MEASURING AND MODELLING OF SOIL WATER DYNAMICS AND RUNOFF GENERATION IN AN AGRICULTURAL LOESSIAL HILLSLOPE

Surface runoff may be generated when the rainfall intensity exceeds the infiltration capacity, or when the soil profile is saturated with water. Indications exist that both types of overland flow may occur in hilly agricultural loess regions. Here, for a loessial hillslope under maize in the southern part of The Netherlands, it was shown, with pressure head and runoff measurements, that Hortonian overland flow occurs during typical summer rain events. Surface runoff was initiated after saturation of the top 5–10 cm of the soil. Deeper in the soil, unsaturated conditions prevailed while runoff took place. Peak runoff discharges at the outlet of the subcatchment occurred a few minutes after peak rainfall intensities were measured. It appeared that SWMS_2D, a two-dimensional water flow model, was capable in simulating observed pressure head changes and runoff. Simulated potential runoff for the transect studied was higher by a magnitude of three than the measured areal average. This indicates effects of surface ponding, and the probable location of this particular transect in a region with high runoff production.     

FLOW SEPARATION IN UNDISTURBED SOILS USING MULTIPLE ANIONIC TRACERS. PART 1. ANALYTICAL METHODS AND UNSTEADY RAINFALL AND RETURN FLOW EXPERIMENTS

Tracers provide one of the few ways of obtaining realistic information on the flows of water and solutes in undisturbed structured soils. Three fluorinated organic acids [pentafluorobenzoic acid, 2,6-diflurobenzoic acid and o-(trifluoromethyl) benzoic acid] and bromide were tested as anionic tracers in situations where the separation of different flow components is of interest. The fluorobenzoates were relatively conservative (approximately 90% for loam soil) although, in some instances, co-elution or complexation may lead to apparently non-conservative behaviour. Tracer mixtures applied to soils, were separated and quantified by high-performance liquid chromatography. The relative mobilities of the tracers were studied during unidirectional steady flow in large undisturbed soil columns brought back to the laboratory. The breakthrough curves showed highly dispersive behaviour, with very early breakthrough of solute and a long tail. Contributions to the column outflow of different simultaneous applications of rainfall and return flow, labelled with different tracers, were separated using multicomponent mixing equations. The results show the importance of preferential flow and relatively immobile storage in the transport process.     

FLOW SEPARATION IN UNDISTURBED SOIL USING MULTIPLE ANIONIC TRACERS. PART 2. STEADY-STATE CORE-SCALE RAINFALL AND RETURN FLOWS AND DETERMINATION OF DISPERSION PARAMETERS

A series of experiments designed to study the separation of flow components from two large undisturbed cores under steady-state rainfall (downward) and return (upward) flows under near-saturated conditions is summarized. The experiments were conducted on soil columns collected from Lancaster University and the Slapton Wood catchment, Devon. The use of the relatively conservative tracers, potassium bromide, o-(trifluoromethyl)benzoic acid and 2,6-difluorobenzoic acid and a combination of application rates made it possible to quantify the different sources of water contributing to the discharge hydrographs. There is significant retention of tracer within the cores, despite the application of several pore volumes of water. The use of steady flow conditions allowed the determination of dispersion coefficients, dispersivity and proportion of ‘mobile’ water content parameters of the advection–dispersion equation. It was found that there were significant differences between the dispersivities at different flow-rates under upward and downward flux conditions and that in the undisturbed cores studied here the apparent proportions of mobile pore water ranged between 0.33 and 1.0, with an apparently complex relationship to flux rate. Prediction of transport in undisturbed soil remains problematic and tracer experiments will continue to be needed to provide a fundamental understanding of the complex flow processes involved.     

