Effects Of 2D And 1D Modeling On Mapping Aquatic Habitat Quality

The distribution of aquatic habitat at the organism scale, i.e. 1 by 1m or smaller is typically predicted from local physical characteristics of stream flow, bed, banks and sediment characteristics and a set of biological preference curves. The flow properties are typically predicted with numerical modeling whereas stream bed and bank characteristics defined from interpolated DEM generated by topographical surveys and field observations. Information on the effects of flow properties and streambed morphology due to numerical modeling dimensionality on aquatic habitat modeling is limited. Two-dimensional (2D) modeling is becoming the most popular method to map micro-habitat but its application is still limited to short reaches and at steady state conditions. One-dimensional (1D) modeling here used in their extended version as pseudo 2D are still applied in aquatic habitat especially where only cross-sectional information is available and the reach domain is several km long. Pseudo 2D modeling predicts velocities along the cross-section from uniform flow relationships and local depths from water surface elevation and local DEM of the streambed. Values between cross-sections are then interpolated. The advantage of pseudo 2D modeling over the full 2D is that it is very efficient and can run at the stream network scale under unsteady conditions. Thus there is still some usefulness in comparing the prediction of these two approaches. We hypothesize that pseudo 2D modeling with very fine spaced cross-sections supported by detailed bathymetry may predict micro-habitat distributions similar of those of 2D modeling. Here, we compared local micro-habitat distributions predicted with a pseudo 2D and fully 2D numerical models of a pool-riffle complex and simple reach. Our results showed that difference in WUA derived from the pseudo 2D and fully 2D modeling is small but the difference in spatial distribution of cell suitability can be considerable under a strict cell-by-cell comparison

Does Hyporheic Intensity Explain Spawning Site Selection?

Pool, riffle and runs are streambed features and important habitats for aquatic species. It is well-known that salmonid species utilize these streambed features as spawning site. Pools are characterized by deep water depth, low velocity and gentle water surface slope, whereas riffles are characterized by shallow depth, high velocity and steep slope. Past studies have used hydrodynamic model simulated hydraulic characteristics such as depth, velocity and shear stress to delineate these features. However, the magnitude of these hydraulic characteristics may vary significantly with the discharge and longitudinal slope of the stream. Additionally, these indexes still do not entirely explain the selection of spawning site. Here we hypothesize that hyporheic flow, which is an advective mechanism, and brings oxygen-rich surface water into the sediment, may help to understand the selection of Chinook salmon spawning sites. The curvature of the water surface has been suggested as a main driver for hyporehic exchange in gravel bed rivers with pool-riffle morphology. We studied the correlation between magnitude of water surface curvatures and locations of Chinook salmon redds in Bear Valley Creek, located in the central Idaho, USA. We used two-dimensional (2D) hydrodynamic model to simulate water surface elevations for low and bankfull discharges. Our results show that redd locations are highly correlated with areas of high potential hyporheic flow as indicated by the water surface curvature

A Cascade Of Models To Guide Reservoir Operations: Application On The Deadwood River System, Idaho, USA

Adaptive management strategies are increasingly being used by resource managers to optimize complex water delivery systems at the scale of entire watersheds. A variety of models have been proposed to evaluate systems in a piecemeal approach that often times operate at different spatial and temporal scales and prove difficult to integrate with associated field data. In the Deadwood River system of Central Idaho, a series of cascading models was utilized to examine potential impacts of reservoir operations on endangered resident bull trout. Results from integrating limnologic, temperature, nutrient, hyporheic, and hydraulic models show that reservoir operations must remain dynamic depending upon the hydrologic conditions (wet vs. dry) present during any given year. Assimilating models that operate at various levels within a watershed will become increasingly important as climate change affects the regional hydrology and water resources operations must adjust to meet current and future demands

Quantification of reservoir operation-based losses to floodplain physical processes and impact on the floodplain vegetation at the Kootenai River, USA /by Rohan Man Benjankar.

The Kootenai River ecosystem has been subject to many human influences, which peaked with the construction and subsequent operation of Libby Dam. The major consequences of these human alterations are modified fluvial processes, altered hydroperiod and nutrient exchange on the floodplain, limited regeneration of riparian forests, and elimination of habitats essential for native fish. The main goal of the current study was to develop an integrated hydrodynamic and vegetation model that subsequently can be used as a tool to quantify operational losses due to Libby Dam and for assessing different restoration strategies.;The integrated hydrodynamic (HD) models were used to simulate historic, pre-dam, and contemporary scenarios for a study area of approximately 200 km 2 of floodplain. A new vegetation model """"CASiMiR-vegetation"""" was developed to simulate the spatial dynamics of vegetation succession and changes between different scenarios. The vegetation dynamics are based on existing theory but adapted to observed field data on the Kootenai River. The model simulates the changing vegetation patterns on an annual basis from a specific initial condition based on spatially distributed physical parameters. The model was calibrated and the robustness of the model was analyzed.;In this pilot study, the effects of the dam operation were for the first time numerically quantified and differentiated from other causes. The HD model results indicated that the active floodplain is almost extinct and different physical processes (inundation extent, water depth, velocity, shear stress) are reduced extensively as compared to the historic condition prior to the dam construction. The vegetation model demonstrated that the colonization phase is drastically reduced, and this has led to the domination of mature phase vegetation in the years since the dam went into place.;In a second stage the effectiveness of breaching levees as a means of restoring some floodplain functions and natural vegetation was assessed. The simulations showed that the floodplain would reconnect with the main channel in a historic 1.1 year flood. The same level of connectivity would not occur in the existing no-breach condition even with a 25 year flood. The vegetation model was then used to simulate that in the area influenced by the levee breach a natural floodplain vegetation pattern could be restored.Thesis (Ph. D., Civil Engineering)--University of Idaho, August 2009

