A TAU-LIKE TEST FOR TREND IN THE PRESENCE OF MULTIPLE CENSORING POINTS1

ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied.     

SOIL CHANGES CAUSED BY MUNICIPAL WASTEWATER APPLICATIONS IN EASTERN SOUTH DAKOTA1

ABSTRACT: Wastewater from a municipal treatment plant was applied in rapid infiltration basins for four years to determine a poorly drained soils effectiveness in removing influent N and P and the soil changes that might limit their removal. About half the total PO₄-P lost from the influent was sorbed in the upper 91 cm of the soil and the other half was sorbed by the soil below the perforated pipe, which was used to drain the basins and collect the effluent for analysis. Drying of the basin soils converted more sorbed PO₄-P to Ca phosphates but the total sorbed was about the same. The in. fluent N decreased, probably by volatilization, because the two basins with surface soil lost soil N rather than gained soil N. The soil total Ca, Mg, and K contents did not change significantly but Na increased slightly. Changes in the physical characteristics of the soils were slight and would have little effect on the longevity of a rapid infiltration basin.     

Evaluating the effectiveness of air quality management within the class I area of great smoky mountains national park

The Clean Air Act Amendments of 1977 designated national parks and wilderness areas larger than 1894 ha to be class I areas for air quality management, setting more restrictive criteria than the National Ambient Air Quality Standards. Class I areas are afforded the greatest degree of air quality protection under the Clear Air Act of 1970. In recent years, several studies have documented air pollution effects in the Great Smoky Mountains National Park (GSMNP), the second-largest class I area in the eastern United States. Air pollution problems of greatest concern in the GSMNP are effects of acid deposition, visibility impairment, and tropospheric ozone. Several recent events have increased concerns about air quality management in the class I area of the GSMNP. A forum, sponsored by the Southern Appalachian Man and the Biosphere Cooperative (SAMAB), was held in March 1992, which involved representative. parties-at-interest and began to address strategies for better management of air resources in the Southern Appalachians. This paper summarizes those discussions and recommendations and reports actions occurring as a result of the forum. Another objective of this paper is to present a conceptual framework for more effective management of the class I area of the GSMNP.     

CAUSES OF PEAK FLOWS IN NORTHWESTERN MONTANA AND NORTHEASTERN IDAHO1

ABSTRACT: Both catchment experiments and a review of hydrologic processes suggest a varying effect of forest harvest on the magnitude of peak flows according to the cause of those peak flows. In northwestern Montana and Northeastern Idaho, annual maximum flows can result from spring snowmelt, rain, mid-winter rain-on-snow, or rain-on-spring-snowmelt. Meteorologic and physical data were used to determine the cause of annual maximum flows in six basins which had the necessary data and were smaller than 150 mi². Rain-on-spring-snowmelt was the most frequent cause of annual maximum flows in all six basins, although there was a strong gradient in the magnitude and cause of peak flows from southwest to northeast. Less frequent mid-winter rain-on-snow events caused the largest flows on record in four basins. Mid-winter rain-on-snow should be distinguished from rain-on-spring-snowmelt because of differences in seasonal timing, the relative contributions of rain vs. snowmelt, and the projected effects of forest harvest. The effects of mixed flood populations on the flood-frequency curve varied from basin to basin. Annual maximum daily flows could not be reliably predicted from rainfall and snowmelt data.     

Determination of optimum minimum flow from a dam by using energy analysis

The proposed restoration of an abandoned hydroelectric dam on the Quinebaug River, Connecticut, is studied using energy analysis. The analysis considers the effects of alternative minimum flow releases, ranging from 0 to 34 cubic meters per second (cms), on the total energy flow of the affected system. The principal system components affected by differing minimum flows are hydroelectric power generation, aquatic habitat, and gross aquatic ecosystem productivity.The minimum flow alternative resulting in the highest annual energy flow in the affected system is considered optimal. From this purely analytical point of view, the optimum minimum flow is 0 cms, due to the short length and low productivity of the regulated reach, and the lack of floodplain interactions.Simulations of longer and more productive river reaches were conducted. For very short, unproductive reaches, in the absence of a floodplain, the contribution of aquatic community productivity to total system energy flow is negligible compared to hydroelectric generation. Optimum minimum flows are higher for longer and more productive reaches. For such cases the operation of hydroelectric dams could reduce total system energy flow because the energy supplied by hydroelectric generation may be offset by losses in aquatic productivity due to diminished riverine habitat.     

Social impact evaluation of the US Resource Conservation and Recovery Act

Debate over environmental policy often focuses on social impacts of those policies, but few empirical studies examine the impacts of environmental regulations once they are implemented. A quasi-experimental design based on survey data is used to assess the social impacts of the US Resource Conservation and Recovery Act (RCRA) on the West Virginia chemical industry. Changes in employment, manufacturing process, product line, and manufacturing costs are evaluated. RCRA seems to have produced changes in manufacturing processes, but we find no statistically significant impacts on.jobs, product line, or manufacturing costs.     

Special species and ecosystem preserves: Colonial water birds in US national parks

An important aspect of developing a philosophical foundation for management of reserves using an ecosystem approach is the exploration of the relationship of ecosystem management strategies to the need for conservation of species of special concern Colonial water birds are species that may deserve special consideration They occur in over 25 US national parks, but in no case do the parks have a monopoly on the total protection or management of these birds As an agency responsible for such populations, the National Park Service engages in activities such as inventory, monitoring, research, and management, using an ecosystem management philosophy Most parks contain only segments of natural ecosystems, and management actions, even those undertaken from an ecosystem perspective, may not be in the best interest of an individual species Management strategies for widely ranging special species require a regional perspective, including plans that take into consideration the differing objectives of the agencies responsible for such species A matrix of the different management strategies in various areas may provide a suitable, perhaps the best, method for protecting special species In practice, any one strategy, such as management of remnant ecosystem patches or intensive single-species management, may not be successful alone