SNOWPACK CHANGES RESULTING FROM TIMBER HARVEST INTERCEPTION,REDISTRIBUTION, AND EVAPORATION1

ABSTRACT: Three processes were examined as causing snowpack changes in forest clearings. Two of the three contribute to increases and one counteracts by reducing snowpack. The two that increase snowpack are redistribution and decreased loss to interception. Snow evaporation from a clearing counteracts snowpack increases. Research has indicated that as vegetation density increases, so too does the loss to interception. As snow in the canopy reaches the limit that the canopy can hold (the threshold amount) evaporation increases. Aerodynamics of the forest canopy were studied as well. As timber is cut, wind patterns are disturbed, creating disruptions in the wind velocity gradient depositing snow in openings. This redistribution leads to an increased snow water equivalent and augments runoff. Snow evaporation was shown to increase proportionally with opening size. Evaporation offsets the water yield gains derived from forest cut. It was found that this offset is inclusive to the measurements of water yield changes in experimental forests. An optimal size of harvest block may be five tree heights in width as suggested by numerous studies.     

THE COSTS OF CONFLICTING ENVIRONMENTAL POLICY: A CASE STUDY IN MILWAUKEE1

ABSTRACT: The history of the Milwaukee water pollution abatement program is examined as a case study to investigate the costs of conflicting environmental policy. The recent U.S. Supreme Court decision concerning the Milwaukee case is described as a milestone in U.S. water pollution abatement policy which will help preclude the type of environmental policy conflict which has been found to be so costly to Milwaukee. The implications to U.S. water pollution abatement policy of the 13-year history of conflict in Milwaukee are presented.     

DESIGN OF SEWER SYSTEMS1

In order to cope with the ever increasing problems of the urban environment, new approaches are being sought to their solution. The objective of this paper is to review and evaluate the merits of certain new methods aimed at finding optimal solutions in sewer design. Based on principles similar to the ones advanced by Deininger [1966] and Holland [1968] the authors propose an integer programming algorithm for optimizing pipe sizes and slopes. The new algorithm is applied to an actual situation and compared with a solution arrived at by a traditional design approach.     

COMBINED SEWER OVERFLOW CONTROL THROUGH IN-RECEWING WATER STORAGE: AN EFFICIENCY EVALUATION1

ABSTRACT: A demonstration and efficiency evaluation project was conducted for the flow balancing method (FBM) facility, a combined sewer overflow (CSO) storage facility at Fresh Creek in Brooklyn, New York City. The FBM is a curtained tank located directly in the receiving water that captures CSO. The CSO floats on top of and displaces Fresh Creek saltwater before it is pumped back to the publicly owned treatment works (POTW). The facility was a pilot scale subject to the full CSOs. The purpose of the project was to show how the FBM can withstand severe weather and tidal conditions and to develop a procedure for estimating CSO control efficiency (percentage of CSO pumped back to the POTW). The procedure proved successful and incorporated specific conductivity as a tracer in mass balance equations. These equations provided estimates of the net percent, capture-pumpback of the CSO using the FBM, including the amount of Fresh Creek water that was included in the pumpback to the P01W. The efficiency was directly related to the volume of the CSO and the pumpback rate and ranged from a low of 3.3 percent for the largest event to a high of 76.9 percent for the smallest event. Recent FBM enlargement should result in substantial increases in CSO control. The FBM facility has operated successfully for over five years, withstanding ice storms, near hurricane force winds and up to 7 ft tidal range.     

