Reservoir Sediment Carbon along the Elwha River after Dam Removal

Abstract

Worldwide, numerous dams are aging and will either need to be replaced or removed within the next few decades. Little is understood about the fate of carbon stored in sediments that become soil when a reservoir is drained due to dam removal. This study assessed the pool of carbon in the sediments of former Lake Mills and Lake Aldwell of the Elwha River. Carbon storage was mapped spatially and by depth. Sediment carbon was also compared with forest soil carbon from former glacial lake sediments. This dam removal project, the largest-known of its kind to date, provides important information regarding the fate of carbon in sediment pools and potential fluxes when reservoir sediments become soil.