Dataset for: Sediment and Nutrient Transport Through a Reservoir Sequence Along a Large River System

Abstract

Reservoirs are highly effective at sequestering both sediments and sediment-bound nutrients, such as silts and phosphorus (P), but are also capable of depositing significant quantities of nutrients with more complex biogeochemical pathways, like nitrogen (N). Because of the growing prevalence of human altered watersheds and regulated rivers, there is a growing need to understand how reservoirs function both individually and as reservoir sequences within large rivers and their watersheds. Models have simulated the overall efficiency and drivers of reservoir nutrient deposition, but few have considered how a sequence of reservoirs alter deposition as an interconnected watershed-sediment-transport-system. In this study, we collected sediment cores from a six-reservoir sequence along a 5th – 6th order stream receiving treated waters from a large metropolitan area in the Southeast United States. Using paleolimnological techniques, we compared nutrient deposition to reservoir morphological qualities and primary producer community structure during the past ~50 years. Our findings suggest phosphorus deposition is associated with reservoir order downstream of the primary nutrient source, nitrogen deposition is linked to reservoir water retention time, and N:P is most strongly linked to reservoir surface area and watershed population density. Our results were strongly influenced by a large upstream and metropolitan nutrient source, fairly common in large rivers, but under different conditions of nutrient loading, reservoirs may express other nutrient depositional patterns.