Matching Items (25)
Description
Hydrology and biogeochemistry are coupled in all systems. However, human decision-making regarding hydrology and biogeochemistry are often separate, even though decisions about hydrologic systems may have substantial impacts on biogeochemical patterns and processes. The overarching question of this dissertation was: How does hydrologic engineering interact with the effects of nutrient loading and climate to drive watershed nutrient yields? I conducted research in two study systems with contrasting spatial and temporal scales. Using a combination of data-mining and modeling approaches, I reconstructed nitrogen and phosphorus budgets for the northeastern US over the 20th century, including anthropogenic nutrient inputs and riverine fluxes, for ~200 watersheds at 5 year time intervals. Infrastructure systems, such as sewers, wastewater treatment plants, and reservoirs, strongly affected the spatial and temporal patterns of nutrient fluxes from northeastern watersheds. At a smaller scale, I investigated the effects of urban stormwater drainage infrastructure on water and nutrient delivery from urban watersheds in Phoenix, AZ. Using a combination of field monitoring and statistical modeling, I tested hypotheses about the importance of hydrologic and biogeochemical control of nutrient delivery. My research suggests that hydrology is the major driver of differences in nutrient fluxes from urban watersheds at the event scale, and that consideration of altered hydrologic networks is critical for understanding anthropogenic impacts on biogeochemical cycles. Overall, I found that human activities affect nutrient transport via multiple pathways. Anthropogenic nutrient additions increase the supply of nutrients available for transport, whereas hydrologic infrastructure controls the delivery of nutrients from watersheds. Incorporating the effects of hydrologic infrastructure is critical for understanding anthropogenic effects on biogeochemical fluxes across spatial and temporal scales.
ContributorsHale, Rebecca Leslie (Author) / Grimm, Nancy (Thesis advisor) / Childers, Daniel (Committee member) / Vivoni, Enrique (Committee member) / York, Abigail (Committee member) / Wu, Jianguo (Committee member) / Arizona State University (Publisher)
Created2013
Description
The partitioning of available solar energy into different fluxes at the Earth's surface is important in determining different physical processes, such as turbulent transport, subsurface hydrology, land-atmospheric interactions, etc. Direct measurements of these turbulent fluxes were carried out using eddy-covariance (EC) towers. However, the distribution of EC towers is sparse due to relatively high cost and practical difficulties in logistics and deployment. As a result, data is temporally and spatially limited and is inadequate to be used for researches at large scales, such as regional and global climate modeling. Besides field measurements, an alternative way is to estimate turbulent fluxes based on the intrinsic relations between surface energy budget components, largely through thermodynamic equilibrium. These relations, referred as relative efficiency, have been included in several models to estimate the magnitude of turbulent fluxes in surface energy budgets such as latent heat and sensible heat. In this study, three theoretical models based on the lumped heat transfer model, the linear stability analysis and the maximum entropy principle respectively, were investigated. Model predictions of relative efficiencies were compared with turbulent flux data over different land covers, viz. lake, grassland and suburban surfaces. Similar results were observed over lake and suburban surface but significant deviation is found over vegetation surface. The relative efficiency of outgoing longwave radiation is found to be orders of magnitude deviated from theoretic predictions. Meanwhile, results show that energy partitioning process is influenced by the surface water availability to a great extent. The study provides insight into what property is determining energy partitioning process over different land covers and gives suggestion for future models.
