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, ......". ..~ . .;. . .... 00 to SECTION 4 PHYSICAL COllllITIONS'TNTHE UPPER COLOMDO RIVER BASIN . The Upper Coloraclo River Basin, d..tailecl, in Figure 2, is riohin mineral, energy, agricultural and recreational resourc..s. ConsideTationof salinity control options requires that a number of physical conditions bereviewecl. In the fol.lowing paragraphs a brief review of the basin's geolo.gy, wllter supply, pres..nt ancl futu-r.,.'dElveilopments of "Water allc! energy, and presentsalbity conditions have been abstracted .from the. large body of available info.rmation. . A SUll\lllS.ry of 'plann..dsalinity control projects ancl their'antioipatecl impact wil:l:.be presentecl in the next chapter. GEOLOGY The geology of t:he basin is extremely variable. since the area has been sUbjected to glaciation, numerous folclings, severe erosion, uplifts and inland seas; and the high mountain ranges are extrell\ely ruggecl with many peaks over 4,20.0: meterS. .. Thia complexv..riation is illt.istr.ated in Flgure3. Ateaawhich are not mountainous tend to be characterized"by spectacular erodecl sedimentary rock ancl desert landscapes of which the Grancl Canyon is the most notecl example. . , .The mountains are formed primarily of igneous ancl very olcl met:amorph:l.c rock.' In general, the water leaving the mountains is of very high;/[uality. Thenomnountainous regions of the basin have ' been subjected to intermittea>.t inundations by great inland seas. Many of the thick' seclin)entary rock forma- tion.. ullc!erlying the basin were deposited at: the, bottom of the seas ancl are consequently high in r....idual salts . Figure 4il1ustr;ltes thearesle"tent of the main sedimentary deposits. .These sedimentary deposits are also the loca- tionof the oil, oil ..hale, 0.0..1, uranitllll, ..ncl other large..potential energy .iresources of the basin.. . . ., .. . a I . ThemostsignUicant fotlllStic!Us in terms ofsalin.itY Ilantl'ibution frOm' irrigated ar..a" ar.. the Mancoa Shales of the Cretaceous Age . Thesesha:l.e', sandstone and mudstone c1.spositsforma thick fotlllStionthat lies between the undei'lying DakC)ta sandstones andthEi ov..rly:f;ng Mesa y..ide'formations.. . Tl>e thickness of the Mancos Shale usually varies from between 900 to 1,500 meters. Due to its great thickness and its ability to be easily eToded, this shale forms many of the large irrigated valleys of "Western Coloraclo ancl eastern Utah. , ..' ..' .~ .,".-, .::', ~'..: , ." ,., . ".... The effect of these shales is illuatrated by Bently et al. (1978). They report that sampling runoff from Spring Creek in the Price River drainages 12 . :_;-