It's high time water managers in the Missouri River basin jump on the environmental flows bandwagon
For the ninth year in a row in the Missouri River basin, the Army Corps of Engineers (Corps) has given progress towards protecting the endangered pallid sturgeon a failing grade. The Corps and the Bureau of Reclamation manage flows from 75 dams throughout the basin, and the Corps in particular determines the flows leaving the basin.
These dams have reduced the timing and extent of flows, the amount of space for young sturgeon to disperse and the spring cues required for the success of the pallid. Loss of preferred habitat and prey has been extensive as backwaters, side channels, and sand bars disappeared from the system, followed by a 70% reduction prey for young fish – aquatic insects. This has turned the flow of water in the Missouri River nearly on its head - sending excessive water downstream in the winter and early fall. As a result, spring and summer flows were more than cut in half – affecting the health of the entire ecosystem and placing the pallid sturgeon at risk of extinction.
Since the U.S. Fish and Wildlife Service asked for improved flows for the pallid sturgeon in 2003,as part of the Biological Opinion for the species, other uses for the water have kept this species from receiving needed flows for spawning. To date the Corps has rejected nearly every proposed change to the amount and timing of flows through dams required by the Fish and Wildlife Service. Scientific data showed that higher, warmer flows out of Ft. Peck dam in Montana would benefit the pallid sturgeon and most other fish species, but the Corps rejected this (Note: In 2011, such flows due to flooding led to record pallid sturgeon numbers). Again scientific studies provided evidence that the floodplain could serve as an important habitat for young fish species, but the Corps rejected this. The Fish and Wildlife Service requested a pulse of flows from Gavins Point in the spring and fall, but again these were rejected. Despite the best available science, the Corps continues to keep fish and wildlife at the bottom of the barrel. In 2013, the Corps’ own Independent Science Advisory Panel stated that “pulses have been of such limited magnitude and durations that they appear to be unable to generate the specific habitat features and conditions that are believed to be important for those species.”
Again, in 2014, pulse flows were denied, even though plenty of water was available. So, again, the species is monitored in hopes that the "no management" mantra will improve conditions for the pallid sturgeon.
The 2011 floods provide a window into benefits of improved flows
According to this last report from the Corps, flows could benefit the pallid sturgeon throughout the basin. The 2011 floods tell this story – one where high flows – even higher than the pre-dam flows, changed fish behavior. The year after the flood, pallid sturgeon in the Upper Missouri River, in Montana and North Dakota (referred to as Segments 2 and 3), were more abundant than any other year, with many moving further upstream. In fact the number of pallid sturgeon below Ft. Peck exceeded the combined total from the previous years – with few present before 2011 floods. The Upper basin also saw the largest number of wild versus hatchery raised sturgeon, a sign that this area could provide a refuge for species recovery. Downstream of Gavins Point, another area where the Corps was asked to release pulse flows, the 2011 floods produced record high pallid counts, nearly doubling the previous high from 198 to 320 adult pallid sturgeon. Other species, such as the shovelnose sturgeon and sauger reached record high numbers as well. Downstream of dams that overflowed, habitat for two other endangered species, the piping plover and least tern were improved by the flood.
Flow experiments in other rivers have benefitted species impacted by dams
Mounting evidence globally suggests that dams can be effectively managed to benefit fish and wildlife species. A recent review of 118 flow experiments at 102 dams, more than 90% of them below dams > 45 ft in height and more than half of these > 150 ft in height demonstrates this. In the review, when flow objectives for fish and wildlife were met, 80% of dam operators modified operations and management to account for these changes to support the fish and wildlife community. The most successful changes in flow were those that maintained or enhanced minimum or baseflows, those that included a range of changes in operating regimes (e.g. minimum flows and pulses/freshets), and those that limited intraday peaking. The least effective practices were those that focused on a single species, those that implemented a high flow pulse, and those that implemented a seasonally variable flow. Operational changes that implemented more than one type of management practice were more likely to succeed. Two examples of such successes are highlighted below.
