SANTA FE, N.M. (AP) — The United States and Mexico unveiled an agreement Wednesday to preserve the overtaxed Colorado River, including spending millions of dollars on conservation and environmental projects and drawing up plans to deal with any shortages amid drought and climate change.

The United States pledged to invest $31.5 million in water conservation projects in Mexico, such as lining irrigation ditches with concrete to reduce leaks and upgrading irrigation equipment to use less water.

The water saved would be divided among the two nations and environmental projects.

In addition to the...