Vorkommen und Bewertung polyzyklischer aromatischer Kohlenwasserstoffe in einem mit kommunalen und industriellen Abwässern belasteten Fließgewässer

The river with a catchment of 5,400 km² is investigated over a length of 230 km at seven stations for the total concentration of six polycyclic aromatic hydrocarbons (PAH) and the total of three carcinogenic polycyclic substances (CPS) in the water by means of thin-layer chromatography. The maximum load occurs in the lower course downstream of large industrial wastewater introduction points with 5.1 μg/l polycyclic aromatic hydrocarbons, whereas in the upper course the maxima are at 2 … 3 μg/l polycyclic aromatic hydrocarbons for a mainly municipal pollution. The average daily load increases from 0.146 kg/d PAH and 0.048 kg/d CPS to 4.168 and 1.401 kg/d, respectively. In the flowing water there cannot be observed any self-purification concerning these substances, by an interconnected storage reservoir seston is reduced and thus also the PAC-concentrations are reduced by 50 … 60%. The PAH-concentration shows a significant positive correlation with the COD-Mn and the ammonium concentration. There is also a good agreement between the concentrations measured and the concentrations calculated from the wastewater load in the longitudinal section of the river.     

京蒙沙源区水库大气磷干、湿沉降污染特征

为阐明典型沙源区水库大气磷干、湿沉降的污染特征及其对水域磷素污染的贡献,为水库富营养化治理提供科学依据,以京蒙沙源区大河口水库库区为研究区,于2014年沿水库岸边布设12个大气沉降监测站点,采集干、湿沉降样品,测定干、湿沉降中总磷(TP)浓度,计算全年各月大气TP干、湿沉降通量和年入库TP污染负荷量.结果表明:研究区大气干、湿沉降季节差异显著,全年各月TP干沉降通量变化范围为4.89~35.76 kg/(km~2·月),主要集中在春季4月和秋季10月.最大TP干沉降通量出现在春季风沙最为严重的4月;湿沉降主要集中在夏季(6—8月),最大TP湿沉降通量出现在降雨量最大的8月,为28.88 kg/(km~2·月),且TP湿沉降通量与降雨量呈显著正相关.2014年大气TP沉降入库污染负荷量为0.719 t,占同期滦河和吐力根河两条河流入库TP污染负荷比率为51.17%,成为影响和限制大河口水库磷营养盐水平的重要源项之一.     

Estimation of baseflow nitrate loads by a recursive tracing source algorithm in a rainy agricultural watershed

Baseflow has become an important source of nitrate nonpoint source pollution in many intensive agricultural watersheds. Uncertainties in baseflow nutrient load separation are caused by the effects of hydrometeorological factors on both baseflow recession and baseflow nutrient load recession. These uncertainties have not been addressed well in the existing separating algorithms, which are based on simple baseflow rate–load relationships. In the present study, a recursive tracing source algorithm (RTSA) was developed based on a nonlinear reservoir algorithm and hydrometeorology-corrected baseflow nutrient load recession parameter. This approach was used to reduce the uncertainty of baseflow nitrate load estimation caused by variations in different load recessions under varying climate conditions. RTSA validation in a typical rainy agricultural watershed yielded Nash–Sutcliffe efficiency, root mean square error-observation standard deviation ratio, and R² values of 0.91, 0.30, and 0.91, respectively. The baseflow nitrate–nitrogen (N─NO₃^–) loads from 2003 to 2012 in the Changle River watershed of eastern China were estimated with the RTSA. The results indicated that baseflow nitrate export accounted for 62.0% of the mean total annual N─NO₃^– loads (18.0 kg/ha). The total baseflow N─NO₃^– export was highest in spring (3.6 kg/ha), followed by summer (3.2 kg/ha), winter (2.3 kg/ha), and autumn (2.1 kg/ha). The contribution of baseflow to total nitrate in the stream decreased in the order of winter (69.88%) >spring (66.59%) >autumn (60.36%) >summer (54.04%). The monthly baseflow N─NO₃^– loads and flow-weighted concentrations greatly increased during the research period (Mann–Kendall test, Z_s > 2.56, p < .01). Without proper countermeasures, baseflow nitrate may represent a serious long-term risk for water surfaces in the future.     

