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The steep and rugged mountains of Southern California contain considerable ground ‐ water storage . A large portion of the runoff is seepage from this storage The variations in runoff distribution depend on the geology, physiography, and soil cover of these mountain areas.
Estimates of the weights of pyroclastic material and lava erupted by Parícutin Volcano from early 1943 to early 1952 have given a pyroclastic weight of some 2230 million metric tons and a lava weight of about 1330 million metric tons, making a total of 3560 million metric tons of solids. The weight of pyroclastic material ranged from a maximum daily average of more than 10 million metric tons in the first two weeks of eruption to a minimum of some 65,000 metric tons in 1951. The weight of lava ranged from a maximum daily average of about 650,000 metric tons in 1943 to a minimum of some 170,000 metric tons in the second half of 1950. The only period for which an estimate of the average daily weight of water vapor expelled by the Volcano could be made was the spring of 1945, when some 13,000 metric tons of water were expelled through the crater daily, besides some 500 metric tons contained in the lava extruded concurrently. Since the weight of pyroclastic material and lava erupted by Parícutin in the spring and summer of 1945 is estimated to have averaged about 1.2 million metric tons a day, the water expelled at that time amounted to about 1.1 pct of the total weight of material erupted. If the proportion of water had been nearly constant throughout the active life of the Volcano, the total weight of water would have amounted to some 39 million metric tons.
The author has developed equations and approximate curves to express the percentage of the total sediment discharge that is carried in suspension above the lowest point reached by the nozzle of a depth‐integrating sediment sampler. He assumes that bed load and suspended load are defined by the equations in a paper by H. A. Einstein [The bed‐load function for sediment transportation in open‐channel flows, U.S. Dept. Agric., Tech. Bull. 1026, 1950]. The percentage is termed the efficiency of sampling. In a vertical strip of unit width, the suspended‐sediment discharge discussed by the author' in effect the product of the mean concentration of the depth‐integrated sample, the water discharge in that portion of the depth above the lowest nozzle position, and a factor for converting the result into desired units, such as tons per day. In contrast, the common operating practice is to compute the suspended‐sediment load as the product of the measured concentration, the total water discharge, and the conversion factor. The difference in computed suspended‐sediment discharge by the two methods is sometimes appreciable as, for example, in the wide, shallow streams that drain the sandhills of Nebraska.
Maxwell and Verrall's interesting study raises a thought. If limestones expand on heating and thereby receive a permanent set, as this paper demonstrates, do we not have here a means of determining the maximum temperature to which a particular limestone was ever subjected and indirectly thereby its maximum depth of burial or other geothermal events in its history?
One of the very obvious geologic phenomena that is continuously in operation throughout the Earth's land surface is erosion , the process of wearing away the soil or the surface mantle. The falling of rain drops on an unprotected slope, the flow of water across land or in a channel, the borings of a rodent, the expansion of a root, the pull of gravity, the gouging of a glacier, or the impinging of wind on an open surface are some of the forces continually at work in this erosion process. The tendency of these forces is to bring everything to a common level and the moment a point of land or a continent rises above its surroundings, gravity, rain, wind, and all the other forces set to work, bringing it back to the level of its nieghbor. The poetic expression “the everlasting hills” is an illusion, for these erosion forces have been operative since the dawn of geologic history and the evidence is conclusive that in this sequence of time numerous generations of hills and mountain ranges have been uplifted and then razed by erosion , the waste and rock debris of one range forming the source material for its successor. We could not have the great deposits of alluvium and the thick beds of conglomerate, sandstones, and shales that occur at present throughout the Earth without erosion to furnish the source material.
