Dissolved trace metals in the shallow aquifers of the Jia Bharali River Basin, North Brahmaputra Plain

The lower Jia Bharali catchment and adjoining areas in central part of North Brahmaputra Plain (NBP) is characterized by more than 800m thick Older and Younger Alluvium deposited by the west flowing Brahmaputra river and the south flowing trans Himalayan rivers. Unconfined, shallow alluvial aquifers of the area with a general southward flow are largely tapped for domestic use through numerous dug well attached with almost every household. Monitoring of 180 dug wells for two hydrological years show strong seasonal fluctuation of the groundwater table linked to the summer monsoon that brings more than 1500mm precipitation in the area between June-September. This study has presents the first ever systematic database on toxic trace elements viz., As, Cr, Fe, Mn, Ni, Pb and Zn from the shallow aquifers in north Brahmaputra plain based on water samples from 50 monitoring wells collected in both dry and wet seasons. The data was analysed with respect to WHO standards for drinking water and significantly, 2 % of the measurements show As in excess of the WHO limit while 60% of the samples in the wet season and as much as 90 % of the same in dry season have Cr content more than the WHO permissible limit. Pb concentration is above permissible limit of 0.05 mg/L in most of the dry season samples although 88 % of the rainy season samples show Pb concentration exceeding this limit. 34 % of the samples in the wet seasons and 86 % of the samples in the dry seasons have Mn above the permissible limit of 0.1 mg/L while in case of Ni, 56 % of the aquifers in the wet season and 72 % of the aquifers in the dry season show Ni content above the permissible limit of 0.02 mg/L. Zn contents of the aquifers are however very low throughout the year.     

孟加拉国布河河道泥沙数学模型计算中几个问题的探讨

针对布河游荡性河道上支汊众多、主流摆动不定、河道防洪能力较差等特性,基于断面输水和输沙相等的概念,将布河宽浅多汊的河道断面合并为等量的单一河道;在分析比较的基础上,确定了部分年份所缺的水沙资料,利用一维非均匀悬移质不平衡输沙数学模型进行验证计算,结果表明计算值与实测值相符较好.在此基础上,作了布河整治方案计算.对一些影响计算结果的因素进行了敏感性分析,指出了其中一些较为敏感的影响因素.     

巴江岩溶流域水文模拟研究

岩溶地区因其多相且不规则的复杂流态使得其水循环模拟及预测较为困难。以石林巴江流域为研究区,将流域内水文气象站点数据与遥感数据相结合,利用MIKE-SHE模型来模拟巴江流域水文过程,该模型对于蒸散发及不饱和带的模拟较为详细。并使用黄家庄水文站2000~2005年的实测日径流量进行率定与验证。结果表明,验证期总水量基本保持平衡,nash-sutcliffe系数为0.84,表明该模型能够模拟短时间内的水流演变过程。在此基础上对模型参数进行敏感性分析,得出降雨量为关键变量,且其空间分布的差异对模拟结果影响较大。     

Re-Os isotope systematics of sediments of the Brahmaputra River system

Re-Os analyses were performed on suspended loads and coarser grained bank sediments of the Brahmaputra River system. Re and Os concentrations of these sediments vary from 7 to 1154 ppt and from 3 to 173 ppt, respectively. ¹⁸⁷Os/¹⁸⁸Os ratios range from 0.178 to 6.8, and thus vary from nearly mantle to very radiogenic crustal values. Nevertheless, most of the sediments have ¹⁸⁷Os/¹⁸⁸Os ratios less than 1.5, and nearly all of the samples of the Brahmaputra main channel have ratios less than 1.2. Thus, as previously suggested, the Brahmaputra is much less radiogenic than the Ganga. The Siang River, the northern extension of the Brahmaputra, is quite radiogenic in Os despite receiving sediments from the Tsangpo River, which flows along a suture zone with ultramafic outcrops. The Brahmaputra main channel has a fairly constant ¹⁸⁷Os/¹⁸⁸Os ratio even though its tributaries contribute sediments with very heterogeneous Os isotopic compositions. These data, along with the corresponding Nd isotopic compositions, suggest that about 60-90% of the sediment in the Brahmaputra system is derived from Himalayan formations (Higher Himalaya and Lesser Himalaya) whereas 10-40% comes from ophiolite-bearing sequences, perhaps eastern equivalents of those of the Transhimalayan Plutonic Belt. Os data also confirm previously published Sr and Nd results, indicating that about half of the sediments delivered to the Brahmaputra are supplied by the Siang River, while the Himalayan and the eastern tributaries account for 40 and 10%, respectively.The lower ¹⁸⁷Os/¹⁸⁸Os of the Brahmaputra River compared to that of the Ganga is due to two factors. One is the more limited presence of the Lesser Himalaya and hence the lower black shale content of the eastern Himalaya. The other is the non-radiogenic Os supplied by the eastern and southern tributaries, reflecting the presence of mantle-derived lithologies in this region. Despite the lower sediment supply from these tributaries, they contribute greatly to the Os budget of the Brahmaputra River. This study indicates that the Brahmaputra River has little effect on the present-day seawater Os budget. However, reconsideration of this budget suggests that the Ganga, which provides the most radiogenic Os of major rivers studied to date, may have significant impact on the marine Os isotopic composition. The Indo-Asian collision cannot be excluded as an important cause of the increase in the marine ¹⁸⁷Os/¹⁸⁸Os over the past 16 million years until the contributions of all of the rivers draining the Himalayan Tibetan Plateau are known.     

