I’m researching river travel for a novel and need to figure out about how long it would take a canoe to go from San Ignacio to Melchor de Mencos via the Mopan River. This would be upstream travel, so I imagine some portage would be required. I expected to find at least some adventure travel stories of people doing this trip, but I can’t find anything.
If highly motivated with lightweight gear, and strong paddlers; I estimate a team could complete this journey in one tough day, roughly starting at sunrise and finishing before sunset. I'm estimating this is a 30k voyage.
It has a total elevation gain of approximately 120 meters. A major factor for this upstream paddle is the consideration of the water flow level. The differences in flow create major contrasts in the amount of effort to paddle upstream. At low water levels, much of this trip is easily done against a mild current. However, this river drains a substantial watershed of Guatemala, where rains in Guatemala regularly bring this stretch of river to flood levels with corresponding extreme currents. Moderate rainfall brings particular areas to greater current intensity. From wikipedia: "The Mopan River's rate of discharge has been measured regularly since 1981 at the river gauge station in Benque Viejo, Belize. According to these measurements, the river's annual mean discharge varies between 20 and 40 m3/s. The highest rate ever recorded was 404 m3/s in November 1990."
There is a rapid at the village of Bullet Tree Falls that requires a portage. There is another area near the village of San Jose Succotz with several drops that could require portaging. Although I haven't explored this entire stretch. The drops that may require portage are infrequent as reflected by the total elevation gain of this route.
I lived briefly along the river near Bullet Tree where I explored by foot and boat so my answer is informed by these personal explorations. I Would be happy to provide more info as I'm able!