex process. Sediment in a river which originates from the land erosion process in the catchment is propagated along with the river flow and finally gets deposited in the reservoir. This has adverse effect such as reduction in storage capacity and increase in backwater levels. For the long term and yearly planning of efficient utilization of reservoir capacity, estimation of sediment deposit is not only sufficient but also estimation of trapped sediment at different levels in the reservoir is required. Differential Global Positioning System (DGPS) based Integrated Bathymetric Survey System for hydrographic survey is used for estimation of sediment deposition pattern in the Koyna reservoir. In this method three or more satellite based GPS receivers are used in differential mode for positioning. Ecosounder is used for depth measurements. GPS reference receiver is located at a known latitude and longitude position and GPS mobile receiver is located on the survey boat. Both the GPS operate in differential mode through a communication link. From this study (2004) it is observed that sedimentation rate in Koyna reservoir is more than 6.5 Ham/100 sq.km/year anticipated in 1949.