« AnteriorContinuar »
The character of the strata filling the lower portion of the valley is shown hy a well (No. 204 in table) drilled near the court-house at Salinas, at an altitude of about 33 feet above sea level.
Record of Salinas well.
Character of strata.
Depth of bottom of formation.
filled with water) --
720 82 0
Black sand and mud..
The gravel brought to the surface consists of small waterworn pebbles from half an inch to 2 or 3 inches in diameter; many of the coarser pebbles were broken in the well.a
It is probable that the abundant supply of ground water is struck in the beds of sand and gravel from 125 to 202 feet in depth. The well appears to have pierced the clays and limestone of the older formation at a depth of 472 feet, or about 410 feet below sea level. This is then an approximate measure of the depth of the detritus filling this portion of the valley.
In 1880 a well was drilled at Castroville to a depth of 178 feet, producing a volume of fresh water, which at high tide flowed in large quantity over the casing and at low tide ceased flowing. This well is near the mouth of Salinas River, and the surface of the ground is 20 feet above the river. a
The gathering ground for this body of underground water is unknown, but the close agreement of the basin with the outcrops of the sand hills on both sides of the valley suggests that this formation may be the source from which the water is indirectly derived by seepage. This idea is strengthened by the fact that the water from the deep wells is of about the same purity as that found in the sand hills, being far purer than the river water, the surface water in this portion of the valley, or the water derived from the older formations. This water may possibly be derived by percolation through deeply buried gravel beds, from the Arroyo Seco or the upper Salinas, but deep borings have not proved that conditions are favorable to this origin.
Southeast of Salinas, as far as Kings City, there are a few pumping plants used for irrigation, some of which draw water from the river. They are described on page 80. The wells in this portion of the valley do not furnish sufficient data on which to base an opinion as to
a Tenth Ann. Rept. California State Mining Bureau, 1890, p. 346.
the underground conditions other than that the supply of ground water is limited except along the river.
The only artesian well noted in Monterey County, except in the vicinity of Salinas, is on the Pleyto ranch (Pl. I), at Mr. Pinkerton's place, one-half mile southeast of Pleyto. The total depth of this well is 145 feet. At depths between 70 and 100 feet the drill was in hard, black rock, and at 100 feet water rose 9 feet. At 145 feet a bed of hard rock was penetrated and the water then flowed over the top of a 7-inch casing. This well is situated in the lower end of a synclinal basin, at a point where one would expect to secure an artesian flow if there is one in that locality. This basin extends northwestward about 20 miles, and there is a possibility that a small artesian flow may be struck in the southeast part of it, between Jolon and Pleyto. At no other point in Monterey County were conditions favorable for artesian wells observed.
It seems probable to the writer that deep wells in the mesa region on the east side of the valley, southeast of Kings City, may yield sufficient water for stock-raising purposes if pumped. This can be proved only by experiment, however.
CLIMATIC FACTORS. In an appendix to a report on the climatology of the arid regions of the United States with reference to irrigation Mr. A. W. Glassford makes the following statements:
Two influences dominate the climate of California, radically dissimilar in every particular, combining in ever-varying forces to produce the resultant which is recorded by observers of the weather. One is the sea, tending always to charge the air with moisture, the other the mountain mass, tending always to discharge the moisture from the air. The combination of these two activities in varying proportions is responsible for the variation in the amount of precipitation, including months of drought. It is necessary to consider these two active and determining forces not merely in their resultant, but, so far as is possible, by resolution into their component forces as well. In the present state of knowledge the resolution can not be complete, yet the extent to which it can be made affords interesting results.
The mountain factor.-The States of California and Nevada abut upon the maximum extension in latitude of the Cordilleran system, by which designation is inclusively implied all those ranges, basins, and valleys which in a looser description are often spoken of as the backbone of the continent and considered to include everything from the eastern ranges of the Rocky Mountains to the Pacific Ocean. Between the parallels of 35° and 40° this system attains not only its greatest breadth, but its greatest general elevation. It extends from eastern Colorado across four States and into the ocean, where but a few miles from the California coast it breaks short off from the continental shelf and plunges to abysmal depths.
a Information furnished by W. Pinkerton.
" Irrigation and water storage in the arid region: House Ex. Doc. 287, Fifty-first Congress, second session, pp. 334-337.
IRR 89-04- 3
Not only is its width greatest between these parallels, and therefore productive of its maximum influence upon the general circulation of the atmosphere, but also by the massing of many of its extreme heights within these same limits it exerts such violent influence of perturbation as is due to sudden uplifting of air bodies to great altitudes. Thus in Colorado there is a chain of peaks all rising to a height of more than 14,000 feet, of which Pikes Peak is the eastern outpost; Utah and Nevada form the Great Basin, on a general level of 5,000 feet; in California the Sierra Nevada has its peaks of 14,000 feet, as well as Colorado, and at the very edge of the sea is another range of mountains lower than the Sierras, yet of marked influence upon the climate and the rainfall in particular. These systems within the limits of the two States now under examination may properly claim more detailed investigation.
