|
<br />"
<br />
<br />.
<br />
<br />Water splitting is baaed upon three criteria.: (1) The Upper Basin
<br />has adequate water in .tonge to me(.t paragraph 602(&) requirements,
<br />(2) Lake Powell has more water in storage than Lake Mead, and (3)
<br />Lake Mead doe 8 not ha ve surplus water.
<br />The water need.cd to meet 602(a) storage requirements is baaed
<br />upon future Upper ~a8in depletions. The water currently availahle to
<br />meet 602(.) storage is calculated a8 the act:ive storage of all Upper Basin
<br />Colorado River Storage Projects (CRSP) reservoirs. If there is in.
<br />sufficient water available to meet the requirement. releasea from Lake
<br />Powell will not exceed those of the 8.23 MAF schedule regardlcu of
<br />the cont~nts of Lake Mead. U 602:{a) storage is available. then an addi.
<br />tional release can be made from Powell to the Lower Basin provided
<br />Mead is storing less than Powell and is not expected to exceed elevation
<br />1190 in October.
<br />
<br />The model considers these constrainte when assessing the potential
<br />lor water splitting. It restrains Powell from releasing too much water
<br />and violating 602{a) storage requirements. and also releases water from
<br />Powell only to the point where Powell and Mead are at equal content8.
<br />As this is done, the October contents are reestimated to reflect possible
<br />changes for demands by CAP and MWO.
<br />It is possible that in a particular month the Lalte Mead flood
<br />criteria could force a release greater than that planned by the water
<br />splitting analysis. In this case, CAP and MWD demands are increased
<br />a,s much as possible to utilize the excess flows. Wat.er not used by
<br />Lower Basin demands is passed on to Mexico and is in excess of tho
<br />1. 5 AiAF (J850.'2 million cubic meters) annual delivery.
<br />The flood operation of Lake Mead is intended to follow closely the
<br />regulations specified in the Corps of EngiDcera Flood Control r~port (I).
<br />Euentially three types of criteria govern the releases from Mead: (I)
<br />Minimum flood storage space in Lake Mead, (Z) specified minimum.
<br />rates of relea6c determined by release tables, and (3)'operations baaed
<br />on inflow foroca,sta. Each 01 these will ,be described separately a~~,
<br />related to the mechanic. 01 the computer model.
<br />, ,~r.'l
<br />
<br />154
<br />
<br />.
<br />
<br />----.---- -
<br />
<br />S6.tJ
<br />I
<br />
<br />Flood storage space is defined' on the first of each month .from
<br />August to January. The minimum flood control storage space ,below
<br />
<br />elevation 1229 (374.6 meters) is as follows:
<br />
<br />Date
<br />
<br />.Min. space required
<br />Million cubic
<br />Acre-feet meters
<br />
<br />August I
<br />September
<br />October I
<br />November
<br />December
<br />January 1
<br />
<br />1,500,000
<br />1,500,000
<br />1,500,000
<br />2,675,000
<br />3,963,000
<br />5,350,000
<br />
<br />1,850.2
<br />1,850.2
<br />1,850. Z
<br />3,299.'6
<br />4,888.4
<br />6,599.2
<br />
<br />Storage space in upstream CRSP reservoirs may apply towards the
<br />above requirements within the following limits: (a) Lake Mead must
<br />have at least 1,500.000 acre-feet of available space and (b) the maxi..
<br />mum creditable storage space shall not exceed the values below.
<br />
<br />Reservoir
<br />
<br />Maximum creditable space
<br />Million cubic
<br />Acre-feet meters
<br />
<br />Lake Powell
<br />Na vajo
<br />Blue Me sa
<br />Flaming Gorge
<br />
<br />3,850,000
<br />1,036,100
<br />748,500
<br />1,507,200
<br />
<br />4,749.0
<br />1,278.0
<br />923.3
<br />1,859. I
<br />
<br />The difference between maximum storage space and the current storage
<br />is used as creditable space up to the values shown above.
<br />From August through September a rule curve is specified which
<br />maintains 1,500,000 acre-leet of flood storage space. In October.
<br />November, and December the model applies aU credi~able upstream
<br />space to the storage required. 1t then checks Lake Mead to provide
<br />at least 1,500,000 acre-feet of spa'ce in Lake Mead.
<br />Beginning in January and continuing through July, the forecast
<br />values are used to regulate releasee and ,contents of Lake Mead. Tht
<br />flow of the Colorado Rive I' at Grand CanY,~n is foreca~led a~d sum~ed
<br />from January to July, February to July, March to, July, etc..!_ until
<br />, ' -",., ,.{".,
<br />July is reached. The objective is to operate Lake Mead to handle all
<br />
<br />155
<br />
|