Roldan Canaquiri shuffles over dried reeds that crackle under his bare feet, and climbs slowly down the riverbank, testing the soft earth with his toes before each step. The big winter rains have come and the river is rising: every day part of the bank collapses into the swirling foam below. But Roldan is not afraid. The Kukama Indigenous elder has lived on the Marañón River in Peru’s northern Amazon for nearly all of his 89 years. Although he’s lost most of his sight and hearing, Roldan never misses his afternoon pilgrimage to bathe in the cooling waters.

He steps into a small canoe. His wife Juana reaches out to steady him. She is never far from his side. In his youth Roldan swam in the Marañón but now he sits on the boat’s wooden bench, lathers up with soap and uses a small plastic basin to rinse with river water.

Juana sits in the bow, washing their clothes. She is nine years younger than her husband and wears a baby-blue dress with frills and puffy sleeves. Her long black hair, spotted with grey and white, is tied in a neat braid. The younger women in her community wear shorts, t-shirts and make-up, but Juana is from a lost era when women weren’t allowed to go to school and still spoke Kukama-Kukamiria, their native language.

In those days marriages were arranged between families. Roldan and Juana’s union was no exception, and yet, after raising 12 children they seem happy and enjoy being together. My husband Miki and I are filming the scene. For nine years, we’ve been working on a documentary with Mariluz Canaquiri, one of the couple’s daughters. As usual Miki and I argue about camera angles and technical challenges. We are drenched in sweat and covered in mosquito bites.

A group of teenagers arrives, the boys joking and shoving each other, the girls giggling and pretending to ignore them. When Roldan was their age, he swam out too far one day and felt someone grabbing his foot, trying to pull him under. ‘It was a river person,’ he says, referring to the spirit universe beneath the Kukama’s waterways. ‘I swam, desperate to reach land, and never bathed in the middle of the river again.’

When Roldan’s grandchildren were young, people still gathered in the evenings to hear him and other elders tell stories by candle or firelight. They learned about fishing, hunting and farming. But they also heard cautionary tales about the river spirits, like pink dolphins that transform into handsome men and carry off young women, or mermaids who lure fishermen to live in their underwater villages. On the upside, the spirits can cure human illnesses and give protection. They are powerful forces and must be respected. So, the elders’ tales are not just entertainment: they’re a way to pass on knowledge and ensure that the next generation takes care of their sacred river.

But now the evening stories have been replaced. Roldan’s great-grandchildren have cell phones and tablets and play video games or watch movies under the mango tree in front of his house which has the best reception. Modest solar panels arrived a few years ago, providing just enough wattage for cell phones and light bulbs. Mariluz and other leaders fought for electricity, yet she worries about the impact on her people’s culture. This is why we’re making the film – to use new technologies to keep the old stories alive.

Despite the changes, the river is still a place where all the generations come together: to bathe, fish, travel and fetch water.

Mariluz says her mother used to carry a 20-litre bucket on her head over the half-kilometer walk to the village, but age has slowed her down.

I fill up Juana’s small bucket with muddy river water and try to carry it back. No matter how slowly I go, water sloshes over the sides and pours down my face. Two young girls run up behind me laughing. One of them takes the bucket, and balancing it perfectly on her head, skips along the path. Not a drop spills.

Of course, she’s been practising for years. She learned it from her grandmother.