Total‐intensity aeromagnetic surveys of the Aleutian Marshall , and Bermuda Islands were completed in 1948. The anomalies associated with the Aleutian volcanoes are attributed mainly to topographic relief and are not an indication of the degree of volcanic activity. Eniwetok presents a magnetic pattern that would be produced by an irregular‐shaped rimmed depression in the basement, modified by the two adjoining seamounts, and differs from Bikini, whose magnetic features would be produced by a broad seamount with irregular surface relief. The Bermuda survey demonstrated magnetic features typical of volcanic rocks. Comparison of an observed and a theoretical profile computed by Press and Ewing indicates that their assumptions are reasonably correct. The Aleutian Trench survey shows anomalies that are attributed to susceptibility contrasts but none that can be correlated with the trench. A traverse from Adak, Aleutian Islands , to Kwajalein, Marshall Islands , exhibited several large anomalies that are presumed to be caused by susceptibility contrasts but may be indications of uncharted seamounts. Two traverses, one from Cape May, N.J., to Bermuda and the other from Bermuda to Long Island , N.Y., reveal a change in the magnetic field approximately 300 miles from the Atlantic Coast that indicates a possible thinning of the sial and an exposure of sima.
A drafting instrument which provides a ruling edge for drawing arcs of circles the radii of which are unusually long is described. A complete range of arcs of different curvature, within the limits prescribed by the construction of the instrument, are obtainable. This instrument was developed originally to allow accurate construction of circular arcs of very low curvature, which are difficult or impossible to draw with an ordinary compass, in constructing stereographic projections . It is apparent, of course, that numerous other applications are possible. To satisfy the authors' needs, a relatively small model was constructed, but the same general construction could be used in larger models.
Records of water levels in limesink ponds in southwestern Georgia and of water ‐table levels in the vicinity of these ponds are used to demonstrate: (1) some ponds with highly impermeable beds are virtually unaffected by water ‐table levels , except when water ‐table levels are above the rim of the impervious materials; (2) interchange of water between pond and water table occurs when beds are relatively permeable. Three phases in the relation between pond level and water ‐table level are recognized: (1) water ‐table level higher than pond level causing ground ‐ water flow into the pond ; (2) ground ‐ water level below pond level but in direct contact with it and measurably controlling rate of seepage from the pond ; (3) ground ‐ water level below pond level but not in direct contact with it and not appreciably controlling rate of seepage from the pond . In phase (3) the water table has a perceptible mound at a point underneath the pond .
Re cords of precipitation, runoff in the Gila River, ground‐water withdrawals for irrigation, and changes in ground‐water level in Safford Valley, Arizona, provide a basis for noting the effect of wet and dry periods on the hydrologic cycle. An unusually wet period 1940–1941, was followed by a period of drought, l942–1952. The irrigable area is limited by natural causes, the area irrigated with surface water is effectively limited by court decree, and less than 1000 acres are irrigated exclusively from wells. Thus relatively little expansion in this irrigated area has occurred during the period concerned to obscure the climatic effects, although cultivation has been more intensive in recent years and the water demand has been correspondingly larger. The wet period of above‐normal stream flow and ground‐water levels provided a cushion that delayed and reduced the effects of the drought. As the ground‐water‐storage in the valley is relatively small, however, withdrawals of ground water as a supplemental supply for irrigation eventually lowered water levels sufficiently to reduce well yields. The concentration of dissolved mineral matter increased in the remaining ground water, making it less desirable for irrigation use than previously.
A method is presented for estimating the discharge of ground water by evapotranspiration of water rising from the water table by capillarity. ‘Potential capillary water loss’ is defined as a measure of the ability of the capillary interstices of a soil to raise water from the water table to the ground surface. Published equations describing soil‐moisture movement and published graphs relating capillary conductivity and capillary potential are used to derive expressions of the relation between ‘potential capillary water loss’ and depth to the water table in a given soil. On the basis of these theoretical relationships, graphs are drawn that show how the depth to the water table affects the ability of a particular soil to raise water to the ground surface under given conditions. The application of these methods is discussed in relation to the estimation of ground‐water losses by capillary rise, the determination of potential evapotranspiration, and the analysis of soil‐tank data. Their essential agreement with empirical profiles of capillary potential obtained in soil tanks demonstrates their usefulness.
The specific yield of a water‐table aquifer is one measure of the amount of water within the aquifer that is available for recovery (development). It is expressed as a percentage or decimal fraction of the total volume of material of which the aquifer is composed. The specific yield may be determined during the course of an equilibrium pumping test by comparing the volume of dewatered material in the cone of depression with the total volume of discharge water. An equation is developed theoretically that expresses the volume of dewatered material in terms of test data. A related equation indicates the magnitude of losses at the pumped well. These equations were tested by applying them to test data tabulated in ground‐water literature.
