since the high water was caused by several warm day's occurring in succession. The discharge from March to June was considered large. The height of the water fluctuated from day to day in the early part of the spring, an effect due almost entirely to changes of temperature. A warm day had an immediate influence in increasing the discharge, while on a cool day the discharge was checked. The variations of temperature from day to night also caused a very perceptible difference in the river height, causing it to fall at night and rise during the day. After the lower snows had disappeared the discharge of the Weiser was kept up by the melting of the snows on the higher ranges. Thus, while the creeks and streams on the west side and the foothills snow furnished the earlier water, the Middle and East Forks and the Little Weiser, heading in the high mountains to the east, contributed the greater part of the later discharge. The table of monthly mean will show most clearly the relative discharge for each month. The latter part of August is the usual time of extreme low water and by the middle of September the river begins to rise slowly. Ice generally forms on the headwaters by the 1st of November, and rarely breaks before the last of March. On the lower river, however, it does not appear until the last of December, and breaks generally by the last of February. The headwaters are little settled; few ranchers are found above Council Valley. There are a few settlers in Indian Valley, on the Little Weiser. At Salubria there is a settlement of four or five hundred people. Middle Valley, on the main Weiser, below Salubria, is quite thickly populated. Irrigation is practiced on all the valleys as far up as Council Valley, the water being taken from the main stream and from its branches and tributaries. Above this point the upper Weiser Valleys are largely devoted to stock-raising. The principal crops are wild hay and alfalfa, grain, and small amounts of vegetables for home consumption. The stock is allowed to graze at will on the immense natural pasturage in the hills during the spring and summer months, but during the winter the cattle are fed on hay. Below the mouth of the last canyon on the Weiser, in which the gauging station is located, the river opens out into a wide bottom, ranging from 1 to 8 miles in width, joining the main Snake River Valley at its lower end. On the north side of the river there are two ditches taken out below the canyon, the Weiser Water Company's ditch and the ditch of the Weiser City Ditch and Irrigation Company, also called the "Mill Ditch." Irrigation in this valley usually begins about May 1. Owing to the wet spring of 1890, it was as late as May 15 before any irrigation was done. The irrigation of the grain crop ceases about June 15, and two waterings are deemed sufficient. Corn is irrigated up to August 1, requiring from three to four waterings. Alfalfa is the most productive crop raised; three crops of nearly 2 tons to the acre each are usually obtained. Alfalfa is watered once for every cutting; it is rarely irrigated later than September 1. Frost may be expected any time after September 15, but it rarely occurs before October 1. On the Owyhee the first or spring flood is caused by the sudden breaking up of the ice and the melting of large quantities of low-lying snows. It is sudden and of short duration, in this respect all of the rivers of this general region being similar, all having their early spring, or more properly, late winter floods. Those rivers having large catchment areas in high ranges which retain the winter snows long into the spring are characterized by a second spring flood, occurring at any time from the 1st of May to the 1st of June. Long after the first snows on the lower tributaries have melted and run off in the early spring the higher snows remain intact, and continue so until the protracted warm weather of the later spring months begins to have effect; this snow then melts and a second flood is experienced. Usually this is more gradual and less spasmodic in its nature. It lasts perhaps several days or weeks, and falls steadily and slowly to the extreme low-water stage, which occurs generally in August. The Malheur River kept a very uniform discharge from the middle of March to the 1st of May. After this it began to fall slowly and steadily to extreme low stage, when it had practically no discharge at the gauging station. The Malheur experienced no second flood, as did the other rivers, there being no mountain catchment area at the headwaters high enough to keep back sufficient snow to create a very perceptible increase in the discharge when warmer weather came. The Weiser River in Idaho has a varied discharge, sudden spasmodic floods are common, and a rise of 2 feet in one night occurred several times during the last spring. When the gauge was established on March 13 at the gauging station on the Weiser it read 44 feet. On the 15th the gauge read 5.1 feet, and the discharge was about 2,400 secondfeet. On March 17 the river had risen to 7 feet, increasing the discharge to 5,500 second-feet, and on March 19 the gauge read 105, rising 2 feet in one night. The discharge was then estimated at 13,000 second-feet. The river then fell to 5.8 on the 29th of March, and the next day it was up to 7.2. Another slight flood occurred on April 23 and 24, and another about the 1st of May, after which date the river began to fall steadily until the low stage. About the middle of August the discharge was only 160 second-feet. Cubic feet per second into acre-feet per month of 30 days.. 43,560 86,400 2,592,000 2,678, 400 acre feet.. 1.9835 59.505 61.488 1.122 Area. 1.153 Area. Cubic feet per second to depth of run-off in inches per month of 31 days. |