Small reservoirs, big impacts: sedimentation and storage-capacity loss in an urban reservoir (Frey Lake, Georgia)

Small anthropogenic reservoirs play critical geo-physical and socio-economic functions. While supporting habitat, managing floods, and trapping sediment, they are highly vulnerable to storage loss from sedimentation. Many studies have emphasized the need for better understanding of sedimentation in small reservoirs. This research quantified spatial patterns of sediment thickness and capacity loss in a small urban reservoir (Frey Lake, Kennesaw, Georgia). Field data from 60 measurement points were spatially interpolated using Empirical Bayesian Kriging (EBK) to map sediment distribution and estimate sediment volume and storage capacity loss. Original water storage capacity is estimated at 32,616 m3, with approximately 18,902 m3 of accumulated sediment, indicating approximately 55–58% loss of storage with 42% capacity remaining. EBK prediction accuracy was evaluated through iterative cross-validation, and storage-loss estimates proved stable across three synthetic sampling densities (n = 60, 580, and 2,953 points). Sediment is thickest near the dam, and available water volume in several smaller zones has been reduced by more than 70%. Such sediment trapping reduces downstream sediment supply, affecting channel morphology and sediment budgets. By characterizing the spatial pattern of sedimentation and storage-capacity loss, this study highlights the role of small reservoirs as major sediment sinks across the temperate Piedmont and similar eco-regions.