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Authors: Verhoef, W.; Gökmen, M.; Advisor: -; Participants: - (2013) - Thesis deals with improving the quantification of hydrological fluxes, particularly evapotranspiration, for continuously or seasonally water-stressed regions; presents an integrated method, which combines remote sensing based evapotranspiration and precipitation estimates with available ground data to establish each component of the water balance; presents a regional framework for an integrated and spatio- temporally distributed assessment of human-induced trends in the hydrology and the associated ecological health of a semi-arid basin where both human activities (i.e. agriculture) and natural ecosystems are highly groundwater- dependent; describes an RS-based and quantitative framework for assessing the limits and variations of sustainable water resources and the ecological water ...
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Authors: Tian, Xin; Advisor: -; Participants: - (2013) - We propose a long-term parameterization scheme for two critical parameters, zero-plane displacement height (d) and aerodynamic roughness length (z0m), that we further use in the Surface Energy Balance System (SEBS). A sensitivity analysis of SEBS indicated that these two parameters largely impact the estimated sensible heat and latent heat fluxes. First, we calibrated regression relationships between measured forest vertical parameters (Lorey’s height and the frontal area index (FAI)) and forest aboveground biomass (AGB). Next, we derived the interannual Lorey’s height and FAI values from our calibrated regression models and corresponding forest AGB dynamics that were converted from interannual carbon fluxes, as simulated from two incorporated ecological models and a 2009 forest bas...
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Authors: Su, Z. ; Timmermans, W.J.; Advisor: -; Participants: - (2016) - Thesis has utility of an automated thermal-based approach for monitoring evapotranspiration; accounting for Atmospheric Boundary Layer variability on flux estimation from RS observations; footprint issues in scintillometry over heterogeneous landscapes An overview of the regional experiments for land- atmosphere exchanges 2012 (REFLEX 2012) campaign; parameterization issues in modelling energy exchange across the air-land interface.
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Authors: Molénat, J.; Advisor: -; Participants: Raclot, D.; Zitouna, R.; Andrieux, P.; Coulouma, G. (2018) - The observation strategy is motivated by monitoring water, sediment, and contaminant fluxes and hydrologic and climatic variables at different spatial scales from cultivated plots and landscape elements to the catchment scale. These measurements have been performed at a fine time resolution over a long‐term scale and by surveying land use, agricultural practices, and soil surface characteristics. The long‐term observation strategy intends to support integrative multidisciplinary research for elucidating the conditions that improve soil and water management and delivery of ecosystem services in a Mediterranean rainfed cultivated context. The observatory has led to scientific insights regarding three scientific objectives: (i) to better understand the fluxes of water, erosion, and con...
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Authors: Brantley, S.L.; Advisor: -; Participants: White, T.; West, N.; Williams, J.Z.; Forsythe, B. (2018) - The Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) was established to investigate the form, function, and dynamics of the critical zone developed on sedimentary rocks in the Appalachian Mountains in central Pennsylvania. When first established, the SSHCZO encompassed only the Shale Hills catchment, a 0.08‐km2 subcatchment within Shaver's Creek watershed. The SSHCZO has now grown to include 120 km2 of the Shaver's Creek watershed. With that growth, the science team designed a strategy to measure a parsimonious set of data to characterize the critical zone in such a large watershed. This parsimonious design includes three targeted subcatchments (including the original Shale Hills), observations along the main stem of Shaver's Creek, and broad topographic and geophysical ob...
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Authors: O'Geen, A.; Advisor: -; Participants: Safeeq, M.; Wagenbrenner, J.; Stacy, E.; Hartsough, P.; Devine, S. (2018) - Sensor networks within the Southern Sierra Critical Zone Observatory (SSCZO) and Kings River Experimental Watersheds (KREW) document changes in the water cycle spanning the west slope of the southern Sierra Nevada in California. The networks were established to document water dynamics throughout the critical zone spanning profile, hillslope, catchment, and watershed scales at key locations that reflect systematic differences in bioclimatic conditions imposed by a strong elevation gradient. The critical zone observatory attempts to constrain the hydrologic budget via representative measurements of streamflow, eddy flux covariance, snow depth, meteorological conditions, and water content and water potential in soil and deep regolith. These measurements reveal the complexity of interac...
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Authors: Atchley, A.L.; Advisor: -; Participants: Kinoshita, A.M.; Lopez, S.R.; Trader, L.; Middleton, R. (2018) - The reduction of evapotranspiration often dominated the new water balance compared with the increase in overland flow, resulting in higher soil moisture. However, this modeling experiment also identified a tipping point where increased overland flow from high burn severity sites eclipses the effect of reduced evapotranspiration on the water balance, causing comparatively drier post‐fire soils. In particular, high burn severity sites approach a threshold that results in larger changes to overland flow than changes in evapotranspiration, potentially moving the site to an overland flow dominated regime. The shifts in water balance components have implications for how site conditions will change under a range of burn severity scenarios.
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Authors: Friedman, S.P.; Advisor: -; Participants: Gamliel, A. (2019) - A previously derived analytical solution to the quasi‐linear form of the water flow equation is used to analyze (i) steady, coupled plant water uptake from a surface water emitter in a confined cylindrical soil domain with a non‐evaporating surface in the presence of a shallow water table, and (ii) water uptake from only the water table in the absence of a surface emitter. Illustrative examples serve to analyze and discuss water‐uptake rates of a subsurface, spherical, conceived root zone and the complex water‐flow patterns occurring in either natural fields with shallow groundwater or artificial lysimeters. The coupled source–sink–water table model is also used to illustrate the dependence of the contributions of surface emitter and water table to the overall water‐uptake rate on c...
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Authors: Lazik, D.; Advisor: -; Participants: Vetterlein, D; Salas, S.M.; Sood, P.; Apelt, B.; Vogel, H.J. (2019) - This variability is attributed to the spatiotemporal heterogeneity of both plant–soil–microbiome interactions and the local conditions governing gas transport. For the characterization of a given soil, the local heterogeneities should be replaced by some meaningful average. To this end, we introduce a line sensor based on tubular gas‐selective membranes that is applicable at the field scale for a wide range in water content. It provides the average CO2 concentration of the ambient soil along its length. The new technique corrects for fluctuating external conditions (i.e., temperature and air pressure) and the impact of water vapor without any further calibration. The new line sensor was tested in a laboratory mesocosm experiment where CO2 concentrations were monitored at two depths ...
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Authors: Ruth, C.E.; Advisor: -; Participants: Michel, D.; Hirschi, M.; Seneviratne, S.I. (2018) - The resulting water‐balance estimates were then compared with those of the lower resolution large lysimeter, whose processing has remained unchanged since its installation. A number of additional, retrospectively applicable processing steps for the large lysimeter were then tested to mitigate the main sources of error for this instrument. Those found to be most beneficial were the application of a 10‐min moving average to the mass measurements and the setting of ET and condensation to zero in hours with liquid precipitation. In spite of the differences in design, a generally close agreement between the two lysimeters was observed, which was further improved with the optimized large‐lysimeter processing. A comparison of the lysimeter mass increases associated with liquid precipitatio...
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