Particulate organic matter transport in the lower Colorado river,South-Western USA

The lower Colorado River from Laughlin, Nevada, to the border with Mexico is one of the most regulated rivers in North America. An analysis of particulate organic matter (POM) transport through the system was made to determine POM concentrations, composition and point of origin, as well as to determine the effect dams had on this transport. Particulate organic matter concentrations generally increased from upstream to downstream, and were dominated by very fine organic detritus (< 25μm size fraction). Reservoirs released more POM than they received during spring and summer, but less during autumn and winter. Reservoirs recycled POM, taking in organic detritus and discharging small limnoplankton. Backwater complexes functioned as filters during storm events, trapping coarse material and releasing fine material. Agricultural drains made only minor contributions of POM, but provided important nutrients for in-channel production of POM. Water diversions forced POM off-channel, whereas sluicing operations reduced inorganic loads in the canals. Despite the presence of six mainstem dams, the lower reaches support a diverse assemblage of detritivorous fishes, similar to that found in the lowermost reaches of natural, unregulated rivers. The food base for this fishery stems from autochthonous production of POM.     

Development of an Expert System for Selection of Dam Type on Alluvium Foundations

. A knowledge-based expert system was developed to aid in the selection of the type of dam. The dam type selector expert system (DTSA ES) was designed to determine the type of dam on the alluvium foundations. Detailed expert knowledge is required to estimate the type of dam and to develop an expert system. The DTSA ES utilizes rules of thumb used by an expert for determining the selection of the type of dam. The DTSA ES was developed using a shell program. The expert system was tested on several dam sites in order to validate the decision obtained. The use of this expert system, containing knowledge about the selection of dam type, can be helpful to students, potential owners or contractors in selecting dam types. The current prototype always needs additional parameters for more detailed analyses of new developments. However, the current DTSA ES is designed to include existing information about dam types.     

Institutional factors affecting fish passage in the Columbia River Treaty renegotiation

ABSTRACT

The United States and Canada have begun renegotiating the Columbia River Treaty, which is an international model for transboundary water governance. This paper identifies six institutional factors that will affect negotiations pertaining to fish passage during the renegotiation of the treaty: geographical advantage, issue linkage, a basin commission, the duration of agreements, negotiating autonomy and side payments. These factors and the methods used to determine them can be applied to other transboundary river basins where basin states have a history of transboundary resource governance. This analysis also serves as a policy-relevant resource for Columbia River Treaty negotiators and stakeholders.     

Sharing Rivers for Peace,Development, and Security

Abstract

Water is a finite resource, and with the considerable upsurge in population, urbanization, and industrialization, it is also becoming an increasingly scarce resource. Many countries in the world rely on river waters, and many of those rivers are shared by two or more countries. Dams on those rivers have been a major source of tensions, disputes, and, in some cases, even conflict between riparian countries because dams could result in massive diversion of river flows. Those developments have, inter alia, highlighted the relevance and importance of the principles of international water law, as reflected in the United Nations Convention on the Law of the Non-Navigational Uses of International Watercourses. The World Commission on Dams has also underscored the importance of, and elaborated on, those principles with regard to dams on shared rivers. This article discusses and analyzes the recommendations of the Commission in this area, and compares them with the principles of international water law as enunciated in the United Nations Convention     

Three-Degree-of-Freedom Rigid Model for Seismic Analysis of Cracked Concrete Gravity Dams

A rigid model with three-degrees-of-freedom is proposed for the purpose of seismic analysis of cracked concrete gravity dams. The model considers the geometry of the dam and all its possible modes of motion: sliding, rocking, rock-sliding, and drifting. The governing equations for all the modes are derived with the Mohr-Coulomb friction assumption at the crack, and corresponding conditions to initiate and maintain the modes are also given. For impact that follows rocking and drifting modes, postimpact velocities of the model are explicitly determined according to the momentum principle and the concept of restitution from classical point collision. Studies with the proposed model on rectangular blocks demonstrate two different types of rocking according to the slenderness. Applications to dams indicate that a large coefficient of friction does not necessarily prevent sliding, and rocking and drifting modes should not be neglected in estimating the stability of concrete gravity dams cracked at the base or at a height.     

Simplified Procedure for Estimating Earthquake-Induced Deviatoric Slope Displacements

A simplified semiempirical predictive relationship for estimating permanent displacements due to earthquake-induced deviatoric deformations is presented. It utilizes a nonlinear fully coupled stick-slip sliding block model to capture the dynamic performance of an earth dam, natural slope, compacted earth fill, or municipal solid-waste landfill. The primary source of uncertainty in assessing the likely performance of an earth/waste system during an earthquake is the input ground motion. Hence, a comprehensive database containing 688 recorded ground motions is used to compute seismic displacements. A seismic displacement model is developed that captures the primary influence of the system’s yield coefficient (ky), its initial fundamental period (Ts), and the ground motion’s spectral acceleration at a degraded period equal to 1.5Ts. The model separates the probability of “zero” displacement (i.e., ? 1?cm) occurring from the distribution of “nonzero” displacement, so that very low values of calculated displacement do not bias the results. The use of the seismic displacement model is validated through reexamination of 16 case histories of earth dam and solid-waste landfill performance. The proposed model can be implemented rigorously within a fully probabilistic framework or used deterministically to evaluate seismic displacement potential.     

Environmental issues of the three gorges project,China

This paper reviews several issues relating to the potential environmental impacts of a planned high dam at Three Gorges on the main course of the Changjiang (Yangtze River).