100039 research outputs found
Sort by
Enhancing Monthly Streamflow Prediction Using Meteorological Factors and Machine Learning Models in the Upper Colorado River Basin
Get PDFStreamflow prediction is crucial for planning future developments and safety measures along river basins, especially in the face of changing climate patterns. In this study, we utilized monthly streamflow data from the United States Bureau of Reclamation and meteorological data (snow water equivalent, temperature, and precipitation) from the various weather monitoring stations of the Snow Telemetry Network within the Upper Colorado River Basin to forecast monthly streamflow at Lees Ferry, a specific location along the Colorado River in the basin. Four machine learning models—Random Forest Regression, Long short-term memory, Gated Recurrent Unit, and Seasonal AutoRegresive Integrated Moving Average—were trained using 30 years of monthly data (1991–2020), split into 80% for training (1991–2014) and 20% for testing (2015–2020). Initially, only historical streamflow data were used for predictions, followed by including meteorological factors to assess their impact on streamflow. Subsequently, sequence analysis was conducted to explore various input-output sequence window combinations. We then evaluated the influence of each factor on streamflow by testing all possible combinations to identify the optimal feature combination for prediction. Our results indicate that the Random Forest Regression model consistently outperformed others, especially after integrating all meteorological factors with historical streamflow data. The best performance was achieved with a 24-month look-back period to predict 12 months of streamflow, yielding a Root Meat Square Error of 2.25 and R-squared (R2) of 0.80. Finally, to assess model generalizability, we tested the best model at other locations—Greenwood Springs (Colorado River), Maybell (Yampa River), and Archuleta (San Juan) in the basin
Water Banking as a Strategy for the Management and Conservation of a Critical Resource: A Case Study From Tunisia\u27s Medjerda River Basin (MRB)
Get PDFThe increasingly adverse impacts of climate change (e.g., rainfall patterns, droughts, and floods), coupled with the ever-increasing water demands, are often translated into a contingent liability for water users\u27 communities. Additional complexities arise due to competing priorities, water rights, and transboundary water sources. Therefore, conventional water management practices should shift toward more comprehensive and responsive integrative approaches, even for systems with limited data. Furthermore, water managers must prioritize dynamic and interactive management techniques for existing systems. One such management technique is water banking, which is the focus of this study. Herein, a dynamic interactive water allocation model, which encompasses the water managers and heterogeneous parties with competing demands, is developed. The voluntary sales of water shares between parties are illustrated through the specific case of the Medjerda River in Tunisia, an excellent example of a transboundary basin with limited hydrologic data and conflicting water use requirements between its upstream and downstream sectors. A set of scenarios is developed for the first analysis with this model: two management scenarios that include the no-water trade and the water banking option; three demand scenarios that include a combination of steady-, low-, and high-water demand conditions; and two hydrologic scenarios that include dry and wet conditions. Based on an economic model, the economic impacts of water banking are calculated using estimates of the costs of water shortages brought to users that illustrate the magnitude. The results show that the water banking technique can improve water resource availability by optimizing the management, operation, and conservation of natural and artificial water storage systems and water distribution infrastructure. Specifically, water banking can offset users\u27 profit losses during severe conditions (i.e., drought), even with limited hydrologic data. This water management technique would allow the Tunisian government to minimize the economic impacts on farmers from drought and to plan for future uncertainties by optimizing the water storage potential in years of abundant rainfall
Investigating Channel Narrowing and Nonnative Vegetation Encroachment in Three Dryland Rivers
No full textWater development and the proliferation of invasive riparian vegetation has led to widespread habitat loss and simplification of rivers in the western United States, contributing to the imperilment of native fishes. Here, we quantify channel narrowing and vegetation encroachment, which are conspicuous indicators of riverine habitat degradation, along approximately 400 km of three dryland tributaries of the upper Colorado River. To accomplish this, we conducted a comparative analysis of aerial photographs from historical (1930s) and contemporary (2010s or 2020s) time periods and utilized Light Detection and Ranging (LiDAR) data and Object-Based Image Analysis (OBIA) to determine contemporary canopy cover of woody riparian species. Coinciding with a general decrease in flows over time, all three rivers underwent substantial channel narrowing; although, the degree