Population control of exotic rainbow trout in streams of a natural area park

Expansion of the distribution of exotic rainbow trout is thought to be a leading cause for the decline of native brook trout since the 1930s in Great Smoky Mountains National Park, USA. An experimental rehabilitation project was conducted from 1976 to 1981 using backpack electrofish shockers on four remnant brook trout populations sympatric with rainbow trout. The objectives were to evaluate the effectiveness of the technique to remove the exotic rainbow trout, to determine the population responses by native brook trout, and to evaluate the usefulness of the technique for trout management in the park.Rainbow trout populations were greatly reduced in density after up to six years of electrofishing, but were not eradicated. Rainbow trout recruitment, however, was essentially eliminated. Brook trout populations responded by increasing in density (including young-of-the-year), but rates of recovery differed among streams. The maximum observed densities ir each stream occurred at the end of the project.The findings suggest that electrofishing had a major negative impact on the exotic species, which was followed by positive responses from the native species in the second and third order study streams. The technique would probably be less effective in larger (fourth-order) park streams, but as an eradication tool the technique may have its highest potential in small first order streams. Nonetheless, the technique appears useful for population control without causing undue impacts on native aquatic species, although it is labor intensive, and capture efficiency is greatly influenced by fish size and stream morphology. To completely remove the exotic fish from selected streams, different technologies will have to be explored and developed.     

RUNOFF PREDICTION USING REMOTE SENSING IMAGERY1

ABSTRACT: Percent imperviousness is an important parameter in modeling the urban rainfall-runoff process and is usually determined using manual methods such as random sampling or conventional accounting methods. In this study two computerized methods are used for estimating the percent imperviousness of urban watersheds using high altitude remote sensing imagery. These methods include the Laser Image Processing Scanner and the Video-Tape Camera system. Imperviousness is directly estimated in the former method while in the latter it is estimated as a function of the statistics of the responses on emulsions of the imagery. The percent imperviousness computed by utilizing remote sensing imagery was used with the conceptual models of rainfall-runoff models. The models were applied to four urban watersheds and the runoff prediction results indicate that imperviousness determined by using remote sensing imagery was as accurate as that obtained by the manual methods, and that the use of remote sensing imagery requires significantly less time and money.     

The new regime for managing US—Mexican water resources

United States-Mexican transboundary water resources management is presently experiencing significant reform resulting from long-term demographic processes in the border region and greater economic integration. The recently concluded North American Free Trade Agreement and supplementary environmental accord modify existing agreements and provide old institution with new mandates. Particularly affected is the International Boundary and Water Commission (IBWC), long the lead agency in binational water management. This essay reviews the development of the new water management regime against the two preceding phases of management reform and considers its implications for improved water management in the border region.     

RELATION BETWEEN STREAM-WATER QUALITY AND GEOHYDROLOGY DURING BASE-FLOW CONDITIONS,ROBERTS CREEK WATERSHED,CLAYTON COUNTY,IOWA1

ABSTRACT: An investigation to determine the relation between stream water quality and geohydrology in the Roberts Creek watershed, Clayton County, Iowa, was conducted during selected base-flow periods in 1988–90. Discharge measurements were made and water samples collected for analyses of nutrients and selected herbicides in 19 subbasins along the main stem and tributaries of Roberts Creek. The areal extent of unconsolidated and bedrock units subcropping in each subbasin was quantified. The hydrologic data were correlated statistically with the geologic data to determine relations. Roberts Creek generally gained water and had larger nitrogen concentrations in subbasins in which bess and alluvial material were underlain primarily by low-permeability till and shale units. Roberts Creek generally lost water and had lower nitrate concentrations in subbasins with subcroppmg karstic units. Nitrogen concentrations decreased in streams underlain by the karstic units because the nitrogen removed by biological processes was not replaced by ground-water inflow. Seepage from Roberts Creek to ground water in areas of subcropping karstic carbonate rocks reduced the flow, which reduced the velocity, causing increased residence time of water in the stream. The additional residence time may allow additional time for biological processes to remove nitrogen from solution. There was no significant relation between dissolved orthophosphate or atrazine and the underlying geology.     

FLOOD FREQUENCY ANALYSIS FOR SMALL WATERSHEDS IN SOUTHERN ILLINOIS1

ABSTRACT: Twenty-two gaging stations were selected for developing a regional flood frequency curve for small (area less than 2 square miles) watersheds in southern Illinois. Five probability functions were compared, and the extreme value type I function was selected to develop the regional flood curve. The curve was generated with the index flood method and also another empirical method that related the function parameters to the watershed area. Estimated peak discharges with various return periods were compared with the results obtained from multiple regression analysis.     

