Seasonal controls on DOC dynamics in nested upland catchments in NE Scotland

Spatial and temporal variability of hydrological responses affecting surface water dissolved organic carbon (DOC) concentrations are important for determining upscaling patterns of DOC export within larger catchments. Annual and intra‐annual variations in DOC concentrations and fluxes were assessed over 2 years at 12 sites (3·40–1837 km²) within the River Dee basin in NE Scotland. Mean annual DOC fluxes, primarily correlated with catchment soil coverage, ranged from 3·41 to 9·48 g m^?2 yr^?1. Periods of seasonal (summer–autumn and winter–spring) DOC concentrations (production) were delineated and related to discharge. Although antecedent temperature mainly determined the timing of switchover between periods of high DOC in the summer‐autumn and low DOC in winter‐spring, inter‐annual variability of export within the same season was largely dependent on its associated water flux. DOC fluxes ranged from 1·39 to 4·80 g m^?2 season^?1 during summer–autumn and 1·43 to 4·15 g m^?2 season^?1 in winter–spring.Relationships between DOC areal fluxes and catchment scale indicated that mainstem fluxes reflect the averaging of highly heterogeneous inputs from contrasting headwater catchments, leading to convergent DOC fluxes at catchment sizes of ca 100 km². However, during summer–autumn periods, in contrast to winter–spring, longitudinal mainstem DOC fluxes continue to decrease, most likely because of increasing biological processes. This highlights the importance of considering seasonal as well as annual changes in DOC fluxes with catchment scale. This study increases our understanding of the temporal variability of DOC upscaling patterns reflecting cumulative changes across different catchment scales and aids modelling of carbon budgets at different stages of riverine systems. Copyright © 2010 John Wiley & Sons, Ltd.     

利用HEC模型分析下垫面变化对洪水的影响——以伊河东湾流域为例

近些年,由于气候变化和人类活动的双重作用改变了流域下垫面的水文特性,探讨研究下垫面变化的水文响应过程具有重要的理论和现实意义.河南伊河洪水虽然量级不大,但发生几率较高,对水库运用和河道冲淤的影响较大.如果洪水变小,伊河下游的造床流量也相应减小,水库控制中常洪水的流量及所需的防洪库容可做相应调整,反之亦然.因此,为了科学...     

Bridge pier failure probabilities under combined hazard effects of scour, truck and earthquake. Part II: failure probabilities

In many regions of the world, a bridge will experience multiple extreme hazards during its expected service life. The current American Association of State Highway and Transportation Officials (AASHTO) load and resistance factor design (LRFD) specifications are formulated based on failure probabilities, which are fully calibrated for dead load and non-extreme live loads. Design against earthquake load effect is established separately. Design against scour effect is also formulated separately by using the concept of capacity reduction (or increased scour depth). Furthermore, scour effect cannot be linked directly to an LRFD limit state equation because the latter is formulated using force-based analysis. This paper (in two parts) presents a probability-based procedure to estimate the combined hazard effects on bridges due to truck, earthquake and scour, by treating the effect of scour as an equivalent load effect so that it can be included in reliability-based failure calculations. In Part I of this series, the general principle for treating the scour depth as an equivalent load effect is presented. In Part II, the corresponding bridge failure probability, the occurrence of scour as well as simultaneously having both truck load and equivalent scour load effect are quantitatively discussed. The key formulae of the conditional partial failure probabilities and the necessary conditions are established. In order to illustrate the methodology, an example of dead, truck, earthquake and scour effects on a simple bridge pile foundation is represented.     

楼盘施工注浆及荷载对唐山矿井水位的影响分析

2010年唐山矿井水位上升速率明显加快,上升幅度明显高于往年同期.本文从地下水动力学和荷载效应角度,利用抽(注)水试验模型和均布荷载下半无限大的弹性空间理论模型,分析井孔附近楼盘施工注浆及建成后荷载作用对井水位的影响.结果表明,距井孔200 ～700m范围内注浆,每天注浆2500 m3,注浆270d,能引起井水位上升8～11m的变化;大面积的楼盘荷载作用可以引起井水位上升约4m的变化.通过对这些影响因素的分析,认为唐山矿井水位的上升异常与楼盘施工注浆及建成后的荷载作用有一定的相关性.     

Changes in metal contamination levels in estuarine sediments around India – An assessment

This review is the first attempt to comprehend the changes in metal contamination levels in surface estuarine sediments with changing time around India. Contamination factor, geoaccumulation index, pollution load index, effects range low and effects range median analysis were used to evaluate the quality of the estuarine sediments (by using the available literature data). This study suggests that estuarine sediments from the east coast of India were comparatively less contaminated by metals than the west coast. Sediments from those estuaries were found to be more contaminated by metals on which major cities are located. An improvement in estuarine sediment quality (in terms of metal contamination) over time around India was noticed. This study provides managers and decision-makers of environmental protection agency with a better scientific understanding for decision-making in controlling metal pollution in estuarine sediments around India.     