ContributorsYang, Jiachuan (Author) / Wang, Zhihua (Thesis advisor) / Huang, Huei-Ping (Committee member) / Vivoni, Enrique (Committee member) / Mays, Larry (Committee member) / Arizona State University (Publisher)
Created2012
Description
Ten regional climate models (RCMs) and atmosphere-ocean generalized model parings from the North America Regional Climate Change Assessment Program were used to estimate the shift of extreme precipitation due to climate change using present-day and future-day climate scenarios. RCMs emulate winter storms and one-day duration events at the sub-regional level. Annual maximum series were derived for each model pairing, each modeling period; and for annual and winter seasons. The reliability ensemble average (REA) method was used to qualify each RCM annual maximum series to reproduce historical records and approximate average predictions, because there are no future records. These series determined (a) shifts in extreme precipitation frequencies and magnitudes, and (b) shifts in parameters during modeling periods. The REA method demonstrated that the winter season had lower REA factors than the annual season. For the winter season the RCM pairing of the Hadley regional Model 3 and the Geophysical Fluid-Dynamics Laboratory atmospheric-land generalized model had the lowest REA factors. However, in replicating present-day climate, the pairing of the Abdus Salam International Center for Theoretical Physics' Regional Climate Model Version 3 with the Geophysical Fluid-Dynamics Laboratory atmospheric-land generalized model was superior. Shifts of extreme precipitation in the 24-hour event were measured using precipitation magnitude for each frequency in the annual maximum series, and the difference frequency curve in the generalized extreme-value-function parameters. The average trend of all RCM pairings implied no significant shift in the winter annual maximum series, however the REA-selected models showed an increase in annual-season precipitation extremes: 0.37 inches for the 100-year return period and for the winter season suggested approximately 0.57 inches for the same return period. Shifts of extreme precipitation were estimated using predictions 70 years into the future based on RCMs. Although these models do not provide climate information for the intervening 70 year period, the models provide an assertion on the behavior of future climate. The shift in extreme precipitation may be significant in the frequency distribution function, and will vary depending on each model-pairing condition. The proposed methodology addresses the many uncertainties associated with the current methodologies dealing with extreme precipitation.
ContributorsRiaño, Alejandro (Author) / Mays, Larry W. (Thesis advisor) / Vivoni, Enrique (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2013
Description
The National Research Council 2011 report lists quantifying the extent of de facto (or unplanned) potable reuse in the U.S. as the top research need associated with assessing the potential for expanding the nations water supply through reuse of municipal wastewater. Efforts to identify the significance and potential health impacts of de facto water reuse are impeded by out dated information regarding the contribution of municipal wastewater effluent to potable water supplies. This project aims to answer this research need. The overall goal of the this project is to quantify the extent of de facto reuse by developing a model that estimates the amount of wastewater effluent that is present within drinking water treatment plants; and to use the model in conjunction with a survey to help assess public perceptions. The four-step approach to accomplish this goal includes: (1) creating a GIS-based model coupled with Python programming; (2) validating the model with field studies by analyzing sucralose as a wastewater tracer; (3) estimating the percentage of wastewater in raw drinking water sources under varying streamflow conditions; (4) and assessing through a social survey the perceptions of the general public relating to acceptance and occurrence of de facto reuse. The resulting De Facto Reuse in our Nations Consumable Supply (DRINCS) Model, estimates that treated municipal wastewater is present at nearly 50% of drinking water treatment plant intake sites serving greater than 10,000 people (N=2,056). Contrary to the high frequency of occurrence, the magnitude of occurrence is relatively low with 50% of impacted intakes yielding less than 1% de facto reuse under average streamflow conditions. Model estimates increase under low flow conditions (modeled by Q95), in several cases treated wastewater makes up 100% of the water supply. De facto reuse occurs at levels that surpass what is publically perceived in the three cities of Atlanta, GA, Philadelphia, PA, and Phoenix, AZ. Respondents with knowledge of de facto reuse occurrence are 10 times more likely to have a high acceptance (greater than 75%) of treated wastewater at their home tap.
ContributorsRice, Jacelyn (Author) / Westerhoff, Paul (Thesis advisor) / Abbaszadegan, Morteza (Committee member) / Vivoni, Enrique (Committee member) / Wutich, Amber (Committee member) / Arizona State University (Publisher)
Created2014
Description
Nitrate, a widespread contaminant in surface water, can cause eutrophication and toxicity to aquatic organisms. To augment the nitrate-removal capacity of constructed wetlands, I applied the H2-based Membrane Biofilm Reactor (MBfR) in a novel configuration called the in situ MBfR (isMBfR). The goal of my thesis is to evaluate and model the nitrate removal performance for a bench-scale isMBfR system.
