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981.
982.
983.
The US Army Engineering Research Development Center (ERDC) uses a modified form of the Revised Universal Soil Loss Equation
(RUSLE) to estimate spatially explicit rates of soil erosion by water across military training facilities. One modification
involves the RUSLE support practice factor (P factor), which is used to account for the effect of disturbance by human activities
on erosion rates. Since disturbance from off-road military vehicular traffic moving through complex landscapes varies spatially,
a spatially explicit nonlinear regression model (disturbance model) is used to predict the distribution of P factor values
across a training facility. This research analyzes the uncertainty in this model's disturbance predictions for the Fort Hood
training facility in order to determine both the spatial distribution of prediction uncertainty and the contribution of different
error sources to that uncertainty. This analysis shows that a three-category vegetation map used by the disturbance model
was the greatest source of prediction uncertainty, especially for the map categories shrub and tree. In areas mapped as grass,
modeling error (uncertainty associated with the model parameter estimates) was the largest uncertainty source. These results
indicate that the use of a high-quality vegetation map that is periodically updated to reflect current vegetation distributions,
would produce the greatest reductions in disturbance prediction uncertainty. 相似文献
984.
O. Thas L. Van Vooren J. P. Ottoy 《Journal of the American Water Resources Association》1998,34(2):347-357
ABSTRACT: In this paper four nonparametric tests for monotonic trend detection are compared with respect to their power and accuracy. The importance of comparing powers at equal empirical significance levels rather than nominal levels is stressed. Therefore, an appropriate graphical method is presented. The effect of the sampling frequency is also assessed using Monte Carlo simulations and a trajectory representation that visualizes the dynamics of the trade-off between the type I and type II errors. These methods are applied to compare four nonparametrical tests (seasonal Mann. Kendall, modified seasonal Mann-Kendall, covariance eigenvalue and covariance inversion) under several conditions. It is concluded with respect to the power that it is not worthwhile for the modified seasonal Mann-Kendall test applied to the AR(1) process considered in this paper to increase the sampling frequency from monthly to biweekly for detecting a monotonic trend of 5 percent, 10 percent, or 15 percent of the process variance. Under these conditions the seasonal Mann-Kendall test is highly liberal, while the covariance inversion and the covariance eigenvalue test are conservative. This research is situated in the development of an efficient sampling design for the Flemish water quality monitoring network. 相似文献
985.
根据对银洞坡金矿的水质水量调查,采用碱性氯化法处理银洞坡金矿尾矿库的含氰废水,在去除氰化物和重金属方面都取得了较好的效果。对实验的结果进行了影响因素分析,提出了采用间歇式方法处理含氰废水的工艺方案。 相似文献
986.
采空区火源位置探测技术现状及发展方向 总被引:3,自引:0,他引:3
概述了国内外采空区火源位置探测技术的现状,着重介绍了温度探测法、气体探测法、磁力探测法、数理解算法、电磁波探测法及电阻探测法等探测技术,并展望了国内外采空区火源位置探测技术的发展方向 相似文献
987.
我国钢铁工业废水治理及其发展趋势 总被引:1,自引:0,他引:1
我国水资源人均拥有量仅为世界人均拥有量的四分之一,而且降水在时空分布上很不均衡。这一现实,决定了节省水资源,保护水环境是我国一项长期的战略任务。文章概要地叙述了钢铁工业废水治理及其发展过程。作者认为,要从根本上解决钢铁工业废水对水环境的污染与破坏,必须采取综合防治措施,并把整套循环用水技术引入生产工艺过程,使废水与污染物都作为资源加以回收,并实现循环利用。上述过程的实质,是模拟大自然生物圈循环运行 相似文献
988.
荒山荒地是我省农业的重要后备,本文将主要探讨这部分资源的开发利用及其原则和方向,为发展农业寻求新的途径与措施。 相似文献
989.
D. P. Larsen N. S. Urquhart D. L. Kugler 《Journal of the American Water Resources Association》1995,31(1):117-140
ABSTRACT: The U.S. Environmental Protection Agency has proposed a sample survey design to answer questions about the ecological condition and trends in condition of U.S. ecological resources. To meet the objectives, the design relies on a probability sample of the resource population of interest (e.g., a random sample of lakes) each year on which measurements are made during an index period. Natural spatial and temporal variability and variability in the sampling process all affect the ability to describe the status of a population and the sensitivity for trend detection. We describe the important components of variance and estimate their magnitude for indicators of trophic condition of lakes to illustrate the process. We also describe models for trend detection and use them to demonstrate the sensitivity of the proposed design to detect trends. If the variance structure that develops during the probability surveys is like that synthesized from available databases and the literature, then the trends in common indicators of trophic condition of the specified magnitude should be detectable within about a decade for Secchi disk transparency (0.5–1 percentiyear) and total phosphorus (2–3 percent/year), but not for chlorophyll-a (> 3–4 percent/year), which will take longer. 相似文献
990.
Charles H. Taylor Jim C. Loftis 《Journal of the American Water Resources Association》1989,25(4):715-726
ABSTRACT: The detection of gradual trends in water quality time series is increasing in importance as concern grows for diffuse sources of pollution such as acid precipitation and agricultural non-point sources. A significant body of literature has arisen dealing with trend detection in water quality variables that exhibit seasonal patterns. Much of the literature has dealt with seasonality of the first moment. However, little has been mentioned about seasonality in the variance, and its effect upon the performance of trend detection techniques. In this paper, eight methods of trend detection that arise from both the statistical literature as well as the water quality literature have been compared by means of a simulation study. Varying degrees of seasonality in both the variances and the means have been introduced into the artificial data, and the performances of these procedures are analyzed. Since the focus is on lake and ground water quality monitoring, quarterly sampling and short to moderate record lengths are examined. 相似文献