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" ~) PARSHALL PROJECT. COLORADO The topsoil is dark brown to black and ranges from 6 to 12 inches in depth. The subsoils are brown to reddish-brmm clay loams generally more than 5 feet deep over gravels or parent material. Alkalinity and salini ty are very low and did not cause any of the lands surveyed to be classified as nonarable. The lands have good drainage characteristics such as deep under- lying gravels, many natural drainage channels, relatively steep topog- raphy, and elevated positions. lJ'dnor drainage-deficient areas may develop under project operation, however, so that some artificial drains were anticipated in making project cost estimates. The arable acreages determined by the 1951 land classification sur- vey were adjusted for use in the present study. First, all 1951 arable acreages Were reduced 10 percent to allow for reductions that might result from a detailed classification to current standards; secondly, the 3,960 acres under the Big Lake ditch to which irrigation is currently being extended w'ere changed from "full irrigation service" to "supplemental irrigation service" designation; thirdly, since no class 3 lands were identified in the 1951 survey but all arable lands below class 2 were identified as class 4, it was now assumed that half of the class 4 lands would meet class 3 standards. The adjusted arable land acreages are tab- ulated by service areas on the fOllowing page. Lands tabulated as being in the Blue River and Sylvan areas are not included in the development plans of this report. All other land areas are in the project plans, as was previously indicated, but not all lands in each area would be served under either of the plans. Water Supply The amount of water available for the Parshall project is dependent upon the outcome of pending water right adjudications as explained in the introduction to this report. The two project plans presented, as previously expla.ined, are based on favorable and unfavorable court rul- ings, respectively, to project sponsors. Water resources , l'iater supply studies made for this report '.ere based on runoff for the la-year period 1951 through 1960. This period includes the criti- cally dry years of 1954, 1955. and 1956, as well as the high runoff years of 1952 and 1957. The period is considered to be a conservative base for the estima.tes of streamflows tha.t ma.;y- be expected in the future. SevElral stream-eaging stations were operated during all or part of the period of study. Locations of these stations and of other discon- tinued stations are shown on the frontispiece map. PeriOdS for 1Vhich runoff records are available at each station are shown on page 10. 8