生态型水源水体生态净化及其影响因素

水库水体污染控制及富营养化防治是保障城市原水供应安全的重要环节.本研究针对金泽水源水库太浦河来水氮、磷浓度较高的特点,自行设计建设了5个面积均为240 m~2的生态净化模拟试验池(A、B、C、D和对照)开展模拟试验,研究了不同水库形态、水生植物种植面积比例及种植方式对水体氮、磷污染物去除的影响.结果表明,通过模拟试验池的生态净化,原水中铵态氮(NH_4~+-N)、总磷(TP)和总氮(TN)的平均去除率分别为50.36%、53.73%和22.25%,C池TN和NH_4~+-N去除率最高分别达到了24.97%和54.61%,D池TP去除率最高,达到62.16%,水体溶解氧(DO)平均浓度提高了1.11 mg/L,平均透明度提高了27.6 cm,均显著高于对照池.水库形态结构、水生植物面积比例及种植方式对水体氮、磷污染物净化效果影响明显,增大水库浅水区面积能有效提高对水体氮、磷污染物的去除能力,增加水生植物种植面积能有效提高水体氮污染物去除和DO、透明度的提升能力,采用浮床种植方式能有效提高水体磷污染物去除和透明度提升能力.本研究结果能为金泽水源水库及其他类似水库的设计和建设提供科学依据.     

Hydrobiological Investigations of the Water Quality of the Water Supply Reservoirs Husinec and Římov

The two eutrophicated reservoirs Husinec (2.6 km³, 35 ha, z_max 18 m, MQ 1.87 m^3/s) and ?ímov (34.5 hm³, 216 ha, z_max 44 m, MQ 4.14 m^3/s) show concentrations of total phosphorus of 10… 50 mg/m³ and chlorophyll contents of 7… 36 mg/m³ in the summer season. For both reservoirs a good correlation exists between the chlorophyll concentration and the density of the phytoplankton (20 · 10³… 13 · 10⁶ ind./l). With average concentrations of 10… 20 mg/m³ chlorophyll a in summer, the water can be treated for producing drinking water only at a higher expenditure. The water quality will be improved by a reduction of the phosphorus load.     

Field‐scale phosphorus losses from a drained clay soil in Sweden

The objective of this study was to determine and discuss field‐scale phosphorus losses via subsurface tile drains. A total phosphorous (Tot‐P) export, which averaged 0·29 kg ha⁻¹ year⁻¹, was measured over a six‐year period from the 4·43 ha drainage system of a Eutric Cambisol in Central Sweden. The main part (63%) was in particulate form (PP) while the remainder was either in phosphate form (PO₄‐P) or in other dissolved or colloidal forms. A very small area, less than 1% of the soil surface, was demonstrated to be hydraulically active by using a staining technique in soil monoliths taken from the field. The stained macropores were few, but were continuous downward, and were relatively evenly distributed among the eight 7 dm² areas that were investigated. The transport from the field mainly occurred in episodes during which the relationship between phosphorus concentration and discharge was characterized by hysteresis loops. On average, half of the yearly P transport occurred in 140 hours. Compared with flow‐proportional and frequent sampling, manual and fortnightly sampling underestimated the transport of Tot‐P and suspended solids (SS) by 59 and 42%, respectively, during the six years studied. Amounts of different phosphorus forms exported through the tile drains were very similar to those reported from other clay soils in Northern Europe and North America. Copyright © 1999 John Wiley & Sons, Ltd.     

