The economics of using sediment-entrapment reduction measures in lake and reservoir design

One of the most important impacts of building and maintaining a reservoir is the loss of storage capacity caused by sediment deposition behind the dam. Sediment deposition in the reservoir reduces the water storage volume and decreases or even negates the utility of the dam, and deteriorates the water quality. The loss of utility of a reservoir as a result of sedimentation or siltation can be considered an economic, environmental, and even a design failure. The objective of this study was to investigate, through an extensive literature search, the suitability and efficiency of several reservoir sedimentation reduction measures practiced in small- and medium-sized lakes. Some of the methods successfully used for reducing sediment entrapment in reservoirs were watershed management, building check dams, bypassing sediment-laden flows, using density currents, flood flushing, drawdown flushing, flushing and emptying, siphoning, and dredging. The mitigation and operation methods so identified were evaluated with respect to their rate of success, cost, environmental impacts, and ease of implementation or retrofitting. The economies expected in using the identified alternative mitigative measures versus more conventional reservoir design were investigated in terms of reduced initial cost of reservoir and/or dredging costs.U.S. Department of the InteriorU.S. Geological SurveyOpe

City of Charleston public water supply: analysis of drought yields from the Charleston side-channel reservoir

"Prepared for the City of Charleston.""April 1996.

Microflares in accretion disks

We have investigated the phenomenon of explosive chromospheric evaporation from an accretion disk as a mechanism for fast variability in accreting sources such as low mass X-ray binaries and active galactic nuclei. This has been done in the context of advection dominated accretion flows, allowing both high and low states to be considered. This mechanism can in principle produce sub-millisecond timescales in binaries and sub-minute timescales in active galaxies. However, even considering the possibility that large numbers of these microflares may be present simultaneously, the power emitted from these microflares probably amounts to only a small fraction of the total X-ray luminosity.Comment: 5 pages, 1 figure, uses older A&A class file; accepted for publication in A&

Benthic sediment conditions and remediation alternatives for Horseshoe Lake, Alexander County

"Office of River Water Quality.""February 1997.""Office of Surface Water Resources: Systems, Information & GIS.""Contract Report 607"--Cover."Prepared for the Division of Fisheries, Illinois Dept. of Natural Resources.

Managed flood storage option for selected levees along the lower Illinois River for enhancing flood protection, agriculture, wetlands, and recreation: Second report, validation of the UNET model for the lower Illinois River

"March 1997.""A division of the Illinois Department of Natural Resources.

Low-flow estimates for Cedar Creek at Galesburg, Illinois

"September 1995.""Prepared for the Galesburg Sanitary District, Galesburg, Illinois.

Basinwide instream flow assessment model to evaluate instream flow needs

Quantification of sufficient or minimum flows needed to sustain the aquatic habitat is necessary for satisfactory resolution of water use conflicts and planning of water allocation strategies. The Instream Flow Group (IFG) of the U.S. Fish and Wildlife Service has developed a methodology to gage the quantity of suitable habitat in a stream. Application of the methodology requires information on the local variations of depth and velocity in a stream reach. Conventional flow models are inadequate for this application, and evaluation of aquatic habitats requires extensive field work. Results obtained in a study reach cannot be applied to other reaches with dissimilar areas. To address the problem of defining the local variation of depths and velocities for regional habitat evaluation, a probabilistic flow model is developed. The probabilistic model incorporates hydraulic geometry relationships to evaluate average flow parameter values without the necessity of field observations. Local variations of depth and velocity values are evaluated from probability distribution models developed from field data collected on the Sangamon and South Fork Sangamon River basins. The flow model simulation for calculating stream habitat suitability with the IFG methodology is illustrated.U.S. Geological SurveyU.S. Department of the InteriorOpe

Reversible plasticity in amorphous materials

A fundamental assumption in our understanding of material rheology is that when microscopic deformations are reversible, the material responds elastically to external loads. Plasticity, i.e. dissipative and irreversible macroscopic changes in a material, is assumed to be the consequence of irreversible microscopic events. Here we show direct evidence for reversible plastic events at the microscopic scale in both experiments and simulations of two-dimensional foam. In the simulations, we demonstrate a link between reversible plastic rearrangement events and pathways in the potential energy landscape of the system. These findings represent a fundamental change in our understanding of materials--microscopic reversibility does not necessarily imply elasticity.Comment: Revised pape

Waves in the solar photosphere

The solar photosphere is a partially ionized medium with collisions between electrons, various metallic ions and neutral hydrogen playing an important role in the momentum and energy transport in the medium. Furthermore, the number of neutral hydrogen atom could be as large as $10^{4}$ times the number of plasma particles in the lower photosphere. The non-ideal MHD effects, namely Ohm, Ambipolar and Hall diffusion can play an important role in the photosphere. We demonstrate that Hall is an important non-ideal MHD effect in the solar photosphere and show that Hall effect can significantly affect the excitation and propagation of the waves in the medium. We also demonstrate that the non-ideal Hall dominated inhomogeneous medium can become parametrically unstable, and it could have important ramification for the photosphere and chromosphere of the sun. The analysis hints at the possibility of solar photosphere becoming parametrically unstable against the linear fluctuations.Comment: 5 Figures and 1 table, accepted for publication in MNRA