A physical assessment of the Provo River Restoration Project was undertaken in order to determine how alterations to the channel were designed, the nature of as-built channel morphology, and the performance of the reconfigured channel in terms of achieving frequent (2-year recurrence) bankfull discharge and increasing transient storage. Measures of channelized and reconfigured channel morphology were obtained using total station survey, digital aerial photography, and pebble counts. Results of geomorphic analysis were compared with similar measurements made by a regional consulting company, and stream channel design data, in order to determine that intended mitigation included reducing channel capacity, increasing sinuosity, decreasing pool spacing, and decreasing the size of bed material. Reconfiguration of the channel resulted in somewhat enlarged cross-sections with reduced mean velocities, increased sinuosity, decreased pool spacing, and decreased bed substrate size. One-dimensional hydraulic modeling suggests that alterations to channel morphology have increased the bankfull channel capacity in most reaches. Modeling results illustrate the fact that the stage of the 2-year recurrence flood is below bankfull at most cross-sections. This result does not follow the intentions of channel design. However, we have observed floodplain inundation in most years since reconfiguration. The occurrence floodplain inundation is being facilitated by overbank flow at a few point locations illustrating the strengths of incorporating variability into design. Known geomorphic controls on transient storage were reconfigured in manner to potentially increase in-channel and hyporheic components of transient storage. Stream tracer tests were utilized in order to determine the degree to which these alterations affected transient storage. Numerical analysis of stream tracer tests suggests that while the relative area of transient storage increased, average residence time of water in storage, and the mass transfer rate of solute between storage and the stream did not change. This suggests that an extensive hyporheic zone may not have been established. Correlations between hydrologic and geomorphic parameters indicate that in-stream storage may have been increased, and quick-exchange hyporheic flowpaths may have been created. (295 pages)

<p>Ecohydrological models are extensively used to evaluate land use, land management and climate change impacts on hydrology and in-stream water quality conditions. The scale at which these models operate influences the complexity of processes incorporated within the models. For instance, a large scale hydrological model such as Soil and Water Assessment Tool (SWAT) that runs on a daily scale may ignore the sub-daily scale in-stream processes. The key processes affecting in-stream solute transport such as advection, dispersion and transient storage (dead zone) exchange can have considerable effect on the predicted stream solute concentrations, especially for localized studies. To represent realistic field conditions, it is therefore required to modify the in-stream water quality algorithms of SWAT by including these additional processes. Existing reach-scale solute transport models like OTIS (One-dimensional Transport with Inflow and Storage) considers these processes but excludes the actual biochemical reactions occurring in the stream and models nutrient uptake using an empirical first-order decay equation. Alternatively, comprehensive stream water quality models like QUAL2E (The Enhanced Stream Water Quality Model) incorporates actual biochemical reactions but neglects the transient storage exchange component which is crucial is predicting the peak and timing of solute concentrations. In this study, these two popular models (OTIS and QUAL2E) are merged to integrate all essential solute transport processes into a single in-stream water quality model known as ‘Enhanced OTIS model’. A generalized model with an improved graphical user interface was developed on MATLAB platform that performed reasonably well for both experimental data and previously published data (R²=0.76). To incorporate this model into large-scale hydrological models, it was necessary to find an alternative to estimate transient storage parameters, which are otherwise derived through calibration using experimental tracer tests. Through a meta-analysis approach, simple regression models were therefore developed for dispersion coefficient (D), storage zone area (A_s) and storage exchange coefficient (α) by relating them to easily obtainable hydraulic characteristics such as discharge, velocity, flow width and flow depth. For experimental data from two study sites, breakthrough curves and storage potential of conservative tracers were predicted with good accuracy (R²>0.5) by using the new regression equations. These equations were hence recommended as a tool for obtaining preliminary and approximate estimates of D, A_s and α when reach-specific calibration is unfeasible. </p> <p> </p> <p>The existing water quality module in SWAT was replaced with the newly developed ‘Enhanced OTIS model’ along with the