Colorado v. New Mexico,
467 U.S. 310 (1984)

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U.S. Supreme Court

Colorado v. New Mexico, 467 U.S. 310 (1984)

Colorado v. New Mexico

No. 80, Orig.

Argued January 9, 1984

Decided June 4, 1984

467 U.S. 310


In this original action, Colorado seeks an equitable apportionment of the waters of the Vermejo River, which originates in Colorado and flows into New Mexico. Historically, all of the river's waters have been used exclusively by farm and industrial users in New Mexico. After a trial at which both States presented extensive evidence, the Special Master recommended that Colorado be allowed to divert 4,000 acre-feet of water per year. His recommendation rested on the grounds that New Mexico could compensate for some or all of the proposed Colorado diversion through reasonable water conservation measures, and that the injury, if any, to New Mexico would be outweighed by the benefit to Colorado from the diversion. In considering New Mexico's exceptions to the Master's report, this Court held, inter alia, that the Master properly did not focus exclusively on the priority of uses along the river, and that other factors -- such as waste, availability of reasonable conservation measures, and the balance of benefit and harm from diversion -- could be considered in the apportionment calculus. 459 U. S. 176. The case was remanded to the Master for additional specific findings to assist the Court in assessing whether the river's waters could reasonably be made available for diversion and in balancing the benefit and harm from diversion. On the basis of the evidence previously received, the Master then developed additional factual findings and reaffirmed his original recommendation. New Mexico again filed exceptions to the Master's report.


1. In this action for equitable apportionment, Colorado's proof is to be judged by a clear and convincing evidence standard. Requiring Colorado to present such evidence in support of its proposed diversion is necessary to appropriately balance the unique interests involved in water rights disputes between sovereigns. The standard reflects this Court's long-held view that a proposed diverter should bear most, though not all, of the risks of erroneous decision. In addition, the standard accommodates society's competing interests in increasing the stability of property rights and in putting resources to their most efficient uses. Pp. 467 U. S. 315-317.

2. Colorado has not met its burden of proving that a diversion should be permitted. Pp. 467 U. S. 317-323.

(a) Colorado has not demonstrated, by clear and convincing evidence, that reasonable conservation measures could compensate for

Page 467 U. S. 311

some or all of the proposed diversion. For example, though Colorado alleged that New Mexico could improve its administration of water supplies, it did not point to specific measures New Mexico could take to conserve water. Society's interest in minimizing erroneous decisions in equitable apportionment cases requires that hard facts, not suppositions or opinions, be the basis for interstate diversions. Moreover, there is no evidence that Colorado has undertaken reasonable steps to minimize the amount of the diversion that will be required. Pp. 467 U. S. 317-321.

(b) Nor has Colorado sustained its burden of showing that any injury to New Mexico would be outweighed by the benefits to Colorado from the proposed diversion. Colorado has not committed itself to any specific long-term use for which future benefits can be studied and predicted. By contrast, New Mexico has attempted to identify the harms that would result from the proposed diversion. Asking for absolute precision in forecasts about the benefits and harms of a diversion would be unrealistic, but a State proposing a diversion must conceive and implement some type of long-range planning and analysis of the diversion it proposes, thereby reducing the uncertainties with which equitable apportionment judgments are made. Pp. 467 U. S. 321-323.

(c) The mere fact that the Vermejo River originates in Colorado does not automatically entitle Colorado to a share of the river's waters. Equitable apportionment of appropriated water rights turns on the benefits, harms, and efficiencies of competing uses, and thus the source of the river's waters is essentially irrelevant to the adjudication of these sovereigns' competing claims. P. 467 U. S. 323.

Exceptions sustained and case dismissed.

O'CONNOR, J., delivered the opinion of the Court, in which BURGER, C.J., and BRENNAN, WHITE, MARSHALL, BLACKMUN, POWELL, and REHNQUIST JJ., joined. STEVENS, J., filed a dissenting opinion, post, p. 467 U. S. 324.

Page 467 U. S. 312

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