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<br />WATER RESOURCES AVAILABILITY <br /> <br />Of major significance to the fQrmuIation of the framework plan <br />is the availability of t1ater of satisfactorv quality. Historically, man <br />has used the waters of the Nissouri Basin since he first arrived here, <br />and its availability has patterned, at least in part, his economic <br />successes, failures, and way of life. <br /> <br />CLIMATE <br /> <br />The basin has a variable climate with seasonal temperatures ranging <br />from -600 to over 1200 with below zero to over 1000 temperatures <br />experienced over much of the area. Averaze annual precipitation varies <br />from 8 - 12 inches in the northwestern plains and 20 - 40 inches in the <br />mountains, to about 44 inches in the southeastern part of the basin. <br />Average rainfall amounts to slightly over 20 inches. <br /> <br /> <br />RUNOFF <br /> <br />Streamflows are made up of two principle parts, that of direct surface <br />runoff during major precipitation and snoWlllelt periods, and from water <br />which passes through the soil mantle. The amount of runoff in the basin <br />is approximately 10 percent of the mean annual precipitation and amounts <br />to an average of 2.3 inches. This varies from a high of over 12 inches in <br />the mountains and southeastern part of the basin to less than 1/2 inch in <br />major portions of the plains. <br /> <br />12 <br /> <br />. <br /> <br />