WSP13018

• File Number: 8040.800
• Description: Colorado Water Resources
• State: CO
• Basin: Statewide
• Date: 1/1/1998
• Author: Varied
• Title: Colorado Reservoir Storage / Water Levels Data 1998 - 2003
• Water Supply Pro - Doc Type: Data

Page 1 of:

Seaholm, Randy

To: Watt, Joe
Subject: RE: Water

Joe

South Platte\Republican
Arkansas
Rio Grande
Gunnison
Colorado Mainstem
Yampa\White
San Juan\Dolores
North Platte

2000 2030
5.181 5.577
2.502 2.604
2.657 2.662
2.405 2.417
.980 1 .296
1.544 1 .550
1.877 1.900
.397 .504

;ompacts

. Yampa\White\ColoradoMainstem\Gunnison\SanJuan\Dolores are governed by the Colorado and
Upper Colorado River Compacts. Colorado is entitled to beneficially consumptively use 51.75% of
the water available to the Upper Basin after allowing for 50,000 AF to Arizona. 7,500,000 - 50,000 =
7,450,000 * .5175 = 3,855,375 AF. However, the most recent hydrologic determination indicates that
only 6,000,000 AF may be available to the Upper Basin long term. 6,000,000 - 50,000 = 5,950,000
* .5175 = 3,079,125. Thus, Colorado can use between 3.079 maf and 3.855 maf, but we are only fairly
certain that 3.079 is available. Colorado is currently using about 2.3 maf with facilities in place to use u~
to 2.6 maf. Thus, there is 479,000 AF that can be developed on the west slope with some certainty.
. On the South Platte, Colorado has the right to and uninterrupted use of all water downstream of
the western boundary of Washington County between October 15th and April 1 st. Between April 1 st
and October 15th of each year Colorado must curtail diversions by water users whos rights are junior to
June 14, 1897 when the flows at stateline are less than 120 cfs.
. The Arkansas River Compact provides for a sharing of water placed into storage in John Martin
Reservoir. Approximately 60% to Colorado and 40% to Kansas.
. On the Republican, Colorado is allocated the benefical consumptive use of 10,000 AF on the
North Fork, 25,400 AF on the South Fork, 15,400 AF on the Arikaree and 3,300 AF on Beaver creek for
a total of 54,100 AF plus the entire supply available on Frenchman and Red Willow. Kansas is allocatee
190,300 AF and Nebraska 234,500 AF.
. On the North Platte, Colorado is limited to the irrigation of 145,000 acres in Jackson County,
storing more than 17,000 AF for irrigation, and exporting more than 60,000 AF in any consecutive 10-
year period.
. On the Laramie, Colorado's uses are limited to 49,375 AF per year.
. On the Rio Grande, the flow out of the mountains is measured at an index station (Rio Grande a
Del Norte, Conejoes at Mogote) and based on that volume, certain amounts must be delivered at the
stateline of confluence of the tributary with the Rio Grande. In high runoff years, upto 70% of the
Conejos flow must be delivered and upto 60% of the Rio Grande index flow. In dry years, the Conejos
has no delivery obligation and the Rio Grande's as little as 25%. Thus, it is often more difficult to compl~
with the compact in wet years. I'll fax you the curves.
. On Costilla Creek, the compact defines a "duty of water" of 1 AF for each 80 acres irrigated and
a calculation of a safe yield prior to each irrigation season and a determination of the length of the
irrigation season.

~s you can see, each compact is very different. In short, there is water to develop on the west slope as
ndicated. There is also some water to develop on the lower end of the south platte, but that doesn't help
)enver and communities high in the basin. Water development opportunities are very limited in the Arkansas
lnd Rio Grande. Thus, new uses largely come at the expense of eliminating some current use, usually

10/23/2003