The use of reservoir sediments as environmental archives of catchment inputs and atmospheric pollution

Abstract

Lakes and reservoirs act as sinks for both catchment and atmospherically derived particulates and so their sediments can provide valuable information on temporal changes in these inputs. While the use of lake sediments as environmental archives is well established, reservoir sediments have less frequently been used as temporal records. Yet, for investigating pollution histories, reservoirs are ostensibly of greater interest: they are generally located close to urban and industrial sources of pollution and accumulate sediment rapidly and over similar time periods to major emissions of pollutants. The lack of interest in reservoir sediments stems from the perception that fluctuating water levels are likely to result in significant sediment disturbance. This perception is sustained, perhaps mistakenly, by a lack of research into reservoir sedimentary systems. There is, therefore, a need to review the available published research on reservoir sedimentation processes and patterns, the relatively few studies that have used reservoir sediments and relevant studies from the lake-sediment literature, and thus critically evaluate the potential and problems of using reservoir sediments as temporal records of pollution. Current understanding of the processes of sedimentation and resulting distributions are reviewed. Some significant differences between sedimentation in lakes and reservoirs are highlighted and the implications for sampling and interpretation of sedimentary records discussed. It is suggested that, at present, a valuable resource is being underutilized and it is demonstrated that, where sediment deposition patterns are taken into account, reservoir sedimentary records can provide important data for reconstructing past atmospheric and catchment pollutant inputs

Examining Storage Capacity Loss and Sedimentation Rate of Large Reservoirs in the Central U.S. Great Plains

“…Consequently, our sediment yield estimates likely are biased low to some degree, considering that smaller upstream impoundments are trapping some sediment that otherwise might have found its way into the downstream KS-FdR. Nonetheless, with KS-FdR found to have >90% sediment trapping efficiency [42][43][44][45] and existing at a much larger scale than all other upstream impoundments, this approach to watershed boundary determination is expected to result in a reasonably accurate estimate of sediment yield for the KS-FdR watersheds. From the most recent survey and watershed extent data in addition to the original surveys, we estimated sediment yield, annual depletion rate, and reservoir half-life (when the reservoir conservation pool is half full of sediment) for the KS-FdR (Table 1) [46].…”

Diatoms as indicators of ecological change in freshwater reservoirs of South East Queensland

“…Diatoms from the planktonic zone will be more indicative of the water quality of the reservoir than diatoms collected in 84 the littoral zone. Secondly, reservoirs as water supply systems experience large fluctuations in water level that are greater than natural systems (Shotbolt et al 2005). During drought conditions the water level of reservoirs can recede to the historic river channel and during large floods the reservoirs fill to capacity.…”

“…Reservoirs are created for many purposes including water supply, river control and flood mitigation (Chapman 1996, Wetzel 2001, Shotbolt et al 2005, Tundisi and Tundisi 2012.…”

“…In contrast, reservoirs are challenging environments to apply paleolimnological techniques because they have complex hydrology (Wetzel 2001) and often large fluctuations in water level (Shotbolt et al 2005). These fluctuations have the potential to disrupt the sediment record (Shotbolt et al 2001) by resuspending and transporting sediment previously deposited in the reservoir (Effler and Matthews 2004) in addition to transporting sediment into the reservoir from the catchment.…”

“…This is especially so in subtropical and tropical regions, that experience episodic rainfall. During major inflow events, sediments eroded from the catchment, including the channel systems in the upper reaches of the reservoir may be scoured and carried further in the main body of the reservoir (Shotbolt et al 2005). These sediments are generally deposited within the deeper basins of the reservoir, and result in allochthonous material being recorded in sediment cores that is not representative of the overlying historical water column Pb as a viable option for sediment dating include changes in sedimentation rates, variation in grain size and groundwater movement into the reservoir (Wasson et al 1987).…”