June 25, 2019
When it comes to a river like the Mighty Missouri, only sometimes does the river reveal its complexity above the surface. While some areas will be littered with visible sandbars, they often hide below calm water undiscernible from the four-meter-deep channel that might run alongside. These are important details for scientists trying to navigate and study the river (for more on those hazards, see previous blog post Boating the Upper Missouri River is not for the faint of heart) but also crucial when trying to understand how, where, and why the newly hatched pallid sturgeon larvae utilize the dynamic conditions present throughout the dispersal stages of their development.
To better understand these complexities, hydrologists are completing the second half of an intensive mapping campaign that began with two weeks of hydroacoustic data collection in early June 2018. This year’s mapping effort just downstream from the Wolf Point, Montana, boat ramp will terminate at the upstream end of the 22 kilometers they mapped in 2018 near Poplar, MT. In total, high-resolution mapping will be completed over 36 kilometers and the upstream boundary will coincide with the location where free embryos are released for the 2019 Drift and Dispersal study.
Crews will continue to mimic the 2018 work by driving transects at 15-meter intervals using acoustic Doppler current profilers and single-beam echosounders to comprehensively map the braided riverway. In addition to the bathymetric data, the crew will be surveying river banks with a portable LiDAR system (see previous post, Mapping the river with lasers). Side channels, backwater pools, and other areas of potential stagnation are being given special attention as it is believed they could be important factors in drifting larvae survival. For more on the study of these areas, keep an eye out for an upcoming blog post on arrested drift and larval stalling.
The data collected will be used to extend and refine high-resolution particle tracking models to better understand how free embryos interact with the complex riverine environment. While the fish and environment of the Missouri River may be difficult to study, these models can prove invaluable in informing future efforts and identifying existing knowledge gaps.