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water development of any size since World War II has become involved in this concept. I am sure that every planning group represented. here recogniz~s that multiple-use is here to stay in any futu re water development. Most water developments include water storage. Wh~n we stop to think about it, the only way to utilize the same storage for flood control on th:e one hand and conservation storage .tor irrigation and power on the other can be had orly if it be known in advance approximately what the inflow to the reservoir will be, By!wayof illustration, Lake Mead is , our largest and a multiple-use reservoir of long standing. i Provision is made for flood con- trol, irrigation, power, and recreation. Water stored here also furnished a major segment of municipal water supply for Southern California through the Metropolitan Water District. Many of you here, particularly from the Bureau of Reclamation, are familiar with the details of how water sup. ply fo.recasts affect operating decisl'ons at La.ke Mead I do know that the snow survey data is in immediate demand, as soon as t is obtained, by the Bureau of Reclamation as well as other operating interests'in the Colorado RiverBasin, Water supply forecasts and the basic data necessary to prepare them will! continue to be in demand for the operation of Glen Canyon, Flaming Gorge, Navajo, Curecapti Unit, and other reservoirs on the main tributaries as well as the participating projects on the Upper Colorado. I I I 1 I I r " f -~1- ! . I Ii , ! I I SNOW COURSE NETWORK ON THE COLORADO RIVER BAS I N , i , I 'j , f , .., I' i 1 I I t; Perhaps th is is as good a ,time as any to describe thelsnow survey network on the Colorado River Basin. There are some changes each year) but we will have to take our figures from the latest report for the 1960 season. At thatitime there were about 160 snow courses located in the Colorado River Basin. This was 12 per cent of the total number in western United States, About 60 are in Colorado, 50in U~ah, 30 in Arizona, and a few each in Wyoming, Nevada, and New Mexico. Snow courses ten~ to be, in the high mountains along major watershed divides so there are nearly anotherlloOsnow courses within 25 miles of the Colorado River Basin. These are located in the Gre~tBasin, the Snake River tribu- tary to the Columbia Basin and on the Missouri, Arkansaii, and. Rio Grande. Measurements on most snow courses are made on the first of the month, February through May, with a few on earlier and later dates. Arizona snow course measure!nents are made every 15 days, January 15 to Apri I I, inclusive. Between 650 and 700 snow course measLl rements are made each season. Some 15 over-snow machines are utilized tr:avelling about 3000 miles each season in reaching the more remote installations. A tota.l of about 125 snow surveyors travel nearly 5000 miles on skis or snowshoes in additionfotravel by aircraft and automo- bile to obtain these snow measurements. Fortunately, m~ny of the snow courses are near highways over divides, particularly in Colorado, . . Air markers are located on 18 existing snow courses !for air observation of snow rlepth on some of the more remote courses in lieu of groun~ me~surements prior to April, The snow density and water content are estimated from densitY data on nearby coursesthat are ground measured. These marker observations have beenisuccessful for early season measu rements but are not considered sUfficiimtly accu ratll for Apri I and later measu re- I ments. ! - 2 - II I' I .\ i i. , .1 I /: 1, Ii Ii i t,