of narrowing varied among rivers (78%, 73%, and 29%). The magnitude of channel narrowing generally matched the deviation from historical spring (i.e., peak) flows, with large decreases in spring flows corresponding to substantially more pronounced channel narrowing. In contrast to patterns of channel narrowing, contemporary woody cover was similarly high among all three rivers (39%, 41%, and 36% of valley bottom area), and a woody vegetation change analysis conducted for one river indicated a substantial increase in woody vegetation along the active channel compared to historical conditions (4% to 74%). These findings underscore a common pattern observed in rivers throughout the basin, where river channels often undergo narrowing and encroachment by invasive vegetation, ultimately leading to habitat simplification. Our findings also emphasize that, when possible, preserving or restoring large magnitude and long duration floods, should be prioritized for the effective conservation of dryland rivers
Tremblings, May 2024
Get PDFClimate change insurance: planting aspen seedlings as fuel breaks
Catherine Schloegel, Program Manager, The Nature Conservancy, Boulder, Colorado
Jordan Mead, Resource Specialist, Summit County Open Space and Trails Department, Frisco, Colorado
As climate impacts accelerate, mountain communities living near forested areas across the West will be at increasing risk of more frequent wildfires. To protect neighborhoods from high-severity wildfires, land managers frequently clear strips of forest around homes and roads. We examined the potential to plant true aspen seedlings in these fuel breaks to increase habitat diversity while maintaining a reduced risk of wildfire. Historically, aspen has acted as a natural fuel break in low- to medium- severity wildfires, although it is less well understood how it will impact contemporary fire occurrence, behavior, and severity. Scientists at the University of Colorado at Boulder are examining the relationship between aspen and fire, and in parallel we are working to generate knowledge about planting and survival
Investigating Short-Period Ripple Events Imaged Simultaneously in the OH and O\u3csub\u3e2\u3c/sub\u3e Nightglow Emissions Near the Mesopause Over Maui, Hawaii
No full textThe characteristics of small-scale, spatially localized ripples, were observed simultaneously in the mesopause airglow layers OH (873 km) and 02 (943 km) from Maui, Hawaii (20.7° N, 156.3° W). The ripples with small horizontal wavelengths (\u3c ~15 km), phase speeds (\u3c ~ 40 m/s), short periods (\u3c ~12 min) and lifetimes of 10-35 min were measured during 1 year period in 2004. They were limited in spatial extent and had ~4-16 wave crests. These measurements were obtained using Utah State University (USU) Mesospheric Temperature Mapper combined with background wind measurements using the University of Illinois meteor radar to study ripple alignment and association with local wind shear. The ripple structures were considered to be the signatures of dynamic (Taylor and Hapgood, 1990) and convective (Fritts et al., 1997; Hecht et al., 1997) instabilities
The Transition From Summer-to-Winter Temperatures Between 70 and ~115 km as Observed With the ALO-USU Rayleigh Lidar
No full textRayleigh-Scatter Lidar Temperature Retrieval Elastic scattering from N2, O2, Ar, and O. Obtain a backscatter profile Convert that profile to a relative density profile From that profile derive an absolute temperature profile [1]. Use: Ideal gas law, Hydrostatic equilibrium, Top temperatur
Supplementary Files For: Interactive Modeling of Bear Lake Elevations in a Future Climate
No full textThe water level, or elevation, of Bear Lake has a significant impact on agriculture, power, infrastructure, and recreation for communities around the lake. Climatological variables, such as precipitation, temperature, and snowfall, all have an impact on the elevation of Bear Lake. As the climate changes due to greenhouse gas emissions, the typical behaviors of these climate variables change, leading to new behaviors in Bear Lake elevation. Because of the importance of Bear Lake, it is vital to be able to model and understand how Bear Lake\u27s elevation may change in the face of different climate scenarios and to gain further insights into the sensitivity of Bear Lake\u27s elevation to these changes. One tool to aid in this pursuit is the creation of interactive plots that allow a user to easily visualize the effect that different climate scenarios have on our model of Bear Lake\u27s elevation. Therefore our project has two primary objectives. First is the modeling of Bear Lake elevation using statistical models, and state-of-the-art Neural Networks. Second is the creation of an interactive application that could be hosted online which makes accessible the results of our modeling efforts, as well as visual access to the historical climatological data. This report details our modeling efforts and a proof-of- concept for an interactive application accessible through a web browser
Multifidelity Comparison of Supersonic Wave Drag Prediction Methods Using Axisymmetric Bodies \u3csup\u3e†\u3c/sup\u3e
