Sanadhya, Pranay, authorArabi, Mazdak, advisorFassnacht, Steven R., committee memberSalas, Jose D., committee member2022-04-132022-04-132010https://hdl.handle.net/10217/234669Covers not scanned.Print version deaccessioned 2022.Distributed watershed models are increasingly used for management of scarce water resources around the world. However, the utility of these models in ungaged or poorly gaged basins is a major issue in the field of hydrological sciences. Performance of watershed models cannot be evaluated for regions with paucity or unavailability of observed streamflow records; thus, a challenge is posed for the effective management of water resources in a region. Regionalization methods that relate watershed characteristics to model parameters are considered as a potential approach to overcome this challenge. The aim of this research is to analyze different regionalization methods and categorize the ones performing efficiently for the regionalization of the Soil and water assessment tool (SWAT) in five major river basins of Colorado. These River basins include: the Arkansas River basin at Canon City, the Cache la Poudre River basin at mouth of canyon, the Gunnison River basin above Blue Mesa dam, the San Juan River basin near Archuleta, and the Yampa River basin near Maybell. SWAT models were prepared for the study watersheds and their performance was evaluated corresponding to naturalized monthly streamflow available for these watersheds. Initially, these prepared models were reconciled with a global sensitivity analysis method known as Fourier Amplitude Sensitivity Test (FAST) to identify sensitive model parameters and the corresponding hydrologic processes they represent. Sensitivity analysis was performed for the two objective functions; mean monthly streamflow and the corresponding root mean square error (RMSE). Results of the sensitivity analysis showed that the majority of sensitive parameters were similar between the watersheds, resulting in a common parameter set selection for Colorado watersheds. Interestingly, sensitivity of parameters was observed to be varying depending upon the objective function. Through this part of the study, the significance of association between snowmelt and sub-surface hydrologic processes for generation of streamflow in mountainous watersheds was realized. Secondly, regionalization methods based on different approaches were used to compute the values of parameters identified as sensitive in the previous step. Later, performances of SWAT models developed for the study watersheds were evaluated by using the parameter values obtained from diverse regionalization methods. These methods included: arithmetic mean approach, approaches based on similarity indices (SI) related to watershed attributes, spatial proximity, Bayesian statistical analysis, and multisite calibration. In order to perform regionalization, a watershed was considered as ungaged and the parameter values for the watershed were obtained by using regionalization methods. Performances of these methods were evaluated by using the jack-knife cross validation technique and computing a performance measure ‘E’. The method based on the weighted arithmetic mean approach using SI and the multi-site calibration approach were observed as the most favorable regionalization methods for Colorado watersheds. Likewise, regionalization methods with average and rather poor performances were also identified. This research analyze the applicability of SWAT in mountainous regions and shows that the distributed hydrologic models like SWAT are capable of flow simulations and hydrologic modeling in mountainous regions like Colorado. Observed interactions between the SWAT parameters related to sub-surface processes and snow related processes helps in understanding the role of these hydrologic processes in magnitude and timing of streamflow generation in mountainous watersheds. This study shows that a great extent of similarity in terms of critical hydrologic processes exists between the major river basins of Colorado and thus helps in selecting a common SWAT parameter set for snow dominated mountainous regions. Performance of regionalization methods as analyzed in this study shows the importance of methods based on weighted arithmetic mean approach and the multi-site calibration approach for performing regionalization of SWAT in snow dominated mountainous regions.masters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Hydrologic models -- ColoradoText