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1.
Abstract

Almost all runoff from the semiarid rangelands of the Southwestern United States results from intense convective storms of short duration. Depth-duration values for precipitation for this region that are developed through standard procedures may be misleading when used for runoff design. Various combinations of short bursts of rain can, and do, plot on average depth-duration curves, but such curves have little practical meaning for small watersheds (100 square miles or less). For design purposes for small watersheds, depths of precipitation for relatively short periods (15-30-60 minutes) for varying return periods and areas are needed. For runoff design for larger watersheds two probability estimates may be needed—the probability of storms of certain intensities and size falling on tributary watersheds of finite sizes, and the probability of storms developing over a multi-tributary system in such patterns as to produce important volumes and peaks of runoff.  相似文献   

2.
Abstract

A series of experiments were conducted on vertical columns of soil in which periodic applications of water were applied to the surface, separated by redistribution processes. The variations of hydraulic head and water content along the column were measured.

Special attention was given in correlating the tensiometer behaviour with the application and disappearance of the head of water at the surface of the column.  相似文献   

3.
Abstract

The study is based on the 121 answers to the international survey on ground water recharge published in I.A.S.H. bulletin n° 87.

After generalities about the aims, benefits, type of devices, recharged aquifers and size of plants, are examined:

—The infiltration devices (basins canals).

—The injection devices (wells).

—The economical aspects of realisations.

Diverse statistical correlations are found, and regression formulas proposed, concerning:

—Connections between permeability, size of devices, and the injection or infiltration rate.

—Connection between the annual input and the capital invested.

The synthesis of these datas conduct to results which may be useful to pepare new-projects of artificial recharge.  相似文献   

4.
Abstract

Results of a comprehensive synoptic-hydrological analysis of major flood events in the Negev (1964–2007) are presented. A low threshold for major flood data was set to be the 10-year recurrence interval of peak discharge and/or flood volume magnitude. Altogether, 75 major flood events, or 133 hydrometrically monitored floods, were extracted. These events were categorized according to synoptic oriented classes by verification of the paired databases of: (a) floods in the study area, and (b) synoptic systems over the Eastern Mediterranean. For the study area, two of the most frequent flood-generating synoptic systems are the autumn Red Sea Trough (RST), 31%, and winter cyclones, 49%. The entire RST series consists of 24 major flood events (55 floods). The synoptic definition was corroborated by analysing the specific form of flood hydrographs and the ratio of flood volume to peak discharge. Regional analysis shows increased contribution of RST events southwards from 30% to 90% with a respective decrease in the number of cyclone events. By comparing two 22-year sub-periods (1964–1985 and 1986–2007), a positive trend in the frequency and magnitudes of RST flood events is discerned. There is also an increased tendency for the occurrence of cyclone floods.

Editor Z.W. Kundzewicz

Citation Shentsis, I., Laronne J.B., and Alpert, P., 2012. Red Sea Trough flood events in the Negev, Israel (1964–2007). Hydrological Sciences Journal, 57 (1), 42–51.  相似文献   

5.
ABSTRACT

From data obtained at stations set up in Chad, the Central African Republic and Congo-Brazzaville, stretching from the desert to the equatorial zone, it has been possible to compare measurements of evapotranspiration and of evaporation with results obtained by using the energy-balance method. Several difficulties arise in these comparisons since the scale of the measurements (small evaporating surfaces) is generally different from that of the climatic characteristics on which evaporation is dependent.

After proposing a model to resolve this problem and fitting the empirical coefficients of Penman's formula, the author has applied this formula to some results derived for stations in Congo-Brazzaville; the potential evapotranspiration calculated in this way is in good agreement with water balance data.

At these stations the evapotranspiration energy may be a constant percentage of global short-wave radiation.

Finally, the energy-balance method has been used at Brazzaville to measure the actual evapotranspiration over grass during the dry season. The result is that actual and potential evapotranspiration were found to be closely related.

These results indicate the importance of solar readiation in the field of hydrometeorology.  相似文献   

6.
ABSTRACT

The authors make a general survey of the methods of measuring soil permeability in the field, looking at them from the point of view of the hydrologist.

In the first part they describe new equipment built by the ORSTOM Centre in Lome, Togo, to apply the Muntz method of vertical infiltration under constant head, equipment using a double cylinder and semi-automatic regulation of the discharge.