Root-associated biofilms of Eichhornia heterosperma Alexander, 1939 contribute to the remediation of the tropical reservoir Porce II,Colombia

Two key factors were identified that enhance remediation of a hypereutrophic reservoir colonised by Eichhornia heterosperma Alexander, 1939. These factors are the high abundance of the microbial community in root-associated biofilms and their high extracellular enzyme activity (EEA). The capacity of macrophytes for nutrients removal has been widely acknowledged. However, there has been little discussion on the role of root-associated biofilms in enhancing phytoremediation. We determined nutrient levels across the reservoir quarterly during two years. We assessed the structure of the microbial community in water, root-associated biofilms, and sediments along with their phosphatase and β-glucosidase activities. We hypothesised that reservoir remediation is enhanced by increased nutrient remineralisation and bioavailability, arising from EEA in root-associated biofilms attached to E. heterosperma. Sedimentation removed 51% of the total nitrogen (TN) and 85% of the total phosphorus (TP) external load. E. heterosperma and its root-associated biofilms removed extra 8% TN and 7% TP. The abundance of the microbial community in root-associated biofilms was generally higher than in water and sediment, being dominated by Alphaproteobacteria and Betaproteobacteria. The EEA in root-associated biofilms ranged 117−1760 μmol g⁻¹ wet weight h⁻¹ for phosphatase and 107−676 μmol g⁻¹ wet weight h⁻¹ for β-glucosidase, indicating high mineralisation rates. These results showed that the microbial community in root-associated biofilms favours reservoir remediation by supplying mineralised nutrients to algae and macrophytes, but the permanent introduction of high nutrient loads exceeds the reservoir capacity for remediation. Improving the trophic state of the reservoir requires thus long-term strategies at basin scale for reducing the nutrient loads.     

江西柘林水库春季浮游藻类、叶绿素a与环境因子的分布、关系及意义

江西柘林水库是长江中游的大型峡谷型旅游性水库,库容79.2×10~8m~3,长115 km.2015年4月在56 km的中心库区走航和定点测量了水库表层水体浮游藻类、叶绿素a(Chl.a)浓度与溶解无机氮(DIN)浓度、溶解无机磷(DIP)浓度、溶解硅(DSi)浓度、水温、浊度和溶解氧浓度等环境因子的分布特征.结果表明:1)水库属于中营养水体,表层主要浮游藻类(细胞丰度1000 cells/L)有34种,平均生物量为0.41 mg/L.主要优势藻类(优势度≥0.02)为硅藻和蓝藻,藻类组成与DIN浓度、DIP浓度、DSi浓度和水温等环境因子关系密切,4种因子对藻类结构的解释水平达60%以上.2)水库水体Chl.a浓度具有显著的次表层叶绿素最大值(SCM)现象,SCM层深度为3~8 m,厚度为2~7 m,SCM层占整个水体的25.2%~74.1%.SCM层的藻类对营养盐吸收消耗致使DIN、DIP和DSi浓度下降,同时藻类的产氧使溶解氧浓度增加.3)水库对DSi具有显著的生物过滤器效应,中、上层约有11%~12%的DSi被生物吸收利用,从上游至下游,累积约有21%的DSi被藻类吸收沉降于库底.4)人类氮、磷排放对水库生态和水质有严重影响,毗邻县城区域水体的Chl.a和DIP浓度分别是自然河段的2.9倍和3倍左右.     

湖北浮桥河水库浮游植物初级生产力及其管理

浮桥河水库浮游植物水柱日生产量变幅为0.34-4.99 g/(m2·d),最低值出现在下游冬季,最高值出现在中游秋季,年平均值2.75 g/(m2·d)季节变化:秋季＞夏季＞春季＞冬季,与浮游植物叶绿素a含量和生物量的季节变化一致;水平分布:中游略高于上游,下游最低,与浮游植物叶绿素a含量的水平分布完全一致表层日生产量占水柱日生产量53.81%.与1980年同期相比,浮游植物初级生产力增加了1.2倍.分析表明,磷含量增加是浮游植物初级生产力提高的关键因子.应用能量收支法估算浮桥河水库鲢鳙渔产潜力为772t,516.0 kh/hm2.从渔业管理和水质管理角度讨论了合理利用浮游植物初级生产力的措施.     

