by Michael Howell
Close to 60 people attended a panel presentation and discussion entitled “Let’s Get Reel: threats and solutions for our waters and fisheries” sponsored by Bitterroot Water Partnership at the Daly Leach conference room in Hamilton last week. Attendees got to hear in detail from local experts how climate change has affected the Bitterroot River watershed and what we might expect in coming decades.
One of the presenters, University of Montana Research Assistant Professor Zachary Hoylman, specializes in ecosystem-climate-hydrology interactions, drought informatics, remote sensing and geospatial data analysis and has worked full time at the Montana Climate Office (MCO) in Missoula since 2018.
As part of his job, Hoylman helps manage the Montana Mesonet Dashboard where the public can access a wealth of climate-related data including soil temperatures, evapotranspiration rate, and volumetric water content, air temperature, precipitation, atmospheric pressure, snow water equivalents and more, all displayed in easy-to-understand graphic formats.
The Mesonet was designed to support decision-making for statewide drought assessments, precision agriculture and rangeland and forested watershed management. The data is collected from weather, soil moisture and snow monitoring stations installed across the state. The network has grown from the initial six stations installed in 2016 to over 100 stations, through support from private landowners, watershed groups, tribes, state agencies and grants from federal entities. In 2020, the MCO was awarded a contract from the U.S. Army Corps to add 205 additional stations. The new stations will be installed every 500 square miles in central and eastern Montana to improve drought assessments and flood forecasting.
Although he studies climate impacts on a very large scale, Hoylman focused his comments at the meeting upon the local impacts in the Bitterroot watershed. He emphasized how important it is to consider the many variables involved in assessing both the current and future status of overall conditions.
For the most part all eyes tend to focus on the snowpack during the winter and how it relates to the average of years past. We tend to key into the snowpack update reports from our six SNOTEL sites which yield data about the snow water equivalent of the snowpack. But this is only one part of the big picture. If you are really concerned about the potential future state of affairs in late summer, you can’t just count on the early spring SNOTEL reports.
One hundred percent snowpack may sound like a good thing. And it is. But it is only an indication of how much water will run off in the spring and does not directly relate to how much water will be available in late summer when the farmers, ranchers, floaters, fishermen, and fish need it the most.
What matters most in this regard has to do with the timing of the melt off, how early and how quickly all that snow melts. The SNOTEL sites are for the most part located in very high elevations where the depths of snow are the highest. But that depth of snow only covers a small area at the mountain tops. The lower areas of snow cover are not as deep but they cover a whole lot more land and contain the bulk of the snow and thus a far greater level of water content. As average temperatures warm up, this snow line will gradually move up the mountain sides, reducing the area of over-all snowpack.
Once the snowpack has run off, the river and its tributaries are dependent upon the groundwater that feeds them through springs and the summer rains. Thus, as temperatures increase and the number of frost free days increase, the flows become more and more dependent upon groundwater aquifers and late season precipitation.
By developing models that accurately reflect historical data back to the 1800s and projecting them forward, the future does not look bad for the Bitterroot in terms of the amount of precipitation. The volume of water we are likely to receive is predicted to remain fairly steady. But when you look at the big picture, the timing of the precipitation and the timing of spring run-off, the picture doesn’t look so good. Our water temperatures are rising across the board. The bulk of our precipitation is shifting into the winter months as late summer precipitation declines. The winters are growing shorter and the run-off is coming sooner. In sum, we are looking at a steady decline in late season flows.
According to Hoylman, the Standard Precipitation Index in the Bitterroot did not change much from 1980 to 2020 across the state. But over that time the average mean temperature has risen in the Bitterroot from 26 degrees Fahrenheit to 30 degrees F. The days above 90 degrees and the number of frost-free days have increased dramatically and we are seeing the impacts. That’s why over the last three years, the Bitterroot has been experiencing drought conditions despite the fact that precipitation levels have remained fairly constant.
The silver lining, according to Hoylman, is that Montana is a headwaters state and the Bitterroot River watershed is a closed system.
“Imagine being in Nebraska,” said Hoylman, “where you are impacted by everyone upstream.” Here in the Bitterroot, on the other hand, at the very headwaters of our river, “we can make decisions now that will affect us in the future, affect our kids, and this gives us some power. Even though things are not going in the best direction, we have the power to affect what happens and we should not take that for granted.”
