The US and Mexico have been embroiled in a long-standing dispute over the dwindling waters of the Colorado River. The river serves over 30 million people and is the lifeblood of the American southwest. But over-use and increasing drought have put pressure on the river, which now almost never reaches the delta in Mexico.
After over a decade of negotiations, last November the US and Mexico finally signed a new treaty to regulate how the two countries will share both water surpluses and water shortages. This has been heralded as an example of progress in water sharing agreements and offers new hope for the delta wetlands.
Under the new agreement, which many consider a historic step, during drought years the US will send less Colorado water to Mexico. In exchange, during years of plenty, Mexico will be allowed to store some of its water north of its border.
In addition, both countries will allocate some water to restore the ecological health of the river’s delta in Mexico. “This agreement demonstrates water supply reliability and healthy river flows can go hand in hand,” said Jennifer Pitt of Environmental Defense Fund, a US based NGO.
During the signing of the treaty, US Interior Secretary Ken Salazar called it “the most important adjustment to rules on the Colorado River since the 1944 treaty.”
Mr. Salazar said he hoped the new agreement would herald the “end of water wars, which in times of drought have pitted those who rely on the river against each other.”
Explosive growth
The US started damming the mighty Colorado River at the turn of the twentieth century, thus enabling the explosive growth of cities like Las Vegas, Los Angeles and Phoenix. Since then more and more Colorado water has been diverted for domestic, industrial and agricultural use. The water of the river was allocated on the basis of flow charts created in the early twentieth century that, in hindsight, covered a temporary high in water flows. Since then, the average annual flow has been lower and is steadily continuing to fall. Based on these water charts 10% went to Mexico, which in 1944 when the treaty was signed, never thought it would need all that water.
But massive growth on both sides of the border resulted in such a rise in water consumption that for more than 30 years the Colorado delta in Mexico has stood dry, except for a few trickles of water in exceptionally wet years. The gigantic wetland that was the delta, and that was essential to migratory birds, turned into desert.
The strict conditions of the 1944 treaty have frustrated both parties for many years. The US was obliged to deliver between 1.5 and 1.8 million acre feet of Colorado water each year to Mexico regardless of the amount of water that was actually in the river. During droughts (such as the current one that started in 2000) the US would have liked to let Mexico share in the reduced flow of water. In wet years Mexican environmentalists would have preferred to have the surplus water reach the delta.
The new bi-national agreement, known as Minute 319, is an addendum to the 1944 treaty. It stipulates that Mexico will receive less water in dry years but permits Mexico, which has very little storage capacity, to stow surplus water in Lake Mead, a federal reservoir on the Colorado River, behind the Hoover Dam in Arizona.
Drought drives water conservation
The ongoing drought has, however, inspired conservation efforts. Las Vegas, in particular, is famous for its water conservation campaigns like Cash for Grass and its water cops that roam the streets in search of water spillage.
“About half of all domestic water use went to watering lawns,” explained the Southern Nevada Water Authority director Patricia Mulroy. “Therefore we initiated the cash-for-grass programme. Residents who changed their lawns into a desert garden received twenty dollars per square metre. With the programme we have saved millions of litres of water since 1999.”
The biggest single consumer of Colorado water, the Imperial Valley agricultural district, has been conserving water by lining irrigation canals with concrete and covering some of them (to avoid evaporation) and introducing drip irrigation. But all of these conservation efforts simply facilitated more urban expansion, especially in San Diego. For many decades, the environment has been the loser.
One of the most notable aspects of the treaty is that it also regulates the allocation of water to restore part of the Colorado Delta. The delta is a critical link supporting nearly 400 species of birds on their journey through the Sonoran Desert across northern Mexico, Arizona and California.
In addition to making water available to support flows in the river, the agreement will fund new restoration projects. This work builds on years of restoration efforts already underway by communities and environmental organisations hoping to regain some of the economic, cultural, and environmental benefits the delta once provided.
The US and Mexican governments will each supply 5,000 acre-feet of water a year to the delta, as will a coalition of environmental organisations. Native plants from the delta will also be restored, which will provide a habitat for migratory birds of the pacific flyway.
The plans that environmental organisations and activists have been working on for years may finally bear results. José Campoy, director of the Upper Gulf of California and Colorado Delta Biosphere Reserve in Mexico, offered a simple hope. “We don’t need much” he explained in his office on the bank of the dry Colorado River. “This used to be a river that went all the way to the ocean”.
The Colorado in pictures
The Colorado riverbed near San Luis Rio Colorado in Mexico is still crossed by a high bridge. Once every few years the sandy bed gets filled up by a flash flood. The 1.5 million acre feet of water that the US delivers across the border into Mexico is all used by cities like Tijuana and Mexicali. The bulk goes into the irrigation of the vast agricultural area that covers the northern part of the delta. The line of agricultural fields slowly moves northwards due to the increasing salinity of the area.
The Central Arizona Project (CAP), near Phoenix is a 500 mile long water canal that supplies Phoenix and Tucson with more than 70% of their water needs. The canal takes its water from the Colorado River. Phoenix, a city of 1.5 million inhabitants, is located in the northeastern reaches of the Sonoran Desert. It has the hottest climate of any major city in the US. The average high temperatures are over 37.8 degrees Celsius for three months out of the year, and have spiked over 49 degree Celsius on occasion. Phoenix and it’s surroundings are home to more than 200 bright green golf courses surrounded by yellow. (© Ronald de Hommel / Johannes Abeling)
For more about the Colorado River visit Disputed Waters.