哈尔滨西泉眼水库夏季浮游植物群落结构动态特征

西泉眼水库作为哈尔滨市第二水源地,事关居民的饮用水安全,而浮游植物群落特征则是水库生态系统健康状况监测与评估的重要研究内容之一,能为水库生态系统健康提供科学支撑.本研究设置13个采样点,对库区和入库河流的浮游植物群落进行对比分析,采样时间为蓝藻水华易发的7月和8月.经镜检,共鉴定浮游植物7门169种,其中绿藻门最多,83种,占总种数的49.11%;硅藻门次之,47种,占总种数的27.81%;蓝藻门15种,占总种数的8.88%;隐藻门最少,仅有2种.浮游植物丰度在10.92×105~88.44×105cells/L之间,均值为51.6×105cells/L,以8月的3#采样点最高;生物量在2.61~22.44 mg/L之间,均值为10.37 mg/L,以8月的5#采样点最高.Shannon-Wiener指数在2.46~4.69之间,均值为3.33,以7月12#采样点最高.研究水域浮游植物优势种群以梅尼小环藻(Cyclotella meneghiniana)、肘状针杆藻(Synedra ulna)、阿氏席藻(Phormidium allorgei)和游丝藻(Planctonema sp.)为主.同时,典范对应分析表明:1)既将西泉眼水库库区和入库河流区分为两个相对独立的生态系统,又展现了同一生态系统内的月份变化趋势,说明西泉眼水库库区和入库河流区的浮游植物群落的时空分布异质性显著;2)库区内河流入库口处、库心和大坝口处浮游植物群落梯级差异显著,入库河流区水质明显优于库区;3)氨氮、硝态氮、总氮和总磷是影响浮游植物种群的主要驱动因子.研究认为,西泉眼水库水体总体上已处于中度富营养水平,并存在进一步富营养化的风险.建议水库管理部门建立水生态系统健康监测与评估预警体系,配套相应的水生态管理制度,并采取适宜的生态修复技术等生态治理措施,以确保哈尔滨市供水水源安全.     

基于Landsat影像的近40年来(1982—2021年)三峡库区水面面积及其蒸发损失变化

三峡水库蓄水引起库区水位抬升,水面面积显著增加,对区域水文循环过程产生了一定影响。为揭示三峡水库蓄水前后水面面积及蒸发损失变化规律,选取三峡库区坝前至寸滩区间作为研究区,利用Landsat影像数据提取1982—2021年水面面积,分区建立水位与面积关系曲线,进而推求库区逐日水面面积。在估计三峡库区水面面积的基础上,结合站点潜在蒸发资料推求水面蒸发损失量。研究结果表明:2010年三峡水库全面运行后,坝前至寸滩库区平均水面面积由蓄水前的372.96km²,增加到761.31km²,较蓄水前增加了1.04倍。同时,三峡水库的蓄泄调节改变了库区河段原有的水文节律,使得库区水面面积的季节性变化特征较蓄水前发生了显著变化。蓄水后,冬季水面面积最大,平均为843.81km²,较蓄水前增加了1.89倍;秋季、春季次之,水面面积分别为818.73和735.28km²,较蓄水前分别增加了97.17%和1.28倍;夏季水面面积最小,为653.03km²,较蓄水前仅增加了39.06%。水库全面运行后,...     

