Water intake towers at Lake Mead, near Las Vegas.

The United States and Mexico expanded a long-term agreement that will allow both countries to continue using the Colorado River while also pushing conservation efforts that may help ensure that water is available during droughts.

The nine-year deal expands a 1944 water treaty and would result in the United States spending $31.5 million on conservation efforts in Mexico. That effort is expected to generate access to more water for 27 million people in California, Nevada and Arizona.

The agreement would also guarantee that Mexico and the United States would take on water supply cutbacks in the event of low water levels in the Colorado River and Lake Mead during droughts.

The signing was led by the International Boundary and Water Commission, which is responsible for overseeing water treaties between the United States and Mexico and is composed of representatives from both countries.

Under the 1944 Water Treaty, Mexico is allotted 1.5 million acre-feet (1,850 million cubic meters) per year of water from the Colorado River. The river has an annual flow of about 14.8 million acre-feet.

Some of the conservation efforts in Mexico funded by the United States reportedly could include relining leaky canals, improving water pump systems and using more advanced runoff capture systems that allow water to be reclaimed and stored, according to officials familiar with the agreement.

Lake Mead has seen its water levels drop since 2002, when it was at 1,152 ft. above elevation. In 2017, it stood at about 1,080 ft.

If Lake Mead reaches 1,075 ft., Nevada, Arizona and Mexico must cut the amount of water they can take from the Colorado River.