Water temperature directly affects biological and chemical processes of fresh water ecosystems. Elevated instream temperatures are commonplace in the Virgin River of southwestern Utah during summer due to a hot desert climate and high water demands that result in low stream flows. This is of concern since the Virgin River is home to two endangered species, the Virgin River Chub (Gila seminuda) and Woundfin (Plagopterus argentissimus). Efforts to model instream temperatures within the Virgin River have been undertaken to help mitigate elevated instream temperatures including the development of a two-zone temperature and solute (TZTS) model. This model was developed to approximate the dominant processes that influence instream temperatures and used both temperature and solute data in parameter estimation. Past model applications highlighted two concerns: (1) how to confidently estimate the high number of parameters and (2) whether Rhodamine WT (RhWT) could be used as a conservative solute tracer within the Virgin River. To begin addressing these issues, spatially representative data were collected to facilitate the physical estimation of two previously calibrated parameters: total average channel width (BTOT) and the fraction of channel width associated with dead zones (β). Methods for analyzing multispectral and thermal infrared imagery were developed to provide estimates of these parameters at different resolutions. Three different TZTS model calibration cases were then evaluated to determine how decreasing the calibrated parameters and increasing the resolution and frequency at which these parameters are estimated improved model predictions and/or decreased parameter uncertainty. While temperature predictions did not change significantly in each of the calibrations, parameter uncertainty was reduced. The concern regarding the use of RhWT resulted in a series of studies to quantify the potential losses of RhWT within this system. A batch sorption study resulted in distribution coefficient values lower than those found in literature. A photodegradation study suggested possible photolysis; however, a dual tracer study conducted within the Virgin River comparing Br- (conservative tracer) with RhWT confirmed that there was insignificant RhWT loss within this system.

Previous studies have shown that ice cover has many positive effects on brown trout (Salmo trutta), including protection from endothermic predators. I tested whether it is the cover provided by the ice itself or the reduction in light that causes behavioral changes in juvenile brown trout. To distinguish between these two effects, behavioural observations were made with and without ice at the same light intensity (500 lux). An additional ice-free, high light (3000 lux) treatment was included to be able to measure brown trout’s response to light reduction. A mink model was used to simulate predation risk to be able to measure the fish’s anti-predator response under these three conditions. I found a significant treatment effect on body and eye coloruration. For eye colouration, I found that fish under ice had a paler eye colouration than fish that experienced high light, which in turn were paler than fish subjected to low light. For body colouration, fish under ice had paler body colouration than fish from the two ice-free treatments, which did not differ from each other. There was no effect of treatment on ventilation rate, time to initiate foraging, time to initiate activity or swimming activity, although both foraging and activity were lowest and swimming activity highest under ice. The changes in body and eye colouration indicate that trout are less stressed under ice, presumably because they perceive ice as a barrier against terrestrial predators. These results suggest that the ongoing climate change, which is leading to shorter periods of sustained ice cover, may have negative consequences for trout populations in the near future. / Tidigare studier har visat att yttäckande is medför många positiva effekter för öring (Salmo trutta), bland annat genom att utgöra skydd mot endoterma predatorer. Jag undersökte om det är den yttäckande isen i sig som medför beteendeförändringar hos juvenila öringar eller om det är det reducerade ljusinsläppet som isen medför. För att separera dessa två effekter gjordes beteendeobservationer med och utan ytis under samma ljusintensitet (500 lux). En ytterligare isfri behandling gjordes, med starkt ljus (3000 lux), för att kunna mäta öringens respons på ljusreduceringen. En uppstoppad mink användes för att simulera predationsrisken, detta för att kunna mäta fiskarnas antipredationsresponser under dessa tre förhållanden. Jag fann en signifikant behandlingseffekt på kropps- och ögonfärg. Under is hade fiskarna en blekare ögonfärg än när de befann sig under starkt ljus, som i sin tur resulterade i blekare färg än när fiskarna utsattes för svagt ljus. När det gäller kroppsfärg uppvisade fiskarna en blekare kroppsfärg under is än när de utsattes för de två isfria behandlingarna, vilka inte skiljde sig från varandra. Behandlingarna gav ingen effekt på gälslagsfrekvens, tid till att initiera födosök, tid till att initiera aktivitet eller simaktivitet, dock var tid till både födosök och aktivitet lägst och simaktivitet störst under is. Förändringarna i kropps- och ögonfärg indikerar att öring är mindre stressad under is, vilket eventuellt kan bero på att de uppfattar isen som en barriär mot terrestra predatorer. Dessa resultat tyder på att den pågående klimatförändringen, som innebär kortare perioder av ihållande yttäckande is, kan medföra negativa konsekvenser för öringpopulationer inom den närmaste framtiden.