I operated the bench-scale isMBfR system in 7 different conditions to evaluate its nitrate-removal performance. When I supplied H2 with the isMBfR (stages 1 - 6), I observed at least 70% nitrate removal, and almost all of the denitrification occurred in the "MBfR zone." When I stopped the H2 supply in stage 7, the nitrate-removal percentage immediately dropped from 92% (stage 6) to 11% (stage 7). Denitrification raised the pH of the bulk liquid to ~ 9.0 for the first 6 stages, but the high pH did not impair the performance of the denitrifiers. Microbial community analyses indicated that DB were the dominant bacteria in the "MBfR zone," while photosynthetic Cyanobacteria were dominant in the "photo-zone".
I derived stoichiometric relationships among COD, alkalinity, H2, Dissolved Oxygen (DO), and nitrate to model the nitrate removal capacity of the "MBfR zone." The stoichiometric relationships corresponded well to the nitrate-removal capacity for all stages expect stage 3, which was limited by the abundance of Denitrifying Bacteria (DB) so that the H2 supply capacity could not be completely used.
Finally, I analyzed two case studies for the real-world application of the isMBfR to constructed wetlands. Based on the characteristics for the wetlands and the stoichiometric relationships, I designed a feasible operation condition (membrane area and H2 pressure) for each wetland. In both cases, the amount of isMBfR surface area was modest, from 0.022 to 1.2 m2/m3 of wetland volume.
I operated the bench-scale isMBfR system in 7 different conditions to evaluate its nitrate-removal performance. When I supplied H2 with the isMBfR (stages 1 - 6), I observed at least 70% nitrate removal, and almost all of the denitrification occurred in the "MBfR zone." When I stopped the H2 supply in stage 7, the nitrate-removal percentage immediately dropped from 92% (stage 6) to 11% (stage 7). Denitrification raised the pH of the bulk liquid to ~ 9.0 for the first 6 stages, but the high pH did not impair the performance of the denitrifiers. Microbial community analyses indicated that DB were the dominant bacteria in the "MBfR zone," while photosynthetic Cyanobacteria were dominant in the "photo-zone".
I derived stoichiometric relationships among COD, alkalinity, H2, Dissolved Oxygen (DO), and nitrate to model the nitrate removal capacity of the "MBfR zone." The stoichiometric relationships corresponded well to the nitrate-removal capacity for all stages expect stage 3, which was limited by the abundance of Denitrifying Bacteria (DB) so that the H2 supply capacity could not be completely used.
Finally, I analyzed two case studies for the real-world application of the isMBfR to constructed wetlands. Based on the characteristics for the wetlands and the stoichiometric relationships, I designed a feasible operation condition (membrane area and H2 pressure) for each wetland. In both cases, the amount of isMBfR surface area was modest, from 0.022 to 1.2 m2/m3 of wetland volume.
ContributorsLi, Yizhou (Author) / Rittmann, Bruce (Thesis advisor) / Vivoni, Enrique (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2014
Description
Sustainability requires developing the capacity to manage difficult tradeoffs to advance human livelihoods now and in the future. Decision-makers are recognizing the ecosystem services approach as a useful framework for evaluating tradeoffs associated with environmental change to advance decision-making towards holistic solutions. In this dissertation I conduct an ecosystem services assessment on the Yongding River Ecological Corridor in Beijing, China. I developed a `10-step approach' to evaluate multiple ecosystem services for public policy. I use the 10-step approach to evaluate five ecosystem services for management from the Yongding Corridor. The Beijing government created lakes and wetlands for five services (human benefits): (1) water storage (groundwater recharge), (2) local climate regulation (cooling), (3) water purification (water quality), (4) dust control (air quality), and (5) landscape aesthetics (leisure, recreation, and economic development).