Integrated Hydrological Modeling to Analyze the Effects of Precipitation on Surface Water and Groundwater Hydrologic Processes in a Small Watershed

The main objective of this study is to evaluate the performance of the integrated hydrological model, MIKE SHE in a small watershed to analyze the effect of two different precipitation sources on model outputs (groundwater elevation and surface water flows). The model was calibrated and validated with observed groundwater elevations and surface water flows measured at the United States Geological Survey (USGS) gage stations in the basin. The model calibration performance for surface water flows (R = 0.80, MAE= 0.20 m3/s, BIAS = −0.14 m3/s, NSE = 0.59) and groundwater elevations (R = 0.74, MAE = 0.45 m, BIAS = 0.08 m, NSE = 0.35) showed that the model was able to predict hydrological processes based on forcing variables in a small watershed. The analysis did not show the model with precipitation at the nearer (NOAA-Edwardsville) gauge station has better performance than the farther gauge station (NOAA-St. Louis). The quantitative analyses for the most sensitive model output variable suggested that precipitation uncertainties had noticeable impacts on surface water flows (0.81% to 11.19%), than groundwater elevations (0.06% to 0.07%), with an average of 6.71% and 0.66%, respectively. Our results showed noticeable differences in simulated surface water flows in spring (12.9%) and winter (36%) seasons compared to summer (11.4%) and fall (4.6%) as a result of difference (6% to 18%) in precipitation, which indicated that uncertainties in precipitation impact simulated surface water flows in a small watershed vary with different seasons. Our analyses have shown that precipitation affects the simulated hydrological processes and care should be taken while selecting input datasets (i.e., precipitation) for better hydrological model performance, specifically for surface water flows

Analyses of Spatial and Temporal Variations of Salt Concentration in Waterbodies Based on High Resolution Measurements Using Sensors

Studies have shown that salt concentrations are increasing in waterbodies such as lakes, rivers, wetlands, and streams in areas where deicers are commonly applied for winter road maintenance, resulting in degraded water quality. As the salt concentration varies spatially and temporally based on environmental and hydrological characteristics, we monitored high resolution (15 min) salt concentrations for a relatively long period (winter and spring season) at different sites (i.e., stream, urban-stream, roadside drain, and parking-lot drain) using multiple electric conductivity-based sensors. The salt concentrations were significantly different from each other considering individual sensors and different sites in both winter and spring seasons, which support past research results that concentration varies spatially. Parking-lot (1136 ± 674 ppm) and Roadside (701 ± 263 ppm) drain measured significantly higher concentration than for Stream (260 ± 60 ppm) and Urban-stream (562 ± 266 ppm) in the winter season. Similar trends were observed for the spring season, however, the mean concentrations were lower in the spring. Furthermore, salt concentrations were significantly higher during the winter (242 ± 47 ppm to 1695 ± 629 ppm) than for the spring (140 ± 23 ppm to 863 ± 440 ppm) season considering different sites, which have been attributed to the winter snow maintenance practice using deicers in past studies. All sites exceed the United States Environmental Protection Agency (USEPA) threshold (salt concentration higher than 230 mg/L) for chronic exposure level for 59% to 94% and 10% to 83% of days in winter and spring seasons, respectively. The study has highlighted the usefulness and advantages of high resolution (spatially and temporally) salt concentration measurement using sensor technology. Furthermore, the salt concentration in waterbodies can vary spatially and temporally within a small spatial scale, which may be important information for managing water quality locally. The high resolution measurements (i.e., 15 min) were helpful to capture the highest potential salt concentrations in the waterbody. Therefore, the sensor technology can help to measure high resolution salt concentrations, which can be used to quantify impacts of high salt concentrations, e.g., application of deicer for winter road maintenance on aquatic systems based on the criteria developed by USEPA

Some like it slow: a bioenergetic evaluation of habitat quality for juvenile Chinook salmon in the Lemhi River, Idaho

Management and conservation of freshwater habitat requires fine spatial resolution and watershed-scale and life-stage-specific methods due to complex linkages among land, climate, water uses, and aquatic organism necessities. In this study, we present a valley-scale microhabitat resolution, process-based bioenergetics approach that combines high-resolution topobathymetric LiDAR survey with two-dimensional hydrodynamic and bioenergetics modeling. We applied the model to investigate the role of lateral habitat, stream morphological complexity, water use, and temperature regimes on aquatic habitat quality distribution of juvenile Chinook salmon (Oncorhynchus tshawytscha) within the Lemhi River (eastern Idaho, USA). Modeling results showed two key aspects: (i) a reduction in diverted flows is not sufficient to improve habitat quality potentially because of a legacy of morphological simplification (directly due to straightening and wood removal and indirectly due to low in-channel flows) and (ii) morphological complexity and connectivity with side channels and margin areas, which are key and vital elements to support suitable habitats that meet or exceed energetic needs to sustain or promote growth of individuals and populations.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author