The Associated Press The Navajo Nation Council has signed off on a proposed settlement that would ensure water rights for its tribe and two others in the drought-stricken Southwest — a deal that could become the most expensive enacted by Congress. The Navajo Nation has one of the largest single outstanding claims in the Colorado River basin. Delegates acknowledged the gravity of their vote Thursday and stood to applause after casting a unanimous vote. Many noted that the effort to secure water deliveries for tribal communities has spanned generations. Council Speaker Crystalyne Curley and other officials stood outside the chamber in Window Rock, Arizona, under a clear blue sky as the wind whipped. She recalled learning about the fight over water rights in school when she was a girl. Momentous…