The Role of Headwater Streams in Downstream Water Quality1

Abstract: Knowledge of headwater influences on the water‐quality and flow conditions of downstream waters is essential to water‐resource management at all governmental levels; this includes recent court decisions on the jurisdiction of the Federal Clean Water Act (CWA) over upland areas that contribute to larger downstream water bodies. We review current watershed research and use a water‐quality model to investigate headwater influences on downstream receiving waters. Our evaluations demonstrate the intrinsic connections of headwaters to landscape processes and downstream waters through their influence on the supply, transport, and fate of water and solutes in watersheds. Hydrological processes in headwater catchments control the recharge of subsurface water stores, flow paths, and residence times of water throughout landscapes. The dynamic coupling of hydrological and biogeochemical processes in upland streams further controls the chemical form, timing, and longitudinal distances of solute transport to downstream waters. We apply the spatially explicit, mass‐balance watershed model SPARROW to consider transport and transformations of water and nutrients throughout stream networks in the northeastern United States. We simulate fluxes of nitrogen, a primary nutrient that is a water‐quality concern for acidification of streams and lakes and eutrophication of coastal waters, and refine the model structure to include literature observations of nitrogen removal in streams and lakes. We quantify nitrogen transport from headwaters to downstream navigable waters, where headwaters are defined within the model as first‐order, perennial streams that include flow and nitrogen contributions from smaller, intermittent and ephemeral streams. We find that first‐order headwaters contribute approximately 70% of the mean‐annual water volume and 65% of the nitrogen flux in second‐order streams. Their contributions to mean water volume and nitrogen flux decline only marginally to about 55% and 40% in fourth‐ and higher‐order rivers that include navigable waters and their tributaries. These results underscore the profound influence that headwater areas have on shaping downstream water quantity and water quality. The results have relevance to water‐resource management and regulatory decisions and potentially broaden understanding of the spatial extent of Federal CWA jurisdiction in U.S. waters.     

冲压机械伤害风险评价信息系统研究

研究冲压机械伤害风险评价信息系统,无论对企业内部事故预防还是对职工健康安全,还是节省国家因事故造成的经济损失,都十分必要。应用计算机编程语言和数据库软件,对冲压作业进行综合管理评价、设备设施的固有危险性评价及劳动卫生与作业环境评价,进而对冲压作业风险进行评价分级,建立动态的冲压机械伤害风险评价数据库管理信息系统。该系统可保存所有评价的项目资料,供应用和参考,实现了对冲压机械伤害风险评价的数据库动态管理,使风险评价分析工作组织化、条理化、系统化。     

煤矿安全生产中人的行为影响因子系统动力学(SD)仿真分析

在构建影响人的安全行为因素因果关系的基础上,运用系统动力学(SD)理论和方法,对影响人的安全行为关键因素进行动态预测,并通过仿真计算、对比分析安全投入增加对系统安全水平的影响。应用该方法建立的煤矿生产中人的安全行为指标水平模型,以求证安全投入与人的安全行为水平的相关性,为煤矿安全管理决策提供一种新的思路,亦有助于政府和煤矿企业科学地明确安全投入方向,降低人因事故率,提高煤矿生产的安全水平。     

基于GIS/AHP集成的洪水灾害综合风险评价——以淮河流域为例

根据影响洪水灾害风险的致灾因子危险性、孕灾环境稳定性与承灾体易损性,以淮河流域为示范研究区,以县为行政单元,综合考虑降雨、径流量、河流、地形、人口、经济等指标,基于GIS与AHP集成方法得到了淮河流域洪水灾害危险性评价图和淮河流域洪水灾害脆弱性评价图,并采用"加"模型计算公式得到了洪水灾害综合风险评价图,进行了相应的结果分析。     