Humans impact rivers in many ways that modify ecological processes yielding ecosystem services. In order to mitigate anthropogenic impacts, scientists are challenged to understand interactions among physicochemical factors affecting large river food webs. An understanding of socioeconomic factors also is critical for ecosystem management. In this dissertation, I explore spatiotemporal patterns in floodplain river food webs and political barriers to management of environmental flows, an important factor influencing river ecology. In Chapter II, I reviewed the scientific literature to test conceptual models of river food webs and predictions of environmental factors that might produce variation in basal production sources supporting consumer biomass. My review indicates that algae are the predominant production source for large rivers worldwide, but consumers assimilate C3 plants in rivers 1) with high sediment loads and low transparency during high flow pulses, 2) with high dissolved organic matter concentrations, and 3) following periods of high discharge or leaf litter fall that increase the amount of terrestrial material in the particulate organic matter pool. In Chapter III, I descrobe field research conducted to examine relationships among hydrology, nutrient concentrations, turbidity, and algal primary production and biomass in the littoral zone of five rivers in Texas, Peru, and Venezuela differing in physicochemical conditions. I used stable isotope signatures to estimate contributions of algal-versus terrestrial-based production sources to consumers during different hydrologic periods. My research indicates that during flow pulses in floodplain rivers, a decrease in algal biomass and productivity, combined with increased inputs of terrestrial organic matter, can result in increased terrestrial support of metazoan consumers in the aquatic food web. In 2007, Texas Senate Bill 3 directed that environmental flow recommendations be developed for river basins. Despite emphasis on use of the "best available science" to develop environmental flow regimes and "stakeholder involvement" to address needs of all water users, for the first two basins to complete the SB3 process, final environmental flow rules did not mimic a natural flow regime. In Chapter IV, I reviewed this process, concluding that incentives for river authorities to increase compromise with diverse stakeholders should result in more sustainable management of freshwater.

No description available.

The Logan River was used as a study site to assess the capabilities of two-dimensional depth-averaged hydraulic modeling in the x-y plane of a natural river for use with instream flow studies. Data were collected to spatially represent the study reach with depth, velocity, northing, easting, elevation, and substrate values using a total station and electronic velocity meter. Computational finite element meshes were generated using four different density levels of geometry data to examine the relationship between field data density and computational mesh on geometry errors. Geometry errors were found to be related to smoothing effects, which removed complex channel geometries while overall mesh geometry errors were related to data density in homogeneous versus heterogeneous channel conditions. Results indicate that required field data can be optimized with lower data densities in homogenous sections of the river channel. Of the two hydraulic models examined, the U.S. Army Corps of Engineers RMA2 model could not be adequately calibrated given the high slope within the study reach and therefore all subsequent evaluations were made utilizing the CDG2D model. CDG2D model performance was best in the lower gradient sections of the test section at both calibrated and simulated flows with increasing errors for water surface and associated depth and velocity errors as channel gradient increased. These results suggest that additional research is needed to define limiting gradients under which application of this class of hydrodynamic model can be expected for practical instream flow assessments.