Climatic and stream-flow controls on tree growth in a Western montane riparian forest

Humans have severely impacted riparian ecosystems through water diversions, impoundments, and consumptive uses. Effective management of these important areas is becoming an increasingly high priority of land managers, particularly as municipal, industrial, and recreational demands for water increase. We examined radial tree growth of four riparian tree species (Pinus jeffreyi, Populus trichocarpa, Betula occidentalis, and Pinus monophylla) along Bishop Creek, California, and developed models relating basal area increment (BAI) and relative basal area increment (RBAI) to climatic and stream flow variables. Between years 1995–1999, univariate regression analysis with stream flow explained 29 to 61% of the variation in BAI and RBAI among all species except P. trichocarpa; growth by P. trichocarpa was not significantly related to stream flows over this period. Stepwise linear regression indicated that species responded differently to climatic variables, and models based on these variables explained between 33 to 86% of variation in BAI and RBAI during the decade of the 1990s. We examined branch growth of P. trichocarpa for sensitivity to differences in stream flow regimes and found that annual branch growth did not vary between a high- and low-flow site, but that annual branch growth was significantly higher in wet years with greater stream flows. Our results support the establishment of site-specific management goals by land managers that take into account all of the important tree species present in riparian ecosystems and their differential responses to altered hydrologic condition. Instream flow requirements for maintaining tree growth and vigor are only one of the species-specific responses that need to be evaluated, and these assessments should attempt to separate experimentally stream-flow (managed) controls from climatic (unmanaged) controls on growth.     

Urbanization's impact on timber harvesting in the south central United States

The impact of urbanization on timber harvesting in the south central United States was investigated. Geo-referenced Census and Forest Inventory Analysis (FIA) data were combined using a geographic information system (GIS) in order to examine the effects of various demographic and biophysical forest inventory characteristics on timber harvesting. These effects were estimated for intermediate and final harvests using a multinomial logit model. The probability for both types of harvests decreased with increasing population density, decreasing forest size, and decreasing distance to urban areas; however, the reduction in intermediate harvests was greater for each variable. Harvesting rates decreased by as much as 19% as population densities increased or distance to urban areas decreased. The results indicated that active forest management is curtailed far beyond the urban boundary. In order to model the impact of urbanization adequately, timber supply projections must also account for its impact on harvesting frequencies in surrounding areas.     

Mechanistic studies of N-nitrosodimethylamine (NDMA) formation in chlorinated drinking water

Studies were conducted to investigate the hypothesis that N-nitrosodimethylamine (NDMA) is a potential disinfection by-product specifically produced during chlorination or chloramination. Experiments were conducted using dimethylamine (DMA) as a model precursor. NDMA was formed by the reaction of DMA with free chlorine in the presence of ammonia and also with monochloramine. We proposed a mechanism for NDMA formation in chlorinated or chloraminated water, which does not require nitrite as in N-nitrosation. The critical NDMA formation reactions consist of (i) the formation of monochloramine by combination of free chlorine with ammonia, (ii) the formation of 1,1-dimethylhydrazine (UDMH) intermediate from the reaction of DMA with monochloramine followed by, (iii) the oxidation of UDMH by monochloramine to NDMA, and (iv) the reversible chlorine transfer reaction between free chlorine/monochloramine and DMA which is parallel with (i) and (ii). A kinetic model was also developed to validate the proposed mechanism.     

Leadership self‐efficacy and managers' motivation for leading change

This study develops and tests a leadership model that focuses on managers' motivation for attempting the leadership of change. The construct of leadership self‐efficacy (LSE) is defined, and a measure comprising three dimensions (direction‐setting, gaining followers' commitment, and overcoming obstacles to change) is developed. Based on Bandura's (1986) social cognitive theory, the primary hypothesis is that high LSE managers will be seen by direct reports as engaging in more leadership attempts. Relationships are also proposed between LSE and several factors that are expected to influence this confidence judgment. Managers' organizational commitment and crisis perceptions are modelled as potential moderators of the relationship between LSE and leadership attempts. The model was tested through surveys distributed to managers (n = 150) and their direct reports (n = 415) in a real estate management company and an industrial chemicals firm. Positive relationships (p < 0.05) were found between the first two dimensions of LSE and managers' leadership attempts. An interaction effect involving organizational commitment was discovered for the LSE/overcoming obstacles dimension (p < 0.05). Several positive relationships were found between LSE dimensions and proposed antecedents, including self‐esteem (p < 0.05), subordinates' performance abilities (p < 0.05), and managers' job autonomy (p < 0.05). Copyright © 2002 John Wiley & Sons, Ltd.     

Satellite and Ground Based Monitoring of Aerosol Plumes

Plumes of atmospheric aerosol have been studied using a rangeof satellite and ground-based techniques. The Sea-viewing WideField-of-view Sensor (SeaWiFS) has been used to observe plumesof sulphate aerosol and Saharan dust around the coast of theUnited Kingdom. Aerosol Optical Thickness (AOT) was retrievedfrom SeaWiFS for two events; a plume of Saharan dusttransported over the United Kingdom from Western Africa and aperiod of elevated sulphate experienced over the Easternregion of the UK. Patterns of AOT are discussed and related tothe synoptic and mesoscale weather conditions. Furtherobservation of the sulphate aerosol event was undertaken usingthe Advanced Very High Resolution Radiometer instrument(AVHRR). Atmospheric back trajectories and weather conditionswere studied in order to identify the meteorologicalconditions which led to this event. Co-located ground-basedmeasurements of PM₁₀ and PM_2.5 were obtained for 4sites within the UK and PM_2.5/10 ratios were calculatedin order to identify any unusually high or low ratios(indicating the dominant size fraction within the plume)during either of these events. Calculated percentiles ofPM_2.5/10 ratios during the 2 events examined show thatthese events were notable within the record, but were in noway unique or unusual in the context of a 3 yr monitoringrecord. Visibility measurements for both episodes have beenexamined and show that visibility degradation occurred duringboth the sulphate aerosol and Saharan dust episodes.