RESUSPENSION OF SEDIMENT BY FOCUSED GROUNDWATER IN LAKE BANYOLES

Resuspension of sediment by subterranean springs occurs in karstic, multibasin Lake Banyoles, Spain. The sediment at the bottom of one of the basins was consolidating when intrusion of groundwater caused resuspension. Here, the lutocline rose nearly 20 m over 10 months. During this episode temperature profiles, sediment size distributions, bulk density, and settling rates showed that the jet-generated turbulence produced strong mixture in the central core of the conic depression forming the basin. Data from another basin where the sediment was always in suspension are presented for comparison. Here, the stratification in density and settling rate of the particles suggest sorting out of the aggregates, with the largest flocs occupying the deepest parts of the basin.