Non‐point source pollution modelling using Soil and Water Assessment Tool and its parameter sensitivity analysis in Xin'anjiang catchment,China

Non‐point source pollution is a key issue in integrated river basin management around the world and has resulted in water contamination, aquatic ecology deterioration and eutrophication. Xin'anjiang catchment is the key drinking water source area for Hangzhou City, China. A promising model (Soil and Water Assessment Tool) was applied to assess the non‐point source pollution and its effect on drinking water. Sensitivity analysis of model parameters was carried out using the Sequential Uncertainty Domain Parameter Fitting 2 sensitivity technique. Water discharge, sediment, total nitrogen and total phosphorus load processes from 2000 to 2010 were simulated, and the spatial distributions of non‐point source pollutants were evaluated at the catchment and administrative country levels. The results show that the hydrological parameters of the Soil and Water Assessment Tool were dominantly sensitive for non‐point source pollution simulation, including CN2, RCHRG_DP, ALPHA_BF, SOL_AWC, ESCO and SOL_K and the characteristic parameters of sub‐basins (viz. HRU_SLP and SLSUBBSN). Also, water quality parameters (viz. CH_EROD, NPERCO, RSDCO and PPERCO, PHOSKD, etc.) have a significant effect on nutrients. The model performance was very satisfactory, especially for runoff, sediment and total phosphorus simulation. The non‐point source pollutant load increased from 2001 to 2010 in the whole catchment. Total nitrogen load increased from 3428 tons (0.59 ton km^?2) to 7315 tons (1.25 ton km^?2), and total phosphorus load increased from 299 tons (0.05 ton km^?2) to 867 tons (0.15 ton km^?2). The contribution of rice land was the largest, accounting for nearly 95%, followed by tea garden (3.56%), winter wheat (1.37%), forest (0.07%) and grassland (0.02%). Moreover, She County and Xiuning County contributed more than half of the non‐point source pollutants. This study was expected to provide a method and reference for non‐point source pollution quantification and to support water quality management implementation in China. Copyright © 2012 John Wiley & Sons, Ltd.     

黄河上游近60年水沙变化特征及其影响因素

由于受人类活动及气候变化影响,黄河上游干流水沙特征发生显著变化。为探究黄河上游水沙变化情况,基于黄河上游5个水文站1964-2019年水沙、遥感影像等数据,利用Mann-Kendall检验法、滑动t检验法、累积距平曲线和双累积曲线等突变检验方法和小波分析法,对黄河上游水沙变化特征进行研究。利用水沙关系曲线及线性回归法等方法估算人类活动和气候对水沙变化的贡献率,并着重讨论梯级水库建设及土地利用变化对水沙的影响。结果表明:1)黄河上游玛曲-小川段流域内降雨量和径流量变化幅度不明显,贵德站、循化站、小川站1986-2019年年均输沙量分别减至1964-1985年的9.8%、24.6%、38.8%,输沙量大大减少。黄河上游玛曲-小川段径流量突变多在1986年,输沙量突变多在1969、1986、2004年,径流量存在8、16、22 a周期,输沙量存在4~8、18~21、27 a周期。2)1969年后,河流输沙能力增强,水沙关系显著改变。在不同时段内,人类活动对径流量变化在1987-2019年贡献率为66.3%,对输沙量变化在1970-1986、1987-2004、2005-2019年的贡献率为72.96%、70.73%、69.7%。人类活动对黄河上游干流水沙影响占据主导因素。3)刘家峡水库淤积最为严重,单库运行期水库淤积量为2.39亿t,排沙比变化范围为1.39%~10.7%。梯级水库联调使得径流量在1964-2004年间减少47.8%,1964-2019年间梯级水库减沙94.8%,梯级水库对输沙量影响远大于对径流量的影响。4)1980-2020年间,草地面积增加了1880.03 km²,增幅3.1%,有利于减少输沙量,草地拦沙效益大于截流效益。     

The effect of drawdown on suspended solids and phosphorus export from Columbia Lake,Waterloo, Canada

