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61.
ABSTRACT: We evaluated the effectiveness of watershed‐scale implementations of best‐management practices (BMPs) for improving habitat and fish attributes in two coldwater stream systems in Wisconsin. We sampled physical habitat, water temperature, and fish communities in multiple paired treatment and reference streams before and after upland (barnyard runoff controls, manure storage, contour plowing, reduced tillage) and riparian (stream bank fencing, sloping, limited rip‐rapping) BMP installation in the treatment subwatersheds. In Spring Creek, BMPs significantly improved overall stream habitat quality, bank stability, instream cover for fish, abundance of cool‐ and coldwater fishes, and abundance of all fishes. Improvements were most pronounced at sites with riparian BMPs. Water temperatures were consistently cold enough to support coldwater fishes such as trout (Salmonidae) and sculpins (Cottidae) even before BMP installation. We observed the first‐time occurrence of naturally reproduced brown trout (Salmo trutta) in Spring Creek, indicating that the stream condition had been improved to be able to partially sustain a trout population. In Eagle Creek and its tributary Joos Creek, limited riparian BMPs led to localized gains in overall habitat quality, bank stability, and water depth. However, because few upland BMPs were installed in the subwatershed there were no improvements in water temperature or the quality of the fish community. Temperatures remained marginal for coldwater fish throughout the study. Our results demonstrate that riparian BMPs can improve habitat conditions in Wisconsin streams, but cannot restore coldwater fish communities if there is insufficient upland BMP implementation. Our approach of studying multiple paired treatment and reference streams before and after BMP implementation proved effective in detecting the response of stream ecosystems to watershed management activities.  相似文献   
62.
ABSTRACT: The number of stream restoration and enhancement projects being implemented is rapidly increasing. At road crossings, a transition must be created from the restored channel through the bridge or culvert opening. Given conflicting design objectives for a naturalized channel and a bridge opening, guidance is needed in the design of the transition. In this paper we describe the use of vanes, cross vanes, and w‐weirs, commonly used in stream restoration and enhancement projects, that may provide an adequate transition at bridges. Laboratory experiments were conducted on vanes and cross vanes to provide a transition for single span bridge abutments and on w‐weirs to provide a transition for double span bridges which have a pier in mid‐channel. The results of the experiments provided design criteria for transitions using each of the three structures. Prior field experience provided guidance on appropriate applications in terms of the stream and bridge characteristics.  相似文献   
63.
ABSTRACT: Many urban and suburban communities in the Midwest are seeking to establish sustainable, morphologically and hydraulically varied, yet dynamically stable fluvial systems that are capable of supporting healthy, biologically diverse aquatic ecosystems — a process known as stream naturalization. This paper describes an integrated research program that seeks to develop a scientific and technological framework to support two stream naturalization projects near Chicago, Illinois. The research program integrates theory and methods in fluvial geomorphology, aquatic ecology, hydraulic engineering and social theory. Both the conceptual and the practical challenges of that integration are discussed. Scientific and technical support emphasize the development of predictive tools to evaluate the performance of possible naturalization designs at scales most appropriate to community based projects. Social analysis focuses on place based evaluations of how communities formulate an environmental vision and then, through decision making, translate this vision into specific stream naturalization strategies. Integration of scientific and technical with social components occurs in the context of community based decision making as the predictive tools are employed by project scientists to help local communities translate their environmental visions into concrete environmental designs. Social analysis of this decision making process reveals how the interplay between the community's vision of what they want the watershed to become, and the scientific perspective on what the watershed can become to achieve the community's environmental goals, leads to the implementation of specific stream naturalization practices.  相似文献   
64.
CO2 storage capacity estimation: Methodology and gaps   总被引:3,自引:0,他引:3  
Implementation of CO2 capture and geological storage (CCGS) technology at the scale needed to achieve a significant and meaningful reduction in CO2 emissions requires knowledge of the available CO2 storage capacity. CO2 storage capacity assessments may be conducted at various scales—in decreasing order of size and increasing order of resolution: country, basin, regional, local and site-specific. Estimation of the CO2 storage capacity in depleted oil and gas reservoirs is straightforward and is based on recoverable reserves, reservoir properties and in situ CO2 characteristics. In the case of CO2-EOR, the CO2 storage capacity can be roughly evaluated on the basis of worldwide field experience or more accurately through numerical simulations. Determination of the theoretical CO2 storage capacity in coal beds is based on coal thickness and CO2 adsorption isotherms, and recovery and completion factors. Evaluation of the CO2 storage capacity in deep saline aquifers is very complex because four trapping mechanisms that act at different rates are involved and, at times, all mechanisms may be operating simultaneously. The level of detail and resolution required in the data make reliable and accurate estimation of CO2 storage capacity in deep saline aquifers practical only at the local and site-specific scales. This paper follows a previous one on issues and development of standards for CO2 storage capacity estimation, and provides a clear set of definitions and methodologies for the assessment of CO2 storage capacity in geological media. Notwithstanding the defined methodologies suggested for estimating CO2 storage capacity, major challenges lie ahead because of lack of data, particularly for coal beds and deep saline aquifers, lack of knowledge about the coefficients that reduce storage capacity from theoretical to effective and to practical, and lack of knowledge about the interplay between various trapping mechanisms at work in deep saline aquifers.  相似文献   
65.