Experimental flows on the Colorado River
The Colorado River, with too little water from the very beginning of reservoir construction, is now undergoing a five year pulse flow experiment – an experiment that recently allowed water to flow to the sea – the first time in sixteen years. In previous years high flow experiments have increased backwater and sandbar habitat by nearly threefold, and have increased trout abundance by two to four times, while decreasing invasive species such as the New Zealand mud snail. As a result of flow experiments and the willingness of water managers to test hypotheses, environmental flow conditions are improving.
The Living Murray program restores water to ecological “icons”
In another arid river system, the Murray River, in Australia, managers established the “Living Murray” program to return water to the ecosystem, by restoring 405,000 acre-feet (132 billion gallons) of water to six ecological “icon” sites. Much like the Missouri River, the Murray River in Australia is set in a semi-arid climate and is highly dependent on flow from its headwaters. Declines in fisheries have been caused loss of reproductive cues, barriers to migration, altered temperature regimes, and loss of vegetation and deep pools. Managers have now set allocations for ecosystems and set caps on water diversions, while establishing triggers for different year types - extremely dry, dry, median, and wet years. In 2012, the agreement resulted in a record delivery of water to the lower basin, providing peak flows in late spring facilitating native fish recruitment, filling temporary wetlands, and maintaining flows over spillways to support fish migration.
Photo Credit: https://www.flickr.com/photos/boatmik/2238308701/
Stakeholders have created demonstration reaches, applying a portfolio of management practices to showcase the cumulative benefits of river rehabilitation to native fish species. As a result of this intense effort, fish such as the moonfish have been recorded for the first time in 15 years, tenfold increase in native fish such as bream, and perch have occurred and invasive carp are disappearing. Flood releases in 2005-2006 initiated flowering of the endangered Moira grass, and the first recorded breeding of four egret species in nearly three decades. The level of response, supported by extensive monitoring demonstrates the importance of flow modification to spawning, YOY abundance, and dispersal.
Managers in the Missouri River basin should learn from these successes
Lessons learned from the studies above indicate that stakeholders should be aware of and take the following steps to ensure efficient management of regulated systems:
- Outcomes are never immediate and stakeholders should be prepared to modify strategies based on sound science.
- A range of possible strategies should be outlined to encompass a range of flow year types (e.g. dry, average, wet) so that stakeholders agree on these strategies prior to stressful conditions.
- A watershed approach should be taken to reduce the impact of any single strategy failing. This should include year-round flow targets, tributary flows, and state water allocation agreements. Optimization models can also be used to determine a range of scenarios and strategies that are the most cost effective, while producing the best outcomes.
- A holistic approach should be taken to data collection so that long term data are collected before and after changes occur. This approach should include an assessment of biological and physical factors and should include multiple species and life history stages.
- Progress should be tracked via clearly established endpoints that reflect the objectives (e.g. % ecosystem function restored) and incorporated into interdisciplinary indices.
- Maintain enforcement of operations and management changes or other watershed level objectives even during stressful periods or fish and wildlife will be placed last even during normal flow years.
These principles provide a framework for the Missouri River. The Corps is in the process of developing an updated management plan for the river and “River Flow” is considered a “Master Variable” for the success of the pallid sturgeon – controlling sediment movement, water temperature, and habitat. Now is the time to take another look at options to protect the pallid sturgeon and all native fish species by implementing the Biological Opinion to comply with the Endangered Species Act. The science clearly demonstrates that substantial changes must be made to the management of the Missouri River in order for the pallid sturgeon to survive.
Photo Credit: https://www.flickr.com/photos/ndguard/5817472362/
Will the Corps accept the science during this round? If not, researchers suggest that the pallid will be extinct by 2018. Evidence clearly demonstrates the importance of a holistic approach. However, patchwork efforts that do not integrate flow management, tributary protection and management, and floodplain and instream restoration and protection will likely fail.
Instead of waiting another decade to protect the pallid sturgeon, experimental flows could be tested now to prevent the loss of this species.