The Yongding Corridor is meeting the final ecosystem service levels for landscape aesthetics, but the new ecosystems are falling short on meeting final ecosystem service levels for water storage, local climate regulation, water purification, and dust control. I used biophysical models (process-based and empirically-based), field data (biophysical and visitor surveys), and government datasets to create ecological production functions (i.e., regression models). I used the ecological production functions to evaluate how marginal changes in the ecosystems could impact final ecosystem service outcomes. I evaluate potential tradeoffs considering stakeholder needs to recommend synergistic actions for addressing priorities while reducing service shortfalls.
The Yongding Corridor is meeting the final ecosystem service levels for landscape aesthetics, but the new ecosystems are falling short on meeting final ecosystem service levels for water storage, local climate regulation, water purification, and dust control. I used biophysical models (process-based and empirically-based), field data (biophysical and visitor surveys), and government datasets to create ecological production functions (i.e., regression models). I used the ecological production functions to evaluate how marginal changes in the ecosystems could impact final ecosystem service outcomes. I evaluate potential tradeoffs considering stakeholder needs to recommend synergistic actions for addressing priorities while reducing service shortfalls.
ContributorsWong, Christina P (Author) / Kinzig, Ann P (Thesis advisor) / Lee, Kai N. (Committee member) / Muneepeerakul, Rachata (Committee member) / Ouyang, Zhiyun (Committee member) / Vivoni, Enrique (Committee member) / Arizona State University (Publisher)
Created2014
Description
Sedimentary basins are defined by extensional tectonics. Rugged mountain ranges stand in stark relief adjacent to muted structural basins filled with sediment. In simplest terms, this topography is the result of ranges uplifted along normal faults, and this uplift drives erosion within upland drainages, shedding sediment into subsiding basins. In southeastern Arizona's Basin and Range province extensional tectonics waned at approximately 3-5 Myr, and the region's structural basins began transitioning from internal to external drainage, forming the modern Gila River fluvial network. In the Atacama Desert of northern Chile, some basins of the Central Depression remain internally drained while others have integrated to the Pacific Ocean. In northern Chile, rates of landscape evolution are some of the slowest on Earth due to the region's hyperarid climate. While the magnitude of upland erosion driven by extensional tectonics is largely recorded in the stratigraphy of the structural basins, the landscape's response to post-tectonic forcings is unknown.
I employ the full suite of modern geomorphic tools provided by terrestrial cosmogenic nuclides - surface exposure dating, conventional burial dating, isochron burial dating, quantifying millennial-scale upland erosion rates using detrital TCN, quantifying paleo-erosion rates using multiple TCN such as Ne-21/Be-10 and Al-26l/Be-10, and assessing sediment recycling and complex exposure using multiple TCN - to quantify the rates of landscape evolution in southeastern Arizona and northern Chile during the Late Cenozoic. In Arizona, I also use modern remnants of the pre-incision landscape and digital terrain analyses to reconstruct the landscape, allowing the quantification of incision and erosion rates that supplement detrital TCN-derived erosion rates. A new chronology for key basin high stand remnants (Frye Mesa) and a flight of Gila River terraces in Safford basin provides a record of incision rates from the Pliocene through the Quaternary, and I assess how significantly regional incision is driving erosion rates. Paired nuclide analyses in the Atacama Desert of northern Chile reveal complex exposure histories resulting from several rounds of transport and burial by fluvial systems. These results support a growing understanding that geomorphic processes in the Atacama Desert are more active than previously thought despite the region's hyperarid climate.