The present writers are familiar only with the Picacho and San Pedro areas, among those cited by the authors, and therefore limit discussion to the occurrence of earth cracks in these areas. The existence of piping is not questioned, and the five conditions suggested by the authors are a justified explanation in the San Pedro area, for example. It is thought, however, that some of the phenomena described as piping are earth cracks whose origins are governed by factors other than those outlined. Once formed, certain earth cracks may facilitate the development of piping by providing ready access to downward and lateral movement of water.
The ground water in the pumping district in Cedar City Valley, Utah is considered by the Utah State Engineer to be fully appropriated, and he has not authorized drilling of irrigation wells there since 1942 except as replacements for wells having established rights. In spite of this regulation, the water levels in representative wells in 1954 were the lowest of record, and four to ten feet lower than the minima recorded during the drought of the 1930's. This recession is attributed in large part to the current drought in the southwestern United States. In the five years ended October 1, 1954, precipitation at Cedar City was markedly less than in any other five‐year period in the past 50 years, and stream runoff was likewise far below average. Ground‐water withdrawal has exceeded replenishment in these drought years, but it cannot yet be concluded that the ground‐water resources are overdeveloped in the sense that pumpage exceeds the long‐term average replenishment to the reservoir.
Electrical‐resistance blocks were calibrated for use in soil‐moisture studies at Seabrook, N.J. Curves from successive laboratory calibrations are positioned differently because of the effects of chemical quality of the water used, drying techniques and other factors. Furthermore, the laboratory curves are displaced from the field calibration curves because of the difficulty of establishing moisture equilibrium in laboratory samples. It is believed that the results demonstrate the general unreliability of laboratory calibrations when compared with field calibrations of soil‐moisture blocks
Numerous investigations of suspended‐sediment discharge have shown that an increase in stream flow usually is accompanied by an increase in sediment concentration. The sediment‐concentration peak during a rise may precede, coincide with, or follow the water‐discharge peak. Observations on the Bighorn River in Wyoming and Montana show a progressive lag in peak concentration behind peak flow. The lag is most apparent when a single storm produces a flood wave that starts many miles upstream from the sampling sections.
h ydrologists are generally aware of the number and complexity of the variables that are encountered in all aspects of hydrology, and the great difficulty of analyzing these factors quantitatively because of inadequacy of basic data. Because of limitations in funds, time, or scientific manpower, it is likely that the basic data will generally be less than the hydrologist's hopes. In this predicament, many students have sought methods whereby it might be possible to determine the approximate effects of various factors, on the basis of meager available information. The authors, by using statistical methods of analysis, have pointed out one way that may well be rewarding in studies of other aspects of hydrology where little basic information is available.
A method that enables good estimates to be made of total sediment load has been tested with data from several western streams. The method, which uses both theoretical and empirical formulas, combines a modification of Einstein's procedure for computing bed‐material load and the usually available data from suspended‐sediment measurements. Basic data, including data from large natural and artificial turbulent flumes, and the results of computations are given.
Releveling of bench marks in 1953 and 1954 by the U. S. Coast and Geodetic Survey indicates that subsidence of the land surface has now exceeded ten feet in two areas of the San Joaquin Valley. In the Tulare‐Wasco (or Delano) area of Tulare County, subsidence which was as much as rive feet in 1940 now has about doubled. The maximum rate of subsidence in recent years has been about 0.8 foot a year. In the Los Banos‐Kettleman City area of western Fresno County, major subsidence extends from Ora Loma on the north beyond Huron on the south, a distance of 70 miles or more. The maximum rate there approaches one foot a year. Plots of subsidence against decline in artesian pressure suggest that pressure decline is a major cause of the subsidence. Compaction of the soil after irrigation is known to have caused substantial local subsidence in the Los Banos‐Kettleman City area, and tectonic adjustment and other causes also may have contributed to the subsidence.