ESTIMATING THE EFFECTIVE HYDRAULIC PROPERTIES OF THE SUBSURFACE AND THEIR SPATIOTEMPORAL RESPONSE TO CLIMATE USING A MODIFIED STREAMFLOW RECESSION ANALYSIS

Between periods of precipitation or snowmelt, the volume and timing of streamflow is largely determined by the properties of the subsurface and the time-varying distribution of groundwater storage. While streamflow during these periods (i.e., baseflow) is commonly treated according to a unique storage-discharge relationship, recent innovations in streamflow recession analysis have allowed novel findings regarding the variability of both the stability of baseflow and its nonlinearity (i.e., the concavity of the hydrograph), as well as the regional clustering of these characteristics. Here, I assess traditional and novel models of streamflow recession behavior using historical streamflow data from over 1,000 watersheds in the continental United States (US). Observed streamflow behavior from only nine watersheds often conforms to traditional models, and streamflow behavior from the vast majority (>99%) of watersheds typically conforms to a parsimonious parallel aquifer model which accounts for subsurface heterogeneity. I then apply this conceptual model alongside remotely-sensed estimates of watershed-scale groundwater storage and climate reanalysis estimates of watershed-scale soil moisture, rates of evapotranspiration, and cumulative precipitation to investigate seasonal patterns in both the stability and nonlinearity of streamflow that vary systematically across large regions. I find that coincident watershed storage is the best predictor of baseflow stability in many regions (particularly the Appalachian Mountains) while evapotranspiration from two to three months previous is the best predictor of baseflow stability in other regions (particularly the Pacific Northwest), and discuss the novel finding that streamflow nonlinearity has increased significantly in most watersheds across the US since 1980. Then, I estimate the effective hydraulic properties of all gaged watersheds in the continental US that are largely dam-free by adapting traditional methods of streamflow recession analysis to account for subsurface heterogeneity. Using these results, I develop models of effective hydraulic properties based on estimates of watershed topography, soils, bedrock, and climate, and apply these models to predict the effective hydraulic properties of all watersheds in the continental US. Key practical results of this analysis include: 1) the finding that streamflow is more stable during periods of extended drought than generally predicted; 2) the identification of regional patterns in the response of streamflow to climate change; and 3) a novel dataset representing the effective hydraulic properties of the subsurface for the entire continental US for use in regional-scale hydrological models.Doctor of Philosoph

Identifying long term empirical relationships between storm characteristics and episodic groundwater recharge

Shallow aquifers are an important source of water resources and provide baseflow to streams, yet actual rates of groundwater recharge are difficult to estimate. While climate change is predicted to increase the frequency and magnitude of extreme precipitation events, the resulting impact on groundwater recharge remains poorly understood. We quantify empirical relations between storm characteristics and recharge to precipitation ratios (RPR) for a variety of geographic and land-use types across North Carolina. Increased RPR correlates with increased storm duration, whereas RPR decreases with increasing storm magnitude and intensity, especially in agricultural and urban areas. Though RPR is generally higher during the winter than the summer, this seasonal effect is magnified in the Appalachian and Piedmont regions. If, as predicted, growing seasons lengthen and storm intensity increases with a warming climate, decreased recharge in Appalachia, the Piedmont, and rapidly growing urban areas of the American southeast could further limit groundwater availabilityMaster of Scienc

Industrial relations in the UK shipping industry since the Second World War

The shipping industry has undergone a period of rapid and fundamental change during the three decades since the end of the Second World War. While these changes have been experienced world-wide and have promoted the implementation of technological advances and the growth of the world fleet, they have occurred during a period which has also witnessed a substantial relative decline in Britain's maritime position. It is the aim of this study to analyse their effect on industrial relations in the U.K. shipping industry

A novel benchmark dataset of daily groundwater recharge using the Water Table Fluctuation Method

<p>A newly developed benchmark dataset of groundwater recharge per unit specific yield (RpSy, n meters) at daily temporal resolution is presented. The data has been obtained through the application of the Water table Fluctuation (WTF) method at groundwater wells within the continental US. To ensure high-fidelity estimates, only wells that meet a set of stringent criteria have been considered.</p><p>The resulting product is a continuous daily RpSy (n meters) time series data for 485 groundwater wells. The data files are provided in the .csv format and consist of two columns for each observation well. The first column lists the local time, while the second column provides the RpSy time series in meters per day. Additionally, a file containing site information for all the selected wells is included. It contains four columns that detail the USGS ID of the groundwater well, its latitude (Lat), longitude (Long), and screen depth (depth, in meters). The data file can be accessed in most text editors and spreadsheets.</p&gt

A Needs-Driven, Multi-Objective Approach to Allocate Urban Ecosystem Services from 10,000 Trees

Urban areas face challenges including vehicular emissions, stormwater runoff, and sedentary lifestyles. Communities recognize the value of trees in mitigating these challenges by absorbing pollution and enhancing walkability. However, siting trees to optimize multiple benefits requires a systems approach that may cross sectors of management and expertise. We present a spatially-explicit method to optimize tree planting in Durham, NC, a rapidly growing urban area with an aging tree stock. Using GIS data and a ranking approach, we explored where Durham could augment its current stock of willow oaks through its plans to install 10,000 mid-sized deciduous trees. Data included high-resolution landcover metrics developed by the U.S. Environmental Protection Agency (EPA), demographics from the U.S. Census, an attributed roads dataset licensed to the EPA, and sidewalk information from the City of Durham. Census block groups (CBGs) were ranked for tree planting according to single and multiple objectives including stormwater reduction, emissions buffering, walkability, and protection of vulnerable populations. Prioritizing tree planting based on single objectives led to four sets of locations with limited geographic overlap. Prioritizing tree planting based on multiple objectives tended to favor historically disadvantaged CBGs. The four-objective strategy met the largest proportion of estimated regional need. Based on this analysis, the City of Durham has implemented a seven-year plan to plant 10,000 trees in priority neighborhoods. This analysis also found that any strategy which included the protection of vulnerable populations generated more benefits than others

Allen et al., Similarity of stream width distributions across headwater systems, data 2017

These files contain the results from Allen et al. "Similarity of stream width distributions across headwater systems". locationStreamSurveys.zip : contains stream hydromorphology data collected in seven headwater catchments in North America and New Zealand. repeatStreamSurveys.zip : contains stream hydromorphology data collected in six repeat surveys in the Stony subcatchment in Duke Forest, NC. streamWidthModelOutput.zip : contains stream width model parameters and output data presented in Allen et al. Note: the code used to analyze these data can be found at https://github.com/geoallen/streamWidthAnalysis2017