Modelling reservoir sedimentation and estimating historical deposition rates using a data-based mechanistic (DBM) approach

The data-based mechanistic (DBM) modelling methodology is applied to the st udy of reservoir sedimentation. A lumped-parameter, discrete-time model has been developed which directly relates rainfall to suspended sediment load (SSL) at the reservoir outflow from the two years of measured data at Wyres dale Park Reservoir (Lancashire, UK). This nonlinear DBM model comprises tw o components: a rainfall to SSL model and a second model, relating the SSL at the reservoir inflow to the SSL at the reservoir spillway. Using a daily measured rainfall series as the input, this model is used to reconstruct d aily deposition rates between 1911 and 1996. This synthetic sediment accret ion sequence is compared with the variations in sand content within sedimen t cores collected from the reservoir floor. These profiles show good genera l agreement, reflecting the importance of low reoccurrence, high magnitude events. This preliminary study highlights the potential of this DBM approac h, which could be readily applied to other sites.