Sediment resuspension in a shallow lake

Different mathematical formulations for the computation of the entrainment rate of sediment into suspension in lakes can produce widely disparate results under a given set of conditions, leading to problematic interpretation. In this paper, the results of a 4-month field campaign on sediment resuspension in a large, shallow, hypereutrophic lake in southern California are presented. The field measurement program included the observation of currents and waves using a Nortek acoustic wave and current (AWAC) profiler, the observation of water temperatures using a thermistor chain, the use of optical backscatter sensors for the measurement of turbidity, a surrogate for suspended sediment concentration, and the use of meteorological data. The paper reports one of the first field experiments in lakes using the AWAC, whose signal strength has not been investigated in detail to date, and the correlation of a set of variables coming from different sources during a relatively long period of time. The contributions of different forcing mechanisms ( waves, currents, and surface seiches) to the sediment resuspension in the lake are quantified, and the signal strength of the AWAC is used to address the vertical distribution of sediment in the water column. A novel relationship between the AWAC's backscatter intensity and turbidity is presented. Turbidity was found to be proportional to w(K), where w is the wind speed measured at 2 m and K ranged from 4.5 to 6.5, depending on the water depth. Finally, the results of modeling the sediment entrainment into suspension in the Salton Sea are shown to be well represented by an extension of the Garcia and Parker formula.