PacifiCorp

Hygroscopic bilayers replicating the morphing capability of plants upon hydration (e.g., pinecone scales, chiral seed pods) have gained much attention in robotics and material science research in the past decade. Due to variations in humidity, hygroscopic bilayers - comprising a passive substrate and an active porous coating - can convert the chemical potential difference of adsorbate species between the surrounding environment and the pore space to mechanical energy, resulting in development of curvature and forces. In this paper, we present a closed-form analytical model that considers the pore structure of the active layer for predicting the morphing of hygroscopic bilayers subjected to adsorption. For free-end cases, the curvature evolution as a function of relative humidity is predicted by combining a bilayer beam theory and a linear surface poroelasticity model for the active porous layer. For fixed-end scenarios, the reaction force generated by the bilayer is predicted using Castigliano's second theorem with the same constitutive model. For validation, we consider two types of hydroscopic bilayers with microporous and mesoporous coatings, as tested by Boudot et al. (2016). A new isotherm equation is introduced to capture the adsorption characteristics of mesoporous media at all humidity levels. The predicted curvature and reaction force curves compared well against the experimental data. Finally, the effects of substrate Young's modulus and the coating's thickness on the response of the bilayer are studied. The proposed model offers straightforward mechanistic description of hydroscopic bilayers, thereby aiding in the future optimization and design of these systems for engineering applications.

Mejica BN, Ebert DA, Tanaka SK, Deas ML. 2023. Managing cyanobacteria with a water quality control curtain in Iron Gate Reservoir, California. Lake Reserv Manage. XX:XXX-XXX.Iron Gate Reservoir, a eutrophic monomictic reservoir on the Klamath River, a Pacific coast river within the United States, stratifies thermally during summer and is subject to cyanobacteria blooms that produce microcystin toxins, causing public health concerns. An impermeable curtain was installed in Iron Gate Reservoir upstream of the powerhouse intake to control the withdrawal depth and improve water quality of releases to the downstream Klamath River. Thermal stratification minimizes vertical downward movement of cyanobacteria-laden near-surface waters, and the curtain was hypothesized to reduce cyanobacteria and toxin concentrations downstream of the curtain and dam. The Wedderburn number, which indicates unstable (mixed) or stratified conditions, was used to calculate mixed layer depths and define conditions under which the curtain would be likely to be effective. Changes in chlorophyll a, cyanobacteria gene, Microcystis spp. gene, and microcystin concentrations were used to quantify curtain effectiveness for different curtain depths and mixed layer depths. When curtain depth extended below the mixed layer, concentrations of total chlorophyll a, total cyanobacteria, total Microcystis spp., and total microcystin in waters downstream of the curtain were statistically significantly reduced by an average of 87, 90, 78, and 64%, respectively. Concentrations were not consistently reduced downstream of the curtain under other configurations. Findings indicate the curtain can be managed to take advantage of stratification within the epilimnion and address issues pertaining to downstream cyanobacteria and associated toxins, and should improve water quality and reduce public health notices for the 305.7 km of river downstream of Iron Gate Dam.

Abstract Water use in the United States reached its lowest level in 2015 in at least four decades. National trends, however, mask local challenges throughout the U.S. In some places, decreases in surface water use were more than offset by increases in groundwater use, leading to net increases in total withdrawals. Other places have seen increasing rates of water shortages caused by mixes of socioeconomic and climate forces. This study examines recent trends in freshwater use and makes projections in future freshwater use over the next 50 years. Projections are based on socioeconomic and climate scenarios from the Intergovernmental Panel on Climate Change Fifth Assessment Report. Scenarios are paired with five climate models from the downscaled Multivariate Adaptive Constructed Analogs (MACA). We find total consumptive water use will decrease by as much as 8% under the best‐case scenario but increase by as much as 235% under the worst‐case scenario. Results depend on both climate and socioeconomic changes, but because agriculture is the dominant use of water in most regions, climate change impacts overwhelm all other factors under hot and dry futures. For the wetter climate models, water use decreases even under the highest emissions levels and highest population growth rates.

Bull trout in the Wallowa River watershed were considered extirpated in the 1950s. In 1997, bull trout from the adjacent Imnaha River watershed were reintroduced into the Wallowa River watershed. We evaluated whether bull trout are currently present in the Wallowa River watershed and, if so, whether they appear to be the result of the 1997 reintroduction. From 2010 to 2018, we captured 181 Salvelinus spp. The majority (64.5%) of these individuals were bull trout. Bull trout in the Wallowa River watershed were more genetically similar to those from the Imnaha River watershed (pairwise F ST = 0.102) than to the other populations we examined. They also exhibited genetic evidence of a recent bottleneck (observed heterozygosity was 0.598, significantly greater than expected). Modeled estimates of size (541–581 mm), survival (<0.0001–0.0015 probability) and age (14–22 years) for the reintroduced fish indicated the bull trout captured in the Wallowa River watershed were unlikely to be remnants from 1997. These results suggest the 1997 reintroduction has resulted in natural reproduction and recolonization of bull trout in the Wallowa River watershed. Whether the abundance and genetic diversity of these bull trout is sufficient to allow the population to persist over an ecological time period is unclear.