A physically-based surface-subsurface hydrologic model for clear creek watershed

Devastating flooding caused by heavy rains brought economic, social, and environmental impacts in many watersheds across the state of Iowa, USA. From 2011–2013, Iowa suffered eight Presidential Disaster Declarations, encompassing more than 70% of the state. The Clear Creek Watershed covers about 270 km2 with three headwater streams converging in Iowa Township. The watershed comprises 60% of agriculture in the form of corn-soybean rotations, 23% pasture and other grasslands, 10% forest, and 7% urban areas. In this study, a fully coupled distributed surfacesubsurface model, PIHM, was used to predict the hydrologic dynamic response of the Clear Creek Watershed over an annual period. The numerical model takes into account interception, through fall, infiltration, recharge, evapotranspiration, and infiltration, enabling discharge through the surface or subsurface into downstream water bodies or aquifer flows. Evapotranspiration is a function of water content in the soil and vegetation characteristics. The model considers the special distribution of land use and soil type. Overland flow is modeled using the diffusive wave approximation of 2D St. Venant equations. River routing is computed using 1D St. Venant equations. Water content in the soil is modeled using Richard’s equation. Water movement in the unsaturated zone is assumed to be vertical and the saturated groundwater region is modeled using the 2D Dupuit approximation. PIHM uses a finite-volume formulation for solving the system of coupled equations. The resulting ordinary differential equation system is solved with the solver SUNDIALS. The model was calibrated and validated with monitoring data. Model details, convergence challenges and model calibration in the Clear Creek Watershed will be presented and discussed.Publicado en: Mecánica Computacional vol. XXXV, no. 19Facultad de Ingenierí

Concurrent Sessions D: Downstream Migrant Surface Collectors-What Works and What Doesn\u27t Work - Evaluation of the Hydraulic Performance of a Free Surface Fish Bypass

In 2004, following consultations with the Federal Energy Regulatory Commission (FERC), the National Marine Fisheries Service (NOAA Fisheries) issued a document that included a Biological Opinion relevant to Priest Rapids Dam. A subsequent Biological Opinion, issued by NOAA Fisheries in 2008, was incorporated with the new FERC license. The 2008 Biological Opinion contained the same requirements as the 2004 Biological Opinion with respect to the survival objectives for downstream migrating juvenile fish. These objectives are 93% survival of juveniles and a juvenile and adult combined survival of 91% for the species listed for protection. Grant PUD is seeking to achieve at least 95% juvenile survival past the Priest Rapids Dam. In the past, Grant PUD spilled roughly 61% of the total river flow at Priest Rapids Dam during the spring fish passage season with the aim of achieving the survival target. A study was undertaken to identify a number of different fish passage alternatives for Priest Rapids Dam including: screening systems, collecting and bypassing fish through surface-oriented openings, and/or through modified turbine passages. The study suggested several options that had the potential to provide high fish passage efficiency and survival in a more efficient manner than high-volume spill programs. Further work concentrated on fish bypass through surface releases with prototype tests being conducted to assess the efficiency of fish collection as a function of bypass flow. Physical and numerical modeling were also undertaken to support the design of surface bypass alternatives. The final bypass design consisted in a modified spillway with elevated ogee crest in bays 20, 21 and 22.This paper presents results of the reduced scaled laboratory and CFD models developed to evaluate different bypass conceptual designs. Two numerical models were used; the commercial code Fluent and the open source code Open Foam. Details of model development and validation with data obtained in the reduced scale laboratory model will be presented. Possible cavitation, loads and impact on the tailrace with the selected bypass were computed and will be discussed

Concurrent Sessions D: Downstream Migrant Surface Collectors-What Works and What Doesn\u27t Work - Numerical Study for a Downstream Fish Collector at Cowlitz Falls Dam

Tacoma Power The Cowlitz River hosts numerous fish species including coho and Chinook salmon, steelhead and cutthroat trout. Hydroelectric dams in the Cowlitz River have significantly contributed to reduced natural salmonid populations. A surface collector built in 1996 at the Cowlitz Falls Dam aimed to help with fish restoration. Through relicensing of their hydroelectric projects on the Cowlitz Falls River, Tacoma Power had agreed to further improve fish passage at Cowlitz Falls Dam with a survival objective of 95%. A numerical study was undertaken to identify a number of different fish collection alternatives for Cowlitz Falls Dam. Forty seven simulations were completed to assess the effect of a bank-oriented surface collector on the forebay hydraulics. Different collector entrances, river flow rates and diffusion strategies were evaluated. The influence of a Behavioral Guidance Structure (BGS) and a Guide Net on the flow field were also investigated. This paper presents details of the model development and validation with field data. Forebay flow patterns for different collector designs will be presented and discussed

Concurrent Sessions D: Downstream Migrant Surface Collectors-What Works and What Doesn\u27t Work - Evaluation of Possible Fish Injury in a Spillway Retrofitted with Deflectors