Instream structures are used to reinforce channel margins, redirect flows, and create habitat, but there is little consensus about their design or whether they function as intended. In this study, 536 instream structures in the state of Maryland were assessed to determine the effect of structure-, project-, and watershed-scale factors on performance. Structures were assessed using a 19 point scoring system based on structural stability, sediment transport, and overall function. Structure-scale variables related to the construction, geometry, and placement, and differed for six structure families: bank protection (BP), full and partial span vanes (FSV), constructed riffles (RF), regenerative stream conveyances, and step pools. Project- and watershed-scale variables related to flow, erosion resistance, and design approach. Relationships between structure scores and explanatory variables were evaluated using regression analysis. Structure performance was strongly influenced by the individual project, suggesting that design quality, construction, and maintenance are as important as specific design features. Structure durability decreased if there was additional urban development following construction. Results also indicated that restoration activities have a "protective effect" on nearby structures. For rock BP, imbricated rock walls performed better than stone toe, due to increased structure height and boulder size. Rock FSVs that were keyed into the bank at angles between 35° and 90° were more durable, while RFs performed best when constructed using downstream grade control and increased substrate depth. The results of this study provide insight into design and project features that contribute to structure success. / Master of Science / Stream restoration aims to rehabilitate streams that have been impacted by humans, and log or rock structures in the channel are utilized to protect the bed and banks, redirect water away from the banks, and create habitat for aquatic organisms. However, there are few design standards for these structures. In this study, 536 instream structures in the state of Maryland were assessed to determine the effect of design and site characteristics on performance. Structures were scored for performance based on structural stability, sedimentation, erosion, and function. Design characteristics related to structure construction and placement, while site conditions related to the project and watershed characteristics. Statistical analyses were used to determine the relationship between structure performance and design and site characteristics. Structure performance was strongly influenced by the restoration project, indicating that design quality, construction, and maintenance are as important as specific design features. Structure durability decreased if there was additional urban development in the watershed following construction. Results also indicated that when structures were used in series, there was a "protective effect" on other nearby structures. Rock walls performed better as height increased, while rock weirs that were constructed into the streambank between 35° and 90° were more durable. These results provide insight into design and project features that contribute to structure success.

Increasing demand and competition for freshwater is threatening instream uses including ecosystem services and aquatic habitat. A standard method of evaluating impacts of alternative water management scenarios on instream habitat is Instream Flow Incremental Methodology (IFIM). The primary outputs of IFIM studies are: 1) habitat rating curves that relate habitat availability to streamflow for every species, lifestage, or recreational use modelled; and 2) habitat time series under alternative water management scenarios. We compiled 428 habitat rating curves from previous IFIM studies across 11 rivers in Virginia and tested the ability to reduce this number based on similarities in flow preferences and responses to flow alteration. Individual site-species combinations were reduced from 428 objects to four groups with similar seasonal habitat availability patterns using a hierarchical, agglomerative cluster analysis. A seasonal habitat availability (SHA) ratio was proposed as a future indicator of seasonal flow preferences. Four parameters calculated from the magnitude and shape of habitat rating curves were proposed as response metrics that indicate how a lifestage responds to flow alteration. Univariate and multivariate analyses of variance and post-hoc tests identified significantly different means for the SHA ratio, QP (F=63.2, p<2e-16) and SK (F=65.6, p<2e-16). A reduced number of instream flow users can simplify the incorporation of aquatic habitat assessment in statewide water resources management. / Master of Science

This study constructed habitat suitability criteria for fishes of the South Fork of the Shenandoah River, in Virginia. The criteria will be used in an IFIM study to produce estimates of the discharge required by fishes in the South Fork. Chi-square tests were used to evaluate whether criteria described habitat use to a statistically significant degree. Secondly, chi-square tests were used to test transferability. The criteria described the habitat use of seven taxa commonly found in the South Fork to a statistically significant degree. Habitat criteria for two taxa did not describe their habitat use to a statistically significant degree. One set of criteria from the North Fork of the Shenandoah transferred to the fish observed in the South Fork. Secondly, this paper examined observer effects of underwater observation. It was of interest to explore how observer effects influenced habitat suitability criteria.

