The San Miguel crossing between Arizona and Mexico is a simple iron gate. Stretching away on either side is a border marked by concrete posts, which are driven into the Sonoran Desert scrub and strung with chicken wire that anyone could duck under without difficulty. For an undocumented migrant on foot, the hard part comes after the crossing: the long walk to safety, dodging the Border Patrol without succumbing to the harsh desert conditions.
On Wednesday morning, Mike Wilson crossed into Mexico to refill the water container at the station he maintains a few yards south of the border, and which has likely saved the lives of migrants who can drink before reaching the US. Some 20 gallons had gone since he last visited a month ago. Sometimes, he says, he finds the 50-gallon barrel bone dry. Wilson, who is 65, belongs to a small but passionate community of activists trying to reduce the number of migrant deaths in a state not known for its sympathy to their plight.
"Arizona has a reputation as an anti-immigrant state," says Todd Miller, author of the book Border Patrol Nation. "But there are many people throughout southern Arizona who organise not only to oppose anti-immigrant laws, but also to go into the desert and provide humanitarian aid... Mike is doing important and wonderful work."
Mr Wilson and his partner Susan have also offered food and temporary shelter to some of the more than 52,000 migrant children who have crossed into the US since October 2013, most of them fleeing violence in Central America. On Friday, Mr Obama met with the leaders of Guatemala, Honduras and El Salvador and urged them to work with the US to help stem the flow of migrants, stating that many of those who have crossed the border will not be able to stay – with only the potential for some "narrow" circumstances for humanitarian or refugee status.
Mr Wilson, though he lives on the outskirts of Tucson, is a member of the Tohono O'odham Nation, a Native American community of 25,000 on a reservation the size of Connecticut, sliced in half by a 75-mile stretch of the US-Mexico border. The Tohono O'odham (meaning "Desert People") have been on this land for thousands of years and, even after the border was drawn in 1854, could pass back and forth unimpeded, often via the San Miguel gate.
After 9/11, however, crossing anywhere but at official checkpoints became illegal. Those Tohono O'odham who lacked the correct paperwork were trapped on the Mexican side. Meanwhile, the Nation found itself at the frontline of a broader border crisis. As the US increased security in the urban areas where they had traditionally crossed, economic migrants from Central America moved to more isolated routes, such as the Sonoran Desert.
By the mid-2000s, tribal officials estimated that as many as 1,500 undocumented migrants per day crossed the border through the reservation. Having survived the treacherous journey through Mexico, many were killed instead by the desert. Since 2001, the Pima County medical examiner in Tucson has received an average of 164 bodies of border-crossers per year. Around half those deaths occurred in the Tohono O'odham Nation, making it the deadliest migrant trail in the US.
Humanitarian groups sprang up to combat the problem, including the NGO Humane Borders, which maps migrant fatalities to identify the most deadly areas of the desert, and then deposits water, food and medical supplies in those spots. The group's executive director, Juanita Molina, says Humane Borders drops up to 1,200 gallons of water per week during July, the most lethal month of the year. "Many Border Patrol officers and people in the community see us not as preventing deaths, but as aiding and abetting," she says.
To Mr Wilson's dismay, the Tohono O'odham Nation sided against the migrants. "They borrowed whole cloth the Department of Homeland Security's narrative, which describes undocumented migrants as potential terrorists," he says. The Nation's leaders even passed a resolution banning outside humanitarian groups from putting out water on the reservation – so Mr Wilson decided to do it himself. "I'm a one-man organisation, by design," he explains. "I have working relationships with other groups from the social justice community. But when I put out water, I do it as a member of the Tohono O'odham Nation."
Mr Wilson's first career was in the US Special Forces, and in 1988 he was posted to El Salvador during its civil war. "We were supposedly advisers, but our mission soon changed," he recalls. "We were to prevent as much as possible the human rights abuses by the military against the civilian population … after my experience in El Salvador, I really asked myself what side of the table of justice I wanted to sit on."
During the US-sponsored Central American civil wars of the 1980s, Tucson was the centre of the Sanctuary movement, a campaign offering safe haven to refugees. That dormant humanitarian infrastructure provided a foundation for more recent human rights efforts.
In 2002, Mr Wilson, by then a Presbyterian lay pastor, set up five water stations – one on the far side at the San Miguel gate, and four spread across the US side of the reservation, which he named St Matthew, St Mark, St Luke and St John. He was forced to replenish the water every couple of weeks. "I could barely keep up with the demand."
That was until Tohono O'odham Police confiscated four of the stations, leaving him with just the one on the Mexican side of the border fence. No one from the Nation's executive was available to talk to The Independent on Sunday, but Mr Wilson suspects the reservation's leadership stymied his efforts because it relies on federal funding for infrastructure, education and housing. "The federal appropriations are buying silence from tribal members," he says.
Since June, Mr Wilson has offered shelter to more than 50 women and children. Their latest undocumented visitors were a Salvadoran woman, her 13-year-old daughter and two toddler sons, who crossed the border last Sunday on their way to the woman's mother, who has lived in Maryland for 25 years. Wilson doesn't like to pry into his guests' pasts, but he can make educated guesses. “The mother probably fled to the US as a political refugee during the Sanctuary movement,” he says. “I didn’t tell the woman that I’d been in El Salvador. It might open old wounds.”