River Revival

River Revival: How Chopping Down Juniper Is Reviving Idaho’s Rivers

In Idaho’s high-desert rangelands, water conservation does not begin at the river’s edge. Instead, it starts much higher on the hillsides, marked by the distinct buzz of a chainsaw and the resounding fall of an old, water-guzzling juniper tree.

Across the sprawling Burley Landscape and as part of the BOSH (Bruneau-Owyhee Sage-grouse Habitat) initiative, Pheasants Forever and Quail Forever are actively collaborating with the USDA’s NRCS, the Idaho Department of Fish and Game, and other key partners. Their mission: to strategically remove water-thirsty juniper and pinyon pine from vital sagebrush country (ID Range, n.d.). This targeted removal, frequently employing mechanical methods, is a deliberate choice. While methods like prescribed fire are also crucial tools for rangeland restoration, mechanical removal is often chosen for its ability to target specific nuisance woody species. The ongoing work not only enhances critical habitat for upland birds, such as sage-grouse, chukar, and Columbian sharp-tailed grouse, but also benefits big game species, including pronghorn and mule deer. Crucially, it is fundamentally reshaping how water moves through these arid ecosystems, yielding significant downstream benefits for fish populations, whitewater enthusiasts, and the communities that rely on healthy, flowing rivers.

From Canopy to Catchment

Recent research conducted across juniper-dominated watersheds consistently affirms the profound hydrologic benefits of tree removal. For instance, a compelling paired watershed study in Oregon, comparing a western juniper-dominated basin to an adjacent sagebrush-dominated basin (where juniper had been removed previously), found that streamflow and springflow rates were generally greater in the sagebrush-dominated watershed (Durfee & Ochoa, 2021). While this study did not find statistically significant differences in groundwater recharge rates between the two watersheds, it highlights the influence of vegetation dynamics on water availability. Further isotope studies in these uplands illuminated a remarkable speed of hydrologic connection, showing that winter recharge from treated areas reached valley aquifers remarkably quickly, often within 4 to 6 weeks. This directly links highland restoration efforts to crucial downstream water supplies (Ochoa, Deboodt, & Ray, 2016).

Across the vast expanses of the Great Basin and Colorado Plateau, comprehensive research syntheses consistently confirm that mechanical removal of pinyon-juniper cover invariably enhances soil water availability, significantly boosts understory vegetation, and improves overall hydrologic function with minimal erosion risk (Williams, Snyder, & Pierson, 2018). These observed positive effects are mirrored in Idaho, where peer-reviewed studies and ongoing federal monitoring have documented tangible gains in water storage and improved flow dynamics within treated areas.

A long-term watershed experiment in Oregon’s Camp Creek region offers particularly compelling evidence of this transformation. This study, initiated in 1994, meticulously tracked streams in juniper-cleared areas, reporting that peak spring flows increased by nearly 48 percent over 13 years post-treatment, climbing from 182 to 269 gallons per minute (Deboodt, 2005). Such a substantial increase translates directly into measurable and vital benefits downstream, playing a crucial role in sustaining critical baseflows and supporting diverse aquatic life well into the late summer months, even transforming previously intermittent streams into perennial ones.

Why It Matters for Rivers

Juniper encroachment is far more than a mere vegetation management concern; fundamentally, it represents a profound water issue. As land manager Connor White succinctly articulates, “It simply outcompetes all other vegetation. They also suck out the available water. The juniper will eventually win” (ID Range, n.d.). These aggressive conifers are remarkably efficient: they intercept rainfall, significantly reduce vital snowpack retention, and relentlessly pull deep moisture from the soil, leading to the desiccation of critical seeps, springs, and riparian zones. When restoration crews meticulously remove these water-guzzling trees, the results can be almost instantaneous: springs often begin to flow again within weeks. Rancher Chuck Hall witnessed this dramatic transformation firsthand on his property: “I cut about 75 big trees, and within a week, 10 days, the spring came back... It always ran, but it ran twice as much or more than it did.”

These are not abstract hydrological shifts confined solely to scientific models. The increased water retention in the soil and a slower, more regulated runoff process work in concert to sustain streamflows longer into the parched summer. For iconic whitewater rivers like the Snake, Payette, and Salmon, this means more reliable and extended flows for rafters and kayakers, significantly bolstering the recreational economy.

