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The Delta by Kathy cousins, Wildlife Mitigation staff biologist

"Pend Oreille Country" can be seen online at https://www.pbs.org/video/pend-oreille-country-ierduv/

I toured the shorelines and deltas around Lake Pend Oreille my first summer working for the Idaho Department of Fish and Game. The lake and surrounding area is so beautiful that one can be lulled into thinking that nothing can be wrong with the lake and everything is wonderful. “God’s country…” as Chip Corsi, the Panhandle Regional Supervisor, often states.

Clark Fork River Delta in the late summer, when Lake Pend Oreille is at its highest water level

However, when fall arrives and the lake is drawn-down 11 feet by the operation of the Albeni Falls dam, the true condition of the lake and its remaining wetlands is revealed. I spent several days walking across the vast mudflats of the Clark Fork River delta during my first winter on Lake Pend Oreille, wandering past the ghost-like tree stumps that are bare and raw to the cold winds. These stumps and their twisted roots are the remnants of a vast wetland forest that once thrived at the mouth of the delta before the construction of dams in the early 1950s. I walked toward an eroding shoreline where the remaining forest is in a slow battle to survive with the altered hydrology of the lake. It left quite an impression on me.

Clark Fork River Delta in the winter when Pend Oreille Lake is at its lowest water level

The high lake level and wind-driven waves in the summer months wash up and saturate the delta’s wetland soils. Then in the winter months, when the lake level is lowered by the operation of the Albeni Falls Dam, the wetland soils, heavy with water, cannot sustain the water weight and slump into the lake bed. Each year the shorelines look the same, and so it is easy not to notice that there is less and less of the wetland forest remaining. Most people do not see the damage, as it is underwater in the summer and, with the exception of waterfowl hunters, very few visit the delta in the winter months.

Measuring erosion on the White Island shoreline, Clark Fork River Delta November 2009

I take the same walk across the delta every winter since my first visit, and note new trees and scrub-shrub brush have slumped away from the forest to become debris in the river channels. More soils are removed by the forces of the lake and river working with the wind and rain. Each year more of the wetland forest disappears, and the mudflats grow larger, and the channels grow wider. Our analysis of historical aerial photographs and bank pin measurements told us that the Clark Fork River delta has been losing between 12 to 15 acres per year, just with the operation of the Albeni Falls Dam.

Aerial photograph of the Clark Fork River Delta in 1946, prior to the construction of the Albeni Falls Dam

It's difficult for me not to think of what was once there and now lost when walking across the mudflats of the Clark Fork River delta. Historical records and photographs from the Bonner County Museum suggest the massive wetland forest that dominated the delta was relatively stable, providing food and shelter for wildlife. The forest was composed of large western red cedar, black cottonwood, alder, Douglas fir, and lodgepole pine, with an understory of willow, hawthorn, snowberry, spirea, and sedges. Low-lying marshes and emergent wetlands were throughout the delta and provided food and cover for resident and migrating songbirds, water birds, and waterfowl. I close my eyes and imagine, but then I open them and see the wounded landscape.

Eroding shorelines in the Clark Fork River Delta October 2010

Lake Pend Oreille has historically been an important waterfowl migration and wintering area for large concentrations of redheads and canvasbacks. Unfortunately, no quantitative data was found to give any indication of waterfowl numbers before the construction and inundation of Lake Pend Oreille by the Albeni Falls Dam. However, what is known from historical records is that emergent wetland plants like bulrushes, sedges and cattails once dominated the delta shoreline and wetland areas. All of these native plant species are important because they provide food in the form of small plant matter (i.e., detritus) to the wetland waters and habitat for terrestrial and aquatic insects – all important building blocks in the food web that supports fish and wildlife. Most of these plant species have disappeared from the wetland areas in the Clark Fork River delta, and an invasive non-native grass, reed canarygrass, has silently taken over.

