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471.
472.
Langan Simon Hodson Mark Bain Derek Hornung Mike Reynolds Brian Hall Jane Johnston Lynne 《Water, Air, & Soil Pollution: Focus》2001,1(1-2):299-312
Current legislation within Europe aimed at limitingecosystem damage resulting from inputs of atmosphericpollution is based on the critical load concept. Mineralweathering rates are central to the calculation ofcritical loads (acceptable levels) of acid deposition.The authors have undertaken a number of studies whichillustrate the complications and limitations inherent inpredicting mineral weathering rates and the implicationswhich these have for critical loads calculations andmapping. Calculated weathering rates and critical loadsfor two acid-sensitive parent materials (greywackes andgranites) are presented and are used to illustrate theimpact that uncertainty can have on critical loadexceedances. The results have obvious implications forportraying the uncertainties of critical loads to policy makers. 相似文献
473.
Curtis C. J. Reynolds B. Allott T. E. H. Harriman R. 《Water, Air, & Soil Pollution: Focus》2001,1(1-2):399-413
Critical loads have for several years been employed bypolicymakers to aid in the development of strategies for aciddeposition abatement. They provide an effects-based approachwhereby an acid deposition flux greater than the critical load(known as critical load exceedance) implies that long-termharmful effects on a selected target organism will occur.Implicit in this approach are two assumptions: first, theexceedance of a critical load will harm the target organism,and second, the severity of biological impact is related to themagnitude of exceedance. However, static models give noindication of when the predicted damage might occur. One suchmodel, the Steady-State Water Chemistry (SSWC) model, employs aseries of empirical relationships to derive the pre-industrial,baseline leaching rate of base cations from measured waterchemistry using the so-called `F-factor'. The SSWC model setsthe critical load relative to pre-industrial base cationleaching (a permanent buffer of acid deposition) and a selectedacid neutralizing capacity (ANC) value which corresponds with aknown likelihood of damage to a biological target organism.Here we interpret the meaning of critical load exceedance as aprediction of steady-state ANC, and explore the relationshipbetween exceedance of the critical load and current chemistry. We demonstrate that a critical loadexceedance with the SSWC model does not necessarily indicatethat the critical chemical threshold (zero ANC) has alreadybeen crossed, and there may be no correlation betweenexceedance and biological status. A reformulation of the SSWCmodel is proposed which provides a direct link between currentdeposition and current chemical conditions, and is thereforemore likely to indicate current biological damage. Thereformulation illustrates the discrepancy between currentchemical status and that predicted by the SSWC model atsteady-state, which is a function of the `F-factor'. 相似文献
474.
Bruce D. Lindsey William J. Gburek Gordon J. Folmar 《Journal of the American Water Resources Association》2001,37(5):1103-1117
ABSTRACT: A study of stream base flow and NO3‐N concentration was conducted simultaneously in 51 subwatersheds within the 116‐square‐kilometer watershed of East Mahantango Creek near Klingerstown, Pennsylvania. The study was designed to test whether measurable results of processes and observations within the smaller watersheds were similar to or transferable to a larger scale. Ancillary data on land use were available for the small and large watersheds. Although the source of land‐use data was different for the small and large watersheds, comparisons showed that the differences in the two land‐use data sources were minimal. A land use‐based water‐quality model developed for the small‐scale 7.3‐square‐kilometer watershed for a previous study accurately predicted NO3‐N concentrations from sampling in the same watershed. The water‐quality model was modified and, using the imagery‐based land use, was found to accurately predict NO3‐N concentrations in the subwatersheds of the large‐scale 116‐square‐kilometer watershed as well. Because the model accurately predicts NO3‐N concentrations at small and large scales, it is likely that in second‐order streams and higher, discharge of water and NO3‐N is dominated by flow from smaller first‐order streams, and the contribution of ground‐water discharge to higher order streams is minimal at the large scale. 相似文献
475.
本次吊扇电机温升水平测试活动采用平行样品试验方案,尽管通过了严格的样品定制、测试和筛选以控制样品离散性,但所收集到的水平测试数据经过稳健统计法和Z值评估法的分析后发现平行样品的离散性对水平测试结果的影响不可忽略,导致所给出的评价结果是具有较大的风险性和不公平性。这意味着该次水平测试活动采用平行样品试验方案一种错误的选择。 相似文献
476.
ESTABLISHING STATISTICAL DESIGN CRITERIA FOR WATER QUALITY MONITORING SYSTEMS: REVIEW AND SYNTHESIS1
Robert C. Ward Jim C. Loftis 《Journal of the American Water Resources Association》1986,22(5):759-767
ABSTRACT: Regulatory water quality management has placed fairly extensive information expectations on routine, fixed-station monitoring without a corresponding emphasis being placed on the need to design monitoring systems to meet these expectations. To correct the situation there is increasing interest in developing more quantitative monitoring system design procedures which incorporate the statistical nature of sampling. In examining the development of such quantitative criteria, this paper describes the roles of statistics in a systematic approach to monitoring - initial design and routine reporting of results - and reviews the use of statistics in each. The paper emphasizes the need to tie the two together, via statistical design criteria, in order for the identified information expectations to be met in a statistically sound manner. However, the use of statistics in water quality monitoring is noted as currently being as much an art as it is a science. 相似文献
477.
Vijay P. Singh Kulwant Singh 《Journal of the American Water Resources Association》1987,23(6):1185-1189
ABSTRACT: The principle of maximum entropy (POME) was used to derive an alternative method for parameter estimation for the three parameter lognormal (TPLN) distribution. Six sets of annual peak discharge data were used to evaluate this method and compare it with the methods of moments and maximum likelihood estimation. 相似文献
478.
Yeou-Koung Tung Larry W. Mays 《Journal of the American Water Resources Association》1981,17(2):262-269
ABSTRACT: In order to promote a uniform and consistent approach for floodflow frequency studies, the U.S. Water Resources Council has recommended the use of the log-Pearson type III distribution with a generalized skew coefficient. This paper investigates various methods of determining generalized skew coefficients. A new method is introduced that determines generalized skew coefficients using a weighting procedure based upon the variance of regional (map) skew coefficients and the variance of sample skew coefficients. The variance of skew derived from sample data is determined using either of two non-parametric methods called the jackknife or bootstrap. Applications of the new weighting procedure are presented along with an experimental study to test various weighting procedures to derive generalized skew coefficients. 相似文献
479.
Norman L. Miller Jinwon Kim Robert K. Hartman John Farrara 《Journal of the American Water Resources Association》1999,35(6):1525-1537
ABSTRACT: Downscaling coarse resolution climate data to scales that are useful for impact assessment studies is receiving increased attention. Basin-scale hydrologic processes and other local climate impacts related to water resources such as reservoir management, crop and forest productivity, and ecosystem response require climate information at scales that are much finer than current and future GCM resolutions. The Regional Climate System Model (RCSM) is a dynamic downscaling system that has been used since 1994 for short-term precipitation and streamflow predictions and seasonal hindcast analysis with good skill. During the 1997–1998 winter, experimental seasonal forecasts were made in collaboration with the NOAA Climate Prediction Center and UCLA with promising results. Preliminary studies of a control and 2°CO2 perturbation for the southwestern U.S. have been performed. 相似文献
480.