Few field studies have assessed the temporal and spatial dynamics of wood in small streams (bankfull widths < 5 m) flowing through forest ecosystems dominated by stand replacing wildfires. Comparisons of instream wood loads associated with clearcut harvesting, wildfire, and undisturbed, old forests are also scarce. The two main objectives of this research were: (1) to document the temporal and spatial variability of wood and its geomorphic role in relation to stand development stage; and (2) to compare wood loads and its geomorphic role in relation to streamside clearcut harvesting, wildfires and older, undisturbed forest stands. This research focused on 38 small streams with gradients less than 14% situated in the plateau regions of south-central British Columbia, Canada. A distinct temporal trend in wood loading was observed, with elevated volumes present 30-50 years subsequent to the wildfire disturbances following a “reverse J-shaped” trend in relation to time since the last major wildfire disturbance. The number of wood pieces was highly variable and few of the wood characteristics exhibited a significant trend in relation to time since the last major wildfire disturbance. Except at the smallest spatial scale (<3 m segments longitudinally along the stream) the spatial distribution of wood followed a random pattern with no trend, indicating that wood loads are related to local wood recruitment processes associated with episodic or chronic tree mortality and low wood transport. Instream wood volumes were three times higher in streams recently (30 – 50 years ago) disturbed by wildfire as compared to the older riparian forest stands, confirming that wildfire disturbance is an important mechanism to recruit wood into streams. No significant differences in wood loads were identified between the streamside clearcut streams and the wildfire-disturbed or older, undisturbed streams. The lack of reductions in wood loads are likely related to the low transport capacity of our study streams, retention of non-merchantable trees and recruitment of slash from harvesting. A lack of morphologic variability was observed in relation to the disturbances indicating that the streams included in this study are relatively robust and unresponsive to wildfire or streamside clearcut harvesting disturbances.

Few field studies have assessed the temporal and spatial dynamics of wood in small streams (bankfull widths < 5 m) flowing through forest ecosystems dominated by stand replacing wildfires. Comparisons of instream wood loads associated with clearcut harvesting, wildfire, and undisturbed, old forests are also scarce. The two main objectives of this research were: (1) to document the temporal and spatial variability of wood and its geomorphic role in relation to stand development stage; and (2) to compare wood loads and its geomorphic role in relation to streamside clearcut harvesting, wildfires and older, undisturbed forest stands. This research focused on 38 small streams with gradients less than 14% situated in the plateau regions of south-central British Columbia, Canada. A distinct temporal trend in wood loading was observed, with elevated volumes present 30-50 years subsequent to the wildfire disturbances following a “reverse J-shaped” trend in relation to time since the last major wildfire disturbance. The number of wood pieces was highly variable and few of the wood characteristics exhibited a significant trend in relation to time since the last major wildfire disturbance. Except at the smallest spatial scale (<3 m segments longitudinally along the stream) the spatial distribution of wood followed a random pattern with no trend, indicating that wood loads are related to local wood recruitment processes associated with episodic or chronic tree mortality and low wood transport. Instream wood volumes were three times higher in streams recently (30 – 50 years ago) disturbed by wildfire as compared to the older riparian forest stands, confirming that wildfire disturbance is an important mechanism to recruit wood into streams. No significant differences in wood loads were identified between the streamside clearcut streams and the wildfire-disturbed or older, undisturbed streams. The lack of reductions in wood loads are likely related to the low transport capacity of our study streams, retention of non-merchantable trees and recruitment of slash from harvesting. A lack of morphologic variability was observed in relation to the disturbances indicating that the streams included in this study are relatively robust and unresponsive to wildfire or streamside clearcut harvesting disturbances.