BOARD02056

• Board Meeting Date: 1/27/2004
• Description: ISF Section - Instream Flow Appropriations - Little Dolores River
• Board Meetings - Doc Type: Memo

The laTgest comparative difference in these gages is PotteT Creek at about 17%. This is well within the
standard error of the regional equation. However, the gage record for each of these creeks is limited.
Therefore, two other creeks with a longer representative period of record were chosen to compare with the
regia J equations.

Escal nte CTeek neaT Delta: Period ofrecoTd; 1977 ~ 1988
Tabeg ache CTeek near Nuc1a: Period of recoTd; 194 7 ~ 1952

Both flhese gages aTe affected by diversions and irrigation. Using data obtained from Colorado RiveT
Decison Support Systems (Colorado WateT Conservation Board, Department ofWateT Resources) that
reflects diversion volumes, along with local estimates of irrigated acreage and retmn flows, the annual gage
volumes were adjusted for these variations to estimate a natural annual volume.

Escalante Creek near Delta:
Mean annual adjusted gage volume: 84,000 ac-fl
Annual volume Tegional equation: 75,000 ac-ft
Tabe ache Creek near Nuc1a:
Mean annual adjusted gage volume: 15,000 ac-fl
Annual volume regional equation: 13,900 ac-ft

The g ge data-regional equation comparison between these two gages coupled with the results from Potter
Creek, Hay Creek, and Spring Creek indicates that the regional equations appaTently provide a reasonably
accurate estimate of the total annual flow volume.

Once ctal annual volumes can be estimated, the question then becomes how to allocate this volume over a
l2-m nth period. A mean annual montWy distribution was calculated using the annual hydrogTaphs from
Potter Creek, Spring Creek, and Hay Press Creek. These Ibree creeks were used since they are the best
unalte cd representations of a natural plateau flow regime. The monthly distribution ofvolwne based on a
perce tage of annual total volume is as follows:

Janua : 0.32
Febru TY: 0.6
MaTch: 1. 0
April: 14.7
May: 55.4
June: 4.6
July: 1.3