I employ the full suite of modern geomorphic tools provided by terrestrial cosmogenic nuclides - surface exposure dating, conventional burial dating, isochron burial dating, quantifying millennial-scale upland erosion rates using detrital TCN, quantifying paleo-erosion rates using multiple TCN such as Ne-21/Be-10 and Al-26l/Be-10, and assessing sediment recycling and complex exposure using multiple TCN - to quantify the rates of landscape evolution in southeastern Arizona and northern Chile during the Late Cenozoic. In Arizona, I also use modern remnants of the pre-incision landscape and digital terrain analyses to reconstruct the landscape, allowing the quantification of incision and erosion rates that supplement detrital TCN-derived erosion rates. A new chronology for key basin high stand remnants (Frye Mesa) and a flight of Gila River terraces in Safford basin provides a record of incision rates from the Pliocene through the Quaternary, and I assess how significantly regional incision is driving erosion rates. Paired nuclide analyses in the Atacama Desert of northern Chile reveal complex exposure histories resulting from several rounds of transport and burial by fluvial systems. These results support a growing understanding that geomorphic processes in the Atacama Desert are more active than previously thought despite the region's hyperarid climate.
ContributorsJungers, Matthew Cross (Author) / Heimsath, Arjun M (Thesis advisor) / Whipple, Kelin (Committee member) / Arrowsmith, Ramon (Committee member) / Vivoni, Enrique (Committee member) / DeVecchio, Duane (Committee member) / Arizona State University (Publisher)
Created2014
Description
This study performs numerical modeling for the climate of semi-arid regions by running a high-resolution atmospheric model constrained by large-scale climatic boundary conditions, a practice commonly called climate downscaling. These investigations focus especially on precipitation and temperature, quantities that are critical to life in semi-arid regions. Using the Weather Research and Forecast (WRF) model, a non-hydrostatic geophysical fluid dynamical model with a full suite of physical parameterization, a series of numerical sensitivity experiments are conducted to test how the intensity and spatial/temporal distribution of precipitation change with grid resolution, time step size, the resolution of lower boundary topography and surface characteristics. Two regions, Arizona in U.S. and Aral Sea region in Central Asia, are chosen as the test-beds for the numerical experiments: The former for its complex terrain and the latter for the dramatic man-made changes in its lower boundary conditions (the shrinkage of Aral Sea). Sensitivity tests show that the parameterization schemes for rainfall are not resolution-independent, thus a refinement of resolution is no guarantee of a better result. But, simulations (at all resolutions) do capture the inter-annual variability of rainfall over Arizona. Nevertheless, temperature is simulated more accurately with refinement in resolution. Results show that both seasonal mean rainfall and frequency of extreme rainfall events increase with resolution. For Aral Sea, sensitivity tests indicate that while the shrinkage of Aral Sea has a dramatic impact on the precipitation over the confine of (former) Aral Sea itself, its effect on the precipitation over greater Central Asia is not necessarily greater than the inter-annual variability induced by the lateral boundary conditions in the model and large scale warming in the region. The numerical simulations in the study are cross validated with observations to address the realism of the regional climate model. The findings of this sensitivity study are useful for water resource management in semi-arid regions. Such high spatio-temporal resolution gridded-data can be used as an input for hydrological models for regions such as Arizona with complex terrain and sparse observations. Results from simulations of Aral Sea region are expected to contribute to ecosystems management for Central Asia.
ContributorsSharma, Ashish (Author) / Huang, Huei-Ping (Thesis advisor) / Adrian, Ronald (Committee member) / Herrmann, Marcus (Committee member) / Phelan, Patrick E. (Committee member) / Vivoni, Enrique (Committee member) / Arizona State University (Publisher)
Created2012
Description
The Colorado River Basin (CRB) is the primary source of water in the
southwestern United States. A key step to reduce the uncertainty of future streamflow
projections in the CRB is to evaluate the performance of historical simulations of General
Circulation Models (GCMs). In this study, this challenge is addressed by evaluating the
ability of nineteen GCMs from the Coupled Model Intercomparison Project Phase Five
(CMIP5) and four nested Regional Climate Models (RCMs) in reproducing the statistical
properties of the hydrologic cycle and temperature in the CRB. To capture the transition
from snow-dominated to semiarid regions, analyses are conducted by spatially averaging
the climate variables in four nested sub-basins. Most models overestimate the mean
annual precipitation (P) and underestimate the mean annual temperature (T) at all
locations. While a group of models capture the mean annual runoff at all sub-basins with
different strengths of the hydrological cycle, another set of models overestimate the mean
annual runoff, due to a weak cycle in the evaporation channel. An abrupt increase in the
mean annual T in observed and most of the simulated time series (~0.8 °C) is detected at
all locations despite the lack of any statistically significant monotonic trends for both P
and T. While all models simulate the seasonality of T quite well, the phasing of the
seasonal cycle of P is fairly reproduced in just the upper, snow-dominated sub-basin.