Spill is considered one of the safest fish passage strategies. However, fish traveling over a spillway can be exposed to elevated stresses due to deceleration, strain rate, or pressure changes during their impact with the tailrace. Spillway deflectors, installed to minimize gas super saturation, deflect water horizontally instituting an additional momentum change that might further increase stress experience by passing fish. In addition, since deflectors completely change the flow pattern in the tailrace, possible fish migration delay is also of concern. In this study, a CFD model was developed to evaluate the effect of spillway deflectors on fish injury and tailrace retention time. Free surface simulations were performed to obtain the flow field in the spillway face and tailrace. A particle tracking technique was employed and the history of acceleration, strain rate and pressure changes were calculated. Numerical results were correlated with biological data found in the literature to obtain the probability of fish injury. This paper presents details of the numerical model and discusses results obtained in the Hells Canyon Dam spillway for four operational conditions, with and without deflectors. According to the model, the inclusion of deflectors in a 7Q10 flow increases the percent of fish with minor injuries from approximately 5% to 10%. The percent of major injury increases from 1% to 3%. Residence time of particles released from the spillway decreases with spillway flowrate. The residence time of particles from the powerhouse is affected by powerhouse entrainment into the spillway region. A small level of entrainment increases the residence time since particles are pulled to a deep low velocity region in the stilling basin. As the lateral flow increases, some particles from the powerhouse join the high velocity surface jets decreasing their residence time. According to the model, deflectors decrease significantly the residence time in the tailrace

Towards full predictions of temperature dynamics in McNary Dam forebay using OpenFOAM

Hydroelectric facilities impact water temperature; low velocities in a reservoir increase residence time and enhance heat exchange in surface layers. In this study, an unsteady three-dimensional model was developed to predict the temperature dynamics in the McNary Dam forebay. The model is based on the open-source code OpenFOAM. RANS equations with the Boussinesq approximation were used to solve the flow field. A realizable κ-ε model that accounts for the production of wind turbulence was developed. Solar radiation and convective heat transfer at the free surface were included. The result of the model was compared with the field data collected on August 18, 2004. Changes in diurnal stratification were adequately predicted by the model. Observed vertical and lateral temperature distributions were accurately captured. Results indicate that the model can be used as a numerical tool to assess structural and operational alternatives to reduce the forebay temperature

Session B8: An Integrative Strategy for Understanding Fish Behavior at Hydropower Forebays

Abstract: In the last decade, CFD with agent-based models has emerged as a useful methodology to design and evaluate fishway efficiency. However, despite using sophisticated modeling approaches, actual fishway performance varies widely. For certain species, expensive operational or structural changes of the bypasses are needed after biological information became available. Understanding the behavior of targeted fish species is therefore essential in locating and designing fishway entrances. This study presents a methodology that integrates biology and engineering to link fish behavior to hydrodynamics using an inverse problem approach. Chinook and steelhead swim paths were measured in the forebay of Rocky Reach and Priest Rapids dams. 3D CFD simulations of hydropower forebays were performed to model and fully understand the hydraulics of the system. Fish thrust magnitude and orientation, calculated by combining measured and modeled data at every measured fish location, were used to characterize fish swimming behavior at the forebay. Probabilistic distributions for fish thrust magnitude and direction were generated to capture the inherent stochasticity of animal behavior and will be presented and discussed

Spillway jet regime and total dissolved gas prediction with a multiphase flow model

<p>A numerical model, based on the open source code OpenFOAM, was developed to predict jet regimes and total dissolved gas downstream of spillways. The model utilizes the volume of fluid method to track the interface between air and water. A detached eddy simulation model is used for turbulence closure. Transport and dissolution of bubbles are predicted using an Eulerian approach. A bubble number density equation was implemented to predict bubble size changes caused by dissolution and compression. Total dissolved gas was computed using a transport equation that includes the mass transfer between bubbles and water. The model simultaneously captured spillway jet regimes and distribution of total dissolved gas in a spillway sectional model of McNary Dam. Model parameters, gas volume fraction and bubble size at the entrainment region, were calibrated to match total dissolved gas measured in the field under different dam operations.</p

Assessing Zebra Mussels’ Impact on Fishway Efficiency: McNary Lock and Dam Case Study

The Columbia River Basin faces a threat from the potential invasion of zebra mussels (Dreissena polymorpha), notorious for their ability to attach to various substrates, including concrete, which is common in fishway construction. Extensive mussel colonization within fishways may affect fish passage by altering flow patterns or creating physical barriers, leading to increased travel times, or potentially preventing passage altogether. Many factors affect mussel habitat suitability including vectors of dispersal, water parameters, and various hydrodynamic quantities, such as water depth, velocity, and turbulence. The objective of this study is to assess the potential for zebra mussels to attach to fishway surfaces and form colonies in the McNary Lock and Dam Oregon-shore fishway and evaluate the potential impact of this infestation on the fishway’s efficiency. A computational fluid dynamics (CFD) model of the McNary Oregon-shore fishway was developed using the open-source code OpenFOAM, with the two-phase solver interFoam. Mesh quality is critical to obtain a reliable solution, so the numerical mesh was refined near the free surface and all solid surfaces to properly capture the complex flow patterns and free surface location. The simulation results for the 6-year average flow rate showed good agreement with the measured water column depth over each weir. Regions susceptible to mussel infestation were identified, and an analysis was performed to determine the mussel’s preference to colonize as a function of the depth-averaged velocity, water depth, and wall shear stress. Habitat suitability criteria were applied to the output of the hydraulic variables from the CFD solution and provided insight into the potential impact on the fishway efficiency. Details on the mesh construction, model setup, and numerical results are presented and discussed