Recent Publications
GROUNDWATER IMPACTS ON STREAM BIODIVERSITY AND COMMUNITIES: A REVIEW
Groundwater discharge into streams influences the biodiversity and health of groundwater-dependent stream ecosystems. These localized upwelling zones may act as biodiversity hotspots, or areas with a heightened amount of endemic species richness and abundance when compared to the surrounding locality. This input water creates environments with unique chemical compositions and water temperatures that serve as ideal habitat for various species within the ecosystem. Although difficult to identify and sample, these underwater groundwater–surface water interaction zones are important for fish spawning, benthic macroinvertebrate biodiversity, microbial communities, and aquatic and riparian vegetation. In this review, we highlight the groundwater characteristics that influence stream biodiversity and community structure. We argue for the importance of increased research on biodiversity indicators of groundwater upwelling zones as well as more public involvement through citizen science practices on the indirect and direct relationships between groundwater and dependent stream ecosystems.
CHILDREN'S BOOKS FOR RESEARCH-BASED OUTREACH AND SCIENCE COMMUNICATION PEDAGOGY
Academics are encouraged to integrate scientific research with the public, but methods of doing so are often transient and insubstantial. Students and future scientists also require training and exposure to the importance of public outreach and science communication within STEM fields. Here, I describe two projects that provide a template for using children's books as an efficient and impactful means of science communication. The first part describes an international research project that culminates in the writing, illustration, and distribution of a children's book. Farzana’s Journey is a children’s book based on multidisciplinary research on the pairing of the physical and human systems in coastal Bangladesh. Written, illustrated, and freely distributed in the Bengali-language, the book is a place-based tool to teach rural Bangladesh communities about the natural world and our scientific findings. Through the development and distribution of the book, we encouraged collaboration and public outreach with scientists, artists, and students concerned with enhancing educational and social opportunities in rural communities. We also ensure a physical tie to the community after the project's culmination. The book sparks children’s curiosity in the local environment, while also demonstrating a means for sustainable educational outreach with impoverished, remote communities. The second part of the paper provides an overview of how this type of science communication can be taught to early career scientists. Students in an intensive learning undergraduate course produce children's books about a scientific concept or process. I describe the curricular context and layout of the course, the assessment of deliverables, and the impacts of the science storytelling process as a model for teaching communication literacy. Together, these efforts demonstrate the potential impact of children's books on science communication efforts among students, early career scientists, and local communities.
SURFACE WATER-GROUNDWATER CONNECTIONS AS PATHWAYS FOR INLAND SALINIZATION OF COASTAL AQUIFERS
Coastal agricultural zones are experiencing salinization due to accelerating rates of sea-level rise, causing reduction in crop
yields and abandonment of farmland. Understanding mechanisms and drivers of this seawater intrusion (SWI) is key to mitigating
its effects and predicting future vulnerability of groundwater resources to salinization. We implemented a monitoring network
of pressure and specific conductivity (SC) sensors in wells and surface waters to target marsh-adjacent agricultural areas in
greater Dover, Delaware. Recorded water levels and SC over a period of three years show that the mechanisms and timescales of
SWI are controlled by local hydrology, geomorphology, and geology. Monitored wells did not indicate widespread salinization of
deep groundwater in the surficial aquifer. However, monitored surface water bodies and shallow (<4m deep) wells did show SC
fluctuations due to tides and storm events, in one case leading to salinization of deeper (18m deep) groundwater. Seasonal peaks
in SC occurred during late summer months. Seasonal and interannual variation of SC was also influenced by relative sea level. The
data collected in this study data highlight the mechanisms by which surface water-groundwater connections lead to salinization of
aquifers inland, before SWI is detected in deeper groundwater nearer the coastline. Sharing of our data with stakeholders has led to
the implementation of SWI mitigation efforts, illustrating the importance of strategic monitoring and stakeholder engagement to
support coastal resilience.