While exact cubic feet per second (CFS) gains remain under intensive study, the underlying mechanisms are progressively more precise. Sap flow data collected between May 2017 and September 2019 provided compelling quantitative evidence: mature western juniper trees consumed up to 144 liters of water per day in wetter years (such as July 2017), approximately twice as much as in drier years. Crucially, during periods of peak water uptake, mature trees used between 45 and 69 times more water than saplings, depending on precipitation levels and soil water availability (Mata-González, Abdallah, & Ochoa, 2020). This stark difference highlights the immense water savings potential inherent in juniper removal, emphasizing its long-term benefits even more than a decade after initial treatment, as sapling regrowth consumes significantly less water. Indeed, the removal of mature juniper can result in an estimated 5,500 cubic meters of water saved per hectare, even after 13-14 years of sapling regrowth (Mata-González, Abdallah, & Ochoa, 2020).

Additional field studies further confirm that mature junipers significantly outpace saplings in water consumption, frequently drawing moisture from deeper soil layers (down to 0.8m or more). This reinforces the profound and lasting hydrological benefits of tree removal (Pflugmacher et al., 2014). This deep water extraction by juniper often leaves deeper soil layers in a perpetually depleted state, critically limiting deep percolation and groundwater recharge (Pflugmacher et al., 2014).

A comprehensive study by Ochoa, Deboodt, and Ray (2016) also reported measurable changes in soil moisture and groundwater dynamics following juniper removal, providing some of the most detailed insights into how direct treatment actions translate into tangible hydrologic outcomes within Western juniper ecosystems. For instance, in the sagebrush-dominated watershed, streamflow accounted for 5.8% of incoming precipitation, whereas in the juniper-dominated watershed, it was a mere 0.3%. Furthermore, mean springflow in the sagebrush watershed was significantly higher at 43.4 liters per minute, compared to 12.6 liters per minute in the juniper-dominated one (Durfee & Ochoa, 2021). These studies collectively indicate that while overall evapotranspiration might be quantitatively similar between juniper and sagebrush ecosystems (83-86% of precipitation), the partitioning of water changes drastically, resulting in considerably more surface and subsurface flow in sagebrush-dominated areas.

Hydrologic models provide a broader, predictive perspective, demonstrating that converting dense juniper woodland to grassland in pinyon-juniper regions can reduce evapotranspiration by 25 to 37 millimeters per year, thereby directly increasing crucial groundwater recharge (Niemeyer et al., 2017). Their research also revealed that the potential for meaningful increases in streamflow is greatest within the northern and western ecoregions of the pinyon-juniper range. This critical area encompasses a significant portion of Idaho. This suggests that Idaho’s BOSH project is strategically positioned within the 29 percent of pinyon-juniper woodlands identified as having the highest potential for considerable streamflow gains through tree removal, particularly in cool-season precipitation regimes where 200-400mm of annual precipitation can yield increases in soil water availability (Williams et al., 2018).

That profound hydrologic shift has powerful and far-reaching ripple effects throughout the entire ecosystem, benefiting a wide array of species (J. Northuis, personal communication). More consistent and cooler flows actively support robust fly hatches, stabilize water temperatures, and significantly improve vital spawning habitat for iconic fish species like White Sturgeon, Snake River Chinook (ESA Threatened), Sockeye (ESA Endangered) Salmon, and Snake River Basin Steelhead (ESA Threatened). Sensitive aquatic species, including the Yellowstone Cutthroat Trout (especially in Eastern Idaho), Northern Leopard Frog, Banbury Spring Limpet (ESA Endangered), and Bliss Rapid Snail (ESA Threatened), all directly benefit from these improved, cooler, and more stable water conditions. Even the countless aquatic insects—mayflies, stoneflies, and salmonflies—that form the essential base of the aquatic food web, feeding fish and thrilling fly anglers, actively thrive in these healthier, re-wetted systems.

The terrestrial benefits are equally significant. The restored rangelands provide enhanced habitat for upland birds such as the Sage Grouse, Chukar, Columbian Sharp-tailed Grouse, Hungarian Partridge, and California Quail. Big game species like Mule Deer, Elk, and Pronghorn Antelope find more abundant forage and improved cover. Critically threatened species, such as Slickspot Peppergrass and Utes Ladies’ Tresses (found only in Eastern Idaho), also see their habitats revitalized. Furthermore, the broader ecosystem supports Burrowing Owls, Long-Billed Curlews, Pygmy Rabbits, and a variety of essential pollinators (J. Northuis, personal communication).

