What can we learn about the Truckee River from up above?

Even while the recent heatwave is over and warming temperatures are ahead, the central Sierra snowpack remains at nearly 300% of normal, with much of the Truckee River watershed at 200%. The heatwave brought regional-wide record temperatures which accelerated the melting of the snowpack, raising the river and enacting a flood watch. This also had officials warning the public to avoid swimming in the river as it is running cold and fast. 

With more snowpack melting soon, we wanted to take a chance to see what rising water across the Truckee River looks like and see what those images can tell us about the river’s health, ecology, and development.

Lake Tahoe is above its natural capacity. Officials call this a Full pool, which equates to a water elevation of 6,225’. The Tahoe Dam was completed in 1913 and allows for an additional six feet of elevation across the lake. This translates to 732,000 acre-feet of water storage for the region. Credit Richard Bednarski.This graph highlights an important threshold for the Truckee River basin, with a record winter behind us, the ongoing drought is all but over. Source: LakesOnline.com

“Having a full reservoir is not a guarantee that you’re going to have a full reservoir in August when you’re talking about drawing it down,” explained Dr. Hausner, associate professor at the Desert Research Institute. He has spent over a decade studying the intersection of ecology and hydrology. His work is focused on studying the impacts of climate change on river ecosystems. 

“A big year of snowfall, even if we get a slow melt and a lot of water moving downward through that soil, [it] isn’t going to counter decades of drought on a groundwater resource,” explained Hausner. The region needs several more winters similar to this year to fully recharge the groundwater and move the drought needle into the green.

Boca Dam was built in 1939 and behind it, lies a popular recreation spot for camping and fishing. Built to provide irrigation water and flood protection for the Truckee Meadows, the reservoir can hold back about 40,000 acre-feet of water at full capacity. This allows water managers to manage flood risk and droughts. Credit Richard Bednarski.The Little Truckee River starts northwest of Donner Summit, just below Mount Lola. It flows generally west before turning south at Stampede Reservoir and onto Boca Reservoir.

“We don’t have a really good handle on what’s going to happen to precipitation with climate change,” said Hausner. “We know that temperatures in the [Great] Basin are going to get warmer.” Among many different climate models, there is an agreed-upon consensus that scientists use to understand what is going to happen to project the future climate. For Hausner, one thing is sure: “Precipitation is all over the map.”

The Little Truckee River meets the Truckee River just below Boca Dam about six miles northeast of Truckee, Calif. Credit Richard Bednarski.

This variability impacts the Truckee River ecosystem. Some models have increasing precipitation while others show a decline or stasis. “So that makes it really difficult to plan for future water resources,” Hausner said.

Not far below the Little Truckee River confluence with the Truckee River, the river tightens up and some of the most dramatic rapids on the entire corridor unfurl below the small community of Floriston. 

In March the region had a series of warmer atmospheric storms, leading to what climatologists call rain-on-snow events. Rain melts snow, essentially causing officials to release water from reservoirs and issue flood watches and warnings. In periods of long-term drought, these climate change driver storms make water management quite challenging.

“The other issue that the climate change brings with the Tahoe Basin is we’re not entirely sure what precipitation is going to do from a quantity perspective,” explained Hausner. Scientists do know that the interaction of increasing global temperatures and precipitation is going to lead to a transition from snow to rain. This ultimately means less water for the region.

As the river meanders east towards Reno, it widens and narrows, following the geography of the canyon. Here it is seen narrowing before turning north just past Mystic Canyon. The Sierra Sun reported that this area was once home to a small dairy operation, operated by Charles L. Wiley, and supplied food for nearby Floriston. Additionally, there was a maintained campground along the old Highway 40, before Interstate 80 was built. 

On top of a reduced snowpack, Hausner said there will most likely be an earlier spring melt-off in the future. Many mechanisms behind snowmelt are at play and will feed off one another as the atmosphere warms. 

“The clouds disappear and that solar radiation is really what drives the snow melt,” explained Hausner. He added that the bluebird days that we all enjoy are problematic during the winter. “Those are the days that are really responsible for melting off a lot of the snowpack.”

This image illustrates what Hausner said is not only beneficial to a river ecosystem but vital to overall health. As the water level rises, water gets pushed over the edge and onto the banks of the river helping to redistribute nutrients and sediment and release the kinetic energy of the river. 

”It’s not the size of the snowpack that is going to be that determining factor for the river and the river ecosystem, but the way that snowpack melts,” explained Hausner. Aside from the first heatwave we had at the end of April, the snowpack has been able to maintain a slow and steady melt, so far.

As the water level rises, the bottom of the riverbed, known as the hyporheic zone, gets more nutrients in the form of oxygenated water from snow melt.

