This case highlights the joint efforts of the governments of Mexico and the United States (US) to solve transboundary water and sanitation problems. The border between Mexico and the US is about 3,100 kilometers long and stretches from the Pacific Ocean to the Gulf of Mexico. The Mexican border area (stretching from the US-Mexico border to 100 km land inwards) is home to approximately 23.8 million inhabitants (5% of the total Mexican population) and hosts some of Mexico’s most important cities. Over the last decades, the towns and villages in this border area have experienced significant rates of population growth, especially since the North American Free Trade Agreement entered into force in 1994. In some places the population grows with about 5% per year, leading to increased water use and the contamination of shared waters bodies such as the Rio Grande (Rio Bravo), New River and the Tijuana River.

In 2000 the Mexican and US government decided to jointly address these transboundary problems and a “Memorandum of Understanding Concerning the Joint Grant Contributions for Drinking Water Supply and Wastewater Infrastructure Projects for Communities in the United States – Mexico Border Area”, was signed by the US Environmental Policy Agency (EPA) and the Mexican National Water Commission (CONAGUA).

To date, both governments have supported the implementation of 51 drinking water supply and wastewater infrastructure projects in Mexico. A total of 464 million US dollars was invested - 232 million from the US Border Environment Infrastructure Fund (BEIF) and 232 million from Mexican programmes. The investments have led to an increased access to drinking water (from 91% to 96%), sewerage systems (from 76% to 88%) and sanitation services (from 72% to 82%) in the period 2000-2010. In the same period, the wastewater treatment capacity in the area increased to 10.6 cubic meters per second.