华北构造区强震短期水氡异常空间图像演化及其前兆判别标志的研究

开展了水氡前兆异常参数提取方法的研究, 并以其提取的结果为输入, 对1985～2002年华北水氡异常参数分布做了全时空扫描, 继而将全部图像与华北地区构造活动性评估的数字化图像进行了叠加, 实现了水氡异常动态扫描与区域构造活动性背景的结合。 在此基础上, 1985年以来华北地区5级以上地震前的水氡短期图像演化情况做了全面分析, 提取出判别异常区的指标以及地震短期异常演化特征, 并提出了华北地区强震前水氡短期前兆的判别标志。     

青海驼路沟钴(金)矿床成矿物质来源的黄铁矿氦氩硫铅同位素示踪

为查明青海驼路沟新型独立钴(金)矿床的成因和成矿物质来源,文章对矿区发育的块状、条带状和浸染状黄铁矿矿石进行了黄铁矿流体包裹体氦氩同位素和黄铁矿硫、铅同位素测试。结果表明,不同类型矿石的成矿流体氦、氩同位素组成基本一致,3He/4He介于0.10~0.31Ra(平均0.21Ra),40Ar/36Ar比值为302~569(平均373),反映钴矿化流体主要来源于在赋矿岩系中深循环的大气降水;矿石黄铁矿硫同位素值分布集中且接近于零,δ34S变化于-4.5‰~+1.5‰,集中在-1.8‰~-0.2‰,显示深部来源;矿石铅以高放射性成因为特征(206Pb/204Pb>19.279、207Pb/204Pb>15.691、208Pb/204Pb>39.627),且自地层围岩→区域早古生代火山岩→矿石依次明显增大,可能指示高放射性成因矿石铅主要是由以深循环大气降水来源为主的热液不断从围岩地层中淋取而来。     

1993年咸宁地震群震害损失及发震成因探讨

1993年7~8月,湖北省咸宁地区发生了一系列ML≤4.1的地震。从地震系列、地表破坏状况和地震宏观等烈度线展布特征出发,深入研究了地震与地质构造及地下水动态变化的关系,得出结论地震群可能为抽取地下水引起的构造变动而诱发。     

风水复合侵蚀研究述评

风水复合侵蚀或风水交互作用是干旱、半干旱地区常见的侵蚀过程。这种风力与流水对同一侵蚀对象 (区域) 的共同作用或交替作用塑造了风蚀水蚀交错区特有的侵蚀地貌景观。作为一个相互联系、影响的复杂系统,风水复合侵蚀具有明显的时空分布特征,其侵蚀过程可以划分为古代过程与现代过程。由于以往的风蚀和水蚀研究相互独立,风水复合侵蚀的研究起步较晚。在研究中存在着尺度转化与研究方法不成熟等问题。对风水复合侵蚀的机理与防治以及土壤复合可蚀性的研究都将成为今后研究中的重点与难点。     

青藏高原中东部水热条件与NDVI的空间分布格局

青藏高原受大气环流和地势格局的共同作用,水热条件及植被空间分布呈现独特的三维地带性特征。但是青藏高原范围广、地势起伏大,水热条件及植被空间分布具有明显区域差异。本文利用青藏高原中东部100个气象站1982²000年的降水、气温资料以及同期NO-AA AVHRR植被指数产品（NDVI）,分析水热条件及植被的空间分布特征。首先,设置经向、纬向海拔渐变样带,考察海拔对水热条件及NDVI空间分布的影响;然后,按500米海拔间隔进行站点分组,分析约束了海拔高差后的经纬位置对水热条件及NDVI空间分布的影响。研究表明:在青藏高原中东部由于海拔高差大,热量条件分布首先受海拔递减规律控制,其次才表现出因太阳辐射差异的纬度地带性;而降水分布则主要受水汽通道位置和方向的影响,北上水汽和东部偏南走向山脉是研究区降水经向特征的主要成因;指示植被状况的年均NDVI,则受水热组合的控制,其分布格局是二者的叠加与综合。     

渤海与环渤海地区年降水量的统计分析

本文以渤海海域及环渤海地区分水岭内为研究区域,利用环渤海地区分水岭内92个气象站点自1971年至2000年30年的降水量资料,基于ARC/INFO地理信息系统支持下的泰森多边形法,对研究区域内的平均年降水量进行了统计分析。结论如下:环渤海地区分水岭以内区域的平均年降水量占整个环渤海地区2000年降水量的63.88%;渤海海域海水直接利用量占该海域平均年降水量的8.82%,其中辽东湾的海水利用量占该湾平均年降水量的3.09%,渤海湾为15.86%,莱州湾为17.38%;辽东湾2002年的海冰资源量占该湾平均年降水量的6.08%。在渤海海域水量平衡的关系研究中,本研究是初步的,基础的。划出分水岭内的研究区域进行平均年降水量的统计较对整个环渤海地区进行统计更具精确性。