RUNOFF EVENT IMPACTS ON A WATER SUPPLY RESERVOIR: SUSPENDED SEDIMENT LOADING, TURBID PLUME BEHAVIOR, AND SEDIMENT DEPOSITION1

Abstract: The impacts of runoff events on external suspended solids loading to Schoharie Reservoir, New York, and patterns of light scattering and sediment deposition in this reservoir are assessed. The assessment is based on monitoring of suspended solids concentrations in the reservoir's primary tributary, detailed vertical profiles of optical backscattering (a surrogate measure of light scattering) in the reservoir water column, and analysis of sediment trap collections, over a seven-month interval of high runoff. These impacts are reported to be tightly temporally coupled and strongly positively related to the magnitude of runoff events. The primary tributary entered the reservoir as a plunging inflow during runoff events, causing conspicuous subsurface peaks in light scattering, with vertical patterns that varied strongly for different events. Deposition quantified by near-bottom trap deployments is reported to be more representative than results from metalimnetic deployments that were generally within, rather than below, the turbid layers. Direct inputs of sediment, transported by density currents, are found to drive deposition, rather than resuspension/redeposition. More than 50 percent of the reported deposition occurred in less than 15 percent of the study period, associated with the four largest runoff events.     

我国春季沙尘暴研究

利用GMS卫星遥感资料,结合地面气象观测资料和中尺度每小时数值模拟,对1998年4月和2000年4月发生的强沙尘大气演变过程进行了详细的分析,初步确定了影响我国的沙尘暴起始源地,并将我国的沙尘暴天气划分为U变化型（停滞型）和移动型（锋面气旋型等）．详细分析了低涡型沙尘暴和东北低涡型沙尘暴的发生、发展的宏观机制     

SIZING OF SURFACE WATER RUNOFF DETENTION PONDS FOR WATER QUALITY IMPROVEMENT1

ABSTRACT: Historically, storm water management programs and criteria have focused on quantity issues related to flooding and drainage system design. Traditional designs were based on large rainfall‐runoff events such as those having two‐year to 100‐year return periods. While these are key criteria for management and control of peak flows, detention basin designs based on these criteria may not provide optimal quality treatment of storm runoff. As evidenced by studies performed by numerous public and private organizations, the water quality impacts of storm water runoff are primarily a function of more frequent rainfall‐runoff events rather than the less frequent events that cause peak flooding. Prior to this study there had been no detailed investigations to characterize the variability of the more frequent rainfall events on Guam. Also, there was a need to develop some criteria that could be applied by designers, developers, and agency officials in order to reduce the impact of storm water runoff on the receiving bodies. The objectives of this paper were three‐fold: (1) characterize the hourly rainfall events with respect to volume, frequency, duration, and the time between storm events; (2) evaluate the rainfall‐runoff characteristics with respect to capture volume for water quality treatment; and (3) prepare criteria for sizing and designing of storm water quality management facilities. The rainfall characterization studies have provided insight into the characteristics of rainstorms that are likely to produce non‐point source pollution in storm water runoff. By far the most significant fmdings are the development of a series of design curves that can be used in the actual sizing of storm water detention and treatment facilities. If applied correctly, these design curves could lead to a reduction of non‐point source pollution to Guam's streams, estuaries, and coastal environments.     

A SCALE‐INVARIANT GAUSS‐MARKOV MODEL FOR DESIGN STORM HYETOGRAPHS1

Abstract. Hyetographs are essential to many hydrological designs. Many studies have shown that hyetographs are specific to storm types and durations. Recent work presented evidence that dimensionless hyetographs are scale invariant. We show that the simple scaling property of rainfall guarantees that the normalized rainfall rates of different storm durations are identically distributed and propose a nonstationary Gauss‐Markov model based on the annual maximum events that arise from the dominant storm type. We derive the unique estimators for the parameters of the Gauss‐Markov model under two constraints that: (a) the typical peak rainfall rate is preserved, and (b) the most likely hyetograph is obtained. One attractive feature of this model is that it allows translating hyetographs between storms of different durations. Two examples illustrate our model.     

湖南省水旱灾害与暴雨径流资源的调控

通过对湖南省1950～2002年水旱灾情、1954～1998年降水量的统计,结合流域自然条件和水利现状综合分析表明:湖南省山丘区水旱灾害交替演进日趋明显,洞庭湖区外洪内涝交织频繁,农村饮水困难人口数量不断增多。7～9月降水量占全年降水量的20%,而4～9月降水量占69%,且多以暴雨形式出现,这一降水特点是导致水安全问题的症结所在。因此,必须充分利用山区有利地形修筑拦蓄小型工程,全方位建设生态环境,挖掘水库群的防洪兴利潜力和提高大型水库的调度水平等措施,调控4～8月的暴雨径流,以减轻水旱灾害,满足供水、发电、航运等方面的需水要求。     

沙尘暴降尘对甘肃大气环境背景值的影响研究

通过近15年来发生在我国西北地区的较大沙尘暴个例,就沙尘暴对甘肃境内大气环境背景值的影响等问题进行了调查、分析和研究.使用降尘背景观测点的大气降尘资料和样品,统计、分析和研究了沙尘暴降尘在各地区的沉降量、分布范围、化学组分和粒度分布特征等问题.研究认为:沙尘暴不只是一种特异的灾害性天气,同时它还是一种跨地区的大范围大气污染现象;在无湿沉降机会时,它会被输送到很远的地方,所影响和污染区域也会更大;沙尘暴还会向下游地区输送有害物质,对生态环境造成潜在和长期的影响;沙尘暴降尘量在甘肃的分布是以河西走廊东部为中心,向大气环流下游地域扩散,形成一个自西向东南迅速递减的梯度分布状态.受沙尘暴降尘的影响,近15年来甘肃省大气自然降尘背景值总体水平呈上升趋势.      