This study examines the effect of drawdown on the timing and magnitude of suspended solids and associated phosphorus export from a 12 ha reservoir located in an urbanized watershed in southern Ontario, Canada. Water level in Columbia Lake was lowered by 1·15 m over a 2‐week period in November 2001. The total phosphorus (TP) concentrations ranged from 63 to 486 µg L^?1 in Columbia Lake and 71 to 373 µg L^?1 at its outflow. All samples exceeded the Provincial Water Quality Objective of 30 µg TP L^?1. Outflow concentrations of suspended solids and TP increased significantly with decreasing lake level and were attributed to the resuspension of cohesive bottom sediments that occurred at a critical threshold lake level (0·65 m below summer level). Suspended solids at the outflow consisted of flocculated cohesive materials with a median diameter (D₅₀) of c. 5 µm. Particulate organic carbon accounted for 8·5% of the suspended solids export by mass. A total mass of 18·5 t of suspended solids and 62·6 kg TP was exported from Columbia Lake, which represents a significant pulse of sediment‐associated P to downstream environments each autumn during drawdown. The downstream impacts of this release can be minimized if the water level in Columbia Lake is lowered no more than 0·5 m below summer levels. Copyright © 2004 John Wiley & Sons, Ltd.     

Chemistry and trophic evolution of Lake Lugano in relation to nutrient budget

Chemical studies performed in the last 50 years on the northern and southern basins of Lago di Lugano are reviewed and discussed in relation to the phosphorus and nitrogen loads from the drainage area.Both basins became eutrophic in the fifties as a consequence of the dense population and industrial activity in the drainage area; the effect of these was aggravated by the meromictic condition of the layer below 100 m in the northern basin.The reduction of phosphorus loads in progress since 1976 has resulted in a significant improvement in the chemical and biological condition of the southern basin and the upper 100 m of water in the northern basin. On the other hand, the balance between dissolved oxygen and reducing substances in the northern basin is shifting toward a decrease of the net oxygen concentration, partly as a consequence of the unusually dry conditions of the last three years.A reduction in phosphorus load down to 18 and 22 t a^–1 in the northern and southern basins respectively is still necessary in order to reduce the lake phosphorus concentration to 30–35 µg O l^–1.     

太湖流域池塘养殖污染排放估算及其空间分布特征

池塘养殖是农业源污染的重要来源之一,尤其在水网密布、渔业发达的太湖流域,控制池塘养殖过程中氮、磷、化学需氧量等污染物的排放,对于减轻水体富营养化程度、恢复水质健康、维持地区社会经济可持续发展具有重要意义.基于野外采样、入户调查、遥感解译等多种手段,结合GIS软件技术,对太湖流域池塘养殖污染物的排放进行了估算.结果表明,20142015年太湖流域总氮、硝态氮、铵态氮、总磷、可溶性磷、COD Cr的年排放量分别为6.1×10^6、1.1×10^6、1.7×10^6、1.3×10^5、1.1×10^5和8.0×10^7 kg.其中鱼类池塘养殖排放系数分别为69.5、12.4、20.1、1.6、1.3和919.8 kg/hm 2;虾类池塘排放系数分别为3.0、0.5、0.9、0.07、0.06和39.3 kg/hm^2;蟹类池塘排放系数分别为6.4、1.2、1.9、0.2、0.1和84.9 kg/hm^2.太湖流域池塘养殖各类污染物排放分布特征为位于太湖西北部、南部和东北部的大部分地区池塘养殖污染物排放较高,位于太湖东部和太湖西南部的池塘养殖污染物排放较低.池塘养殖业发达、饲料肥料投入高、养殖密度大等是造成该流域池塘养殖污染物排放较高的主要原因.针对太湖流域池塘养殖减排治理,建议推行合理的池塘污染治理管理政策与策略,综合考虑饲料利用率与投放量、养殖面积、养殖密度、养殖生物生态混养,以及一些科学养殖管理措施和净化养殖废水的技术措施等.     

