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<br />BLACK CANYON INFORMATION PAPER
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<br />Oct,2000
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<br />runoffwould there be spills which would course through the canyon in addition to normal
<br />regulated flows,
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<br />This regulation will drastically alter the historic flows through the monument. These have
<br />already been somewhat changed by diversion 10 the Uncompahgre River Basin by means of a
<br />tunnel taking offfrom the GunnisonRiver ve,ry shortly above the east monument boundary, The
<br />degree of regulation resulting from this diversion-does not appear to have drastically changed
<br />the character of flows through the monument, with great ",shtl'ig spring to"ents.jollowed by
<br />minimum summer flows that are comparative~1 unimpressive, There are years of record,
<br />although very rare, when flow has practicanv ceased, leaving only scattered pools along the
<br />canyon bottom, ,. ,
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<br />It is the historic flows which, over hiindredso,/miJliohs' of y~ars, haye carved the spectacular
<br />gorge down through the basic;pre-camhrianieologicalformation to depths rangingfrom 1,730
<br />feet to as much as 2,425 feet, creating a great earth gash which is, in places, deeper than the
<br />widthfrom rim to rim, Other naturalweatheringforces have combined with the river to create
<br />this natural wonder, Spalis, chips, and gravels falling unhindered to the canyon bottoni are
<br />annually swept away by the great spring tidalflushes of the river,
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<br />Evidently with the flow of the riverregulated "nd equalized by the Curecanti Dam 'this annual
<br />spring flushing would no longer take place unless the tknn could be operated'in such a way as to
<br />release large volumes of water during flood periods, The National Park Service would, of
<br />course, be concerned with any development which would alter natural conditions in the
<br />monument,
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<br />As far as recommendations for Curecanti Reservoir, the Service noted: It is especially
<br />recommended that consideration be given to pos~ibilities of providing the weir in the na"ow
<br />gorge between the lower and upper reserVoii' hasins, by means of which a constant, or nearly
<br />constant water level could be maintaineq in the latter. (p, 209)
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<br />There is also a discussion of the effects of the proposed Crystal Reservoir on the monument. The
<br />Service states: The monument and its primary values have been described by the National Park
<br />Service as follows: 'Black Canyon is notable for its narrowness, depth, ruggedness, great
<br />expanses of sheer walls, and interesting gorge formation, The rims of the gorge are only 1,300
<br />feet apart at their nearest approach, yet the gorge ranges from 1,630 to 2, 425feet in depth
<br />within the monument, At one location the channel of the Gunnison River na"ows to only 401eet
<br />in width. For many millions of years this river has beenjuriously carving its channel deeper and
<br />deeper through this probably Archean complex at a greater speed than all combined natural
<br />processes can widen it, The tools which the river uses are the sand and gravel that it carries,
<br />mainly in periods of flood The hardness of its rock formation and the joint, or fracture, system
<br />account for the sharp, ragged sheerness of tit., canyon walls, The rolling hills, which rise above
<br />the canyon rim and which formerly entrenched the flow of the Gunnison River, are carved from
<br />sedimentary rocks, These rocks are so much younger than those of the gorge itself, which
<br />immediately underlies them, that during this gap of time life developed from the single plant cell
<br />10 the monstrous dinosaur, This tremendous break in the record of geological time is as
<br />B-6
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<br />002712
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