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<br />[Section 1802(a)J. In concert, the GCD-EIS recommends a Preferred Alternative
<br />that preserves a mass balance of sand, and therefore fisheries habitats, in
<br />the main channel.
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<br />The GCD-EIS recommends a modified low fluctuating flow alternative (MLFF) as
<br />the Preferred Alternative. The MLFF has a minimum release of 5,000 cubic feet
<br />per second , (cfs) between 7:00 p.m. and 7:00 a.m. (at night), and 8,000 cfs as
<br />a minimum release from 7:00 a.m. to 7:00 p.m. (day time flows). The maximum
<br />release is 25,000 cfs, with a maximum daily flow range of 5,000 cfs, 6,000 cfs
<br />or 8,000 cfs, depending on the monthly release volume (during low, medium or
<br />high volume months, respectively). Ramping rates under the Preferred
<br />Alternative are 4,000 cfs/hr up and 1,500 cfs/hr down. The Preferred
<br />Alternative also provides for a 1 to 2 week-long beach/habitat-building flow.
<br />This high, steady, release will be used to evaluate the applicability of high
<br />flows as a strategy for future adaptive management of the Colorado River.
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<br />Flooding was an essential characteristic of the pre-dam river. Current dam
<br />operations have virtually eliminated this dynamic element of the natural
<br />ecological process. Although a program of reduced daily flow fluctuation
<br />(Interim Operations) was implemented in 1991 to conserve a mass balance of
<br />tributary-derived sand, occasional high flows are thought to be required to
<br />restore high elevation sand deposits and characteristic aquatic habitats, such
<br />as backwaters. Backwaters are used as rearing habitats by young native fish.
<br />The proposed test flow will improve understanding of how flooding influences
<br />ecosystem geomorphology, biological and cultural (archeological and
<br />traditional land use) resources, and ecosystem processes. Data collected
<br />during the test flow will demonstrate the extent to which planned flooding can
<br />be used as an ecosystem management tool. '
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<br />DESCRIPTION OP THE TEST PLOW
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<br />Description of Plow
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<br />The test flow will begin on or about 22 March, 1996 (see Attachment A). The
<br />first 4 days will consist of a constant 8,000 cfs flow. On 26 March, 1996,
<br />discharge will be increased at an upramping rate of 4,000 cfs/hr until a flow
<br />of 45,000 cfs is reached. Flows will be held essentially constant at 45,000
<br />cfs for 7 days (until 2 April, 1996), with flow changes less than +/- 1000
<br />cfs. Discharge will then be decreased to 8,000 cfs in the following manner:
<br />(1) Between flows of 45,000 cfs and 35,000 cfs, the down-ramping rate will be
<br />1,500 cfs/hr; (2) Between flows of 35,000 cfs and 20,000 cfs, the down-ramping
<br />rate will be 1,000 cfs/hr; and (3) Between 20,000 cfs and 8,000 cfs, the down-
<br />ramping rate will be 500 cfs/hr. Discharge will be maintained at +/- 8,000
<br />cfs for 4 days (through 7 April, 1996). It is believed that this staggered
<br />down-ramp will more closely mimic the reduction of flows after a natural
<br />flood. The 8,000 cfs constant flows preceding and following the 45,000 cfs
<br />release will permit aerial photography, and, on-the-ground evaluation of
<br />sedimentation patterns and impacts to river resources. Interim Operations
<br />will resume on or about 8 April, 1996.
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