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Total suspended solids (TSS), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) loads were calculated for all stages of the dam removal process (dewatering, breaching, and removal) at various points upstream, within, and downstream of Lowell Mill Impoundment on the Little River, North Carolina. The impoundment dewatering exported loads of TSS, DOC, and TDN which were all 1–2 orders of magnitude less than loads associated with historic floods. Conversely, floods exiting the former impoundment following dam removal produced TSS, DOC, and TDN loads comparable to, but slightly greater (1.2–1.75 times) than historic floods. Exported loads were greatest following the complete removal of the dam, most...
Ecological and economic systems are open systems that require energy to change the thermodynamic states of materials from naturally occurring to more valued forms. These changes are accompanied by information flows and changes in the order of systems and their surroundings. In this paper, thermodynamics is used to assess these system changes and relate them to the knowledge present in a system. Particular emphasis is given to (1) the fundamental relationships among material, energy and information flows, and changes in order and knowledge, (2) the role of equilibrium and non-equilibrium thermodynamics in assessing system change, (3) the increasing role of material and energy flows through economic systems, and (4)...
We compared the relative influences of biochemical uptake processes and dynamic hydrology and geomorphology (hydrogeomorphology) on molybdate reactive phosphorus (MRP) retention within a stream. MRP concentrations were measured upstream and downstream of a 4.5-km reach undergoing dynamic channel adjustment in response to downstream dam removal. Geomorphic adjustments following removal produced measurable changes in velocity and depth, and decreases in MRP retention. Paired upstream and downstream measurements of MRP concentration were used to compute three retention metrics: uptake rate, mass transfer coefficient, and uptake length, which were used as model parameters. Modeling results showed that changes in channel...
Categories: Publication; Types: Citation
Although ?70 dams have been decommissioned in Wisconsin over the past 30 y, little is known about the physical and ecological effects of dam removal on riverine ecosystems. The purpose of our study was to document changes in channel form and macroinvertebrate assemblages following the removal of a low-head, run-of-river dam from the Baraboo River,Wisconsin, in January 2000. We surveyed cross sections and collected benthic macroinvertebrate samples in 6 reaches (an upstream reference reach, reaches immediately above and below the dam that was to be removed, and sequential unimpounded and impounded reaches further downstream) in a multiple-dam sys- tem. Surveys were conducted in December 1999, before dam removal,...
In this paper, we synthesize a series of small dam removal studies to examine how changes in channel form can affect riparian vegetation, fish, macroinvertebrates, mussels, and nutrient dynamics. Each of the ecosystem attributes responded to the disturbance of dam removal in different ways and recovered at very different rates, ranging from months to decades. Riparian vegetation appeared to require the greatest time for recovery, while macroinvertebrates had the least. Mussel communities were the most adversely affected group of species and showed no signs of recovery during the time period of the study. Based on these and other studies, we suggest that ecosystems may follow two trajectories of recovery following...
[1] We examined channel response following the removal of low-head dams on two low- gradient, fine- to coarse-grained rivers in southern Wisconsin. Following removal, channels eroded large quantities of fine sediment, resulting in deposition 3–5 km downstream. At one site (Baraboo River), upstream changes were rapid and included bed degradation, minimal bank erosion, and sediment deposition on channel margins and new floodplain. Sand was transported through the former impoundment and temporarily deposited downstream. At the second site (Koshkonong River), head-cut migration governed channel adjustments. A deep, narrow channel formed downstream of the head- cut, with negligible changes upstream of the head-cut. Fluvial...
Categories: Publication; Types: Citation