ABSTRACT: The method of identifying dry stream reaches in carbonate terrane as surface indicators of potential ground-water reservoirs offers a valuable exploration technique that is more rapid and less expensive than traditional exploration methods involving random test drilling. In areas where dry stream reaches occur, subsurface drainage successfully competes with surface drainage, and sheet-like dissolution openings have developed parallel to bedding creating the ground-water reservoir. The occurrence and hydraulic characteristics of such reservoirs are highly variable, as attested to by the wide range of well yields. Union Hollow in south-central Tennessee is the setting for a case study that illustrates the application of the dry stream reach technique. In this technique, dry stream reach identification is based on two types of readily acquired information: (1) remotely sensed black and white infrared aerial photography; and (2) surface reconnaissance of stream channel characteristics. Test drilling in Union Hollow subsequent to identification of the dry reach proved that a localized ground-water reservoir was present.  相似文献   
66.
ABSTRACT: Geographic Information Systems (GIS) were used to assess the relationships between land use patterns and the physical habitat and macroinvertebrate fauna of streams within similar sized watersheds. Eleven second or third order watersheds ranging from highly urbanized to heavily forested were selected along Lake Superior's North Shore. Land use patterns within the watersheds were quantified using readily available digital land use/land cover information, with a minimum mapping resolution of 16 ha. Physical habitat features, describing substrate characteristics and stream morphology, were characterized at sample points within each stream. Principle component and correlation analyses were used to identify relationships between macroinvertebrates and stream physical habitat, and between habitat and land use patterns. Substrate characteristics and presence of coarse woody debris were found to have the strongest correlations with macreinvertebrate assemblage richness and composition. Agricultural and urban land use was correlated with substrate characteristics. Algal abundance, associated with macroinvertebrate compositional differences, was correlated with housing density and non-forest land covers. The use of readily available spatial data, even at this relatively coarse scale, provides a means to detect the primary relationships between land use and stream habitat quality; finer-resolution GIS databases are needed to assess more subtle influences, such as those due to riparian conditions.  相似文献   
67.
ABSTRACT: Detailed studies of long-term management impacts on rangeland streams are few because of the cost of obtaining detailed data replicated in time. This study uses government agency aquatic habitat, stream morphologic, and ocular stability data to assess land management impacts over four years on three stream reaches of an important rangeland watershed in northwestern Nevada. Aquatic habitat improved as riparian vegetation reestablished itself with decreased and better controlled livestock grazing. However, sediment from livestock disturbances and road crossings and very low stream flows limited the rate of change. Stream type limited the change of pool variables and width/depth ratio, which are linked to gradient and entrenchment. Coarse woody debris removal due to previous management limited pool recovery. Various critical-element ocular stability estimates represented changes with time and differences among reaches very well. Ocular stability variables tracked the quantitative habitat and morphologic variables well enough to recommend that ocular surveys be used to monitor changes with time between more intensive aquatic surveys.  相似文献   
68.
The solution chemistry of forested streams primarily in western North America is explained by considering the major factors that influence this chemistry — geological weathering; atmospheric precipitation and climate; precipitation acidity; terrestrial biological processes; physical/chemical reactions in the soil; and physical, chemical, and biological processes within streams. Due to the complexity of all these processes and their varying importance for different chemicals, stream water chemistry has exhibited considerable geographic and temporal variation and is difficult to model accurately. The impacts of forest harvesting on stream water chemistry were reviewed by considering the effects of harvesting on each of the important factors controlling this chemistry, as well as other factors influencing these impacts ‐ extent of the watershed harvested, presence of buffer strips between streams and harvested areas, nature of post‐harvesting site preparation, revegetation rate following harvesting, pre‐harvesting soil fertility, and soil buffering capacity. These effects have sometimes reinforced one another but have sometimes been counterbalancing or slight so that harvesting impacts on stream water chemistry have been highly variable. Eight major knowledge gaps were identified, two of which — a scarcity of detailed stream chemical budgets and knowledge of longitudinal variation in stream chemistry — relate to undisturbed streams, while the remainder relate to forest harvesting effects.  相似文献   
69.
ABSTRACT: In urbanizing areas, the usual increase in flood flows also increases erosional capability of streams. In order to evaluate such tendencies quantitatively, 25 stream reaches were studied, and were classified as to whether erosion of the channel and banks was light, medium, or heavy. Analysis of characteristics indicated that (1) densely developed areas are correlated with greater erosion, (2) wide stream buffers of natural vegetation are correlated with lesser erosion, and (3) there is no definite correlation of erosion to slope or characteristics of soil. Erosional stream instability can be avoided by retention of storm water runoff, creating additional channel roughness or reducing channel slope during floods by drop structures, such as culverts, which restrict flow. Channel straightening and general bank protection should be minimized in such streams. Design of culverts should take such effects into consideration.  相似文献   
70.
The agricultural production from the Lower South Platte Basin in Colorado represents a significant portion of the state economy. Until the early 1950's the production had developed almost exclusively by use of river water. Drought conditions combined with improved well technology resulted in an inordinate amount of well development in the valley during the period 1952-56. These wells were used for supplemental supply in many cases, but the application of sprinkler irrigation brought many acres of here-to-fore dry land into irrigated production. As a result of the vast amounts of groundwater withdrawal by the newly developed wells, senior surface appropriators found a decreasing amount of water available for use in the streams. The legislature, observing the doctrine of prior appropriation, ruled that all surface and ground water in a tributary would be treated and administered as one resource. This, of course, spelled doom for the well-oriented segment of the economy. Analysis of a segment of the river on an inflow-outflow basis was made with careful determination of all inflow-outflow in the study reach to include correlations required to determine ungaged side-channel in-flow and unmetered irrigation wells. Results indicate that wells have intercepted normal return flows to the river resulting in a decreased amount of surface water during the irrigation season. Stream depletion appears to equal the expected consumptive use of well water which ranged between 40% to 50% of the groundwater extraction.  相似文献   
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