When the topic of willows/birch/cottonwood comes up, I get 2 questions. Well, one question and 1 complaint, lol. The complaint is always about anglers getting their backcast caught in them! The question is why plant them when they do take up so much water that fish need? The short answer is that these plants are a vital component to the health of the stream, alluvial groundwater, wildlife and riparian zone.
The “stream and riparian zone” refers to a flowing body of water (the stream) and the land immediately bordering it, characterized by unique vegetation and soil conditions directly influenced by the presence of water, essentially the “stream bank” area; this bordering land is called the riparian zone. The plant life in a riparian zone often includes trees (cottonwoods/birch), shrubs (birch/willows), grasses (native), and sedges specifically adapted to moist soil conditions. Riparian zones play a crucial role in maintaining healthy aquatic ecosystems by filtering pollutants, stabilizing stream banks, providing shade to cool water temperatures, and offering habitat for various wildlife. IMPORTANTLY, A riparian zone stores water primarily through its dense vegetation, which acts like a sponge by absorbing surface water through its root systems, allowing it to infiltrate the soil and be held underground, effectively replenishing groundwater and slowly releasing it back into the stream during dry periods; this also helps to stabilize stream banks and prevent erosion, further enhancing water storage capacity.
Most of the Little Sandy has a poor riparian zone. Thin soils and poor vegetation prevent a proper functioning zone. This is where willows and cottonwoods can help to build banks, facilitate root structure to help absorb moisture and stabilize the banks. In high water, generally October through May at least, the bankfull/floodplain water will be absorbed into the riparian zone and maintained as storage water. During June through September as the flows decrease below bankfull, the bank then will slowly release water into the stream potentially buffering the effects of a semi-arid region and drought. Yes, Cottonwoods for example can take up to 150-200 gallons of water per day during growing season and from sunrise to sunset due to high evapotranspiration. However, cottonwoods are important in the cycle between surface (stream) water and alluvial (subsurface) groundwater as the tree utilizes the groundwater particularly during limited surface water supply and quite significantly. As night arrives, the uptake ceases and the groundwater is restored and ready for another day providing a consistent use while helping to maintain the riparian zone, minimum river and alluvial groundwater levels. It can do this because the river bank has good porosity and permeability to maintain this water cycle.
Cottonwood restoration in the Little Sandy may take up some water in the beginning, but in a few years provide a valuable resource in the end, particularly with the weather cycles of late. 10 to 20 in the Little Sandy should not be a cause for concern as that number would be like throwing a deck chair off the Titanic given the length of the Snake River.
Oh, yes, as for that tangled backcast, practice your roll cast!