Model performances degrade in the larger sub-basins that include semiarid areas, because
several GCMs are not able to capture the effect of the North American monsoon. Finally,
the relative performances of the climate models in reproducing the climatologies of P and
T are quantified to support future impact studies in the basin.
southwestern United States. A key step to reduce the uncertainty of future streamflow
projections in the CRB is to evaluate the performance of historical simulations of General
Circulation Models (GCMs). In this study, this challenge is addressed by evaluating the
ability of nineteen GCMs from the Coupled Model Intercomparison Project Phase Five
(CMIP5) and four nested Regional Climate Models (RCMs) in reproducing the statistical
properties of the hydrologic cycle and temperature in the CRB. To capture the transition
from snow-dominated to semiarid regions, analyses are conducted by spatially averaging
the climate variables in four nested sub-basins. Most models overestimate the mean
annual precipitation (P) and underestimate the mean annual temperature (T) at all
locations. While a group of models capture the mean annual runoff at all sub-basins with
different strengths of the hydrological cycle, another set of models overestimate the mean
annual runoff, due to a weak cycle in the evaporation channel. An abrupt increase in the
mean annual T in observed and most of the simulated time series (~0.8 °C) is detected at
all locations despite the lack of any statistically significant monotonic trends for both P
and T. While all models simulate the seasonality of T quite well, the phasing of the
seasonal cycle of P is fairly reproduced in just the upper, snow-dominated sub-basin.
Model performances degrade in the larger sub-basins that include semiarid areas, because
several GCMs are not able to capture the effect of the North American monsoon. Finally,
the relative performances of the climate models in reproducing the climatologies of P and
T are quantified to support future impact studies in the basin.
ContributorsGautam, Jenita (Author) / Mascaro, Giuseppe (Thesis advisor) / Vivoni, Enrique (Committee member) / Wang, Zhihua (Committee member) / Arizona State University (Publisher)
Created2018
Description
Urbanization, a direct consequence of land use and land cover change, is responsible for significant modification of local to regional scale climates. It is projected that the greatest urban growth of this century will occur in urban areas in the developing world. In addition, there is a significant research gap in emerging nations concerning this topic. Thus, this research focuses on the assessment of climate impacts related to urbanization on the largest metropolitan area in Latin America: Mexico City.
Numerical simulations using a state-of-the-science regional climate model are utilized to address a trio of scientifically relevant questions with wide global applicability. The importance of an accurate representation of land use and land cover is first demonstrated through comparison of numerical simulations against observations. Second, the simulated effect of anthropogenic heating is quantified. Lastly, numerical simulations are performed using pre-historic scenarios of land use and land cover to examine and quantify the impact of Mexico City's urban expansion and changes in surface water features on its regional climate.
Numerical simulations using a state-of-the-science regional climate model are utilized to address a trio of scientifically relevant questions with wide global applicability. The importance of an accurate representation of land use and land cover is first demonstrated through comparison of numerical simulations against observations. Second, the simulated effect of anthropogenic heating is quantified. Lastly, numerical simulations are performed using pre-historic scenarios of land use and land cover to examine and quantify the impact of Mexico City's urban expansion and changes in surface water features on its regional climate.
ContributorsBenson-Lira, Valeria (Author) / Georgescu, Matei (Thesis advisor) / Brazel, Anthony (Committee member) / Vivoni, Enrique (Committee member) / Arizona State University (Publisher)
Created2015