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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

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   

3.
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   

4.
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   

5.
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   

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.
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   

8.
9.
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   

10.
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   

11.
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   

12.
Abstract

Existing models for generating synthetic daily streamflow data are unsuitable for reproducing the predominant features of daily flows, the rising and recession of flood flows, the peaks of the floods, the volume of the waves and the range. In this paper, a model is presented which is able to reproduce the important features of daily flows. In the model the measured record of daily data is assumed to be the output of a linear system. The input of the system consists of pulses, occurring on certain days. The pulses are convoluted with the system function in order to produce the output. The form of the system function depends on the magnitude of the output. First, the days on which pulses occur, the magnitude of pulses, and the form of the system function as a function of the system output, are determined. Subsequently, a model was developed for the generation of the pulses. The model consists of a combination of two processes. Using a Markov chain model, the sequence of dry and wet days (days with and without pulses) is generated. Thereafter, a pulse of certain magnitude is assigned to each wet day. A modified first-order autoregressive process is used to produce these correlated pulses. The random components of the pulses are taken from a transformed exponential distribution. The periodicity of the flows within the year is reproduced by using different model parameters for each month of the year. The model yields good results for small and medium size basins, especially as far as peak flows, the volume of the waves, and the range are concerned. A sequence of daily flows from at least 20 years is required for input data.  相似文献   

13.
Abstract

The necessary and sufficient conditions for non-zero phase shift and non-zero attenuation in linear flood routing can be derived from the continuity equation alone and are found to depend on the existence of an imaginary part in the expression for frequency or in the expression for wave number. It is shown that in linear flood routing the phase lag between flow rate and area of flow is directly related to the attenuation per unit wave length. The effects of using various forms of the momentum equation, in addition to the continuity equation, are exemplified by deriving analytical expressions in terms of the frequency, both for attenuation per unit channel length and for phase shift, for the kinematic wave, the general diffusion analogy, and the complete St. Venant equation.  相似文献   

14.
Abstract

The rivers Gard, Herault and Vidourle which go down very rapidly from the Cevennes into the Mediterranean sea, between very steep slopes, are particulary able to transport débris as a consequence of their very big floods. Nevertheless, during the floods of the autumn 1958, which were of a bi- or tricentenial frequency, only the loams, clays and sands were able to reach the sea during the flood. Shingle was transported in great quantities but only upon short distances, of no; more than 2 or 3 km. Even in such torrents, the transport of shingle is very long, and the greater part of the shingle actually present in the river bed was swept out from the foot of the slopes during the last cold period of the Quaternary, under periglacial conditions. The construction of a dam, at the Moulin de Bertrand in the Hérault valley, which does not allow the transit of shingle, did not result in the modifications in the conditions of transport of the pebbles downstream: the pebbles which are presently transported do not come from the upper valley, but are reworked from the accumulations built up in the bed before the construction of the dam.  相似文献   

15.
Summary

The Hooghly is a tidal river and Calcutta one of the most important ports of India is situated on it. The tidal effect stretches to over 175 miles length up to Nabadwip where two nonperennial rivers Bhagirathi and Jalangi, both taking off at different sites from the Gangesmeet and discharge their rain water (freshets) into the Hoogly all through the summer months. Other rivers join it also downstream. Annual tide tables are published for three places on the river viz Sagar, Diamond Harbour and Garden Reach.

In this paper lunitidal intervals, durations of rise and fall, mean high water, mean low water, mean tide level and mean sea level planes and mean ranges have been shown to go through periodic seasonal changes. It has been shown that different tidal planes have changed differently in the intrior of the river indicating changes in tidal regimes and in the river bed. Whereas variations in yearly sea levels since 1882 have not been appreciable at Sagar, these at Garden Reach have changed considerable at indicating sometimes an improvement in the channel, other times worsening of the channel. Four 19 yearly cycles of mean sea-level at Garden Reach have been analysed to give phaselags different from Zero and large variations in amplitudes. To carry this study further one period of 19 years each for Sagar, Madras and Vishakhapatnam on East Coast and 4 periods each for Bombay and Aden in the Arabian Sea have also been analysed to see the possibility of nodal variations being constant in amplitude and phase over large areas of the ocean. 19-yearly cycles in the differences between MTL &; MSL have been examined for Bombay, Madras and Garden Reach. The effects of freshets on various planes have been analysed and the curves of annual freshets and MTLs at Garden Reach are found to run closely parallel. The variations in yearly high water and law water planes above MTLs of the corresponding years after corrections for the longitude of the moons' node have been found to be inappreciable. Theoretical extreme high water and low water planes have been found to be more extreme than actually recorded planes which are very near M.H.W.S. and M.L.W.S. planes indicating there are no predominant effects of winds and storms on the tides in the river. The mean ranges at Garden Reach have been found to be steadily increasing. Theoretical effects of increase in range and lowering of MSL on MHW and MLW plane has been found to agree with actual values. Monthly average temperatures and salinities show distinct annual cycles. High temperatures occur at the same times as low salinities and high mean sea levels. Vertical density structure may be responsible for a large part of annual variation in the sea level at Sagar which is a region of particular interest on account of opposite influences of seasonal monsoons, drainage of rivers and oceanic currents. Seasonal variations in average monthly pressure have been related to variations in mean sea levels and it is found that as the pressures decrease, the height of MSL increases. Tide in Hooghly has been found to be progressive type of wave. Rates of travel of tidal streams outside Sagar and rates of streams in the river have been given also, stating the effects of freshets on tidal streams. Bores in Hooghly have been examined. Shapes of tidal curves and profile of the bore at Garden Reach have been drawn. Rates of propagation of the bore from Doodsons' formulae have been compared with actual values and a remarkable agreement has been found. The rise of tide in 10 minutes and 30 minutes which is the time taken for the steep rise to disappear has been correlated with range of tide and a useful table has been included. Tides in Hooghly are predicted by applying harmonic shallow water corrections to open sea primary predictions at Sagar. As the freshets are unpredictable an approximate relationship has been worked out between the departures of actual freshets from num freshets of the years of analyses and departures of actual from predicted tides. From a knowledge of actual freshets the predictions can be corrected almost, daily.