Delta shorelines dominated by reed canarygrass slumping into the Clark Fork River, April 2008

From an ecological perspective, reed canarygrass competitively excludes other native plant species and limits the biological and habitat diversity of the delta’s wetland and riparian habitats. Reed canarygrass thrives in highly disturbed environments and now dominates all of the remaining herbaceous layers of marsh, meadow, scrub-shrub, and forested wetlands found in the delta. The only habitat types not dominated by reed canarygrass in the delta are the mud flats, as these areas are too deep to support the grass during the growing season. Stream banks dominated by this grass competitively exclude native shrubs and tree species such as willow, black cottonwood, and red alder; the lack of these stream-side plants has direct and indirect effects on aquatic and terrestrial invertebrates (i.e., bugs), and, therefore, deleterious effects on wildlife and fish species that eat these bugs.

Currently, about 82% of all remaining vegetation cover in the Clark Fork River delta is reed canarygrass. In all honesty, I was so taken aback by the beauty of the area when I first arrived that I did not notice reed canargygrass; but now this grass has my full attention.

Soils removed by the operation of the dam expose the root system of trees in the Clark Fork River Delta November 2013

Although at first it may seem like an impossible task – to preserve, protect and perpetuate the wildlife habitats in the Clark Fork River delta– this task is being accomplished with the coordination of several agencies and the communities that live around the lake. With everyone working together, a portion of the delta was protected in 2015. Through a Letter Agreement with the State of Idaho and the Bonneville Power Administration in 2012, funds were made available to initiate the first phase of a multi-phase project to protect wildlife habitats in the delta, and then, behind the protection, restore a diversity of wetland plants.

Construction of a protective breakwater structure in the Clark Fork River Delta February 2015

Construction of a portion of Phase I of the restoration project began in November 2014 and was completed by March 2015. Over 50,000 tons of rock, transported across two bridges and then placed to protect shorelines, and 51,000 willows were embedded in the rock to provide wildlife habitat. The construction effort also resulted in over 40 acres of submerged areas being raised (by moving 260,000 cubic yards of fill) so that these areas are now above the lake’s summer full pool. A total of 100,500 plants were planted between April and June and hundreds of volunteers participated in the designing, planning and planting efforts.

Clark Fork High School students planting at the Clark Fork River Delta May 2015

The planting efforts were made especially challenging in that most of the planting occurred prior to the lake level being raised to its summer elevation. All of the 79,000 emergent plugs (i.e., native plant species like bulrushes, sedges, and cattails) were planted before the lake elevation was raised to the summer full pool in late-June. Elevation hubs were installed, and using the hubs and a laser level, the highwater mark was delineated with spray paint as a guide for the volunteers as they planted the emergent plugs.

Newly installed willow whips and emergent plants on the Clark Fork River Delta Project, June 2015

Vegetation surveys completed after the construction and planting efforts show the average proportion of native plants within the newly created island habitats increased while the cover of introduced plants like reed canarygrass was reduced. By all indications, the establishment of woody plants from nursery stock (either container or bare root) seems successful so far. Reed canarygrass is greatly reduced in the restored areas but not eliminated. There is an ongoing effort to further suppress reed canarygrass. If that effort is successful, then, as hoped, the vegetation diversity may be improved and bulrushes, sedges, and cattails will once again dominate wetland areas in the delta.

Willows and emergent plants in the Clark Fork River Delta one year after a construction and planting effort, August 2016

Funding for the completion of the Clark Fork River Delta Restoration Project was secured on August 30, 2018, when the State of Idaho and Bonneville Power Administration signed the “Northern Idaho Memorandum of Agreement for Wildlife Habitat Stewardship and Restoration.” As a consequence, the second phase of the proposed delta restoration project can move forward. I understand that what was lost cannot be returned; but my experiences working in North Idaho have taught me that we can protect some of the remaining wildlife habitats in the delta, and with continued effort we can improve these habitats, so that they will support the fish and wildlife we all enjoy. I no longer need to close my eyes to imagine what was lost, and I can visualize a delta thriving with a diversity of native plants and wild animals.