(case involves adjudication of water rights by state of New Mexico and court rejects challenge to water rights priority determination in the Nambe-Projoaque-Tesque river system; matter has been ongoing since 1966; deadline for priority filing missed by 6-months with no explanation; plaintiff argued denial of motion to vacate was appealable under the collateral order doctrine; doctrines three elements (conclusively determined disputed question, resolved important issue separate from merits of case, and effectively unreviewable on appeal from final judgment) must be shown; plaintiff did not meet the unreviewable requirement; timeliness of a priority objection is a procedural issue; issue can be resolved after final judgment in the case; court held collateral doctrine did not apply).