<p> The population and industrial complexes of Choctaw County obtains much of its water from an aquifer system in the Tertiary age Wilcox unit of the Mississippi Embayment. Utilizing 20 years of physical chemistry (P-Chem) analysis, potentiometric groundwater records of Choctaw County public water wells as well as industrial P-Chem analysis and surface and ground water level records from an industrial complex, this study examined the changes to the hydrosphere that has taken place since 1995. Analysis of the hydrosphere shows that over the last 20 years, there has been a drop in the potentiometric surface of the Wilcox aquifer system. The analysis also shows changes in the P-Chem of the hydrosphere, changes such as a decrease in the concentration of free CO2 and chloride, and fluctuations of Alkalinity. Comparisons between groundwater records taken from the industrial complex and other locations around Choctaw County, show little variation in the physical chemistry.</p>

<p> Groundwater is an essential input to agriculture world-wide, but it is clear that current rates of groundwater use are unsustainable in the long term. This dissertation assesses both current use of groundwater for country- to global-scale agriculture, and looks at the future of groundwater. The focus is on 1) quantifying food directly produced as a result of groundwater use across spatially-varying agricultural systems, 2) projecting future groundwater demands with consideration of climate change and human decision-making, and 3) understanding the system dynamics of groundwater re-use through surface water systems. All three are addressed using a process-based model designed to simulate both natural and human-impacted water systems. </p><p> Irrigation can significantly increase crop production. Chapter 1 combines a hydrology model (WBM) with a crop model to quantify current crop production that is directly attributed to groundwater irrigation in China. Unsustainably-sourced groundwater &mdash; defined as groundwater extracted in excess of recharge &mdash; accounted for a quarter of China&rsquo;s crop production, and had significant spatial variability. Climate variability and groundwater demand magnified one another in hot and dry years, causing increased irrigation demand at the same time as limited surface water supplies. </p><p> Human decisions about water resource management can impact both the demand and sustainability of groundwater use. Chapter 2 takes an interdisciplinary approach to projecting India&rsquo;s future (to 2050) groundwater demands, combining hydrology and econometric modeling. The econometric model projects how humans make decisions to expand or contract the irrigated land area of crops in response to climate change. Even in areas with precipitation increases, human decisions to expand irrigated areas led to increasing demands for groundwater. We additionally assessed the potential impact of a large water infrastructure project to alleviate groundwater demands in India, and found that maximum alleviation (up to 16%) was dependent upon the storage volume and location of new reservoirs. </p><p> One proposed method for reducing the world&rsquo;s demand for groundwater is to increase the efficiency of agricultural water use. However, these same inefficiencies cause a portion of extracted groundwater to enter surface water systems; it can then be reused, creating a complex system in which groundwater demand does not linearly decline with increased water use efficiency. Chapter 3 quantifies the amount of groundwater that enters surface water systems, the number of times this water is reused for agriculture, and the minimum amount of groundwater required by current agricultural systems in the hypothetical scenario of perfect irrigation efficiency.</p>

<p> The goal of this study is to characterize spatial variability of snow water equivalent (SWE) at the meter scale. The study includes measurement of SWE with a new pressure sensor and use of meteorological sensor data to investigate physical properties within the snowpack that can affect sensor measurement. The new sensor, which can continuously measure a load equivalent to up to 5.5 meters of snow, is designed to be smaller and less expensive (&lt; $1,500) than traditional pressure sensors (> $10,000). Manual snow cores and detailed snow pit analyses were performed to assess accuracy of the sensors and identify physical properties that may be related to sensor measurement error. SWE sensor response and accuracy were assessed between sensors and through comparison with bulk precipitation gage, manual SWE measurements, and snow pillows. SWE sensor readings compared favorably to other measurement methods, particularly in early and peak season. Spatial variability of SWE during the melt season of the two low-snow years during the study period confounded our ability to compare multiple sensor readings for validation. Spatial variability of SWE at study sites was calculated from sets of manual SWE measurements. The correlation length of 80 cm, determined using semi-variograms, highlights the small scale variability in SWE. Statistical resampling of manual measurements suggests that a minimum of ten manual measurements are needed to get within 10% of the spatial average of SWE. Although SWE can remain relatively stable during the melt period, this can be a result of increased density with decreasing snow depth, suggesting that simple inferences about SWE from depth measurements are not appropriate.</p>

