COLD WATER PATCHES IN WARM STREAMS: PHYSICOCHEMICAL CHARACTERISTICS AND THE INFLUENCE OF SHADING1

ABSTRACT: Discrete cold water patches within the surface waters of summer warm streams afford potential thermal refuge for cold water fishes during periods of heat stress. This analysis focused on reach scale heterogeneity in water temperatures as influenced by local influx of cooler subsurface waters. Using field thermal probes and recording thermistors, we identified and characterized cold water patches (at least 3°C colder than ambient streamflow temperatures) potentially serving as thermal refugia for cold water fishes. Among 37 study sites within alluvial valleys of the Grande Ronde basin in northeastern Oregon, we identified cold water patches associated with side channels, alcoves, lateral seeps, and floodplain spring brooks. These types differed with regard to within floodplain position, area, spatial thermal range, substrate, and availability of cover for fish. Experimental shading cooled daily maximum temperatures of surface waters within cold water patches 2 to 4°C, indicating a strong influence of riparian vegetation on the expression of cold water patch thermal characteristics. Strong vertical temperature gradients associated with heating of surface layers of cold water patches exposed to solar radiation, superimposed upon vertical gradients in dissolved oxygen, can partially restrict suitable refuge volumes for stream salmonids within cold water patches.     

DIFFERENTIAL ACCUMULATION OF SELENIUM AMONG AXIAL MUSCLE,REPRODUCTIVE AND LIVER TISSUES OF FOUR WARMWATER FISH SPECIES1

Bluegill (Lepotmis macrochirus), largemouth bass (Micropterus salmoides), white catfish (Ictalurus catus), and channel catfish (Ictalurus punctatus), collected from an electric power plant cooling reservoir and a municipal water supply reservoir near Roxboro, North Carolina, were analyzed for selenium concentrations in axial muscle, reproductive and liver tissues. Fishes from the municipal water reservoir had lower selenium concentrations (≤0.2-2.1 μg/g - wet weight) than found in the cooling reservoir fishes (1.6-70.0 μg/g - wet weight) but similar distributions of concentrations among the tissues was evident. Selenium was differentially accumulated, with higher concentrations in liver tissues (0.7-70.0 μg/g - wet weight), followed by female reproductive tissues (0.7-25.0 μg/g - wet weight), axial muscle tissues (≤0.2-23.0 μg/g - wet weight) and male reproductive tissues (0.2-7.2 μg/g - wet weight).     

Impact of right-of-way construction on vegetation in the Red Lake Peatland,northern Minnesota

During the winters of 1978–79 and 1979–80, a 500-kV electrical transmission right-of-way (r-o-w) was constructed across the Red Lake Peatland in northwestern Minnesota, the largest contiguous peatland in the lower 48 states of the USA. Immediately before, and for two years following construction, vascular vegetation was monitored within the r-o-w and in undisturbed control areas. Monitoring was carried out in five vegetation types: a thicket swamp, a low shrub bog, a graminoid fen, a treed bog, and a treed fen. Evaluation of construction impacts was based on vegetation structure, irrespective of species composition, and on community composition (species data for low shrubs and herbs). Construction eliminated trees from the r-o-w. Vegetation structure, excluding trees, was markedly altered in the two bog types and the treed fen type in the first postconstruction growing season. By the second season, measurable recovery to control levels had begun. The sample plots were placed into a previously developed vegetation classification system for the Red Lake Peatland, on the basis of herbs and low shrubs. There was a shift in composition in the low shrub bog and in the treed vegetation types following construction. Results of both methods of data analysis were consistent. Major vegetation changes following construction occurred in the low shrub bog and treed types. The open, low-stature fen types showed almost no changes related to construction. Even in the affected types, all vegetation strata except trees were returning to their preconstruction status by the second growing season following construction.     

COMPUTATION OF UNSTEADY FLOWS IN THE ALABAMA RIVER1

ABSTRACT: An application is described of the branch-network flow model, BRANCH, to the upper Alabama River system in central Alabama. The model is used to simulate one-dimensional unsteady flows and water surface elevations in approximately 60 river miles of the Alabama River system. Preliminary calibration was made using 72 hours of observed data. Simulated discharges are about 10 percent lower than observed discharges at higher discharge rates and computed flows lag observed flows by about 30 minutes.     

EROSIONAL POTENTIAL OF STREAMS IN URBANIZING AREAS1

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.     

ENVIRONMENTAL FEATURES FOR FLOOD CONTROL CHANNELS1

ABSTRACT: The environmental effects of flood control channel modifications such as clearing and snagging, straightening, enlargement, and/or paving can be quite severe in some cases. Information review reveals that several environmental features have been incorporated into the design, construction, operation, or maintenance of recent flood control channel projects to avoid adverse environmental impacts and enhance environmental quality. Typically, these features have been proposed by conservation agencies and designed with minimal quantitative analysis. Environmental features for channel projects include selective clearing and snagging techniques, channel designs with nonuniform geometry such as single bank modification and floodways, restoration and enhancement of aquatic habitat, improved techniques for placement of excavated material, and revegetation.     

AFS-830型双道原子荧光光度计同时测定饮用水中砷、汞

主要探讨应用AFS-830型双道原子荧光光度计，在饮用水监测中同时测定水中砷、汞的方法和技术。此法是在硝酸介质，以硼氢化钠作还原剂，进行原子化，被测元素原子激发出荧光强度值在一定范围内与被测元素的浓度成正比。砷与汞的检出限分别为0．0618和0．0158ug／L。     

NATURAL RESTABILIZATION OF STREAM CHANNELS IN URBAN WATERSHEDS1

ABSTRACT: Stream channels are known to change their form as a result of watershed urbanization, but do they restabilize under subsequent conditions of constant urban land use? Streams in seven developed and developing watersheds (drainage areas 5–35 km²) in the Puget Sound lowlands were evaluated for their channel stability and degree of urbanization, using field and historical data. Protocols for determining channel stability by visual assessment, calculated bed mobility at bankfull flows, and resurveyed cross‐sections were compared and yielded nearly identical results. We found that channel restabilization generally does occur within one or two decades of constant watershed land use, but it is not universal. When (or if) an individual stream will restabilize depends on specific hydrologic and geomorphic characteristics of the channel and its watershed; observed stability is not well predicted by simply the magnitude of urban development or the rate of ongoing land‐use change. The tendency for channel restabilization suggests that management efforts focused primarily on maintaining stability, particularly in a still‐urbanizing watershed, may not always be necessary. Yet physical stability alone is not a sufficient condition for a biologically healthy stream, and additional rehabilitation measures will almost certainly be required to restore biological conditions in urban systems.     

基于正交试验方法的毛细矩形槽道平均流速影响因素分析

目的分析毛细矩形槽道平均流速的影响因素。方法通过公式推导毛细矩形槽道平均流速的有关影响因素,并且从中提取出部分因素,选用三因素三水平的正交试验表对流速进行分析,三因素分别为槽道宽度、槽道深度、槽道长度。通过CFX仿真得出对应的平均流速。结果得到了各因素水平变化对毛细矩形槽道平均流速的影响程度。槽道宽度及槽道深度对于毛细槽道平均流速具有比较大的影响,并得到最优的水平组合。结论对于毛细矩形槽道平均流速的影响因素给出了比较清晰的剖析,对于毛细矩形槽道传热的优化分析具有一定的参考意义。