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Journal Articles
Testing alternative conceptual models of river-aquifer connectivity and their impacts on baseflow and river recharge processes This study simulates the dynamics of exchange fluxes between Brazos River Alluvium Aquifer and the Brazos River, TX, USA. Seven conceptual models for the connection between the river and the aquifer were simulated in HYDRUS 2D using small-scale, high-resolution transects… 
Use of PhenoCam Measurements and Image Analysis to Inform the ALMANAC Process-based Simulation Model Near-surface remote sensing has been used to document seasonal growth patterns (i.e. phenology) for plant communities in diverse habitats. Phenology from this source may only apply to the area within the images. Meanwhile ecosystem models can accommodate variable weather and… 
Assessing Forest Level Response to the Death of a Dominant Tree within a Premontane Tropical Rainforest Small-scale treefall gaps are among the most important forms of forest disturbance in tropical forests. These gaps expose surrounding trees to more light, promoting rapid growth of understory plants. However, the effects of such small-scale disturbances on the distribution of… 
Topographic and Landcover Influence on Lower Atmospheric Profiles Measured by Small Unoccupied Aerial Systems (sUAS) Small unoccupied aerial systems (sUASs) are increasingly being used for field data collection and remote sensing purposes. Their ease of use, ability to carry sensors, low cost, and precise maneuverability and navigation make them a versatile tool for a field… 
Monitoring agroecosystem productivity and phenology at a national scale: A metric assessment framework Effective measurement of seasonal variations in the timing and amount of production is critical to managing spatially heterogeneous agroecosystems in a changing climate. Although numerous technologies for such measurements are available, their relationships to one another at a continental extent… 
Effect of multilayered groundwater mounds on water dynamics beneath a recharge basin: Numerical simulation and assessment of surface injection Interactions between groundwater mounds caused by a geologic layer contrast affect the efficiency of managed aquifer recharge in arid areas. However, research has rarely examined the roles of groundwater mounding size variations on soil water dynamics in a stratified vadose… 
Optimizing Multiwell Aquifer Storage and Recovery Systems for Energy Use and Recovery Efficiency As more aquifer storage and recovery (ASR) systems are employed for management of water resources, the skillful operation of multiwell ASR systems has become very important to improve their performance. In this study, we developed MODFLOW and MT3DMS models to… 
Modeling profiles of micrometeorological variables in a tropical premontane rainforest using multi‐layered CLM (CLM‐ml) Abstract This study updates the multi‐layered Community Land Model (CLM‐ml) for hillslopes and compares predictions from against observations collected in tropical montane rainforest, Costa Rica. Modifications are made in order to capture a wider array of vertical leaf area distributions,… 
Modeling land surface processes over a mountainous rainforest in Costa Rica using CLM4.5 and CLM5 This study compares the performance of the Community Land Models (CLM4.5 and CLM5) against tower and ground measurements from a tropical montane rainforest in Costa Rica. The study site receives over 4,000 mm of mean annual precipitation and has high… The pan-tropical response of soil moisture to El Niño The 2015–16 El Niño event ranks as one of the most severe on record in terms of the magnitude and extent of sea surface temperature (SST) anomalies generated in the tropical Pacific Ocean. Corresponding global impacts on the climate were… HPeye: Measurement of above‐canopy meteorological profiles using unmanned aerial systems Unmanned aerial systems (UASs) are becoming valuable environmental data collection tools, allowing the user freedom to attach sensors and to launch at a moment's notice while also collecting spatially precise data all at a relatively low cost (Simic Milas et… Precipitation mediates sap flux sensitivity to evaporative demand in the neotropics Transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding of how tropical trees regulate sap flux in response to climate variability remains elusive. With a progressively warming climate,… Simulating groundwater uptake and hydraulic redistribution by phreatophytes in a high-resolution, coupled subsurface-land surface model Highlights Belowground processes in Earth system models continue to present challenges. ParFlow.CLM modified to include more realistic root water uptake functions. New model capable of predicting groundwater uptake, hydraulic redistribution. Model compares favorably to eight years of data from AmeriFlux… The Importance of Bank Storage in Supplying Baseflow to Rivers Flowing Through Compartmentalized, Alluvial Aquifers Abstract As water grows scarcer in semiarid and arid regions around the world, new tools are needed to quantify fluxes of water and chemicals between aquifers and rivers. In this study, we quantify the volumetric flux of subsurface water to… 
Assessing aquifer storage and recovery feasibility in the Gulf Coastal Plains of Texas Abstract Study region The Gulf Coast and Carrizo-Wilcox aquifer systems in the Gulf Coastal Plains of Texas. Study focus Aquifer storage and recovery is a water storage alternative that is underutilized in Texas, a state with both long periods of… Upscaling transpiration in diverse forests: Insights from a tropical pre-montane site Upscaling water use of individual trees to stands using sap flux techniques is a common method for partitioning site water balance, but few such studies have occurred in the tropics. Increasing interests in the role of tropical forests in global… 
