Surface Flow Type Research Articles

The role of physical biotopes in determining the conservation status and flow requirements of British rivers

This paper examines the practical use of physical biotopes as the basic component of instream physical habitat. These are identified by dominant flow type as a particular combination of substrate and hydraulic parameters will have a characteristic surface flow type. Eleven rivers representing a range of geomorphological features and physical biotopes were selected, and depth, velocity, and substrate data were collected at metre intervals in subjectively-spaced transects. Flow type was recorded at each sample “cell” and transects classified on the basis of dominant flow type. Combined hydraulic indices were calculated in order to characterise more completely a particular biotope and to facilitate comparisons among different discharges and sites. The subjective classification of flow types was tested statistically by discriminant analysis and units were shown to be hydraulically discrete in terms of Froude number and other combined hydraulic indices. Identification of physical biotopes by flow types has been incorporated into the Environment Agency's (formerly National Rivers Authority) River Habitat Survey (RHS). The RHS is based on 500 m reaches selected randomly within a stratified selection from a national grid, to characterise the physical features of rivers in England and Wales, and to provide an objective method for assessing habitat quality. Biotope mapping at different flows was undertaken to establish how the biotope sequence differs among sites and with increasing discharge. Threshold discharges at which biotopes change are related to flow duration data to predict annual patterns of biotope ‘patchiness’ and ‘diversity’. Flows may then be manipulated to maintain ‘natural’ or ‘desirable’ biotopes. Sustainable management of aquatic systems and their biota would require flow management of critical reaches or biotopes, at key life-stages of target organisms.

The role of physical biotopes in determining the conservation status and flow requirements of British rivers

Abstract This paper examines the practical use of physical biotopes as the basic component of instream physical habitat. These are identified by dominant flow type as a particular combination of substrate and hydraulic parameters will have a characteristic surface flow type. Eleven rivers representing a range of geomorphological features and physical biotopes were selected, and depth, velocity, and substrate data were collected at metre intervals in subjectively-spaced transects. Flow type was recorded at each sample “cell” and transects classified on the basis of dominant flow type. Combined hydraulic indices were calculated in order to characterise more completely a particular biotope and to facilitate comparisons among different discharges and sites. The subjective classification of flow types was tested statistically by discriminant analysis and units were shown to be hydraulically discrete in terms of Froude number and other combined hydraulic indices. Identification of physical biotopes by flow types has been incorporated into the Environment Agency’s (formerly National Rivers Authority) River Habitat Survey (RHS). The RHS is based on 500 m reaches selected randomly within a stratified selection from a national grid, to characterise the physical features of rivers in England and Wales, and to provide an objective method for assessing habitat quality. Biotope mapping at different flows was undertaken to establish how the biotope sequence differs among sites and with increasing discharge. Threshold discharges at which biotopes change are related to flow duration data to predict annual patterns of biotope ‘patchiness’ and ‘diversity’. Flows may then be manipulated to maintain ‘natural’ or ‘desirable’ biotopes. Sustainable management of aquatic systems and their biota would require flow management of critical reaches or biotopes, at key life-stages of target organisms.

Application of the hydraulic biotope concept to the classification of instream habitats

A simple matrix developed by a small group of ecologists, geomorphologists and an hydraulic engineer at a workshop in February 1995 was proposed as a standardised classification tool for the recognition of hydraulic biotopes, instream flow environments recognised on the basis of surface flow type and substrate class. Research was carried out in the Buffalo River, South Africa, to test the validity of this classification with respect to measurable hydraulic attributes. Hydraulic biotopes were classified at a number of sites representing a range of stream morphologies, channel scale and discharge. The hydraulic attributes at each sampling point were measured. Using simple measures of flow depth, velocity and bed roughness, hydraulic indices were calculated to describe both the near bed conditions (shear velocity and ‘roughness’ Reynolds number) and the mean flow in the water column (Froude number and Reynolds number). Results indicate that hydraulic biotope classes can be considered as significantly different in terms of flow hydraulics. Hydraulic characteristics appear to be consistent within classes across different spatial scales. An assessment of the influence of discharge showed that differences are recognised in the classes of the lower energy environments (pool and run) but despite considerable within class variability, no significant differences were observed across discharges in the higher energy environments. The hydraulic biotope classification and associated hydraulic biotope matrix shows good potential as a standardised method for classifying instream environments over a range of channel scales and discharges.

Denitrifying sites in constructed wetlands treating agricultural industry wastes: A note

Abstract The denitrification potential (rate of denitrification under anoxic conditions and in the presence of excess nitrate and glucose) was measured in different zones of constructed wetlands receiving anaerobic/aerobic treated meat processing and dairy‐shed effluents. The wetland receiving meat processing effluent was of the surface flow type and about 67% of the influent nitrogen was in the nitrate form. Most of the denitrifying potential in this wetland was in the surface mat of decaying plant material. The dairy‐shed wetland was of the subsurface flow type and received an effluent that contained little nitrate (<1%). In this wetland denitrifying potential increased from the inlet to the outlet. The patterns of denitrifying activity suggest that nitrogen removal in wetland systems may be improved by better contact between the effluent and decaying plant material on the wetland surface.

USE OF SURFACE FLOW OF SPRING WATER FOR HYDROCHEMICAL PROSPECTING OF ORE DEPOSITS

Small streams fed by subsurface run-off, subject to ore-oxidation activity, alter in chemical composition and are thus useful in hydrochemical prospecting for ores. Surface-flow types most favorable to hydrochemical prospecting are identified; and, the optimum time of the year established for positive identification of oxidizing-ore occurrences by surface-water chemical composition. The author chose the Lory plateau in Northern Armenia as the area of investigation. The topography of the area is mountainous; elevations above sea-level range from 1100 to 2700-2800 meters. Its climate is temperate alpine, and the annual precipitation of 650 to 750 millimeters is heaviest during the period from April to June. Sedimentary and effusive tuffs, of Middle Jurassic to middle Eocene age, contain numerous polymetallic, chalcopyrite, copper-arsenic, pyrite, and other ores; minerals are principally sulfides. A high-intensity water cycle resulting in abundance of springs and surface flows is characteristic of the region...