He said one thing we could consider, for example, is the “irrigation efficiency paradox.” Irrigation withdrawals for agriculture take water out of the stream, thereby reducing the flows. By focusing upon agricultural use efficiency and switching to sprinkler irrigation, that withdrawal can be significantly reduced or more acreage can be added to the growing operation. But in some places, like along the Yellowstone River, studies have shown, paradoxically, that flood irrigation can actually increase base flows and produce increased late season flows. Flood irrigation takes muddy springtime water and puts it through a holding filter producing late season flows of colder, cleaner water.
Mike Jakober, a fisheries biologist on the Bitterroot National Forest for over 30 years, discussed the impacts of forest fires on the fish populations in the Bitterroot. He said when he started working on the Bitterroot National Forest, impacts from fires were a negligible factor on fish populations. However, in the late 1990s there were some larger and hotter fires burning that began to show impacts, starting with a 60,000 acre fire in the Selway in 1996 and booming in the year 2000 when 375,000 acres burned, followed by several years of fires of significant size and intensity.
“Now there is hardly a stream on the forest that hasn’t had some part of its watershed burned,” said Jakober. Hot fires can raise water temperatures in streams significantly by removing vegetation that shades them and it can take years for that vegetation to recover. The heat from the fires can kill up to 90% of the fish in a stream immediately and it can take a lot of time for the fishery to recover.”
Jakober said that there was an abundance of pre-fire data on the books in 2000, so the Bitterroot Forest decided to instigate some fish population counts to try to get a handle on the recovery and how it might proceed. They did some extensive sampling between 2000 and 2004 and then decided to continue it through 2022.
The results of all that study showed some species were doing surprisingly well, but some others not so good. The surprise was how quickly and efficiently the Westslope Cutthroat Trout performed. In the first four years the numbers in most streams showed populations greater than before the fires. Skalkaho Creek was the exception. And this held true up through 2022. This is good news for the native fish population that he estimated might represent 80% to 90% of the total trout population in the Bitterroot.
On the other hand, the native population of Bull Trout are not faring well at all and they are fairly well extirpated and absent from most streams in the Bitterroot, with a few remnant populations surviving in high elevation waters in a couple of creeks.
Brook Trout populations also suffered significantly from pre-fire conditions but show signs of slow recovery over the long term.
Brown Trout populations, a non-native species that has been in the Bitterroot River for decades, are hanging on and are sending a few pioneers into new areas, the exception being Skalkaho Creek where Brown Trout populations are actually booming.
Montana Fish, Wildlife and Parks fisheries biologist Jason Lindstrom, with 17 years of experience, the last five on the Bitterroot watershed, reported on the results of the last 30 years of water temperatures in the Bitterroot. He said that out of 62 monitoring sites, 60% showed increasing temperatures, 18% remained constant, and 16% showed declines in temperature. All 12 Index Sites monitored since the 1990s showed increased temperatures. Sleeping Child Creek showed the greatest increase, rising from 52 degrees to 59 degrees in mean temperature over the last 30 years.
Lindstrom said that total trout populations in the river were not doing too bad, in fact pretty good in the upper sections but declining a bit from Stevensville downstream. All of this while fishing pressure has been on the increase with unprecedented increase in the last few years. The Bitterroot River is the most fished river in Region 2 and the 5th most fished river in the state. With catch and release rules in place, hook scars have been observed on 70% of the Cutthroats in fish counts on the lower West Fork. He said that Hoot Owl restrictions on fishing hours which are invoked when the water temperature exceeds 73 degrees over three consecutive days have been implemented on sections of the river several times from 2000 through 2020 and starting in 2003 they have been invoked on the entire river. He said a new trigger for Cutthroat was adopted that would be invoked at 66 degrees.
“What once was occasional will probably become annual,” he said. He said the Pike population on the lower Bitterroot River first observed in the 1950s was growing stronger and that they are now showing up as far upriver as Hamilton. On an alarming note he reported the catch of a couple of Small Mouth Bass in the lower Bitterroot River as well.
“Small Mouth Bass can really change fishery dynamics,” said Lindstrom.
KynsLee Scott, a longtime fishing guide and conservationist working for American Rivers and Wild and Scenic Rivers Protection, gave some advice and instructions for anglers on how to take water temperatures and encouraged them to enact their own Hoot Owl restrictions voluntarily when appropriate. She also encouraged fisherpeople to re-think their “glory photos” and consider taking photos of the fish in the nets or leaving the nets, or at least holding them partially submerged. She said it also helps to consider “size selective” fishing by leaving the younger, more vulnerable fish to grow which helps establish a more robust and balanced fishery.
“It’s not just about the fish you are catching,” said Scott. “It’s about the fish you will catch in the future.”