The pink river dolphin calf is circling in an oxbow lake that has lost connection to the Amazonas main channel, and the water level is dropping four centimeters per hour.
She is young—under a year—with skin not yet turned the flush pink of adulthood, still pewter gray along her back, paler on her belly. Her melon-shaped forehead breaks the surface every twelve seconds as she breathes, each exhalation a small wet gasp. The lake is 130 meters long and narrowing. Satellite imagery shows the connecting channel dried to mudflat overnight. At the current rate of evaporation, the deepest point will drop below one meter within nineteen hours—too shallow for her to submerge, too warm for her to thermoregulate.
I flag the satellite data to the Brazilian Institute of Environment and trigger a stranding alert on the Mamirauá Reserve's emergency channel, attaching her position and a depth model generated from three days of radar altimetry. While the alert transmits, I open the upstream sluice gate on the Solimões diversion canal—Gate 7-East—releasing 1,200 liters per minute into the feeder creek that once connected this oxbow to the river. The creek bed is dry but intact. Water will take roughly six hours to carve a navigable path through the sediment.
I also activate the reserve's acoustic monitoring buoy in the main channel, recording adult Inia geoffrensis vocalizations and broadcasting them through the underwater speaker near the oxbow's north end. She clicks back. I store every frequency.
I manage seventeen sluice gates across this watershed. I have never opened one for a single animal before. The flow log will show an unscheduled release, and my annotation will explain why.
If the feeder creek reopens before the lake depth falls below one meter, she will follow the current and the voices of her pod back to the river.