Year.

SNOWFALL IN THE SIERRA (IN INCHES AND TENTHS)-Continued.

SUMMIT.

Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Annual.

NORTHERN SIERRA NEVADA.

By Mr. J. A. EDMAN, E. M.

The relation of snowfall to water supply can not be predicated upon the bare statement of precipitation and depth of snow alone, as so many other factors must be taken into consideration. To refer to the reports of observers to the Weather Bureau: What does an inch of snow stand for? It may mean all the way from one-ninth to one-fourth of an inch of water. Again, the absolute water contents of the settled snow depends not alone on its depth, but its relative compactness at the time of measurement, and may vary from one-seventh to one-third of an inch of water for one inch of snow.

The only conditions in the northern part of the Sierra Nevada under which a heavy snowfall insures a steady water supply are as follows: First, early rains beginning in October and gradual enough to soak into the surface without running off in sudden floods; second, abundant snows in December and January, with occasional rains, so that the snow may settle and become compact, and freezing of the surface soil prevented; third, occasional snowstorms during February and March, and an early but not too warm spring. Heavy precipitation and snowfall under other conditions do not insure an abundant water supply, as was well illustrated during the season 1889-90, when the precipitation at Edmanton reached 137.35 inches, and the depth of solid snow on the 15th of March attained 14 feet. Elaborate computations of the precipitation for that season in the Feather River basin, in connection with a record of flow at the Golden Gate mine near Oroville, showed that only 30 per cent of the water estimated passed off by the river during the spring and summer months. In this instance the spring of 1890 was marked by a very high temperature, and the first deep snows of 1889 fell on bare and frozen ground. The general water supply during that season was but little above the average. At this altitude (4,750 feet) and section of country it takes nearly 20 inches of water to fill the surface soil and start the deeper springs running, and even more after a very hot and dry summer.

The above-mentioned facts are well illustrated by the weather conditions during the seasons 1899-1900 and 1900-1901, as will appear from the subjoined tables:

An inspection of the above table will show the precipitation about equal for the two seasons, but the snowfall of January, 1901, far in excess of that of the corresponding month of 1900. The table, however, does not show that the conditions precedent during this season were specially favorable in contrast with the previous season, as the storms of October, 1899, were concentrated in a few days and the water passed off rapidly in injurious floods, while the rainfall of October, 1900, was well distributed over the whole month and largely seeped into the ground. The rains of December, 1899, fell on frozen ground and largely ran off, while in December, 1900, the thoroughly saturated ground received a cover of snow, to be reenforced in January, 1901, by heavy snows, now (January 26) averaging 4 feet in depth at this station, which acted upon by the warm surface soil feeds the streams independent of the general temperature conditions. Given a fair supply of snow during February and March it is reasonable to predict a good water supply during the summer of 1901.

AT EDMANTON STATION.

By Mr. J. A. EDMAN, Voluntary Observer.

The months of February and March, 1901, present a marked contrast to each other in regard to precipitation and also in snowfall, the record being as follows:

The preponderance of rain during February is notable, as the mean temperature for the month was 35.2°, as compared with 40.1° for March. The rains of February having been almost continuous for eight days, and accompanied by strong winds and a mean temperature during the storm period of 40.3°, induced a rapid melting of the snow, and as a result the depth of snow (70) inches) at the beginning of the rainstorm was, at its close, reduced to an average of 40 inches. This reduction in the volume of the snow I have estimated as equivalent to 7 inches of water, making a run-off during a little more than ten days of 16.47 inches of water, and causing proportionate floods in the mountain streams.

The precipitation during March was much below the normal, and being mainly in snow, added 10 inches to the depth up to the 15th, which, although reenforced by a light snowstorm on the 27th, was reduced during the prevailing clear and comparatively mild weather of the latter half of the month to an average of 30 inches by the 1st of April. This depth of snow is roughly estimated, as great variation occurs according to exposure to sun and wind, many southern slopes now presenting large bare spaces, while drifts 5 feet deep may be seen on northern declivities and in sheltered spots in the canyons.

Ever since the high water of February the streams in this section of the Sierra have furnished a constant and but slightly varying water supply, which is being utilized by the miners, and which is apt to continue, and even to increase, during April and May, dependent on the temperature. The precipitation for the season, up to date, at this station, is 70.68 inches.

The depth of snow on April 1, within a radius of 6 miles from this station, may be estimated as follows: In the zone below 3,500 feet altitude, little or no snow is found. From 3,500 to 4,000 feet, but little is seen on southern exposures, but an average of 20 inches on northern slopes and in the hollows. From 4,000 to 5,000 feet, about one-half of southern exposures are bare, and the snow there remaining does not exceed 20 inches in depth, while the northern slopes average fully 35 inches in depth. From 5,000 to 6,000 feet, bare spots occur on wind-swept southern exposures to an extent of 25 per cent in area, while the average depth of the whole zone may be given at 50 inches. From 6,000 to 7,000 feet, a few bare spots occur on windy points, while over the whole zone the snow probably averages fully 70 inches in depth. Three inches of the old snow may be estimated equivalent to 1 inch of water. The rains of February extended above the 7,000 feet zone in this region. The later snows have not reached below the 3,500 feet limit.

So far the outlook for a long-continued and regular water supply within the Feather River drainage area is very promising, providing normal temperatures prevail during April and May.

CALAVERAS COUNTY.

By Mr. C. E. PRINDLE, Voluntary Observer.

The snowfall in the mountains of eastern and northern Calaveras County is several feet short of the average up to five and six years ago. The snows this winter have been light, and the rains have extended higher into the mountains than usual. The earth contains more springs and water at this date than it has for five years past. There is more water in the Calaveras River and all branches of the Mokelumne River (except the North Fork, which heads in Blue Lakes) than for several years past at this date, it being mostly rain water and not water from the snows. Dependence is not placed as much on the snowfall for a summer supply of water as in former years, for the reason that great forest fires have been so destructive to timber and undergrowth of late years that the snows do not remain on the ground long, but disappear from a month to six weeks earlier than formerly. Spring rains are more to be depended upon than snow for a summer supply of water.

Parties who have to-day returned from the higher range of mountains state that the snowfall is very light, in many localities there being none at all, where last year at this date there was 4 feet. Snow has fallen several times, but being followed by rain it did not remain long on the ground.

LAPORTE.

The following record of snowfall at Laporte, Plumas County (elevation 5,000 feet), was made by Mr. Charles W. Hendel, voluntary observer. The record shows a yearly average of 299 inches. The snowfall for January, 1901, was 96.5 inches:

Year.

a Includes 7 inches in June and 2.5 in September.

CUYAMACA, 1888-1900.

By Mr. G. H. NELSON, Voluntary Observer.

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Jan. Feb. Mar. Apr. May. Oct. Nov. Dec. Total. Year. Jan. Feb. Mar. Apr. May. Oct. Nov. Dec. Total.