Leaf surface traits and water storage retention affect photosynthetic responses to leaf surface wetness among wet tropical forest and semiarid savanna plants While it is reasonable to predict that photosynthetic rates are inhibited while leaves are wet, leaf gas exchange measurements during wet conditions are challenging to obtain due to equipment limitations and the complexity of canopy–atmosphere interactions in forested environments. Thus,… Comparison of Tree Transpiration under Wet and Dry Canopy Conditions in a Costa Rican Premontane Tropical Forest Spatial and temporal variation in wet canopy conditions following precipitation events can influence processes such as transpiration and photosynthesis, which can be further enhanced as upper canopy leaves dry more rapidly than the understory following each event. As part of… Attitudes of Incoming Civil Engineering Students toward Sustainability as an Engineering Ethic This study presents the results of a survey of new civil engineering students at a large, conservative, land-grant university. Students were asked a set of questions about engineering ethics and professional issues; these were designed to determine their opinions on… Using Envision to Assess the Sustainability of Groundwater Infrastructure: A Case Study of the Twin Oaks Aquifer Storage and Recovery Project The ISI (Institute for Sustainable Infrastructure) Envision rating system is designed to be a comprehensive sustainability assessment that can be applied to a wide range of infrastructure projects, including water supply. With water supply resiliency, a prominent concern in many… Mapping Potential Groundwater-Dependent Ecosystems for Sustainable Management Ecosystems which rely on either the surface expression or subsurface presence of groundwater are known as groundwater-dependent ecosystems (GDEs). A comprehensive inventory of GDE locations at an appropriate management scale is a necessary first-step for sustainable management of supporting aquifers;… A groundwater–soil–plant–atmosphere continuum approach for modelling water stress, uptake, and hydraulic redistribution in phreatophytic vegetation Modelling groundwater uptake provides a powerful tool for examining the tight linkage of phreatophytic vegetation with spatial and temporal variations in groundwater and soil moisture. Here, a physically based modelling framework was developed to simulate groundwater uptake and hydraulic redistribution… A statistical method for estimating wood thermal diffusivity and probe geometry using in situ heat response curves from sap flow measurements The heat pulse method is widely used to measure water flux through plants; it works by using the speed at which a heat pulse is propagated through the system to infer the velocity of water through a porous medium. No… Understanding ecohydrological connectivity in savannas: a system dynamics modelling approach Ecohydrological connectivity is a system level property that results from the linkages in the networks of water transport through ecosystems, by which feedbacks and other emergent system behaviours may be generated. We created a system dynamics model that represents primary… Characterizing ecohydrological and biogeochemical connectivity across multiple scales: a new conceptual framework The connectivity of ecohydrological and biogeochemical processes across time and space is a critical determinant of ecosystem structure and function. However, characterizing cross-scale connectivity is a challenge due to the lack of theories and modelling approaches that are applicable at… Groundwater uptake by woody vegetation in a semiarid oak savanna Groundwater can serve as an important resource for woody vegetation in semiarid landscapes, particularly when soil water is functionally depleted and unavailable to plants. This study examines the uptake of groundwater by deciduous blue oak trees (Quercus douglasii) in a… Modeling Vadose Zone Processes during Land Application of Food-Processing Waste Water in California’s Central Valley Land application of food-processing waste water occurs throughout California's Central Valley and may be degrading local ground water quality, primarily by increasing salinity and nitrogen levels. Natural attenuation is considered a treatment strategy for the waste, which often contains elevated… An analysis of soil moisture dynamics using multi-year data from a network of micrometeorological observation sites Soil moisture data, obtained from four AmeriFlux sites in the US, were examined using an ecohydrological framework. Sites were selected for the analysis to provide a range of plant functional type, climate, soil particle size distribution, and time series of… Water quality in Lemoa, Guatemala A variety of water supply sources are used in the rural Guatemalan Highlands. Formal municipal systems are rare, but villagers frequently form local water committees that construct spring-based supply systems. Recent work has indicated that groundwater may be a viable… Modeling of a Groundwater Circulation Well Removal Action Alternative This paper presents the basis for using groundwater circulation wells (GCWs) for removal actions focused on contaminated domestic water supplies. A properly placed GCW could be used to pretreat water before it enters a domestic well. Commercial software was used…
Book Chapters
Understanding and measuring plant water use Plant uptake of water is controlled by two interconnected balances at the land surface: the partitioning of energy arriving as solar radiation and the partitioning of water arriving as precipitation. Evapotranspiration (ET) is the critical link between the two, as… The Dynamics of Energy, Water and Carbon Fluxes in a Blue Oak (Quercus douglasii) Savanna in California, USA Oak trees and their savanna woodlands have played many important roles in the history, development and ecology of California, and the American West (Pavlik et al. 1991; Tyler, Kuhn, and Davis 2006). Starting with the Spanish Mission period through today,…
Theses
