PUB00090

• Year: 1995
• Title: SJR 94-32 Concerning the Management, Conservation, and Preservation of the Water Resources of Colo.
• Author: CWCB
• Description: An inventory of readily available water data for each major river basin within the state, including compact limitations and other information.
• Publications - Doc Type: Tech Report

the compacts, some flood flows which cannot be managed by existing water resource
developments also leave the state. Table 1.2 presents a list of the major international and
interstate documents that affect Colorado's use of water.

Table 1.1 provides useful information on the long term average water supplies available for
diversion and use as of 1970. Table 1.1 shows native (natural or undepleted) water supplies
totalled 15,583,000 acre-feet in 1970 and that Colorado consumed an estimated 5,268,000 acre-
feet of water. This resulted in approximately 10,315,000 acre-feet of water leaving the state.

The information in Table 1.1 has not been updated since 1970 on a statewide basis and, will
require a considerable effort to do so. Nonetheless, a comparison was made of historic long
term average basin outflows through 1993 shown on Figure 1.1 to 1970 basin outflow values
on Table 1.1. The historic long term average outflow totalled 10,434,000 acre-feet, which is
considered to be about the same as in 1970.

The Colorado River Basin is the only basin in the state for which updated information is
available for the entire basin. This information is current as of 1985 and is displayed in Table
l.la. This data shows that although consumptive uses have increased by approximately 500,000
acre-feet since 1970, the basin's natural flow has also been higher and thus the increase in
consumptive uses have been masked.

Other factors to consider are the requirements and obligations of International Treaties, Interstate
Compacts, and U.S. Supreme Court decisions. These documents must be evaluated before
reaching any conclusions concerning basin outflows and unused compact entitlements. It would
require considerable text and detail to explain the constraints imposed upon Colorado by each
compact and federal decrees. However, it is clear the following basins are being depleted at or
near the limits of depletions or consumptive use established in these documents:

. The Arkansas River Compact (1948)
. The Rio Grande Compact (1938)
. The La Plata River Compact (1922)
. The Republican River Compact (1942)
. The Costilla Creek Compact (1944 Rev. 1963)
. Nebraska v. Wyomin~, 325 U.S. 589 (1945) (The North Platte River)
. Wyoming v. Colorado, 353 U.S. 953 (1957) (The Laramie River)

The Colorado River Basin and South Platte River Basin still have the potential for additional
depletions based on estimates of current use under the compacts. A more complete discussion
of the legal documents effecting the Colorado River is contained in Appendix C. In short,
Colorado is entitled to consumptively use up to 3.079 million acre-feet under the 1970 "Criteria
for Coordinated Long Range Operation of Colorado River Reservoirs" and current hydrologic
conditions in the basin. This is significantly less than the 3.855 million acre-feet of consumptive
use that Colorado believed would be available to it when the compacts were originally

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