Contaminant degradation in physically and chemically heterogeneous aquifers

This paper examines the importance of the correlation between hydraulic conductivity (K) and degradation rate constant (k) during the transport of reactive contaminants in heterogeneous aquifers. We simulated reactive transport in an ensemble of two-dimensional heterogeneous aquifers. Two sets of transport simulations were conducted: one in which a perfect positive correlation was assumed between ln(K) and ln(k), and one in which a perfect negative correlation was assumed. We found that the sign of the correlation has important consequences for the contaminant transport. Qualitatively, a negative correlation leads to significantly more pronounced "fingering" of the contaminant plume than does a positive correlation, with potentially important consequences for downgradient receptors. Quantitatively, the expected behavior (as quantified by the contaminant mass remaining in the aquifer) is statistically different between the positive and negative cases: on average, more contaminant mass persists when K and k are negatively correlated. Also, the negative correlation leads to more variability between realizations of the ensemble, whereas a positive correlation induces relatively little variability between realizations. We discuss the implications of these findings for the management of contaminated aquifers.     

地震灾害综合应急能力评估研究

汶川大地震在给我国带来巨大的悲痛和损失的同时，也检验了我国政府的突发事件应急能力。此次抗震救灾凸显出我国地震灾害应急能力存在的一些不足。建立“突发事件综合应急能力评估指标体系”的目的是为了评估政府的突发事件应急能力，以评促建。地震灾害由于其不同于其它突发事件的特性，其应急管理也有其特定的内容。现以地震灾害特征为标准，选取13个省市为样本，套用已有评估指标体系，分析和评估我国地震灾害应急能力。研究认为，我国应加强地震灾害应急能力建设，同时认为已有评估指标体系能满足使用要求。     

阿海水电站新源沟砂石加工废水处理工艺浅谈

新源沟砂石加工系统生产废水SS浓度高,采用水力旋流/加药絮凝/多级沉淀工艺处理,运行结果表明,处理出水水质满足《污水综合排放标准》（GB8978-1996）一级标准中的给定限值70mg/L,达标出水全部回用。     

无锡市生态足迹的系统动力学仿真研究

以生态足迹衡量居民对生态资源的需求，构建了包含社会经济、环境、人口、资源子系统的无锡市生态足迹系统动力学模型，分析了各因素对生态足迹系统的驱动作用和相互关系。基于模型预测了无锡市“十二五”期间的生态足迹数值，显示未来5年无锡市的生态足迹将继续呈现递增趋势，反映出居民对生态资源需求和对环境潜在压力不断增大。因此，市政府需重视居民的生态需要，不断改善生态环境，持续推进生态城市建设工作。     

安全生产支撑模式及架构探讨

用系统论方法分析安全生产工作的整体性概念,指出安全生产支撑体系构建应以系统论的科学理论为基础,并提出在社会主义市场经济条件下,制度支撑、组织支撑和技术支撑共同构成稳定完整的安全生产支撑模式。在架构上,安全生产支撑体系可细分为若干各具特点的服务与支持系统,包括法律法规、安全标准、政策措施、企业安全管理、政府安全监管、事故应急管理、科技创新、中介服务、宣传教育等体系,该体系相对独立、相互联系,共同构成完整的安全生产支撑体系框架。     

The role of satellite and decentralized strategies in water resources management

Existing and projected water shortages and related factors have helped focus attention on the need for water reuse. With recent technological advances in wastewater treatment, it is now possible to produce reclaimed water of any quality. Thus, the use of reclaimed water will depend on the reuse opportunities and the cost of the required infrastructure. Historically, centralized wastewater treatment facilities have served the needs of organized societies since the mid 1800s. However, as there are limited options for expansion of most existing centralized facilities, the use of satellite and decentralized wastewater management systems offers significant advantages including being close both to the source of wastewater generation and to potential water reuse applications. The comparative advantages of satellite and decentralized wastewater management systems for a number of water reuse applications are presented and discussed in this paper. Selected case studies are presented to demonstrate the utility of satellite and decentralized wastewater management. Specific issues associated with the application of such systems in existing and in new developments are examined and discussed.