Get PDFLow-fidelity analytic and computational wave drag prediction methods assume linear aerodynamics and small perturbations to the flow. Hence, these methods are typically accurate for only very slender geometries. The present work assesses the accuracy of these methods relative to high-fidelity Euler, compressible computational-fluid-dynamics solutions for a set of axisymmetric geometries with varying radius-to-length ratios (R/L). Grid-resolution studies are included for all computational results to ensure grid-resolved results. Results show that the low-fidelity analytic and computational methods match the Euler CFD predictions to around a single drag count (~1.0 × 10–4) for geometries with R/L ≤ 0.05 and Mach numbers from 1.1 to 2.0. The difference in predicted wave drag rapidly increases, to over 30 drag counts in some cases, for geometries approaching R/L ≈ 0.1, indicating that the slender-body assumption of linear supersonic theory is violated for larger radius-to-length ratios. All three methods considered predict that the wave drag coefficient is nearly independent of Mach number for the geometries included in this study. Results of the study can be used to validate other numerical models and estimate the error in low-fidelity analytic and computational methods for predicting wave drag of axisymmetric geometries, depending on radius-to-length ratios
Lower Limb Muscle Activation in Young Adults Walking in Water and on Land
Get PDFPrevious research has shown that exercise interventions requiring increased activation of the tibialis anterior (TA), the primary ankle dorsiflexor, can improve walking performance in individuals with foot drop. Correspondingly, heightened drag forces experienced during walking performed in water may augment TA activation during the swing phase of gait, potentially leading to improved walking gait on land. Therefore, this study aimed to compare surface electromyographic (sEMG) activation in the TA and medial gastrocnemius (GM) during gait performed in water versus on land. Thirty-eight healthy, recreationally active young adults, comprising 18 females and 20 males, participated in the study. Each participant completed 2 min walking trials under five conditions: land 2.5 mph, land 3.5 mph, water 2.5 mph, water 3.5 mph, and water 3.5 mph with added jet resistance. Stride kinematics were collected using 2-dimensional underwater motion capture. TA and GM, muscle activation magnitudes, were quantified using sEMG root-mean-square (RMS) amplitudes for both the swing and stance phases of walking. Additionally, TA and GM co-activation (Co-A) indices were estimated. Two-way within-subjects repeated measures analyses of variance were used to evaluate the main effects of and interactions between the environment and walking speed. Additionally, paired sample t-tests were conducted as a secondary analysis to investigate differences between walking in water at 3.5 mph with and without added jet resistance. Main effects and interactions were observed across various stride kinematics and sEMG measures. Notably, TA sEMG RMS during the swing phase of walking gait performed at 2.5 mph was 15% greater in water than on land (p \u3c 0.001). This effect increased when walking gait was performed at 3.5 mph (94%; p \u3c 0.001) and when jet resistance was added to the 3.5 mph condition (52%; p \u3c 0.001). Furthermore, TA Co-A was increased during the stance phase of gait in water compared to on land (p \u3c 0.001), while GM Co-A was reduced during the swing phase (p \u3c 0.001). The findings of this study offer compelling evidence supporting the efficacy of aquatic treadmill walking as a potential treatment for individuals suffering from foot drop. However, further research is needed to evaluate whether a causal relationship exists between heightened TA activation observed during aquatic treadmill walking and improvements in voluntary dorsiflexion during gait
A Theory of Conditional Party Opposition
Get PDFThis paper takes a critical look at executive power in the United States. Recent years have shown an increase of executive power that many people including: scholars, media, and the public have become skeptical of. The new norm has been for the executive to bypass Congress in order to accomplish policy goals. Traditionally the separation of powers between the executive, legislative, and judicial branches has been the remedy to executive power. This thesis, however, argues that scholarship has largely ignored the role of political parties in government. Due to this, scholarship has misunderstood the role parties play in the separation of powers. The inter branch dynamics of “ambition counteracting ambition” became replaced by competition between political parties and loyalty to political office was replaced by loyalty to political party. In turn, this causes the structural separation of powers to fail when the government is unified.
I argue that parties can serve as a solution to expanding executive power by creating a new separation of powers based on party opposition. The Theory of Conditional Party Opposition argues that under necessary conditions, parties create a strong division in government that prohibits the executive from expanding their powers. I test this by examining six different presidencies on the issue of immigration. I find that under certain conditions of party opposition and when and issue itself is salient, parties become a new separation of powers and subsequently stop executive power