In the second part, the authors make a mathematical analysis of the Porchet method of horizontal infiltration in a borehole full of water: they show that results may be interpreted even with heterogeneous (multi-layered) soils and that the calculations are simplified using a computer programme.

In conclusion they deal with some results of measurements obtained by the two methods, and examine their accuracy and their correlation with the physical and hydrodynamics characteristics of the soils.  相似文献   

7.
Abstract

Reserves stand for the gravific or releasable water volume stored up in an aquiferous level. It is possible to distinguish regulative, geological and potential reserves. Their calculation is necessitating the knowledge of hydrogeological structures and the determination of specific yield or coefficient of storage. The use of recession curves allows speedy valuations.  相似文献   

8.
Abstract

The problem of non-steady flow of water in a soil-plant system can be described by adding a sink term to the continuity equation for soil water flow. In this paper the sink term is defined in two different ways. Firstly it is considered to be dependent on the hydraulic conductivity of the soil, on the difference in pressure head between the soil and the root-soil interface and some root effectiveness function. Secondly the sink is taken to be a prescribed function of the soil water content. The partial differential equation applying to the first problem is solved by both a finite difference (FD 1) and a finite element (FE 1) technique, that applying to the second problem by a finite difference approach (FD 2). The purpose of this paper is to verify the numerical models against field measurements, to compare the results obtained by the three numerical methods and to show how the finite element method can be applied to complex but realistic two-dimensional flow situations. Two examples are given. The first concerns one-dimensional flow and it compares numerical results with those obtained experimentally in the field from water balance studies on red cabbage (Brassica oleracea L. ‘Rode Herfst’) grown on a clay soil in the presence of a water table. The second example describes two-dimensional flow in a complex field situation in the Netherlands where flow takes place under cropped field conditions through five anisotropic layers. Water is supplied to the system by infiltration from two unlined ditches and is withdrawn from the system by evapotranspiration and by leakage to an underlying pumped aquifer.  相似文献   

9.
Synopsis

A method of synthesis has been used to combine the variables characterising sediment transport in laboratory flumes into nondimensional functional equations. These equations are used to provide a basis for logical data correlations. By selecting appropriate nondimensional groups the effect of variation of individual variables such as flume width, sediment grain size, etc., can be determined. It has been found that work of this nature is hampered by the small amount of data available from rational experimentation. Much of the published data is unsuitable for direct use in correlations but may be of use in the future once the trend of results has been predicted by more limited but more basic data. When sufficient data for the transport of light weight materials is available correlations of the type presented may provide a secure basis for the choice of bed material for hydraulic models.  相似文献   

10.
利用DE算法反演地壳速度模型和地震定位   总被引:11,自引:3,他引:8       下载免费PDF全文
利用差异演化(Differential Evolution)非线性全局优化算法,设计了一种反演地壳速度模型和进行地震定位的方法,并给出了反演结果的具体分析.利用有限差分算法计算速度模型的走时场,可以节省大量的计算量,加快计算过程.反演得到的地壳速度模型和地震的震源参数可以直接用于地震层析成像研究,还可以利用地震层析成像得到的三维速度结构对地震重新定位,从而得到较为精确的震源参数.地壳速度模型的反演方法也可以用于三维速度结构的反演.  相似文献   

11.
本文利用GCITEM-IGGCAS模式,从电动力学耦合作用和直接上传两种作用方式,详细模拟研究了DE2潮汐4种Hough波模分量对电离层的影响.我们将不同种类的Hough波模分别输入到模式当中作为底层边界条件,驱动模式模拟得到电离层的电子密度变化,从中分离两种作用机制的响应进行分析.模拟结果发现电离层对DE2的4种Hough波模的响应都表现为半年变化,波峰出现在春季和秋季,波谷则出现在冬季和夏季.一天的变化特性上,赤道对称波模的响应出现明显的4个峰值和谷值,其他3种波模响应主要表现为一个峰值和谷值.4种波模当中赤道对称波模对电离层的作用最为明显,占据主导地位,对电离层的影响表现为波动效应,其中3波分量的响应最强,主要由电动力学作用控制.其他3种波模对电离层则是削弱作用.本研究可以帮助我们更深刻的理解非迁移潮汐对电离层的作用方式和效果.  相似文献   

