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- All Subjects: Water resources management
- Genre: Masters Thesis
- Creators: Semken, Steven
Description
The North American Monsoon (NAM) is characterized by high inter- and intra-seasonal variability, and potential climate change effects have been forecasted to increase this variability. The potential effects of climate change to the hydrology of the southwestern U.S. is of interest as they could have consequences to water resources, floods, and land management. I applied a distributed watershed model, the Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator (tRIBS), to the Beaver Creek basin in Arizona. This sub-basin of the Verde River is representative of the regional topography, land cover, and soils distribution. As such, it can serve to illustrate the utility of distributed models for change assessment studies. Model calibration was performed utilizing radar-based NEXRAD data, and comparisons were done to two additional sources of precipitation data: ground-based stations and the North American Land Data Assimilation System (NLDAS). Comparisons focus on the spatiotemporal distributions of precipitation and stream discharge. Utilizing the calibrated model, I applied scenarios from the HadCM3 General Circulation Model (GCM) which was dynamically downscaled by the Weather Research and Forecast (WRF) model, to refine the representation of Arizona's regional climate. Two time periods were examined, a historical 1990-2000 and a future 2031-2040, to evaluate the hydrologic consequence in the form of differences and similarities between the decadal averages for temperature, precipitation, stream discharge and evapotranspiration. Results indicate an increase in mean air temperature over the basin by 1.2 ºC. The average decadal precipitation amounts increased between the two time periods by 2.4 times that of the historical period and had an increase in variability that was 3 times the historical period. For the future period, modeled streamflow discharge in the summer increased by a factor of 3. There was no significant change in the average evapotranspiration (ET). Overall trends of increase precipitation and variability for future climate scenarios have a more significant effect on the hydrologic response than temperature increases in the system during NAM in this study basin. The results from this study suggest that water management in the Beaver Creek will need to adapt to higher summer streamflow amounts.
ContributorsHawkins, Gretchen (Author) / Vivoni, Enrique R. (Thesis advisor) / Semken, Steven (Committee member) / Mays, Larry W. (Committee member) / Arizona State University (Publisher)
Created2012
Description
The American Southwest is one of the most rapidly growing regions of the United States, as are similar arid regions globally. Across these landscapes where surface water is intermittent and variable, groundwater aquifers recharged by surface waters become a keystone resource for communities and are consumed at rates disproportional to recharge. In this study, I focus on the controls of runoff generation and connectivity at both hillslope and watershed scales along a piedmont slope. I also investigate the effects of plant phenology on hydrologic connectivity and runoff response at the hillslope scale during the summer monsoon season. To carry out this work, I combine existing hydrologic instrumentation, a new set of runoff plots with high-resolution monitoring, near-field remote sensing techniques, and historical datasets. Key analyses show that a rainfall intensity (I30) of 10 mm/hr yields runoff production at three scales (8, 12700, and 46700 m2). Rainfall, runoff, and soil moisture observations indicate a Hortonian (infiltration-excess) dominated system with little control imposed by antecedent wetness. Hydrologic connectivity analyses revealed that <15% of total rainfall events generate runoff at the hillslope scale. Of the hillslope events, only 20% of the runoff production leads to discharge at the outlet. Vegetation was observed to effect individual plot runoff response to rainfall. The results of this study show that 1) rainfall intensity is a large control on runoff production at all three scales (8, 12700, and 46700 m2), 2) proportions between bare and vegetated space effect runoff production at the hillslope scale, and 3) runoff connectivity decreases, and channel losses increase as you move downstream on an individual storm basis and across a 30-year historical record. These findings indicate that connectivity from the hillslope to outlet scale can be an evolving process over thehistorical record, reliant on both rainfall intensity, plant and bare soil mosaics, and available channel storage.
ContributorsKeller, Zachary Theodore (Author) / Vivoni, Enrique R (Thesis advisor) / Whipple, Kelin X (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2021