IRRIGATION IirVESTIGATIONS ON CACHE CREEK, 159 



of low water with the purpose of loosening the material, so that it may be carried 

 down by the current. The water of the lake, starting at the riffle from a state of 

 rest over a not verj' steep grade, has little transporting power and, with the flat 

 grade and clogged channel of the section below, any material moved in this way from 

 the riffle is deposited at a point a little lower down. While the diversion of Siegler 

 Creek and the work on the riffle ma}-, for the time being, prevent the raising of the 

 water level, the ultimate effect is to make the bar a more permanent and effective 

 obstacle to the passage of the water. The outlet of the lake being thus impeded, the 

 water accumulates during the i"ainy season, causing a fluctuation in the surface from 

 extreme low to extreme high water of some 12.7 feet. The ordinarv range of fluctu- 

 ation is much less than this. The variation between mean high and mean low water 

 is about 5.5 feet. The highest stage was reached January- 25, 1895, and the lowest 

 November 20, 1898. The extreme of high water causes great inconvenience to 

 dwellers on lands contiguous to the lake and also interferes serioush- with naviga- 

 tion, the ordinary wharves and landings under such conditions being all submerged. 

 The lake is not deep at any point, the extreme depth over a small area ranging from 

 40 to 50 feet. Along the borders, especially in the neighborhood of the points where 

 it is desirable to make landings, the water is shoal and grown up with tule or coarse 

 water grasses. At extreme low water a considerable body of this tule land is par- 

 tialh' drained and a large area of mud flats exposed to the action of the sun, producing 

 conditions which are a serious menace to the health and prejudicial to the reputation 

 of the towns on the lake as health resorts. The approach to the ordinarv landings is 

 also cut off at such times, thus interfering with the navigation of the lake. By the 

 improvement and control of the outlet all these difficulties might be overcome. This 

 would require the straightening, widening, and deepening of the channel from the 

 lake to the point where the stream begins to fall rapidly, and the construction of a 

 system of regulating works adequate for the passing of a large volume of water when 

 the level of the lake approaches the high-water danger point. When the danger is 

 past, these gates could be closed and the water passed down through the channel as 

 needed for use below. Hy so conserving the waters the level of the lake need never 

 fall to the low stage which it now often reaches. If the range of levels were confined 

 to from 3 feet above extreme low water to 8 feet above, the evil effects of both 

 exti'emes would be avoided; it would then be possible to make permanent wharves 

 and to reclaim all land above the high-water mark fixed. Siegler Creek could be 

 disposed of by diverting it into the lake farther west, above and south of the point 

 where the channel leaves the lake proper. The waters of Siegler Creek would be 

 thus conserved and the debris which now interferes and chokes the channel would 

 gradualh' fill up and render useful a considei-able body of now worthless tule land 

 near the lower end of the lake, which affords a large evaporating surface, without 

 adding materialh* to the available storage capacity of the lake. 



In the accompanying plate (XIV) the upper diagram shows graphicallj- the 

 rainfall in inches on Clear Lake watershed for each month for a period of nine years, 

 1891-1899. It is the average reported by three observers: D. C. Eumsey. of Lake- 

 port; F. M. Porter, of Kono Tayee, and W. A. Maxwell, of Kelseyville. The 

 second diagram shows the fluctuations of the surface of Clear Lake in feet for the 

 same period and is constructed from three sets of observations made by D. C. Rumsey, 



