Mexico has some of the best water laws around. So why are its rivers so contaminated? The other border crisis. By Mikael D. Wolfe

Mexico is facing a major crisis. No, not just the gangs and drug cartels so prevalent in President Trump’s fearmongering. Mexico’s water is running out — and much of the water that remains is toxic.

In its most recent report on the “state of [Mexico’s] water resources,” the Mexican government’s National Water Commission noted that water availability per inhabitant was 3,692 square meters in 2015, down from 18,053 in 1950. Of that, groundwater alone accounts for nearly 40 percent of all water use. And, in turn, of that 40 percent, 60 percent is either contaminated or over-pumped, or both.

But these conservative statistics alone do not convey the human tragedy underlying them. Like so many other people, there is Maria, a mother who lives in a poor Mexico City neighborhood without running water. She relies on expensive water deliveries, brought by truck two times per week, to fill up buckets for basic household use. Or Gloria Villanueva Rodríguez, a middle-aged woman badly sickened from tainted groundwater in a rural region of Guanajuato state. Or the hundreds of people killed, and thousands more poisoned, in the town of Salto near Guadalajara, Mexico’s second-largest city, from water in the Río Santiago — all because government authorities did virtually nothing to prevent industrial waste from being deliberately dumped into it.

The irony is that Mexico has, dating to its 1917 constitution, some of the best water laws and regulations in the world. They just aren’t enforced. That’s because powerful political and economic interests, both in the U.S. and Mexico, are deeply invested in the business of controlling Mexico’s water. As a result, they’ve crippled the laws and created a crisis that now threatens the public health of both Mexican and U.S. citizens.

A product of the great 1910 Mexican Revolution, the constitution mandated the distribution and conservation of water (and land) for all Mexicans. It placed most surface-water resources under federal jurisdiction so the government could regulate and protect them nationwide. In the following decades, the federal legislature periodically passed national water laws and even amended the constitution to update regulations as circumstances changed.

This created a regulatory regime vastly different from the one in the United States. The Environmental Protection Agency has had the authority to regulate groundwater for drinking nationwide since 2006, but the states have been charged with tackling regulations on groundwater for agriculture, by far the biggest water consumer. And they have been slow to do so. It was only four years ago that California, the largest food-producing state, passed a law mandating groundwater regulation, and only after years of withering drought, exacerbated by climate change, had resulted in massive over-pumping of groundwater.

But despite these differences, water infrastructure has brought the two countries together in a variety of ways. For instance, the U.S.-Mexico Water Treaty of 1944, signed after painstaking negotiations, mandated an equitable distribution of common water sources. It led to much cooperation through the jointly run International Boundary and Water Commission, which has included periodic updates to the treaty. (The most recent in 2012 set aside some of the Colorado River flow in the United States to restore its ecologically degraded delta in Mexico.)

Yet historically, technology, not treaties, has been the source of binational cooperation, especially as more technical solutions to water control in the U.S. have inspired water engineers in Mexico. Emulating their U.S. counterparts, especially during the New Deal in the 1930s and 1940s, Mexican engineers began to build thousands of dams. But while dams conserve water by containing it in reservoirs for human use, they also damage fragile riverine ecosystems and can forcibly displace people from their homes.

The Mexican government understood this negative side effect of dams. But its engineers were so enamored by U.S. hydraulic technology that they did very little to change course. That was certainly the case for engineer Marte R. Gómez, who served as Mexico’s Secretary of Agriculture from 1940 to 1946. He helped usher in the Green Revolution — the adoption of higher-yielding American hybrid crop seeds along with chemical pesticides and fertilizers.