SHOULD DAMS BE MODIFIED FOR THE PROBABLE MAXIMUM FLOOD?1

ABSTRACT: The probable maximum flood (PMF) currently serves as the design standard for many U.S. dams. Floods used for design have increased and currently thousands of dams in the U.S. would be overtopped and possibly fail using the latest calculated PMF at each dam site. Some researchers have suggested that modifying dams to accommodate the PMF could be wasteful. Objections to using the PMF for dam modification include: (1) larger spillway capacity may increase annual downstream flood losses, (2) benefit‐cost ratios may be low, (3) construction accidents associated with dam modification may cause fatalities, and (4) the dollar amount spent to save lives by making dams safer is often very high. Based on these objections, a procedure is presented for evaluating the effectiveness of a proposed dam modification. A change in spillway design policy is recommended. Accepting the status quo at a dam that cannot accommodate the PMF may be the best course of action.     

河南水旱灾害危险性时空特征研究

河南省地处南北气候过渡带,水旱灾害频发。综合利用灾害数据资料及信息扩散模型,从致灾和承灾两个层面对河南省水旱灾害进行风险评估与时空特征研究,为加强水旱灾害的风险评估和管理提供理论依据。结果表明:①1988-2007年间发生水灾的年份主要是2003、2000、1998、1996、 2005,旱灾年份是1997、2001、1999、1992、1988;②当降水距平百分率为20%、30%、40%时,发生水灾的概率分别为0.10、0.06、0.04,当降水距平百分率为-20%、-30%、-40%时,发生旱灾的概率分别为0.13、0.07、0.03;③水灾在5%、10%和15%受灾率时的风险概率分别为0.81、0.54、0.35,即1~3 a一遇之间,当受灾率大于20%时,风险概率为0.22,大约4.5 a一遇;而旱灾在5%、10%、15%、20%、25%受灾率时的风险概率分别为0.87、0.72、0.58、0.47和0.38,即1.2 a、1.4 a、1.7 a、2.1 a和2.6 a一遇;④旱灾发生频率大于水灾,空间上具有较大的区域差异,水旱灾害高风险区主要是驻马店、南阳、平顶山一带,旱灾大于水灾的区域主要是三门峡、洛阳、郑州、焦作、安阳、许昌,水灾大于旱灾的区域主要是信阳、漯河、开封、商丘、周口、濮阳,水旱灾害均较小的是济源和鹤壁。     

新疆强对流暴雨的气候特征和概率分布模式研究

应用1980—2001年的6h降水量资料和雨量时程方程，首次给出了新疆地区强对流暴雨的划分标准；分析了强对流暴雨的气候特征、大气环流背景、影响系统、变化趋势和概率分布模式；发现，20世纪90年代强对流暴雨次数有明显的增加，Poisson分布拟合强对流暴雨频率分布尚好，还计算了各地每年(雨季)强对流暴雨发生n次以上的概率。     

Antioxidant responses to benzo[a]pyrene, tributyltin and their mixture in the spleen of Sebasticus marmoratus

It has been reported that there is an interaction between Benzo[a]pyrene （BaP）, a widespread carcinogenic polycyclic aromatic hydrocarbon, and tributyltin （TBT）, an organometal used as an antifouling biocide. This study was therefore designed to examine the potential in vivo influence of BaP, TBT and their mixture on splenic antioxidant defense systems of Sebastiscus marmoratus. The fish were exposed to water containing environmentally relevant concentrations of BaP, TBT and their mixture. Spleens were collected for biochemical analysis after exposure for 7, 25, 50 d and after recovery for 7, 20 d. Cotreatment with BaP and TBT for 7 d potentiated the induction of glutathione peroxidase （GPx） activity by BaP or TBT alone. The cotreatment for 25 and 50 d resulted in inhibition of GPx activity, which was similar to the effect of TBT. Splenic glutathione S-transferase （GST） activities were significantly elevated in S. marmoratus exposed to BaP starting from 7 d and remained high up to 25 d. However, no further activity change was found with prolonged exposure. Cotreatment of BaP and TBT primarily inhibited the GST activity, which was similar to the effect of TBT. Cotreatment with BaP and TBT for 25 or 50 d potentiated the depletion of GSH （glutathione） by BaP or TBT alone. MDA （malondialdehyde） contents in spleen of S. marmoratus were not significantly altered compared with the control during the test period. Spleen, as an immune organ, is sensitive to exposure of BaP or TBT. It should have an effective mechanism to counteract oxidative damage. Antioxidative defense systems in spleen of S. marmoratus should be considered as potential biomarkers. Short-term exposure of BaP or TBT could result in induction of antioxidant defense system. A significant decrease of these indices, such as GSH, GST, GPx might indicate more severe contamination.     

