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<br />CHAPTER IIIhDESIGN
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<br />16. General. - The destructive Republican River flood of 1935, which occurred dur-
<br />ing a critical agricultural period and aUer 70 years of recurring drouR"ht throughout the
<br />Republican River watershed, directed national attention to the flood control and irri-
<br />gation needs of the area. The flood with its loss of 110 lives and property damage of
<br />$9. ODD, 000 stimulated surveys of the Republican Rh-er basin by the Corps or Engi-
<br />neers, the Department of Agriculture, and the Bureau of Reclamation for evaluating
<br />the basin's flood, irrigation, and power requirements.
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<br />In October 1944 an agreement was concluded between the Bureau of Recla-
<br />mation and Corps of Engineers to construct a multipurpose dam on the South Fork of
<br />the Republican River at Hanny site No.1 (see sec. 10), The Bonny reservoir would
<br />permit the irrigation of some 6,500 acres of land in addition to providing the flood
<br />control primarily proposed for the Hale reservoir. Since the Bonny reservoir would
<br />be located about 4 miles above the Hale site comparable flood control benefits were
<br />considered to be available.
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<br />Discussions regarding the suitability of the Bonny Dam site were of a contra.
<br />versial nature and extended from 1946 until actual construction was begun in 1948,
<br />The geologists focused their attention on the permeability of the foundation materials,
<br />while the designers concentrated on the consolidation factors to be reckoned with in the
<br />location of the spillway and outlet works, Because of the considerable concern ex-
<br />pressed by both designers and geologists regarding a probable high rate of percolation
<br />through the Ogallala sediments, numerous open-end percolation tests were conducted
<br />during the drilling operations.
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<br />In' August 1947, a construction engineer was appointed for the construction of
<br />Bonny Dam. Subsequently the final stage drilling proRram and additional survey were
<br />started. Early in the fiscal year 1948 supplemental fund!> for flood control were made
<br />available and work progressed under an accelerated program,
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<br />The Chief Engineer was advised b)' the District Manager on May 19, 1948,
<br />that issuance of specifications for Bonny Dam had been authorized and funds in the
<br />amount of $1,808,000, scheduled to cover estimated contract earnings for the fiscal
<br />year 1949, were available, SpecHications were issued on August 30, 1948, and actual
<br />construction initiated on December 8, 1948.
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<br />17. Hydrololl'Y - The greater portion of the 1935 flood in the upper Republican
<br />River area onglnated lfl the South Fork draInage basin. Bonny reservoir storage,
<br />therefore, was planned to control a similar occurrence. A study of the magnitude and
<br />occurrence of floods, in consultation with the Corps of Engineers who are charged with
<br />the responsibility for allocation of flood control storage capacity and for flood control,
<br />resulted in the selection of 128,820 acre.feet as the most practicable reservoir capa-
<br />C'ity for flood control. The normal reservoir formed would be approximately 3 miles
<br />long, 1 mile wide, and cover 2,042 acres. On the basis of water supply studies cover-
<br />ing the period 1929 to 1947, inclusive, the average annual runoff at the dam site during
<br />this period was estimated at 34,500 acre-feet. The maximum annual runoff occurred
<br />in 1935 and was estimated at 103,000 acre-feet; the minimum runoff, occurring in 1940,
<br />was estimated at 12,800 acre-feet. It was estimated that ..'hen runoff is depleted to
<br />allow for upstream water uses, the average annual inflo..' at Honny reservoir will be
<br />30,800 acre-feet. The controlted reservoir capacity of 170,160 acre-feet at elevation
<br />3ilO provides for flood control, irrigation storage, sediment retention, and conserva_
<br />tion of one of our most important natura! resources. Additional capacity required for
<br />surcharge increases the reservoir to a total capacity of 348,390 acre-feet.
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<br />At the top of the irrigation pool, the reserVOIr will contain 41,340 acre.feel
<br />of storage capacity for irrigation, silt retention, and dead storage. Of the 41, 340 acre~
<br />fet"t of capacity at elevation 3672, 16,000 acre-feet have been allocated for sediment
<br />control. This sediment storage allocation, hO'""ever, is for 100 years, and the unfilled
<br />capacit). during the earlier years of the reservoir operation may be used for irrigation
<br />storage. Figure 4 shows the area-capacity-discharge curves.
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