Analytical Solutions to the Linearized Boussinesq Equation for Assessing the Effects of Recharge on Aquifer Discharge1

Boggs, Kevin G., Robert W. Van Kirk, Gary S. Johnson, Jerry P. Fairley, and P. Steve Porter, 2010. Analytical Solutions to the Linearized Boussinesq Equation for Assessing the Effects of Recharge on Aquifer Discharge. Journal of the American Water Resources Association (JAWRA) 46(6):1116–1132. DOI: 10.1111/j.1752-1688.2010.00479.x Abstract: There is a need to develop a general understanding of how variations in aquifer recharge are reflected in discharge. Analytical solutions to the linearized Boussinesq equation governing flow in an unconfined aquifer provide a unified mathematical framework to quantify relationships among lag time, attenuation and distance between aquifer recharge and discharge and the effect of an up-gradient no-flow boundary. We applied this framework to three types of recharge: (1) instantaneous, (2) periodic, and (3) constant rate for a finite duration. When the temporal scale of recharge exceeds the diffusive aquifer time scale, recharge will be reflected in discharge quickly and with little attenuation. When aquifer time scale is large, most recharge events are shorter in scale than that of the aquifer, resulting in large attenuation. Attenuation is more sensitive to boundary effects than lag time, and boundary effects increase as recharge time scale increases. Boundary effects can often be ignored when the recharge source is farther than 1/3 of the domain length away from the no-flow boundary. We illustrate analytical results with application to the economically critical Eastern Snake River Plain Aquifer in Idaho. In this aquifer, detectable annual and decadal cycles in discharge can result from recharge no farther than 20 and 60 km away from the discharge point, respectively. The effects of more distant, long-term recharge can be detected only after a time lag of several decades.     

NOx Reduction in a Gas Fired Utility Boiler by Combustion Modifications

Data on the effect of several combustion modifications on the formation of nitrogen oxides and on boiler efficiency were acquired and analyzed for a 110 MW gas fired utility boiler. The results from the study showed that decreasing the oxygen in the flue gas from 2.2% to 0.6% reduced the NO_x formation by 33% and also gave better boiler efficiencies. Flue gas recirculation through the bottom of the firebox was found to be ineffective. Staged combustion was found to reduce the NO_x emissions by as much as 55 % while decreasing the efficiency by about 5%. Adjustment of the burner air registers reduced the NO_x formation by about 20 ppm. The lowest NO_x emissions of 42 ppm (at about 3% O₂) in the stack was obtained for air only to one top burner and 0.5% oxygen in the flue gas.     

Reactive nitrogen and public policies for environmental protection

A core goal of both US and European pollution control policies has been to establish rules and regulations pertaining to the movement of reactive-nitrogen (Nr) through the environment. This is manifest in US federal legislation such as the Clean Air Act Amendments and the Clean Water Act Amendments and in various protocols of the United Nations Economic Commission for Europe (UNECE) and its Convention on Long-Range Transboundary Air Pollution (CLRTAP). In this paper, we begin by reviewing the two US laws and their effectiveness and make some comparisons with the approaches used mainly in Europe by the UNECE and CLRTAP. Next we use the Mississippi drainage/Gulf of Mexico hypoxia case study to highlight the importance of applying a "systems approach" to address the reactive nitrogen problem at the regional scale. After briefly posing a number of unanswered questions related to nitrogen control policies, we conclude by sketching a blueprint for future actions related to the development of improved policies to regulate reactive nitrogen.     

SOME CONJUNCTIVE DESALTING STUDIES EN THE UNITED KINGDOM1

ABSTRACT .Operating rule procedures are developed for the optimal use of desalination in conjunction with surface water impoundments. Results obtained from the use of hill-climbing and dynamic programming methods are compared. Benefits to be obtained from the integrated use of desalination are demonstrated through a case study for the Barcelona area of Spain.     

Community-based Disaster Management During the 1997 Red River Flood in Canada

This paper examines the relationship between community preparedness and response to natural disaster and their level and pattern of community development. This is done by investigating preparation and response to the 1997 Red River Flood by three rural communities in Manitoba, Canada. The communities were selected because of their different ethnic mix and associated level and pattern of community development. The hypothesis was supported that the level and pattern of community development affect community capacity to respond to flooding. Communities characterised by higher levels of physical, human and social capital were better prepared and more effective responders to the flood. However, where the pattern of community development was characterised by high levels of social capital, decision-making processes were complicated.     

State of the marine environment at Little Bay Arm,Newfoundland and Labrador,Canada, 10 years after a "do nothing" response to a mine tailings spill

In 1989, the tailings pond dam at the site of a former copper mine near Little Bay, Newfoundland and Labrador, Canada, ruptured and tailings spilled into Little Bay Arm. At the time, no action was taken to arrest the flow of tailings or to mitigate the effects of the spill. To date, no action has been taken to repair the dam and tailings continue to flow into Little Bay Arm. As a result, the marine environment around Little Bay Arm has become contaminated with heavy metals from the tailings. However, the tailings are not the only source of heavy metals to the ecosystem. An old slag heap and what is presumably concentrated copper ore spilled during the loading of ore freighters, are also contributing to the ecosystem's metal load. Marine sediment throughout the Arm contained elevated concentrations of Cu, Ni, Zn, As, V, Co, and Mn. Beach material also contained elevated concentrations of metals with material near the slag heap being the most contaminated. At this site, Cu concentrations were in excess of 5000 mg kg(-1) dry weight, Zn greater than 3000 mg kg(-1) and Co concentrations exceeded 700 mg kg(-1). The highest concentrations of metals in biota were found near the slag heap, near the tailings dam breach, and at the site of the former concentrate loading dock. Despite elevated metal concentrations, the tailings and nearby sediment were not devoid of life. Bivalves and seaweed were abundant in the area and there were no obvious signs of tissue damage or disease in soft shell clams (Mya arenaria) living in the tailings. These clams may be suffering from chronic exposure to the tailings, however, evidence of lipid peroxidation in the clams was inconclusive.     

Simulation modeling and resource management

Simulation models are becoming increasingly important as tools for synthesizing and applying information in almost all aspects of land management. They are particulary valuable for predicting and comparing outcomes of alternative decisions and assumptions. Models also permit managers to consider and integrate the potential influences of a large number of variables.     

Human impact on beach and foredune vegetation of North Padre Island,Texas

Vehicular and pedestrian traffic decreased top and root production, percent cover, and diversity of vegetation, and modified species composition on beach and foredune areas of Padre Island National Seashore and Nueces County Park. Degradation of vegetal cover was directly related to the type and intensity of traffic; species in heavily trafficked areas represented earlier successional stages than those in comparable undisturbed areas.