In the words of Jeremy Maestas, highlighting the monumental scale of this undertaking, “The BOSH project stands to be the largest single restoration effort we have ever undertaken in the sagebrush biome. Just to put this in context, it is probably 5–6 times larger than any similar area we have undertaken to address this conifer issue” (ID Range, n.d.).

The Big Picture

The BOSH and Burley efforts represent a robust and scalable blueprint for water-smart restoration across the arid West. They meticulously fuse upland and aquatic priorities, vividly demonstrating how landscape-level thinking can effectively bridge the critical gap between habitat recovery and hydrological function. This integrated approach serves as a compelling model for other dryland systems facing the relentless spread of conifer encroachment, particularly in regions where juniper has expanded dramatically, such as in Oregon, where it has increased from 1.5 million acres to over 6 million acres since 1934 (Deboodt, 2005).

With millions invested and more than 140,000 acres treated so far, the effort is rapidly gaining momentum, critically gaining water. The project’s immense scale perfectly matches the urgency of the problem at hand. Junipers continue their relentless spread across Idaho, Utah, Oregon, and Nevada, systematically drying out vital watersheds and pushing native wildlife into ever-shrinking strongholds. However, with the strategic deployment of chainsaws, the strength of robust partnerships, and the precision of innovative, science-backed interventions, restoration is now moving faster than encroachment in key areas, offering a tangible path to a wilder, healthier world.

The transformation of Idaho's rangelands is a testament to what is possible when conservation embraces rigorous ecological science and committed collaborative action. It is a horizon-to-horizon effort, a powerful narrative of revitalization where chainsaws are wielded not for destruction, but for the restoration of life-giving water and the return of a vibrant, resilient ecosystem. This is not merely about cutting trees; it is about re-wilding the West, one watershed at a time, ensuring that the rivers flow strong for generations to come.

References

Deboodt, T. (2005). Watershed response to western juniper control. Oregon State University Extension Service. https://www.oregon.gov/oweb/Documents/Camp-Creek-Paired-Increasing-Water-2009.pdf

Durfee, N., & Ochoa, C. G. (2021). The Seasonal Water Balance of Western-Juniper-Dominated and Big-Sagebrush-Dominated Watersheds. Hydrology, 8(4), 156. https://doi.org/10.3390/hydrology8040156

ID Range. (n.d.). BOSH project restores sagebrush sea at a grand scale. Retrieved from https://idrange.org/range-stories/southwest-idaho/bosh-project-restores-sagebrush-sea-at-a-grand-scale/

Mata-González, R., Abdallah, M. A. B., & Ochoa, C. G. (2020). Water use by mature and sapling western juniper (Juniperus occidentalis) trees. Journal of Arid Environments, 179, 104196. https://www.sciencedirect.com/science/article/pii/S1550742420300981?via%3Dihub

Niemeyer, R. J., Link, T. E., Heinse, R., & Seyfried, M. S. (2017). Climate moderates potential shifts in streamflow resulting from changes in pinyon-juniper woodland cover in the western US. Hydrological Processes, 31(17), 3261–3272. https://onlinelibrary.wiley.com/doi/full/10.1002/hyp.11264

Ochoa, C., Deboodt, T., & Ray, G. (2016). Soil moisture and groundwater dynamics in western juniper. Society for Range Management Conference Paper. https://ecohydrology.oregonstate.edu/pubs/soil-moisture-and-groundwater-dynamics-western-juniper-woodlands

Pflugmacher (former: Mollnau), Candy & Newton, Michael & Stringham, Tamzen. (2014). Soil water dynamics and water use in a western juniper (Juniperus occidentalis) woodland. Journal of Arid Environments. 102. 117–126. 10.1016/j.jaridenv.2013.11.015.

Williams, C. J., Snyder, K. A., & Pierson, F. B. (2018). Spatial and Temporal Variability of the Impacts of Pinyon and Juniper Reduction on Hydrologic and Erosion Processes Across Climatic Gradients in the Western US: A Regional Synthesis. Water, 10(11), 1607. https://www.mdpi.com/2073-4441/10/11/1607