Quantifying Embedded Water in Agricultural Goods for Sustainable Water Use in Mexico Mexico is known to be a large user of groundwater resources for the production of food commodities and most of the production is located in water stressed regions. This study explores the embedded (virtual) water of the agricultural goods produced… Modeling Groundwater Recharge in the Brazos River Alluvium Aquifer (BRAA) using CLM 4.5 Traditional hydrologic modeling has partitioned water cycle into its different component (i.e. rainfall, run-off, or groundwater models). An alternative approach will be described in this research project. Over most of the river alluvium aquifers around the world, those processes are… Effect of Pumping Rates on Long-Term Aquifer Storage and Recovery Well Performance for Conservative and Reactive Transport Scenarios Recovery of injected water is one of the most important aspects of an aquifer storage and recovery (ASR) system and is determined by hydrogeologic, operational, and chemical factors. A common series of reactions resulting in deterioration of water quality is… Influence of land-use change and agriculture practice on water, carbon, and energy fluxes The expansion of the urban area and agriculture field in the past centuries converted many natural prairies to crop fields and residence places, which brought many problems that influenced the interactions between biosphere and atmosphere. However, the effects caused by… Recharge Uncertainty Analysis of Major Aquifers in Texas While the reduction of the groundwater available volume in the state of Texas of urban, agricultural, and industrial use has been dealt with in different ways, the first step is to assess the current and future behavior of the aquifers… 
Numerical Modeling of Water Flux Interactions Between the Brazos River Alluvium Aquifer and the Brazos River: Testing of Alternative Conceptual Models Quantitative characterization of the dynamics of water exchange fluxes between rivers and aquifers is necessary for water resources management, water quality, environment and ecology of the river-aquifer systems. The main uncertain factors for predicting river–aquifer exchange fluxes are aquifer and… Feasibility Study and Numerical Modeling on Managed Aquifer Recharge Using Dry Wells in Harris County, Texas Managed aquifer recharge (MAR) has been adopted as a modern water management strategy to store water into subsurface during surplus periods for future recovery. As one application of MAR, dry well is installed in vadose zone and can be used… 
Earth Systems Modeling in the Brazos River Alluvium Aquifer: Improvement of Computational Methods and Development of Conceptual Model Traditional hydrologic modeling has compartmentalized the water cycle into distinct components (e.g. rainfall-runoff, river routing, or groundwater flow models). In river valley alluvium aquifers, these processes are too interconnected to be represented accurately by separate models. An integrated modeling framework… The Temporal Variation of Vertical Micrometeorological Profiles in a Lower Montane Tropical Forest Earth system models recently began to implement a multilevel canopy modeling approach to represent vertical variation in biophysical and microclimate parameters. To inform such modeling efforts, this study seeks to characterize the variability and causal relationships between vertical sub-canopy profiles… Fate and Transport of Polymeric Nanoparticles in Saturated Porous Media The application of engineered nanomaterials has improved many traditional groundwater remediation technologies; however, the development of novel nano-scale remediation technologies remains limited. magnetic shell crosslinked knedel-like (MSCKs) are novel polymeric nanoparticles whose application towards groundwater remediation is promising. MSCKs differ… Reactive Transport Modeling of Natural Attenuation in Stormwater Bioretention Cells and Under Land Application of Wastewater Natural attenuation is a cost effective method to treat wastewater applied into soil. The natural attenuation process includes diffusion, dispersion, microbial activity, oxidation, mineral precipitation, sorption, and ion exchange to mitigate hydrocarbon, nutrient, metals, and solids. Vegetation also plays an… Hillslope Hydrological Processes in a Costa Rican Rainforest: Water Supply Partitioning Using Isotope Tracers Costa Rican tropical premontane rainforests are among the world's most valuable ecosystems in terms of diversity of animals, plants, and natural resources. These environments are dependent on water resources which fluctuate in quantity during the dry and wet seasons and… Numerical modeling of focused remediation using a groundwater circulation well Groundwater circulation wells (GCWs) allow for the in situ treatment of contaminated water resources. Focused remediation with a GCW could be used to treat groundwater before it enters an existing domestic well already in use. GCWs have been installed at the former…
Dissertations
Improving Predictions of Soil and Plant Evapotranspiration in Vadose Zone and Land Surface Models This study focuses on the surface hydrology to contribute to its better parameterization through inter-comparison and direct improvement with two scopes: (1) soil evaporation process, and (2) the forest hydrological/physiological process based on Community Land Model (CLM). In soil evaporation… Improving Adoption of Aquifer Storage and Recovery in Texas The first study identifies hydrogeologically feasible locations for ASR across the Gulf Coast and Carrizo-Wilcox aquifer systems in Texas, using transmissivity, hydraulic gradient, well density, depth to aquifer, and depth to groundwater using a GIS-based index. Corpus Christi, Victoria, San… Study of Multi-Scale Plant-Groundwater Interactions Groundwater serves as one of the main and reliable water sources for human-being and groundwater dependent ecosystems (GDEs). GDEs are threatened by insufficient groundwater supply, due to increasing groundwater extraction and climate change. Sustainable groundwater management should address the water… Measuring and modeling interactions between groundwater, soil moisture, and plant transpiration in natural and agricultural ecosystems Plant transpiration serves a critical function in the terrestrial hydrologic cycle, acting as the primary link between the atmosphere and subsurface stores of water. To properly manage our water resources under changing and uncertain climate conditions, we will first need…