Board Meeting 12/09/1998

• Board Meeting Date: 12/9/1998
• Description: ISF Section - Additional Information Regarding the Water Availability Analysis for the Tennessee Creek Instream Flow Recommendation
• Board Meetings - Doc Type: Memo

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3) ESF claims that staff relied on erroneous flow data because staff did not subtract
out Pueblo's discontinued Ewing Ditch wintertime trans-basin diversion;
4) ESF claims that staff did not account for the undecreed ditch diversions on
Tennessee Creek and East Tennessee Creek.

Staff Analvsis

Staffs imtial water availability analysis consisted of reviewing historic gage records for
Tennessee Creek, East Fork of the Arkansas River and the Arkansas River mainstem.
Staff also met with Steve Witte and his water commissioners on August I, 1996, to
discuss any water availability problems. The Division Engineer or his staff identified no
major water availability problems at that time. Staff also relied on its discussions with
local water users. Since staffs initial analysis, staff has collected additional information
and has received additional information from the ESF and the PBWW.

Additional Data Reviewed

Staff has reviewed all of the additional data provided to it by ESF and PBWW. In an
effort to further refine the original Tennessee Creek instream flow recommendation staff
has calculated the amount of water available at the top of the instream flow reach in
addition to its original calculations of the amount of water available at the bottom of the
reach. Table I shows the results of staffs additional water availability analysis.
To determine the amOunt of water available at the top of the proposed instream flow
reach staff:

I Calculated what the natural flow in Tennessee Creek would be using an area
apportionment method based on median flow data from the Tennessee Creek
gage;
2 Compared measured median flows from the Halfmoon Creek near Malta gage,
this gage has a period of record from 1946. The Halfmoon Creek drainage basin
is very similar in size and in location to the Tennessee Creek drainage basin above
the proposed instream flow segment.
3 Averaged the results from the above two methods to determine the median
monthly flow upstream of the proposed segment (see table below).

Method OCT NOV DEe JAN FEB MAR APR MAY JUN JU!. Ava SEP
1 4.1 4.1 3,3 2,9 3.3 3.3 8.2 36 41 16 5,8 4,9
2 10 4,0 3,0 3,0 3,0 3,0 4.5 45 120 97 31 14
3 7,1 4,0 3.1 2,9 3.1 3.1 6,4 41 ' '82 57 18 9,5

It is staff s opimon that method I, the basin apportionment method under estimates the
predicted flow at the upstream terminus. The reason for this is the diversion records for
the Bomestake Trout Club show that the average diversion from Longs Gulch into their
trout ponds in August equals 6 cfs (see Figures 1&2). This diversion flows through the
club ponds and returns to the creek. This clearly shows that for"the predicted flow of 5.8
cfs for the month of August by the basin apportionment method is low. Staff also feels
that method 2, may over estimate the flow in the late summer months and underestimate