The agreement will allow the U.S. to retain a greater share of the water from the river during a drought and permit Mexico to store water in a reservoir north of the border during periods when the river runs high.
"We have chosen collaboration over conflict; we have chosen cooperation and consensus over discord," said U.S. Interior Secretary Ken Salazar, the BBC reported.
"The Colorado River, in so many ways, makes us one people, and together we face the risk of reduced supplies in years ahead."
The Colorado River flows 1,450 miles from the Rocky Mountains in Colorado to the Gulf of California in Mexico, supplying some 30 million people across seven U.S. and two Mexican states with water.
The recent accord amends a 1944 treaty, which granted Mexico 1.5 million acre-feet of water each year and supplied some 3 million homes with water. [One acre-feet is equal to 43,560 cubic feet of water].
The new agreement accounts for periods of drought and higher precipitation based on the level of water stored in the reservoir at Lake Mead, which stretches across Nevada and Arizona.
Mexico will now be able to store up to 250,000 acre-feet of water at Lake Mead to be accessed at anytime.
Under the agreement, Mexico will also receive $10 million for the repair of irrigation systems damaged by a 2010 earthquake, according to the BBC.
Water agencies in California, Nevada and Arizona have also agreed to purchase water from Mexico, totaling some $21 million in payments that are expected to go toward environmental remediation in wetland areas of Mexico.
"These are big political steps for Mexico to take," said Jeffrey Kightlinger, general manager of the Metropolitan Water District of Southern California, which purchased some of Mexico’s water, the AP reported.
"Chances are we won't have a surplus and we won't have a shortage, but, if we do, we'll have the guidelines in place on how we're going to handle it."