The characteristic orographic feature of this region is the Sierra Nevada, and it is as well the predominant climatic instrument both for California, to which it gives the rain, and for Nevada, from which it withholds it. The geographer and the geologist unite in considering this the most interesting and important link in the Cordilleran system, and the climatologist must unhesitatingly and without reserve give adhesion to their judgment. In brief description it is a long and elevated mountain chain, on the whole the most conspicuous on the continent. It displays its greatest prominence when viewed from the west, because on this side it falls almost to sea level, while upon its eastern slope it merges into the general high altitudes of the interior plateau. But it does not, however, border immediately on the ocean, since for all its course there lies between its foothills and the sea beach a chain of lower mountains, known as the Coast Ranges. * * *
These, the Coast Ranges, are sufficiently important in their relations to precipitation to merit inore close consideration. The most important part of the Coast Ranges is that which fences off the great valley of the Sacramento and San Joaquin rivers from the sea. In this portion of their length, where they may be clearly distinguished from all series of inosculating elevation, they have a length of fully 400 miles, and in width vary from 40 to 70 miles; in this particular it is to be noted that their eastern limit is fixed with considerable precision of definition at a practically constant distance from the western limit of the Sierras; the expansions are uniformly made by encroachments upon the sea. The system comprises a multitude of subordinate ranges, some large, some small, but almost all distinguished by names bestowed upon them during the former Spanish occupation of the country, with a few Indian names yet preserved for characteristic peaks. The general trend of the subranges, as of the system at large, is with a tendency toward parallelism with the coast. In proportion to distance from San Francisco, where the system is broken through at sea level by a gap but a mile in width, the summits and the general elevation are found to be higher, and this is true both north and south. * * * From Mount Hamilton the ridge of 3,000 feet elevation continues without interruption and almost in a right line to the Tehachapi country and its coalescence with the same level of the Sierra system. * * *
Having thus indicated the orographic skeleton of the country, it comes next in order to examine the valleys infolded between these mountains.
As it is the greatest, so is the Great Valley of California the most important; it frequently takes the names of the rivers which traverse it and is known in its northern portion as the Sacramento Valley, and in its southern half as the San Joaquin Valley. It is fenced on the east by the Sierra Nevada, on the west by the Coast Ranges, and at north and south by the coalescence of its side walls. Between these walls it has a length of about 450 miles and maintains the average breadth of 40 miles. * * *
In the Coast Ranges are many fertile valleys, which vary greatly in size and conditions, according to position. * * * North of the [San Francisco] bay the valleys uniformly open into the Sacramento Valley, and each has a name which has nearly the value of a trade-mark in the markets for farm, orchard, and vineyard produce. * * * South of the bay, on the dry eastern slope of the Coast Ranges, not a valley is to be found of any moment. · West of the summits are to be found several fertile valleys. Of these the valley of Santa Clara and Alameda open on the Bay of San Francisco, and the valleys of the San Benito and the Salinas open on the Pacific at the Bay of Monterey. * * *
The oceanic factor.–This presentation of the mountain masses of the region under study has been made for the purpose of showing what influences may be counted on as constantly exerted to discharge the moisture from the atmosphere. Another influence is constantly exerted to charge the atmosphere with moisture, and this influence should be examined in turn. It is found in the Pacific Ocean, which washes the entire coast of California. * * *
The largest of all the oceans, the Pacific, is least subject to perturbing influences of a local character. Its conditions are constant over large areas; its currents, both of wind and water, are drawn in broad, sweeping curves, in which extent of space and time of passage serve to override all mere local or temporary modifications. Thus it is enabled to present almost the ideal problem of oceanic circulation and to array upon the climate of California, and in a modified degree that of Nevada, a few masses of simple influence which become involved and difficult of study only through the continental disturbances.
Without interruption that part of the North Pacific Ocean which may be considered as modifying the climate of California stretches away over nearly 100 degrees of longitude. To the west it is bounded by the extreme Orient. * * * The northern limit is drawn by the Aleutian Islands, and the eastern border is the shore of North America. To the south no consistent mass of land appears to hem this ocean in, yet the barrier is none the less strong because it may be measured only with the instruments of the meteorologist. It exists at the thirtieth parallel of north latitude. Below this bounding line is the region of northeast trade winds and the westward drift of the equatorial current, and these two serve sufficiently to bound in wind and water the great basin above. * * * ..
The winds upon this basin are of the system of the passage winds which are developed upon the surface of the earth by the descent from high altitudes of upper currents. In general these winds vary with the latitude from southwest, westerly, to northwest. * * *
The Californian parallels lie entirely within the northern zone of the passage or antitrade winds, and are therefore under an atmosphere with a uniformly eastern progression as a part of the general system of atmospheric circulation of the globe. * * *
The wind drawn in from sea by the general circulation of the atmosphere may be taken to have in suspension the maximum amount of moisture, and, other things being equal, to approximate the saturation amount theoretically to be expected in air of a given pressure and at a given temperature.
Throughout California the general drift or movement of the atmosphere is to the southeast. Over the land, however, the direction and velocity of the wind are much modified by the trend of the mountain ranges and intervening valleys, as well as by diurnal and seasonal changes in temperature. Along the coast the north west passage winds blow with remarkable regularity during the summer, and more or less constantly during the entire year. The diurnal changes in