THE STATUS OF NONPOINT SOURCE POLLUTION: ITS NATURE,EXTENT AND CONTROL1

Nonpoint source pollution remains as the primary reason for the designation of many of the Nation's streams as “water quality limited.” This means that even with the application of technology-based effluent limitations on point sources, ambient water quality standards will not be met. This paper explores several of the reasons why nonpoint sources are so difficult to come to grips with. These reasons include: (1) the inability to expand the definition of nonpoint sources to encompass nonengineering attributes, (2) the relatively primitive state of characterizing nonpoint sources, (3) the lack of prior success in conducting programs to study and alleviate nonpoint problems, and (4) an uncertain approach to providing incentives for control practices.     

“气候变暖”对雅砻江水资源的影响

本文引入几种统计模型探讨“气候变暖”对水资源的影响。这些模型经实测资料验证，模拟和预测效果了。在一定环境条件下，利用它们预估“气候变暖”对雅砻江未来水资源的影响，获得令人满意的成果。     

SEASONAL PUMPING VARIATION EFFECTS ON WELLHEAD PROTECTION AREA DELINEATION1

ABSTRACT: Delineation of a welihead protection area (WHPA) is the key element in welihead protection programs for drinking water supplies. WHPAs are often delineated under idealized conditions using simple steady-state assumptions, which lead to an incorrect estimation of area and geometry. In this paper, we compare the results from a simple steady-state procedure commonly employed in WHPA delineation with a more complex transient approach that allows consideration of seasonal variation in pumping rates. We also introduce a transient procedure to delineate time-related capture zones using a numerical ground water flow and transport model. Welihead delineation is examined for two municipal wells in Tipton, Oklahoma, using a ten-year time-of-travel criterion. In the steady-state procedure, where we assumed constant pumping rates, we used GPTRAC, a semi-analytical model, and MOC, a numerical model. The capture zone delineated by GPTRAC is comparable in shape with the capture zone delineated by MOC but not in size due to the differences in solution schemes. In the transient procedure, we used MOC and considered the seasonal variation in pumping rates. The capture zones delineated in this procedure were larger than the capture zones delineated by the steady-state procedure using the same model. Further analysis showed that a higher drawdown was predicted in the transient procedure than in the steady-state procedure, which is the reason for larger capture zones.     

A DYNAMIC BACTERIAL MODEL FOR A RECREATIONAL LAKE1

ABSTRACT A dynamic mathematical model was constructed to examine bacterial contamination problems affecting Ford Lake, a small recreational lake in Southeast Michigan. The model was calibrated and verified using summer dry weather averaged data and data from three wet weather surveys. Model simulations demonstrated that the major bacterial contamination was attributable to storm related perturbations affecting two point sources: the Huron River and the Ypsilanti Sewage Treatment Plant. The nonpoint source contribution was relatively minor. The Model is currently being used by the State of Michigan Department of Natural Resources as a management tool for assessing the effectiveness of planned pollution abatement strategies     

基于TM影像的人口密度数字模拟——以北京地区为例

居住区影像是人口分布客观真实的定性表现,对这种定性的数据源进行合理量化即可获得人口实际分布数据。在分析TM影像各个波段特征的基础上,选取5、4、3波段进行图像逻辑运算,比较精确地提取出居住区影像。计算居住区面积并依据面积大小将居住区分为3类,根据人口户籍统计值计算出3类居住区相对的人口分布比例系数kj。然后生成与居住区矢量投影相同的1km网格,利用图层叠加统计每个网格内的居住面积lj,居住区矢量与区县界矢量叠加统计每个区县内的居住面积Am,计算网格人口分配系数ki×lj/Am,依据该系数对人口总数进行网格化模拟,以得到人口密度空间分布规律。以北京地区为试验区进行人口模拟,结果显示北京中心区最大人口密度为16 661人/km2,其他地区最大人口密度是8231人/km2。在模拟结果的基础上估算乡镇级人口,对比分析乡镇级估算人口和实际调查人口对结果进行验证,对比数据表明该算法所得到的人口分布与实际人口分布较为相符。     

我国双车道公路事故预测模型研究中数据采集

事故预测模型的研究可为公路设计人员提供有效的安全设计工具。该研究需要大量基础数据的支撑,数据采集量的大小、数据质量和数据分析水平直接决定研究成果的优劣。笔者在双车道公路事故预测模型研究过程中,对我国双车道公路安全影响要素进行分析,确定基于现有条件下比较理想的数据采集对象,总结了数据采集的方法及其不足之处。具体包括数据采集的范围,样本量的需求,事故数据、交通组成数据、路侧、接入口和路线数据采集的方法、数据处理方式等。     

Modeling Stream Channel Characteristics From Drainage‐Enforced DEMs in Puget Sound,Washington, USA1

Abstract: Mapping stream channels and their geomorphic attributes is an important step in many watershed research and management projects. Often insufficient field data exist to map hydromorphologic attributes across entire drainage basins, necessitating the application of hydrologic modeling tools to digital elevation models (DEMs) via a geographic information system (GIS). In this article, we demonstrate methods for deriving synthetic stream networks via GIS across large and diverse basins using drainage‐enforced DEMs, along with techniques for estimating channel widths and gradient on the reach scale. The two‐step drainage enforcement method we used produced synthetic stream networks that displayed a high degree of positional accuracy relative to the input streams. The accuracies of our estimated channel parameters were assessed with field data, and predictions of bankfull width, wetted width and gradient were strongly correlated with measured values (r² = 0.92, r² = 0.95, r² = 0.88, respectively). Classification accuracies of binned channel attributes were also high. Our methodology allows for the relatively rapid mapping of stream channels and associated morphological attributes across large geographic areas. Although initially developed to provide salmon recovery planners with important salmon habitat information, we suggest these methodologies are relevant to a variety of research and management questions.     

区域环评中大气环境容量估算的研究进展

综述了大气污染物区域环境容量的主要影响因素、用于其计算的空气质量模型以及大气环境容量的研究步骤。现阶段应用较广泛的大气环境容量的预测模型有A-P值法模型、箱模型、线性优化模型、ADMS模型及多种模型相结合的复合模式等，通过研究分析，提出了存在的主要问题及其有效的解决途径。     

达州市国内旅游市场回归预测模型研究

旅游市场预测可以帮助旅游地掌握市场需求的变化及其发展趋势，是旅游地制定发展战略和市场营销决策的基本依据。以达州市国内旅游市场为研究对象，主要从统计学的角度，建立达州市国内旅游市场的预测模型，并结合达州市旅游业的发展战略趋势，对达州市国内旅游市场进行预测，这对达州市旅游业的健康发展具有一定的指导意义。     

企业安全生产主因素辨析的模糊数学模型及应用——来自电网企业的实证研究

应用模糊数学的思想建立了企业的安全主因素辨析的模糊数学模型。运用在电网企业调研的实际数据,分析和证实了影响电网经营企业安全的主要因素,它们依次是管理、员工素质、电网结构、环境。对电网企业而言,员工素质和电网结构在短期内具有不易变的特点,管理是影响安全效果的最活跃的因素。在对“管理”要素作为二级分析时,辨析出8个安全管理方面的“要素”,其分别影响着电网安全生产。研究结果对电网安全管理实践有一定的指导意义。