12.
Abstract

Artificial recharge is a very suitable approach in the overall water resources management of a given area. What are the matter, the purposes and the past of recharge, the factors and the problems to be taken into account, the methods and the economics of this practice? Those are some questions to which the paper tries to give answers. Several examples are quoted as well as two projects in the Middle-East and North Africa.  相似文献   

13.
Abstract

One of the scale problems in hydrology is to relate nonlinearity in basin response to size and other factors. On the Sputka basin (103.4 km2), three groups of unit hydrographs were identified, each group having a common shape parameter, N, of the Nash model and each, therefore, representing one dimensionless response. The existence of the three dimensionless responses can be explained in the first place by there being different spatial rainfall patterns for the events from which they were derived. The time parameter, K, within the individual groups depends primarily on the initial flow and on the skewness of the rainfall time pattern. However, when the conditions of rainfall uniformity and of a minimum depth are strictly met, and the initial flow is in a certain range, the basin behaves in a linear fashion.  相似文献   

14.
卫星观测结果表明高纬场向电流区的磁场和电场扰动有很高的相关性.这种相关性可用两个模型来解释,第一个模型是静态模型,观测到的扰动被认为是静态空间变化,磁场和电场的正交分量之比△B_x/E_x 表示高度积分的电离层Pedersen 电导率∑p;第二个模型是阿尔芬波模型,观测到的扰动被解释为Doppler—shifted 阿尔芬波,比值△B_x/E_x 的倒数是阿尔芬波速V_A°本文应用DE2的观测资料研究了这个比值随空间尺度的变化,我们发现,对于空间尺度大于60km或时间长于8s的变化,比值几乎不随空间尺度改变,然而对于尺度较小的变化(用截止周期短于4.0s的数值滤波可以得到这种变化),该比值展示了明显的空间尺度依赖性。对于长波长结构,计算出的比值近似等于根据电离层模型得到的。对于短波长变化,此比值近似等于1/V_A,从前者到后者的转变常常开始于时间尺度4.0-8.0s,在白天一侧,之间的相关性通常高且转变明显可见,因此,静态模型适应于尺度超过8.0s(或64km)的变化;而对于尺度小于4.0s(或32km)的变化,阿尔芬波疚越来越电离层高度上,短路效应京戏得明显了,然而,所阳天顶角的关系和已发表的电导率模型中Pedersen电导率与太阳顶角的关系是一致的。  相似文献   

15.
16.
胶东郭城地区盆地边缘砾岩型金矿区高密度侵位闪长玢岩-二长斑岩.煌斑岩.为了从微区角度限定脉岩成因及形成时代,对斑晶矿物和锆石分别进行了电子探针分析(EPMA)和LA-ICP-MSU-Pb定年研究.岩相学研究见角闪石斑晶包裹黑云母及出现长针状磷灰石现象,矿物化学结果显示辉石及角闪石斑晶幔部均出现了MgO(Mg^#),Cr2O3含量急剧升高的组成特点,斜长石斑晶具有反环带,揭示脉岩为壳幔混合作用的产物.锆石阴极发光图像显示其具有典型岩浆生长振荡环带,测年结果表明二长斑岩(GS1)和闪长玢岩(GS2)分别形成于(114±2)和(116±1)Ma,出现了部分胶北地体早期岩浆事件的继承或捕获锆石.两类脉岩锆石REE组成类似,Nb/Ta比值接近,暗示一致的岩浆源区.锆石HREE富集及明显的负Eu异常,反映源区未有石榴石出现.结合前人研究成果,显示胶东矿集区不同类型金矿区内脉岩侵位及金矿化具有相同的时代和构造背景.同时也暗示了胶东地区强烈的壳幔作用及岩石圈底侵减薄发生在早白垩世,与中生代早期的拆沉作用代表了岩石圈巨厚减薄的不同阶段.  相似文献   

17.
ABSTRACT

In this paper, the author relies on Darcy's law and on an hypothesis formulated from experimental considerations to establish a semi-empirical formula for the calculation of the discharge of partially penetrating wells of free aquifer sunk in isotropic soils.

This relatively simple relation applied to 27 cases studied under an experimental design or numerical computations, reveals itself to have an unexpected accuracy.

Starting from previous formula, the author establishes another one for partially penetrating wells bored in anisotropic soils.  相似文献   

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