考虑内力状态的大跨高墩连续刚构桥地震易损性分析

为研究考虑内力状态的连续刚构桥的地震反应及易损性情况,以一座非规则大跨高墩连续刚构桥为对象,基于MIDAS/Civil和OpenSees平台分别进行施工过程模拟和非线性动力分析,并采用等效荷载法将内力等效荷载附加到OpenSees模型上,使其处于对应的等效内力状态;选取40组典型的速度脉冲型近断层地震动记录为输入,采用增量动力分析法进行考虑内力状态的地震易损性分析,对比分析了考虑内力状态与否对连续刚构桥地震易损性的影响。结果表明:所采用的内力等效荷载方法能够较好地考虑成桥内力状态;考虑内力状态与否对成桥阶段主墩和引桥墩的地震易损性具有很大影响,不考虑内力状态时将严重低估主墩和引桥墩的地震损伤概率。     

Joint probability analysis of water and sediment and predicting sediment load based on copula function

The Jinsha River comprises the upper reaches of the Yangtze River, which is the river section with the highest sediment content. Monitoring of sediment transport in the Jinsha River is done to the guarantee for the normal operation of the Three Gorges Reservoir. In the current study, a copula function was used to do a joint probability analysis of the water and sediment in the Jinsha River Basin (JRB), further a sediment load prediction model based on the copula function also was constructed. The results show that the average annual flow from 2001 to 2018 at the outlet of the Jinsha River (Yibin station) is about 60.43 billion m³, and the average annual sediment load is about 58.82 million t. The linear correlation coefficient between annual flow and annual sediment load is 0.28. The best marginal distribution for annual flow and sediment load is Pearson Type Three (PE3) and Generalized Normal (GNO), respectively, and the best fit for the combined distribution of the two variables is the Frank copula function. The synchronous probability of water and sediment occurrence is 0.459, and the asynchronous probability is 0.541. Based on the copula prediction model, the sediment load can be effectively simulated, and the correlation coefficient between the simulated sequence and the measured sequence reached 0.93. The current study provides important significance for the analysis of water and sediment in the JRB, which is beneficial to the management of Three Gorges Reservoir sediment discharge in the upstream and downstream.     

三维层状场地的精确动力刚度矩阵及格林函数

本文对Wolf二维层状场地精确动力刚度矩阵进行推广,给出了三维层状场地的精确动力刚度矩阵。刚度矩阵具有对称的特点,且因刚度矩阵是精确的,计算结果不受土层单元厚度的影响,可以大大提高计算效率。文中对刚度矩阵进行了数值验证。利用三维层状场地动力刚度矩阵,计算分析了基岩上单一土层场地的动力响应。最后作为动力刚度矩阵的另一重要应用,给出了表面或埋置矩形均布荷载或集中荷载的动力格林函数计算方法。     

Distributed hydrological modelling of a heavily glaciated Alpine river basin

Abstract

A glacier submodel was successfully integrated into the distributed hydrological model WaSiM-ETH to simulate the discharge of a heavily glaciated drainage basin. The glacier submodel comprises a distributed temperature index model including solar radiation to simulate the melt rate of glaciated areas. Meltwater and rainfall are transformed into glacier discharge by using a linear reservoir approach. The model was tested on a high-alpine sub-basin of the Rhone basin (central Switzerland) of which 48% is glaciated. Continuous discharge simulations were performed for the period 1990–1996 and compared with hourly discharge observations. The pronounced daily and annual fluctuations in discharge were simulated well. The obtained efficiency criterion, R², exceeds 0.89 for all years. The good performance of the glacier submodel is also demonstrated by integrating it into the hydrological model PREVAH.     

Simulating the daily discharge of the Mandovi River,west coast of India

Abstract

A hydrological modelling framework was assembled to simulate the daily discharge of the Mandovi River on the Indian west coast. Approximately 90% of the west-coast rainfall, and therefore discharge, occurs during the summer monsoon (June–September), with a peak during July–August. The modelling framework consisted of a digital elevation model (DEM) called GLOBE, a hydrological routing algorithm, the Terrestrial Hydrological Model with Biogeochemistry (THMB), an algorithm to map the rainfall recorded by sparse raingauges to the model grid, and a modified Soil Conservation Service Curve Number (SCS-CN) method. A series of discharge simulations (with and without the SCS method) was carried out. The best simulation was obtained after incorporating spatio-temporal variability in the SCS parameters, which was achieved by an objective division of the season into five regimes: the lean season, monsoon onset, peak monsoon, end-monsoon, and post-monsoon. A novel attempt was made to incorporate objectively the different regimes encountered before, during and after the Indian monsoon, into a hydrological modelling framework. The strength of our method lies in the low demand it makes on hydrological data. Apart from information on the average soil type in a region, the entire parameterization is built on the basis of the rainfall that is used to force the model. That the model does not need to be calibrated separately for each river is important, because most of the Indian west-coast basins are ungauged. Hence, even though the model has been validated only for the Mandovi basin, its potential region of application is considerable. In the context of the Prediction in Ungauged Basins (PUB) framework, the potential of the proposed approach is significant, because the discharge of these (ungauged) rivers into the eastern Arabian Sea is not small, making them an important element of the local climate system.

Editor D. Koutsoyiannis; Associate editor S. Grimaldi

Citation Suprit, K., Shankar, D., Venugopal, V. and Bhatkar, N.V., 2012. Simulating the daily discharge of the Mandovi River, west coast of India. Hydrological Sciences Journal, 57 (4), 686–704.