珠江口盆地陆架区岩石圈伸展模拟及裂后沉降分析

本文根据伸展盆地发育的挠曲悬臂梁模型,以二维正、反演相结合的方法,计算了珠江口盆地陆架区1530测线北段的岩石圈伸展系数,分析了其裂后沉降规律。由正演模拟,发现盆地1530测线北段的裂陷由北向南逐渐发育,其陆架岩石圈的平均伸展系数为1.2和较大凹陷处的岩石圈理论伸展系数变化在1.08～1.24之间。整条剖面裂后沉降的实测值比理论值大2.5km左右,本文分析造成这一差值的最大可能是裂后异常沉降的存在。由前人成果可知,陆坡区也存在其他大的异常,对于陆架和陆坡区的异常,本文认为它们之间以及它们与其他南海陆缘之间都可能有关联,它们的产生可能是某种共同机制的结果。珠江口盆地陆架区的实测裂后沉降速率明显不同于逐渐减小的理论变化规律,而是存在两期(30～18.5Ma和18.5Ma至今)由快到慢的变化。在30～23.8Ma沉降速率集中在140～190m/Ma,之后23.8～18.5Ma减小至35～65m/Ma。18.5～16Ma的沉降速率迅速增大到300m/Ma,随后16Ma至今又减小至75～110m/Ma。其中18.5～16Ma的沉降速率最大,并与当时陆架坡折的形成和海平面的快速上升相对应,也与前人在陆坡区白云凹陷发现的17.5～15.5Ma裂后重大加速沉积的时间一致,因此本文推测珠江口盆地18.5～17.5Ma可能存在一重大构造事件,引起盆地从陆架到陆坡的裂后快速沉降的发生。但对于构造事件的成因、准确时间及其范围都有待进一步的研究。     

无定河流域下游段河冰形成演变的数学模型研究

冰凌是北方河流冬春季常见的现象, 由于环境因素的变化, 河道冰情也在不断的变化, 甚至在一些地区出现凌汛灾害. 根据冰塞形成发展的机理, 利用水力学模型和热力学模型模拟研究了无定河流域下游段丁家沟至白家川的每年春季河流水位、封河日期和开河日期. 模拟结果较为理想, 并分析了形成凌汛的原因, 旨在给该区域水循环研究、水资源的开发利用、水土保持等工作提供有力的科学技术支持.     

乌鲁木齐河流域柴窝堡盆地地下水可持续开采方案分析

针对柴窝堡盆地与河谷区水资源开发过程中引起的水质恶化,湖泊面积萎缩及生态环境恶化等一系列问题,设计了地下水开发的情景模拟方案:现状开采方案,增加补给量方案,减少开采量方案和增补减采联合方案。运用柴窝堡盆地与河谷区数值模型对这些方案进行了模拟,分析了各种开采方案下地下水水均衡状态以及地下水水位的动态变化。结果表明:增补减采联合方案既实现了最大开采量的目标,又保证了最小入湖量和最低水位的约束条件,是可持续开发方案。因而,柴窝堡盆地与河谷区水资源开发利用的重点应放在恢复天然河道水流增加地下水的补给量,充分利用地下水库的调蓄功能保证城市供水安全,同时改善水生态环境。     

陆架坡折盆地强制海退及正常海退沉积——以珠江口盆地珠江组-韩江组为例

关于强制海退形成的沉积体对应层序中体系域的问题,一直是国内外争论的焦点。结合Exxon公司建立的层序地层沉积模型,将强制海退沉积体对应于早期低位体系域以及晚期高位体系域,正常海退沉积体对应于晚期低位域前积体、高位域早期前积体。以珠江口盆地坳陷期的珠江组—韩江组为例,将其划分为7个三级相对海平面变化旋回,对应7个三级层序。相对海平面变化是可容纳空间的外在响应。在陆架坡折之上产生的高位域晚期前积体和陆坡及以下地区发育的低位域早期低位扇体;在陆架坡折带及以下形成的低位前积楔、坡折带及以上形成的高位早期前积体,是有利的油气储集体。     