FOG DRIP,WATER YIELD,AND TIMBER HARVESTING IN THE BULL RUN MUNICIPAL WATERSHED,OREGON1

Analysis of recent streamflow data from the Fox Creek Experimental Watersheds in the Bull Run Municipal Watershed, Oregon, indicates a significant recovery from the impacts on summer water yield due to a loss of fog drip upon timber harvesting. Measurable impacts and their associated recovery are notable only during the months of June and July. Recovery begins about five or six years following harvest, possibly due to renewed fog drip from prolific revegetation. Watershed positioning with respect to prevailing weather systems and the extent of burning or removal of slash and residual vegetation during logging appear to be important factors in predicting the impact of fog drip reduction associated with planned harvest. Apparently, once the temporary reduction in summer yield is offset by renewed fog drip, the expected increase in yield due to decreased evapotranspiration can be observed. Redistribution of fog drip may be a major factor in the measurements of local interception and water yield.     

盘龙江上段截污工程社会效益和生态系统服务价值评估

通过背景资料收集、问卷调查、条件价值评估等方法,对昆明市盘龙江上段截污工程的社会效益进行了评估,估算了环境整治后盘龙江上段的生态系统服务价值。研究结果表明：昆明市盘龙江上段综合整治具有良好的社会效益,体现出较高的生态系统服务价值。     

合流制排水系统溢流污染控制策略的系统动力学分析

为了探索城市合流制排水系统溢流污染的控制策略,基于合流制排水系统结构特征,应用系统动力学方法构建了溢流污染控制系统动力学模型。该模型分为污染源产生子系统、收集运输子系统、污水溢流子系统、污水处理子系统及受纳水体子系统5部分,每个子系统相互作用构成完整的系统动力学模型。将该模型应用于镇江市老城区合流制排水系统溢流污染控制规划,从排水系统的源-流-汇三方面(包括源头减污、过程控污、末端治污和综合集成),模拟分析各种溢流污染控制策略的效能。     

高水力负荷对人工湿地处理精养虾塘排水效果的影响

通过水平潜流人工湿地处理精养虾塘排水的中试试验,探讨了在不同高水力负荷条件下[1.10～5.34 m3.(m2.d)-1]人工湿地对有机物、氮磷以及悬浮物的去除效果,以期为其设计运行提供参考.结果表明,水力负荷与COD、TN、TP、SS的去除率呈负相关;COD、TN、SS去除速率随水力负荷的升高,先升后降,最高分别达到69、1.8和117.6 g.(m2.d)-1;TP的去除速率随水力负荷的升高变化并不明显.人工湿地在水力负荷2.52～3.24 m3.(m2.d)-1范围内运行时,污染物去除总量最高处理效果最佳.     

基于遥感的千烟洲人工林蒸散及其组分模拟研究

论文通过改进遥感蒸散模型的关键参数,结合遥感数据和气象观测数据,对2003—2008年江西千烟洲人工林生态系统蒸散及其组分进行模拟,并利用涡度相关技术获取的蒸散实测数据对模型模拟结果进行验证和评价。结果表明:①年均蒸散总量模拟值比实测值偏低2.4%,决定系数与均方根误差分别为0.83和0.61 mm·d^-1。②土壤蒸发、林冠截留蒸发和植被蒸腾分别占总蒸散量的12%、23%和65%。其中,土壤蒸发季节及年际变化相对稳定;林冠截留蒸发季节变化明显且在不同年份差异较大;植被蒸腾季节变化明显,但年际变异较小。③1—3月植被光合作用较弱,植被蒸腾与蒸散比小于30%。随着植被蒸腾的增强,从4月开始植被蒸腾与蒸散比迅速增加,在生长旺季(7月底)可达到约90%。由于该模型所需数据在区域尺度较易获取,从而为开展区域尺度中亚热带人工林生态系统蒸散及其组分模拟提供方法支撑。     

苏州城区雨水管道沉积物典型污染物分布特征

分别采集了苏州城区商业区、历史文化保护区、文教区和生活区等典型样点的雨水管道沉积物,分析沉积物粒径分布和各分级粒度下碳、氮和磷含量及污染负荷的分布特征.结果表明,各样点沉积物颗粒的中值粒径(D50)为16.55～327.50μm,从大到小为:商业区＞生活区＞历史文化保护区＞文教区,D50与沉积物中总有机碳(TOC)、总...