<p> With future climate change and increased water demand and scarcity in the Colorado River Basin, the Bureau of Reclamation estimates that the costs of salinity damage will increase for Colorado River users and will exacerbate the current salinity challenges. This study focuses on saline and sodic soils associated with the Mancos Shale formation in order to investigate the mechanisms driving sediment and salinity loads in the Price-San Rafael River Basin of the upper Colorado River. A Walnut Gulch rainfall simulator was operated with a variety of slope angles and rainfall intensities at two field sites (Price, Dry-X) near Price, Utah in order to evaluate how the amount and spatial distribution of vegetation affects salinity in runoff. For each simulated rainfall event, the time-varying concentrations of major cations, anions, and sediment in runoff were measured. Principal component analysis revealed that the two field sites are generally different in runoff water chemistry and soil chemistry, likely due to the difference in parent material and soil indicative of their location on different geologic members. The Dry-X site also has substantially greater total dissolved solids (TDS) and sediment in runoff, soil sodium absorption ratio (SAR), and soil cation exchange capacity (CEC) than the Price site. Despite these differences, a consistent positive linear relationship between the plot-averaged sediment and TDS concentration was found across both sites. The Rangeland Hydrology Erosion Model (RHEM) was calibrated to provide unbiased estimates of sediment in runoff from 23 runs of the rainfall simulator. RHEM simulated the plot-plot variability best at Dry-X compared to Price. Sensitivity analysis of the RHEM input parameters showed that the splash and sheet erodibility coefficient (Kss) and the effective saturated conductivity coefficient (Ke) had the largest influence on the model&rsquo;s sediment and discharge outputs, respectively. The regression that predicted TDS concentration from sediment was applied to RHEM outputs to show that the model could be used to provide salinity estimates for different storm intensities on this part of the Mancos Shale. The potential influence of vegetation canopy cover on sediment production from these two sites was inferred by running RHEM with canopy cover values ranging from 0% to 100%. This changed sediment output by 111% to -91% relative to the present vegetation cover. Measures of the geometry of soil and vegetation patches at Dry-X, such as fractal dimension index and proximity index, showed a relationship to error residuals from RHEM. As the vegetation becomes less isolated, more uniform, and the tortuosity of the bare soil area increases, observed sediment decreases relative to RHEM predictions. The results of this study will help land management agencies assess the feasibility of mitigation strategies for reducing sediment and salinity loads from the saline and sodic soils of the Mancos Shale formation and indicate a possible benefit to incorporating the parameters that describe the spatial pattern of vegetation in RHEM.</p>

14 pp. / Arizona Watershed Stewardship Guide: Geologic Processes Arizona Watershed Stewardship Guide: Watershed Ecology Arizona Watershed Stewardship Guide: Watershed Hydrology Arizona Watershed Stewardship Guide: Watershed Soils / Arizona Watershed Stewardship Guide was created to help individuals and groups build a mutual foundation of basic knowledge about watersheds in Arizona. It is intended to help Arizonans understand and be good stewards of their watersheds. This guide was designed to compliment the mission of the Arizona Master Watershed Steward Program to educate and train citizens across the state to serve as volunteers in the monitoring, restoration, conservation, and protection of their water and watersheds. This guide consists of 10 self-contained modules which teach one or more important aspects of watershed science or management to a public adult audience.