辽河流域径流过程模拟的空间尺度效应分析

针对分布式水文模型的尺度问题,在辽河流域,采用SWAT模型,研究不同DEM分辨率及不同子流域大小导致模拟结果的不确定性。研究结果表明:①DEM分辨率对流域平均高程、流域面积和子流域数量影响较小,而对流域平均坡度有显著的影响,因此径流模拟时需要进行坡度订正。对于河网提取,DEM分辨率为500m时提取的河网与基准河网吻合程度较高。②子流域面积过大,数量过少时,模拟结果与基准结果偏差较大,而在划分一定阈值波动范围内径流对子流域数量敏感性较低。     

闽江流域灾害性洪水形成机理分析

分析了形成闽江流域灾害性洪水的气侯条件，地理环境和暴雨条件以及社会影响因素，归纳了灾害性洪水的主要特征，提出了防治灾害性不的建议。     

叶尔羌河流域水文特性分析

介绍了叶尔羌河流域基本情况，根据流域内主要控制站的多年水文资料，从降水、蒸发、径流、洪水、泥沙、冰情、水质等方面对流域的水文特性进行了分析。     

基于Gamma Test的非线性降雨径流回归模型研究

Gamma Test是一个与模型无关的数据分析方法,可以解决建立回归模型时面对的模型精度评价、划分率定和验证的数据及模型输入因子选择这三个问题.本文以英国的River Tone流域为例,应用Gamma Test方法分析数据,指导建立双层BP神经网络降雨-径流模型.结果表明,Gamma Test可以指导优化输入因子,精简模型结构,防止过拟合.     

洮河流域水文特性

介绍了洮河流域的基本概况，从降水、蒸发、径流、暴雨、洪水、泥沙、水质等方面分析了该流域的水文特性，概括地反映了洮河流域水文情势的基本特点和水文要素的地域分布特征，并分析了水旱灾害的一般规律。     

地形对黄河流域太阳辐射影响的分析研究

起伏地形中太阳总辐射由直接辐射、散射辐射、周围地形反射辐射三部分组成,依据各部分太阳辐射产生机理的不同,分别设计模型以综合考虑天文因素、大气因素、宏观地理因素、局地地形因素（坡向、坡度、地形相互遮蔽）是必须的。基于数字高程模型（DEM）数据和遥感影像,在全面考虑各种因素的基础上,建立了依托常规气象站观测资料的起伏地形下太阳总辐射计算模型,完成了黄河流域1km×1km分辨率太阳总辐射分布式模拟。结果表明：受坡地自身遮蔽和周围山地相互遮蔽的影响,总体平均而言,山地接收的太阳总辐射较平地少;局地地形对太阳辐射的影响程度随季节而变,在太阳高度角较低的季节,局地地形的影响较为显著。     

Dynamic Analysis of Yinggehai Basin through Analogue Modeling

INTRODUCTIONYinggehai basin lies between the Indochina plate and theSouth China plate,it develops along the southeast elongationof the Red River fault zone. Complex structures,hugesediments,ultrahigh pressure and hot fluid diapirs make it aworldwide hot spot.Most of the research work has been donein the Neogene strata and the areas along the edges of thebasin. Because of the huge depth of the sediments,thelimitation of seismic exploration and the special geophysicalposition,it is very h…     

Modeling pollutant migration in the Upper Palar River Basin, Tamil Nadu, India

 Palar River Basin, a crystalline rock region in North Arcot District (Tamil Nadu), India, possesses vast groundwater potential along and near the river course and its lands are fertile. Serious contamination of both surface water and groundwater has been reported in this basin as a result of uncontrolled discharge of untreated effluents by the tanning industries for the last three decades. The health of the rural farming community and people working in the tanning industries has been seriously affected and they are suffering from occupational diseases such as asthma, chromium ulcers and skin diseases. About an 11000 hectares area of fertile land has lost its fertility. Total dissolved solids (TDS) concentration in groundwater at some pockets varies from 3000 to 10000 mg/l. As the discharge of effluents is continuing, a prognosis of further pollutant migration is carried out using a mathematical model. A numerical model of the Upper Palar River Basin was developed using the finite difference technique coupled with method of characteristics and used to predict TDS migration for the next 20 years. Sensitivity analysis was carried out to identify the parameters which are influencing the contaminant migration. Sensitivity analysis shows that advection and not dispersion is the predominant mode of solute migration in Palar Basin. Prognosis using the model confirms that the polluted area zone as well as the concentration of pollutants in the groundwater will continue to increase in future. The study also indicated that even if the pollutant sources are reduced to 25% of the present level, the TDS concentration level in the groundwater, even after 20 years, will not be reduced below 50% of its 1992 level. Received: 20 June 1998 · Accepted: 26 October 1998     

闽江流域水文特性分析

在统计在大量实测资料的基础上,分析了闽江流域的降水、蒸发、径流、泥沙等年内年际变化及地区分布规律,以及暴雨洪水特性和大型水利工程对水文特性的影响。     

奎濉河流域"98·8"暴雨洪水分析

1998年8月中旬,奎濉河流域发生了一场暴雨洪水,分析了该场暴雨洪水的暴雨特性、洪水特性及其重现期,有助于对该流域暴雨洪水特点的认识.