A large number of tables and only the essential graphs have been included to illustrate the contents.  相似文献   

16.
Summary The position of the very important climatic limit, definited byBenevent, which separates the humid climate of north Alps and the dry climate of south Alps, is first described. The method used for synoptic study of alpine precipitations is then exposed: it consists in plotting for every day on a great scale chart the amounts of rain measured in the alpine rain-jauge stations and in comparing this result with the isohypses charts at the 700, 500 and 300 mb levels.  相似文献   

17.
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   

18.
Abstract

The Rhone changed progressively, from SE to NW, his underflow and his upperflow, advancing together in that direction. The study of the evolution of erosion show the Rize is a relic of the ancient flow. The like processus is proper to many rivers.  相似文献   

19.
Summary The scheme of a seism caused by the slipping of a transcurrent fault is examined and the law of the variation of the seismic superficial displacement v/s distance to the fault is given, assuming that no extra stress is produced at the base of the broken layer. Taking a simple example for the preseismical strain, it is possible to find an order of magnitude of the extent of the fault in depth. An application to the San Francisco seism of 1906 gives a depth of about 13 km.
Resumo Oni ekzamenas skemon de sisma ekmovo e fendego transkuranta kaj oni donas la leon de la supraa ekmovo kiel funkcio de la distanco al la fendego, en la hipotezo ke tiu movo ne produktas novan streon e la bazo de la fendita tavolo. Prenante simplan ekzemplon por la antaùsisma deformio oni povas determini proksimuman amplekson de la profundeco atingita de la fendo. Aplikado al la sismo de San Francisco de 1906 donas por la profundeco cirkaùe 13 km.
  相似文献   

20.
Résumé On compare, en premier lieu, les crochets magnétiques donnés par le Bulletin de l'I.A.G.A. avec les crochets visibler sur les enregistrements de Tamanrasset entre 1949 et 1957. 33% des crochets sont retrouvés, et on étudie leur fréquence. Celle-ci suit le cycle solaire, esdt minimum l'hiver et plus élevéc l'après-midi que le matin. L'obíssance à la loi deMcNish ne semble pas prouvéc. L'amplitude la plus probable est de 7 . — On étudie ensuite des phénomènes ressemblant aux crochets (faux crochets) et caractérisés par une allure bien définie des dérivéesdH/dt etdD/dt. Leur fréquence ne suit pas le cycle solaire, est minimum à l'équinoxe et uniforme dans le cours de la journée. L'amplitude la plus probable est de 7 à 10 , et la durée de développement de l'ordre de 5 minutes. La direction du vecteur perturbation est NNW ou SSE, avec prédominance du SSE, ce qui correspond dans l'ionosphère à un courant WSW-ENE. L'existence des faux crochets peut expliquer certaines confusions dans l'identification des crochets.
Summary First of all, we compare the magnetic crochets given by the I.A.G.A.-Bulletin with the crochets we can see on Tamanrasset records between 1949 and 1957. We find out 33% of these crochets and we study their frequency. It follows the solar cycle, it is minimum during winter and greater in the afternoon than in the morning. Obedience toMcNish law does not seem to be proved. The more probable amplitude is 7 . — Then we study phenomena looking like crochets (false crochets) which are caracterised by a well definite feature ofdH/dt anddD/dt. Their frequency does not follow solar cycle, it is minimum et equinox and level during the course of the day. The more probable amplitude is from 7 to 10 , and the development plasts about 5 minutes. The direction of disturbance vector is NNW or SSE, with predominance of SSE, which sould correspond to a WSW-ENE stream in the inosophere. The existence of false crochets may explain some confusions when we identify crochets.
  相似文献   

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