丹江口水库浮游植物群落时空变化及其与环境因子的关系

研究丹江口水库在完成高水位蓄水期间浮游植物群落的时空动态特征可为丹江口水库的水质保护与生态系统结构优化及健康管理提供一定科学依据。本研究基于2018—2020年的水库浮游植物监测数据,结合同期水库水体的理化参数,分析了丹江口水库浮游植物在不同年度、季度及空间的变化特征,以及影响浮游植物群落结构变化的主要环境因子。结果显示该区域共检测出浮游植物7个门类,其中蓝藻门、硅藻门、绿藻门、隐藻门为优势类群。2018—2020年浮游植物年均密度分别为1.96×10⁶、2.55×10⁶和5.07×10⁶ cells/L,呈现出逐年增高趋势。浮游植物季度密度表现为秋季>夏季>春季>冬季,在夏秋季节蓝藻门和绿藻门占优势,春冬季节硅藻门和隐藻门占优势,同时硅藻门在四季中均占据生长优势。空间上库区浮游植物密度明显高于支流,且汉江库区浮游植物密度高于丹江库区,其中蓝藻门和绿藻门主要在库区大量出现,而支流则以硅藻门和隐藻门为主。RDA分析显示,影响丹江口水库浮游植物的主要环境因子是水温,其次为化学需氧量、氨氮和总磷。在不同季节和...     

CONTRIBUTION OF NITROGEN SPECIES AND PHOSPHORUS FRACTIONS TO STREAM WATER QUALITY IN AGRICULTURAL CATCHMENTS

The contribution from agricultural catchments to stream nitrogen and phosphorus concentrations was assessed by evaluation of the chemical composition of these nutrients in agricultural runoff for both surface and subsurface flow pathways. A range of land uses (grazed and ungrazed grassland, cereals, roots) in intensive agricultural systems was studied at scales from hillslope plots (0.5 m²) to large catchment (>300 km²). By fractionating the total nutrient load it was possible to establish that most of the phosphorus was transported in the unreactive (particulate and organic) fraction via surface runoff. This was true regardless of the scale of measurement. The form of the nitrogen load varied with land use and grazing intensity. High loads of dissolved inorganic nitrogen (with >90% transported as NH₄-N) were recorded in surface runoff from heavily grazed land. In subsurface flow from small (2 km²) subcatchments and in larger (>300 km²) catchments, organic nitrogen was found to be an important secondary constituent of the total nitrogen load, comprising 40% of the total annual load.     

Water quality improvement through five constructed serial wetland cells and its implications on nonpoint-source pollution control

ABSTRACT

Constructed wetlands can be used for reducing nonpoint-source pollution and providing ecological services in a watershed. This paper presents a field monitoring study on water quality improvement in constructed wetlands of five cells in series. The wetland system covers 59.9 ha, or 0.08% of the watershed area; it diverts 7.3 million m³ (hm³) water (or 4.3% annual flow) from a degraded river. The results showed that the hydraulic retention times (HRT) of the five cells ranged from 5 to 15 days, 18.4% inflow was lost to seepage and increased evapotranspiration (ET) in the wetlands; the wetlands retained 99.1% total suspended solids (TSS), 60.9% total phosphorus (TP), and 54.4% total nitrogen (TN) from the inflow. Major reductions of TSS and TP were observed in the first two large cells that occupied 57% of the total wetland area. The smaller cells did not show advantages over the bigger ones in pollutant retention as reported in some studies. Although significant water quality benefit can be achieved by the constructed wetlands, the increased water loss may be a concern, particularly in dry regions.

EDITOR Z.W. Kundzewicz; ASSOCIATE EDITOR T. Okruszko     

Development of storage capacity and morphology of the Aswan High Dam Reservoir

ABSTRACT

A digital elevation model (DEM), as well as satellite images, was used to detect the changes in the morphology and storage capacity of the Aswan High Dam Reservoir (AHDR) over the past five decades. Study findings indicate that the total storage capacity of the AHDR estimated by the DEM decreased by 12%. This decrease is mainly in the live and the dead storage capacities. The morphology of the reservoir changed in the southern part and at the entrance of the lacustrine part. A gradual conversion of the entrance to the riverine part was observed. The surface area of the AHDR decreased at low water levels because of sedimentation. The average reduction of the surface area between water levels of 140 and 168 m a.s.l. is about 15%, which is equivalent to almost 10 km³.