UNCERTAINTY OF EXTREME FLOOD ESTIMATES INCORPRATING HISTORICAL DATA1

ABSTRACT: The ability to predict extreme floods is an important part of the planning process for any water project for which failure will be very costly. The length of a gage record available for use in estimating extreme flows is generally much shorter than the recurrence interval of the desired flows, resulting in estimates having a high degree of uncertainty. Maximum likelihood estimators of the parameters of the three parameter lognormal (3PLN) distribution, which make use of historical data, are presented. A Monte Carlo study of extreme flows estimated from samples drawn from three hypothetical 3PLN populations showed that inclusion of historical flows with the gage record reduced the bias and variance of extreme flow estimates. Asymptotic theory approximations of parameter variances and covariances calculated using the second and mixed partial derivatives of the log likelihood function agreed well with Monte Carlo results. First order approximations of the standard deviations of the extreme flow estimates did not agree with the Monte Carlo results. An alternative method for calculating those standard deviations, the “asymptotic simulation” method, is described. The standard deviations calculated by asymptotic simulation agree well with the Monte Carlo results.     

黑龙江省洪水资源化探讨

洪水是可利用的宝贵资源,科学、合理的开发利用洪水是解决水资源短缺的重要途径.要加大宣传力度,提高认识,统一规划,协调发展,充分利用森林、草原、湿地的生态功能保护洪水资源.     

2014—2018年冬季长三角强霾事件及天气形势影响分析

利用2014-2018年环保部空气污染监测资料以及同期NCEP/NCAR再分析资料,统计分析了冬季长三角地区强霾污染过程中大尺度环流背景场及气象要素对强霾污染的影响.结果表明：2014-2018年冬季长三角地区共发生5次强霾污染过程,每年冬季的12月和1月是强霾污染事件发生的高频时期.当大气中相对湿度维持在较高的水平并且维持较小的风速时,更有利于污染物的累积从而导致强霾污染事件的发生.雾霾天气的发生发展与大气环流有着密切联系,在强霾污染过程发生初期,污染物大多伴随冷空气由北向南输送至长三角地区,对流层中层500 hPa的大尺度环流形势多以纬向环流为主.严重污染发生时,长三角地区受平直西风气流影响,对流层低层850 hPa等压线较为稀疏,长三角地区受均压场或高压控制频繁,稳定的大气层结使污染物更易在近地层累积,随后大风伴随冷锋过境将污染物快速清洁导致PM_2.5浓度迅速降低.     

珠三角冬季PM2.5重污染区域输送特征数值模拟研究

利用嵌套网格空气质量模式系统(NAQPMS)及其耦合的污染来源追踪模块,针对2013年1月珠三角区域的PM_(2.5)重污染过程输送特征进行了数值模拟研究.结果表明,污染气团首先形成于广州、佛山地区,并在弱偏北风的作用下南移加强,影响整个珠三角区域.重污染期间,广州(64.9%)、佛山(58.9%)的PM_(2.5)主要来自本地贡献,是区域输送最主要的来源地区;中山(51.9%)、珠海(66.2%)的PM_(2.5)主要来自外来贡献,是区域输送主要的受体地区.重污染期间,广州和佛山对中山的PM_(2.5)日均贡献率之和总体保持在25%以上,污染最重时达到40%.交通(26%)、工业(24%)、扬尘(16%)、火力发电(15%)和生物质燃烧(8%)是对中山贡献最大的5类源:工业源中山本地与外来输送贡献率基本相当;交通和扬尘源以中山本地贡献为主,贡献率分别为55%和67%;火力发电和生物质燃烧源以外来输送为主,贡献率分别为56%和62%.各类排放源的外来输送中,以广州、佛山所占的比例最大.     

Risk factors in urban road traffic accidents

INTRODUCTION: The urban road traffic accident (RTA) risks for the city of Zagreb, Croatia, from 1999 through 2000 were analyzed with the aim of reducing the increasing injury incidence. METHOD: Simple and bivariate analysis using chi(2), odds ratio, and confidence interval of 95% was used to determine risks in three outcome groups: killed, severely, and mildly injured. RESULTS: There were 528 RTA victims consisting of 260 severely, 213 mildly injured, and 55 killed at the scene of an accident and during transportation. More fatal accidents occurred during night hours (OR=3.78; 95% CI, 2.08-6.85), on urban road links (OR=2.33; 95% CI, 1.30-4.19), and at exceeding speed limit (OR=2.56; 95% CI, 1.43-4.61). More people were injured than killed on urban junctions (OR=5.27; 95% CI, 2.21-12.57). The highest combined risk of dying or being severely injured was found in males, driving at excessive speed, on urban links, and during bad visibility (OR=16.15; 95% CI, 3.901-66.881). CONCLUSION: These results will influence the urban traffic police enforcement measures, which will change inappropriate behavior of drivers and protect the least experienced road users.