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1 24 CLIMATE The unit area has a temperate climate with weather characteristics similar to those of the Western Great Plains. The region is normally semiarid, although precipitation varies widely from year to J.'ear. Pre- cipitation fmd temperatures are influenced by the great arr mas~es and weather fronts which periodically sweep across the Great Plams Province. The temperate climate which is accompanied by abundant sun- shine with warm days a~d cool nights d~g the gr~wing se~on, makes the area especially favorable for agrIculture and Its assocIated industries. Although the natural precipitation is adequate.to support only highly speculative dryland farming and livestock .gr.azmg, a Wlde variety of crops with high yields may be grown when lITlgatlOn water . is sufficient. Climatic data at selected stations within the umt area are summarized in table 3. Station TABLE 3.~UMATIC DATA (193HO) Average Annual Temperature (degrees F.) annual precipitation frost-free (Inches) Average, Average, feriOd Maximum Minimum J.~ January days) 12.86 109 -41 73.9 24.3 148 14.10 106 -33 73.9 24.8 140 15.32 109 -38 7M 27.7 145 f!f~~;;~~:::::::'::::: HISTO!tY The unit area was part of the larger area ceded to the United States as the Louisiana Purchase in 1803. Subsequently, the South Platte area became a part of the Kansas-Nebraska Territory and later was included as a part of the Colorado Territory established by Congress in 1861. The Colorado Territory was admitted to the Union on August 1, 1876, as the 38th State. . During the decade 1880--89, homesteaders began assunnng con- trol over lands in the South Platte River Valley and surrounding rangelands which formerly had been held by cattle barons. Thus began the cash grain and livestock economy in the uplands and the irrigation farming in the valleys, now prevalent in the area. Large irrigation areas along the lower part of the valley were not developed to any great extent, however, until about the turn of the century, when increased water supplies, consisting of return flows from up- stream irrigation, became available and legislation was passed which authorised the formation of irrigation districts. This legislation pro- vided the means for farmers to cooperate in financing and constructing extensive and complex irrigation facilities. By 1910, several irrigation districts had constructed works to irrigate dry lands, but most of the districts constructed reservoirs to store water for irrigated lands which were inadequately supplied by direct-flow rights. This period of ex- pansion continued until the beginning of World War I. Since then, activities have been generally limited to maintenance and improve- ment of existing works. 25 . Subsequently, as 'a result of chronic water shortages, it became evident that most of the irrigation districta had overestimated the available water supplies and had overextended their service areas. At the beginning of the severe drought of the 1930's, these water shortages became 'widespread, and many farmers developed ground water for irrigation. As the drought continued throughout the 1930's, ground-water development in the South Platte River Basin expanded rapidly. . However, it had been apparent for a considerabl.e tune that addi- tional surface water for irrigation would be requITed-particularly in the upper portion of the basin. The only l'ractica~le means of resolving the situation was by transmountain ImportatIOn of water from headwater sources on the western side of the Continental Divide. Accordingly, in 1935, the Public Works .Administration granted funds for a survey by the Bureau of ReclamatIOn of what was called the Grand Lake-Big Thompson project. The project was subsequently found, feasible by the Secretary of the Interior and was approved by the President on December 21, 1~37. Funds were in- cluded in the Interior Department ApproprIation Act of 1938 (50 Stat. 564, 595) for construction of the project in accordance with the plan described in Senate Document N,? 8~ of the 75th <;ongress. Concurrently with the Federal authorlZatIOn of the proJect, the Northern Colorado Water Conservancy Di.strict w~ formally organized in 1937 8Jld entered into a contract Wlth the Umted States, through the Bureau of Reclamation, on July 5, 1938, for the repay- ment of }!roject construction costs on. what became known as the Colorado-Big Thompson project.. .. Most of the available Colorado-BIg Thompson Importations have have been used initially ,in the ~pper, basin a~ove the Narrows area. The lower basin-that lJ3, the N arrows ServIce area-has benefited from the use of return flows. However, most of the return flowsl or their equivalent have been utiliZed by means of ground water with- drawals, leaving surface flows in ?he river about- the s~e ~ before the Colorado-Big Thompson project return flows rn,a~rIaIized. Thirty-three irrigation systems now serve lands Wlthin the Lo'yer South Platte Water Conservancy District. Four oll'stream reservoITS, Jackson Lake Prewitt North Sterling, and Julesburg (Jumbo) serve about 10 to 12 ditch' systems in th!, conserVancy district. No.ne of these reservoirs has sufficient capaCIty to assure adequate su.pphes for the systems served. The remainder of the di~ s;y:sterns m the conservancy district rely on streamflows for therr major source of sUPl'ly. . d Many irrigators have constructed wells for pumpmg groun. water for supplemental irri!(ation. On the basis of data collected ~ 1961 there were 875 operatmg wells in the Narrows service area. Additional wells have been constructed since then, but the ll1!~ber has .n~t been 'determined. Under future ffwith" project conditIOns) .the IrrI- gators would continue to rely on ground water for meetmg part of the total irrigation requirement. . . POPULATION The Narrows Unit service area is contained in four counti~- Morgan, Logan, Washington, and Sedgwick. The total populatIOn