“When you have high flows in the river, you have oxygenated water that’s being pushed into that hyporheic zone,” said Hausner. “It stimulates geochemical cycling, it stimulates the growth of particular algae and bacteria that process some of the contaminants in the water.” He added that high-water events, like what we saw recently, have both ecological benefits and drawbacks.

Here is where Steamboat Ditch begins its 32-mile journey to the south end of the valley. It was built in 1880 and “has developed into a habitat for local wildlife and its adjacent maintenance roads have become walking, hiking, and biking trails,” wrote Christian Filburn in 2020 for Nevada Today. A project to convert the ditch to pipes was put on hold in 2021 after residents who live near the ditch raised concerns. 

Steamboat Ditch is a well-known entity in the Truckee Meadows. This diversion dam allows for a flow of around 50 cubic feet per second (cfs). For comparison, the river is currently flowing around 2,400 cfs in Reno.

Another diversion dam built in 1880 diverts water for mostly public use, unlike the Steamboat diversion, which supplies water for mostly private and corporate uses. This diversion provides a higher flow rate, reaching an average of 95 cfs, and runs 12 miles, terminating at Rancho San Rafael Park. 

“[The Truckee River] is a snowmelt-dominated basin, which we take for granted in this area, but that’s relatively rare across the global hydrology,” said Hausner. The watershed is predominantly fed by snow, making future lower snow levels a potential risk to the ecosystem.

As the Truckee River enters Reno, it becomes channelized. 

Rivers tend to migrate as they meander through a floodplain and during natural high-water events, water spills over the riverbank and could potentially erode the floodplain, creating a new course for the river. A braided river is the perfect example of this in action. This process effectively eliminates erosion by slowing the water down and allowing sediment to precipitate out of the water. 

“What that does is it concentrates the energy of the water and so rather than having this floodplain to dissipate the energy, this ability to meander, and to cut away parts of the bank, and to deposit parts of the bank and to just move, it has to stay into the same channel,” explained Hausner. This increases the slope of the river and in turn, makes the water run faster. Without engineered stabilization, it will erode the river banks through the incision.

Here the river once again narrows as it is forced into a channel after Wingfield Park just before the Sierra Street bridge. 

“It’s no longer connected to that floodplain,” said Hausner. “If you get a big flow through there, it doesn’t then rise up out of its banks and dissipate its energy. It just cuts down even further.”

While the Steamboat ditch terminates near the headwaters of Steamboat Creek, the creek itself flows north and meets the river just before it exits the valley. The turbidity of the Truckee is evident here as the clearer, less active Steamboat Creek enters the river. With more water, the river moves faster and picks up more sediment, reducing the clarity of the water. Credit Richard Bednarski.After the river leaves the valley it cuts through the Virginia Hills and finds the room to once again unfold onto the landscape. This is particularly evident here, near USA Parkway, where the river meanders and old paths are once again filled due to the increased snowmelt.

The health of the river is really dependent on the entire community. It’s where we get our water, both for drinking and irrigation. And water decisions made now can have long-lasting effects.

Derby Dam was built under the Newlands Reclamation Act. Passed by Theodore Roosevelt in 1902, this legislation allowed for the diversion of waterways throughout the arid southwest. The water is diverted to Fallon, Nev. for irrigation.

Derby Dam was solely responsible for draining Winnemucca Lake, a marshland-lake oasis for not just migratory birds, but the Numu, or Northern Paiute people. The lake slowly receded due to restricted flow to Pyramid Lake, Truckee River’s terminus, and was officially cut off when a dam and road were built between the two lakes.

With the river running at higher levels, water trickles over the road/spillway of Derby Dam, which is hundreds of feet away from the actual dam. 

The dam also threatened the health of Kooyooe Pa’a Panunadu, or Pyramid Lake. Within 60 years of water diversion, the lake dropped nearly 90 feet in elevation, placing both the endemic Cui-ui, a species of sucker fish, and Lahontan Cutthroat trout in peril.

A look at the Derby Dam installation. 

After decades of tension and debate, a modern-day water-rights deal was reached amongst the many stakeholders. Originally signed in 2008 and slowed by litigation, the deal will send almost 3,000 acre-feet of water to the Pyramid Lake Paiute Tribe. This will not only benefit the Numu, but the endemic fish, the Cui-ui and Lahontan cutthroat trout. 

Stepping out of his scientist shoes, Hausner believes it is not just important to take care of the river for utilitarian reasons, but for ecological ones as well. 

“It’s important to not screw up the place where you live, it’s important to sustain wildlife and to live in a way that you can’t avoid your impact on nature,” he explained.

“We can do things as responsibly as we can, but it’s [a] really important thing to keep in mind and it’s worth investing time and effort and money in doing that sustainably.”

This story was originally published with The Sierra Nevada Ally.