PREDICTIVE MODEL FOR NITRATE LOAD IN THE BULL RUN WATERSHED,OREGON1

ABSTRACT: Predictive models for nitrate in four streams in the Bull Run Watershed in the Cascade Mountains of Oregon were developed from a record of 17 years of nitrate samples. The models are time series regression models written in terms of Log(nitrate load). The independent variables are logarithm of 14-day mean daily stream discharge, current day's precipitation, logarithm of the previous day's precipitation, total precipitation for the previous seven days, a hydrograph position variable that indicates rising or falling limb, and average maximum air temperature for the preceding 14 days. The models describe annual cycle and seasonable trends and variations in nitrate load, but are unable to describe large day to day variations like those associated with hydrograph peaks.     

河流水质灾害中的S—P方程稳态分析和临界氧亏计算

污染物对水环境的影响主要发生在枯水期，此时水流状态处于稳态．Streeter－phelps（S－P）方程能预测简单稳态条件下的水质状况，并具有较高的计算织亏的精度．     

自然灾害变动的集成预测模型及其应用

本文提出了以非线性回归拟合发展趋势、正弦函数逼近周期变动和马尔可夫链刻划随机扰动的集成预测模型，并应用于山东省农业自然灾害成灾面积的变动规律模拟，得到了较好的预测效果。理论和实践表明，集成预测模型优于传统的单模型预测，为预测具有复杂机制的自然灾害演变提供了一种新方法。     

热辐射的破坏准则和池火灾的破坏半径

热辐射破坏是发生在开放气环境中的池火灾的主要破坏机理。本文讨论了热辐射的破坏准则，提出预测池火灾破坏半径的方法，进行了数值模拟计算，分而和时纳了池火灾的基本规律     

A framework to assess regional environmental impacts of dedicated energy crop production

Numerous studies have evaluated air quality and greenhouse gas mitigation benefits of biomass energy systems, but the potential environmental impacts associated with large-scale changes in land-use patterns needed to produce energy crops have not been quantified. This paper presents a framework to assess the potential soil, water, and biodiversity impacts that may result from the large-scale production of dedicated energy crops. The framework incorporates producer economic decision models with environmental models to assess changes in land use patterns and to quantify the consequent environmental impacts. Economic and policy issues that will affect decisions to produce energy crops are discussed. The framework is used to evaluate erosion and chemical runoff in two Tennessee regions. The analysis shows that production of dedicated energy crops in place of conventional crops will significantly reduce erosion and chemical runoff.     

PESTICIDES IN GROUND WATER: DO ATRAZINE METABOLITES MATTER?1

ABSTRACT: Atrazine and atrazine-residue (atrazine + two metabolites - deethylatrazine and deisopropylatrazine) concentrations were examined to determine if consideration of these atrazine metabolites substantially adds to our understanding of the distribution of this pesticide in groundwater of the midcontinental United States. The mean of atrazine.residue concentrations was 53 percent greater than that of atrazine alone for those observations above the detection limit (> 0.05 μg/l). Furthermore, a censored regression analysis using atrazine-residue concentrations revealed significant factors not identified when only atrazine concentrations were used. Thus, knowledge of concentrations of these atrazine metabolites is required to obtain a true estimation of risk of using these aquifers as sources for drinking water, and such knowledge also provides information that ultimately may be important for future management policies designed to reduce atrazine concentrations in ground water.     

THE ARMA MODELS APPLIED TO THE FLOW OF KARSTIC SPRINGS1

ABSTRACT: Autoregressive moving average (ABMA) models have been applied to study the flow series of the karstic springs of La Villa, Fuente Mayor (Spain), and Aliou (France). The theoretical meaning of the parameters involved in the model upon applying it to a simplified scheme of the emptying of a karstic aquifer is first analyzed. The types of transformations necessary to apply these models to the flow series that lack normality and have strong periodic components are also indicated, as are the advantages of this type of model and the physical significance of the parameters obtained, with respect to the standpoint of hydraulics, ranging from rather homogeneous aquifers (La Villa) to extremely karstic (Aliou), including aquifers with intermediate characteristics (Fuente Mayor).     

A COMPARATIVE STUDY OF A SWEDISH AND A CHINESE HYDROLOGICAL MODEL1

ABSTRACT: There are a large number of conceptual hydrological models available today. It is not easy to immediately identify the similarities and differences between the different models. The Swedish HBV model and the Chinese Xinanjiang model are two examples of conceptual, semi-distributed, rainfall-runoff models. The Xinanjiang model was designed for use in humid and semi-humid regions, with no routine for the snowmelt runoff, whereas the snow routine is an important part of the HBV model in many applications. The model structures of the two models may be described in four routines, compared in this paper. The integral structures of them are similar, but there are some differences, especially in the runoff production routine. The physical significance and physical definitions of some model parameters were analyzed. Both models were tested in two basins. Both models gave similar results, and both models performed well in the application. The similarity of the results obtained by different model structures leads to the following two conclusions. First, more effort should probably be spent on the improvement of input data quality and coverage than on the development of more detailed model structures only. Second, inference about basin behavior and characteristics from the values of calibrated model parameters must be made with great caution.     

单一震源地震发生的等效物理模型

建立了模拟单一潜在震源区地震孕育和发生的等效物理模型，给出了通过调整各次地震之间断层位移速率来拟合已有地震序列的方法。通过考虑模型参数的不确定性，提出了在未来一定年限内潜在震源区发生震级在不同震级段的概率预报方法。通过两种等效物理模型的对比，本文认为就工程地震危险性评定而言，可用简单的滑块－弹簧模型代替滑块－弹粘塑性模型