Climate variability and landscape characteristics interact to define specific catchment hydrological response. Catchments are considered fundamental landscape units to study the water cycle, since all aspects of the land surface component of the hydrological cycle come together in a defined area, which enables scientific research through mass, momentum and energy budgets. The role of climate-landscape interactions in defining hydrologic partitioning, particularly at the catchment scale, however, is still poorly understood. In this study, a catchment scale process-based hydrologic model (hillslope storage Boussinesq- soil moisture model, hsB-SM) was developed to investigate such interactions. The model was applied to 12 catchments across a climate gradient. Dominant time scales (T.S.) of catchment response and their dimensionless ratios were analyzed with respect to climate and landscape features to identify similarities in catchment response. A limited number of model parameters could be related to observable landscape features. Several T.S. and dimensionless numbers show scaling relationships with respect to the investigated hydrological signatures (runoff coefficient, baseflow index, and slope of the flow duration curve). Some dimensionless numbers vary systematically across the climate gradient, pointing to the possibility that this might be the result of systematic co-variation of climate, vegetation and soil related T.S. Each of 12 behavioral hsB-SM models were subsequently subjected to each of 12 different climate forcings. Mean deviations from Budyko's hypothesis controlling long-term hydrologic partitioning (represented by the evaporation index, E/P, dependence on the aridity index, PET/P) were computed per catchment and per climate. The trend observed per catchment could be explained by the dimensionless ratio of perched aquifer storage-release T.S. and mean storm duration T.S. The trend observed per climate could be explained by an empirical relationship between fraction of rainy days and average daily temperature during those days. Catchments that produce more E/P have developed in climates that produce less E/P, when compared to Budyko's hypothesis. Also, climates that give rise to more E/P are associated with catchments that have vegetation with less efficient water use parameters. These results suggest the possibility of vegetation and soil co-evolution in response to local climate leading to (catchment scale) predictable hydrologic partitioning.

<p>Lakes and wetlands cover a large portion of the earth’s surface and play a crucial role in hydrology. They provide permanent and temporary storage for water within the landscape allowing for greater infiltration and evaporation along with a reduction in peak flooding events. Lakes and wetlands also provide many other non-hydrological benefits such as their ability to improve water quality and provide wildlife and fisheries habitat. Despite their known benefits, wetland destruction has been a prominent issue for many years. This study quantifies the hydrologic effects of lakes and wetlands by introducing a parametrization method for hydrologic model simulations in the North American Land Data Assimilation System (NLDAS) domain. Lake profiles were created based on the geospatial lake depth-area relationship through interpolation of known lake depths and areas throughout the domain. Wetlands were parametrized based on topographic wetness index (TWI) calculated using high-resolution DEM imagery. Wetland profiles were created using a binning technique along with the DEM and land use classifications. The Variable Infiltration Capacity (VIC) macroscale hydrologic grid-based model and its associated lake and wetland algorithm were used to quantify the effects of lakes and wetlands on streamflow. Profiles were generated for every corresponding VIC grid cell in the NLDAS domain, but for this study two watersheds, the Buttahatchee River in Mississippi and the Black River in North Carolina, were selected to test the parametrization and quantify the impact of lakes and wetlands on watershed hydrology. The Buttahatchee River watershed contains 6.6% lakes and wetlands, which were predominantly clustered near the stream channel, and the Black River watershed contained 19.2% lakes and wetlands which were spread out across the entirety of the watershed. Simulated daily streamflow with and without the lake and wetland algorithm activated was used to evaluate impacts on flood frequency as well as components of the water balance. Flood magnitude decreased due to the presence of lakes and wetlands. This decrease was 5.8% and 29.6% for a 10-year return period flood for the Buttahatchee River and the Black River sites, respectively. Mean annual flowrate decreased significantly as a result of lakes and wetlands indicating storage of water in the lakes and wetlands allowed for a greater degree of evapotranspiration. There were 1.6% and 10.9% decreases in average streamflow rates as well as corresponding 0.3% and 4.1% increases in annual evapotranspiration in the Buttahatchee River and Black River watersheds, respectively. While lakes and wetlands reduce peak flood events and decrease average streamflow rates through increased storage and evapotranspiration, the magnitude of these impacts varies based on the quantity and distribution of lakes and wetlands in the watershed as well as the climate and vegetation present. </p>

