The Southern Nevada Water Authority plans to spend up to $7.5 million in Mexico over the next 10 years in exchange for more Colorado River water. Authority board members unanimously approved the payments Thursday as they gave their blessing to a sweeping water-sharing agreement the U.S. and Mexico are expected to sign next month. The new pact, known as Minute 323 to the Mexican Water Treaty of 1944, spells out how much Mexico would have to reduce its river use during a shortage on the Colorado and how much extra water the nation would get in a surplus.