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Show SAN JUAN BASIN. SAN JUAN DRAINAGE AREA. The San Juan River and its tributaries drain a large part of southwestern Colorado, northwestern New Mexico, southeastern Utah, and northeastern Arizona. The drainage area is a high plateau of sedimentary origin resting at the northeast corner on the San Juan and minor mountain ranges from which practically all of the stream flow is derived. The character of; the basin changes radically near Farmington, at the junction of the I^a Plata, Animas, and San Juan rivers. Below this point the San Juan receives no perennial streams, excepting the Mancos, whose flow is negligible. The San Juan lias cut a deep gorge through the country from Farmington to its junction with the Colorado, containing only a few small scattered areas susceptible of irrigation. Its tributaries enter in similar canyons but contain little or no water except when heavy local rainstorms cause sudden violent floods-to enter the San Juan. Above Farmington, the area to the south is a rough mesa region without water supply, and in many places deeply dissected. North of the river and lying largely in Colorado is a highly irregular plain sloping sharply from the mountains. The streams originating in the higher mountains enter deep canyons close to their sources, these canyons gradually widening out and getting shallower as the San Juan Kiver is approached, creating a highly irregular plain bounded by the San Juan Kiver on the south and by a line passing through Edith, Bayfield, Durango, La Plata, and Cortez on the north, extending well into Utah. Through thin, plain the San Juan and its various tributaries have cut channels whose depth is in general proportional to the volume of water carried. Interstream diversions are necessary for the reclamation of this area as many of the streams have insufficient water for the reclamation of land immediately adjacent and such diversions are in most cases not difficult. The total water supply, while far in excess of the demands for the available acreage, presents physical difficulties of diversion which will leave a large flow in the San Juan proper. The irrigable lands have a deep loam soil of sedimentary origin,, characterized by its high fertility. Most of the area has numerous, drainage channels, though seepage to the extent of waterlogging is. apparent in some of the old flatter areas. Elevations range from 5,000 to 8,000 in the irrigable areas and from 4,000 to 14,000 within the whole basin. Precipitation ranges from 8 inches, or less, at the mouth of the San Juan to probably 50 inches in some of the mountains. In the irrigable arear precipitation ranges from 10 to 24 inches and the mean annual temperature from 40° to 48°. The entire region is characterized by mild winters, hot summer days, and the occurrence of rains in the late summer season. 158 |
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Original book: [State of Arizona, complainant v. State of California, Palo Verde Irrigation District, Coachella Valley County Water District, Metropolitan Water District of Southern California, City of Los Angeles, California, City of San Diego, California, and County of San Diego, California, defendants, United States of America, State of Nevada, State of New Mexico, State of Utah, interveners] : |