The 7-day precipitation forecast from the National Oceanic and Atmospheric Administration issued on May 27 showed local rainfall potential of approximately 5 inches for portions of north Missouri (figure 1). Unfortunately, this forecast was relatively accurate and heavy rainfall swelled the Missouri River as the major storm moved through the mid-west.
Heavy rainfall during the last part of the week caused episodes of local flash-flooding and pushed the Missouri River over the National Weather Service floodstage of 23 feet at Jefferson City just before midnight on May 30, 2013. Water levels finally crested at just over 30 feet on Sunday, June 2.
High flow presents several challenges and opportunities to researchers attempting to track pallid sturgeon in the Lower Missouri River. First, we face the fundamental logistical challenge of finding boat ramps that are open, and if open, are not covered with mud and woody debris. Flood waters can complicate the task of locating open boat ramps by causing road closures on low-lying roads, especially those in the floodplain approaching boat ramps (figure 2).
Rising water can mobilize and carry large amounts of woody debris (figure 3), which severely complicates tracking, recapture and larval sampling efforts. This woody debris isn’t just tree branches and limbs. Entire large trees, roots and all, are frequently seen being swept downstream in the muddy current.
It can also be a challenge for crews to hear the telemetry transmitters of pallid sturgeon during flood flows because the debris and rushing water increases the noise in the telemetry signal, like static on a radio station. Additionally, flood waters can increase habitat complexity by inundating sandbars and dikes, which can interrupt the transmitter signal (see previous blog entry “Sometimes It Takes Two”). Although river conditions may occasionally prevent us from tracking these endangered sturgeon during high water, tags implanted inside fish will continue to record depth and temperature, and we will retrieve the data when the fish are recaptured later this year (see blog entry “Where Are You When I’m Not Looking”).
But the floodwaters also supply opportunities. Some scientists have hypothesized that flood stages are instrumental in providing larval sturgeon access to near-shore and overbank areas. High-water events present the opportunity to characterize habitats and drift in these areas. In addition, high water helps habitat modeling studies that require sufficient depths that hydroacoustic boats can collect depth and velocity data over a broad range of habitats.