<p>Southwest Foods in Lafayette, Louisiana has multiple underground storage tanks that leaked petroleum products over a period of time, releasing numerous toxic constituents of concern into the surrounding soil and groundwater. During the assessment phase of risk evaluation, the Synthetic Precipitation Leaching Procedure (SPLP) test was used to measure the leaching potential of possibly contaminated soils and lithologies when exposed to acidic rainfall. However, during the site investigation, SPLP data produced erratic results that apparently are related to the type of geologic material (?soil?) involved. These erratic results could have major implications for assessment, remediation, and the establishment of Risk Evaluation/Corrective Action Program (RECAP) standards in the state of Louisiana. Incorrectly applied RECAP standards could ultimately mean contaminants of concern could reach points of exposure (POEs), and potentially harm nearby residents and the environment. Previously, lithological composition had not been considered when evaluating the environmental impact of the test. At the site, numerous geotechnical soil boring logs were completed, and soil samples were sent to analytical laboratories for analysis of contamination. Soil analytical data compiled by the laboratories along with samples acquired from multiple groundwater monitoring wells at the site provided an in-depth view into the degree of contamination at Southwest Foods and produced the first signs of erratic SPLP test results. Contour maps of contamination and groundwater potentiometric levels were created to show both the level of contaminants in soil and the possible migration paths of affected groundwater. The SPLP sample data were evaluated and categorized into lithological subgroups for further examination. The lithologies, or soil types (with USCS symbols), that produced erratic results (i.e., some ?passed? and some ?failed?) for the SPLP analyses included ?clay, high plasticity? (CH) and ?clayey silt/sandy silt/silt? (ML). The results for ?silty clay/sandy clay? (CL) were more consistent. The inconsistent SPLP data could result in incorrect application of site-specific RECAP standards and the subsequent cleanup at Southwest Foods and conceivably at other contaminated sites as well.

<p> Aquifer mergence zones are erosional unconformities that hydraulically join interlaying aquifers. In the East Newport Mesa in Orange County, Southern California, aquifer mergence zones may provide a pathway for potentially impaired low-quality groundwater of the shallow, semi-perched aquifer to migrate into the underlying regional, potable, confined aquifers. Major ion and stable isotope results imply that vertical mixing is occurring locally between the discrete shallow and deep groundwater endmembers. Vertical mixing is suggested by anomalously young radiocarbon age-dates of deep groundwater units. Radon-222 results show that shallow groundwater is discharging from the mesa, and is also actively intruded by surface water. Mixing of shallow and deep waters at these mergence zones may pose a threat to the deeper regional aquifer system. </p><p>

<p> Hyperspectral and polarimetric imaging of the ocean, both below and above the water surface, has increased the interest of the Ocean Color (OC) scientific community for decades in an attempt to answer questions related to climate change, monitoring of water quality, assessment of the impact of anthropogenic activities on marine life and underwater ecosystems, detection and characterization of underwater targets. These needs are recognized by worldwide efforts devoted to acquiring accurate time series measurements in open-ocean and coastal waters by OC satellite imagery to produce reliable high-quality data records, which can be used both in support of operations and in climate studies. The reliability of satellite observations of the open-ocean and coastal zones requires these remote instruments to be regularly assessed and validated against actual in-situ measurements along with related atmospheric corrections. However, despite improvements in satellite data and retrieval algorithms, accurate retrievals in coastal waters remain challenging. </p><p> Modern hyperspectral imagers usually carry out their measurements on moving platforms, aircrafts or orbiting satellites, using push-broom scanning techniques for the acquisition of 3-D data cubes (along-track, cross-track and spectral). These data, however, may not always reflect accurately the temporal variability of measurements in a very dynamic atmosphere-ocean environment, especially in coastal areas. In recent years, new technologies have made possible the exploration of snapshot hyperspectral and polarimetric imaging of the ocean in an attempt to improve the accuracy of existing methods and exploring the pixel-by-pixel variability of the signal measured, often neglected in standard approaches. </p><p> The work presented in this thesis investigates and discusses imaging of underwater polarimetric targets in various water types and the estimation of parameters of the veiling light and the attenuation coefficients responsible for image degradation and blurring as a function of the water properties. In above water observations the effects of atmospheric aerosols and wind speed on the surface reflectance coefficients are studied along with the pixel-by-pixel variability of water-leaving radiance (<i>L_w</i>) and its relationship to water constituents for different coastal waters and atmospheric conditions, the impact of this variability on the uncertainties in above water measurements and satellite retrievals. Validation of all results has been achieved by the comparison with the comprehensive Vector Radiative Transfer simulations of the Atmosphere-Ocean System, as well as measurements by a number of other collocated radiometric and polarimetric instruments. </p><p>