利用EP/TOMS遥感资料分析我国上空沙尘天气过程

利用EP/TOMS卫星遥感资料,并结合地面气象观测记录,分析了影响我国典型沙尘暴天气的发生、发展和传输过程.定义了使用EP/TOMS气溶胶指数定量描述沙尘天气强度的指标体系,并对1998年3-4月间发生的沙尘天气的强度及其演变进行了详细的分析.结果表明:利用EP/TOMS 气溶胶指数并结合气象观测资料,可以对大规模的沙尘天气进行及时判别、监视,并预报影响范围及传输路径;同时,利用TOMS气溶胶指数建立起来的指标体系可以半定量化地描述沙尘暴天气的强度和影响范围.      

滇池柴河小流域暴雨径流氨氮的输移过程研究

氨氮通过暴雨径流的冲刷和土壤颗粒物的携带进入水体,对受纳河流、湖泊造成污染。以柴河小流域为单元,从输出源、输移过程、河道汇集过程这几个方面对2011年7、8月2场暴雨径流中的氨氮进行分析。结果表明:氨氮主要是吸附于土壤颗粒表面进行输移,所以土壤颗粒流失是氨氮流失控制的关键;氨氮浓度跟沉降时间的Pearson相关性均在-0.855(P<0.05)之上,呈显著负相关;2场暴雨中,均是颗粒物粒径小于0.000 8 mm的水样的氨氮浓度较大,说明粒径较小的颗粒物对氨氮的吸附量较大;氨氮的入河系数与污染源及输移过程氨氮含量的Pearson相关性在0.914(P<0.05)以上,说明入河系数与污染源及输移过程含量密切相关。氨氮的入河系数为0.12⁰.22,说明研究区域80%以上的氨氮被边坡、沟渠截留,效果良好,值得认真对待。     

厦门市城市绿地雨洪减排效应评价

城市绿地在对雨水的渗透、滞留和调蓄方面具有非常显著的作用,能够有效削减城市的雨洪流量,缓解内涝压力.以海绵城市试点——厦门市为典型区,在日降雨数据、土地利用数据、土壤类型数据、城市绿地空间分布数据和城市建成区空间范围数据等多源数据的支撑下,系统评价了厦门市建成区城市绿地的雨洪减排效应.其中,雨洪减排效应的实物量通过SCS（Soil Conservation Service）模型进行评估,价值量则利用替代市场法进行估算.结果表明:2010年厦门市单位城市绿地削减的雨洪径流深为262.28 mm,削减的雨洪径流总量为4 385.40×104 m3,减排服务价值为2.75×108元;2015年单位城市绿地削减的雨洪径流深为335.77 mm,削减的雨洪径流总量为7 634.37×104 m3,减排服务价值为5.49×108元.城市绿地面积、降水量及其时程分配是影响城市绿地雨洪减排效应的关键因子,在其共同驱动下,2015年厦门市城市绿地的雨洪减排效应较2010年显著增加.研究显示,SCS模型在数据输入和参数率定等方面具有显著优势,能够在地理空间上连续模拟厦门市整个建成区的产流量,进而实现行政区单元和城市绿地类型单元雨洪减排效应的双重评价,3种城市绿地类型（乔木、灌木和草本）单位面积的雨洪减排效应并无明显差异,受绿地面积支配,厦门市80%的城市绿地雨洪减排效应由乔木绿地产生.      

基于碑刻记录的嘉陵江清代洪水发生规律及成因研究

基于历史文献法收集整理了《四川两千年洪水史料汇编》中嘉陵江清代洪水碑刻的碑文记录,并利用Gibbs-Mirtin多样化指数法分析洪水碑刻记录的空间分布特征。结果发现:清朝时期,嘉陵江流域共有洪水碑刻记录55通,月份明确可辨的有36通。空间上整体分布不均,下游多于中上游,其中嘉陵江干流28通(20通有明确月份;Gibbs-Mirtin多样化指数为0.46,上游仅有零星分布,相对集中于中下游),渠江16通(10通有明确月份;Gibbs-Mirtin多样化指数为0.71,各河段均有分布),涪江11通(6通有明确月份;Gibbs-Mirtin多样化指数为0,仅集中于下游的重庆市)。洪水碑刻记录在年内主要分布于6、7、8、9四个月,洪水碑刻清晰记录了清代1679年(2通)、1840年(3通)、1870年(17通)、1903年(2通)4次特大洪水,洪水碑刻记录的嘉陵江流域清代洪水的发生频率为7 a一洪。清代嘉陵江洪水碑刻记录反映了流域夏秋季洪水较多,这与嘉陵江流域的亚热带湿润季风气候、多洪齐发的扇状水系、低山丘陵-谷坝地形、松散的土壤质地以及"湖广填川"时期毁林垦荒导致的水土流失与河道淤积有关。