regression equations for storage parameters. Water quality predictions using the modified SWAT model (Mir-SWAT) for a study catchment in Germany showed that the improvements in process representation yields better results for dissolved oxygen (DO), phosphate and Chlorophyll-a. While the existing model simulated extreme low values of DO, Mir-SWAT improved these values with a 0.11 increase in R² value between modeled and measured values. No major improvement was observed for nitrate loads but modeled phosphate peak loads were reduced to be much closer to measured values with Mir-SWAT model. A qualitative analysis on Chl-<i>a</i> concentrations also indicated that average and maximum monthly Chl-<i>a</i> values were better predicted with Mir-SWAT when compared to SWAT model, especially for winter months. The newly developed in-stream water quality model is expected to act as a stand alone model or coupled with larger models to improve the representation of solute transport processes and nutrient uptake in these models. The improvements made to SWAT model will increase the model confidence and widen its extent of applicability to short-term and localized studies that require understanding of fine-scale solute transport dynamics. </p>

Die Verschmutzung von Süßgewässern mit organischen Mikroschadstoffen ist ein Problem, das sich weltweit zunehmend verschärft. Die vorliegende Doktorarbeit soll zu einem besseren Verständnis des Verhaltens einzelner Mikroschadstoffe und deren Transformationsprodukten in Flüssen beitragen, sowie die Rolle relevanter Einflussfaktoren untersuchen. Verhalten verschiedener Stoffe wurde im Oberflächenwasser eines urbanen Flusses analysiert. Es zeigte sich, dass die Sonneneinstrahlung für einige Verbindungen der wichtigste Einflussfaktor ist, während andere eher biologisch abgebaut wurden. Die Mahd von Makrophyten hatte ebenfalls stoffspezifische Folgen auf den Abbau. Um langfristige Variabilität von Stofftransport besser zu verstehen wurde eine neue Methode zur Schätzung des Stofftransports anhand von Schwankungen der elektrischen Leitfähigkeit getestet. Einige Stofftransportparameter änderten sich über die Jahreszeiten hinweg und transiente Speicherung unterschied sich zwischen den Flussabschnitten. Um im Besonderen den Einfluss von mikrobieller Diversität und von hyporheischem Austausch zu bewerten, wurde ein Meskosmenexperiment mit 20 rezirkulierenden Fließrinnen entwickelt. Es konnte festgestellt werden, dass vor allem mikrobielle Diversität einen starken Einfluss hat. Der neue Versuchsaufbau kann zukünftig für die Untersuchung weiterer Variablen Verwendung finden. Schließlich wurden Mikroschadstoffe und Transformationsprodukte in der hyporheischen Zone der Fließrinnen analysiert. Das Verhalten war sowohl stoffspezifisch als auch fließwegspezifisch. Die Ergebnisse unterstreichen die Bedeutung des oberflächennahen, hyporheischen Austauschs auf den Stoffabbau. Im Allgemeinen konnte die hohe Variabilität des Abbaus von Mikroschadstoffen mit besonderer Relevanz der hyporheischen Zone und der mikrobiellen Diversität nachgewiesen werden. Diese Faktoren sollten in zukünftigen Forschungsvorhaben besonders berücksichtigt werden. / Contamination of freshwaters with organic micropollutants is a worldwide emerging problem. The present thesis aims to contribute to a better understanding of the variability of the behaviour of individual micropollutants, the formation of transformation products in rivers and the specific role of relevant influencing factors. The behaviour of several substances was investigated in the surface water of an urban river by accounting for spatial and temporal dynamics. Solar radiation was identified to be the major driver for some compounds, while others were more susceptible to biodegradation. The response to macrophyte removal was also compound-specific. To better understand long-term variability of solute transport on a reach-scale a new method to estimate solute transport by use of electrical conductivity fluctuations was proposed and tested. Some solute transport metrics changed over the seasons and transient storage differed between river sections. To specifically assess the influence of microbial diversity and hyporheic exchange, a mesocosm experiment with 20 recirculating flumes was developed. It was found that microbial diversity in particular had a strong impact and the novel setup was suggested to be a useful method to test other variables in the future. Finally, the behaviour of micropollutants and transformation products in the hyporheic zone of the flumes was investigated on a centimeter-scale. The behaviour was found to be compound-specific as well as flowpath-specific. But several compounds were degraded most on the shortest, most oxic flowpath. The findings highlight the importance of shallow, small-scale hyporheic exchange for turnover of micropollutants. Generally, the high variability of micropollutant degradation depending on relevant influencing factors, specifically hyporheic exchange and microbial diversity, has been demonstrated. These factors are of great importance and need to be addressed and considered in future research.