SURFACE WATER-GROUNDWATER CONNECTIONS AS PATHWAYS FOR INLAND SALINIZATION OF COASTAL AQUIFERS
Coastal agricultural zones are experiencing salinization due to accelerating rates of sea-level rise, causing reduction in crop yields and abandonment of farmland. Understanding mechanisms and drivers of this seawater intrusion (SWI) is key to mitigating its effects and predicting future vulnerability of groundwater resources to salinization. We implemented a monitoring network of pressure and specific conductivity (SC) sensors in wells and surface waters to target marsh-adjacent agricultural areas in greater Dover, Delaware. Recorded water levels and SC over a period of three years show that the mechanisms and timescales of SWI are controlled by local hydrology, geomorphology, and geology. Monitored wells did not indicate widespread salinization of deep groundwater in the surficial aquifer. However, monitored surface water bodies and shallow (<4 m deep) wells did show SC fluctuations due to tides and storm events, in one case leading to salinization of deeper (18 m deep) groundwater. Seasonal peaks in SC occurred during late summer months. Seasonal and interannual variation of SC was also influenced by relative sea level. The data collected in this study data highlight the mechanisms by which surface water-groundwater connections lead to salinization of aquifers inland, before SWI is detected in deeper groundwater nearer the coastline. Sharing of our data with stakeholders has led to the implementation of SWI mitigation efforts, illustrating the importance of strategic monitoring and stakeholder engagement to support coastal resilience.
AN ON-CAMPUS STREAM RESTORATION PROJECT AS INTERDISCIPLINARY SENIOR CAPSTONE EXPERIENCE
Senior capstones and practicum courses can provide environmental studies majors with real-world skill sets and pride in
their environmental engagements. This article presents a capstone project that connected students with on- and off-campus
communities and produced measurable environmental change through stream restoration. Students researched ecological
and historical aspects of the land, developed campus community awareness of the stream, created a restoration plan, and
conducted a community cleanup of Snyder Branch Creek. Students planted over 120 riparian plants, removed 900 gallons
of invasive species, stabilized 200 linear feet of stream bank, educated the community on the ecological importance of the
area, and crafted a restoration plan for the remaining stream channel. Students reported increased pride in the program and
campus as well as improvement in career readiness.
Groundwater pumping causes salinization of coastal streams due to baseflow depletion: Analytical framework and application to Savannah River, GA
Groundwater-surface water interactions and associated water management issues are complicated by the risk of salinization along coastlines. Groundwater pumping can be a driving factor of streamflow depletion and allow for increased stream saltwater intrusion. In this study, we develop an analytical framework combining two analytical approaches to calculate the length of saltwater intrusion at high slack water and the stream depletion rate due to groundwater pumping. We test this framework using data from the Savannah River in southeastern U.S and use it to explore saltwater intrusion in the surface water system. The analytical approach produces an accurate estimate of the position of the salt front at approximately 56 km inland. Current pumping rates decrease streamflow by less than 1%, resulting in an increase in the saltwater intrusion length of 100 m. Increased groundwater pumping scenarios, however, show a risk of extending the saltwater intrusion length up to 4 km inland. In these cases, effects from pumping-induced saltwater intrusion would equal or exceed the impacts of sea-level rise or geomorphic change. Salinity is a critical factor in the ecological balance of this estuarine ecosystem and this analytical approach allows for investigation of hypothetical groundwater development in the region. We show, for the first time, the direct link between groundwater pumping and coastal stream salinity that should be an important management consideration all along developed coastlines.
Multicriteria Decision Analysis of Drinking Water Source Selection in Southwestern Bangladesh
Decision analysis methods provide opportunities to explore alternatives for drinking water resources in impoverished, rural regions of developing countries. With varying success, southwestern Bangladesh communities currently use multiple drinking water sources, including rainwater harvesting, ponds, pond sand filters, managed aquifer recharge (MAR), and tubewells. This study uses a variety of multicriteria decision analysis (MCDA) methods to assess the probable success of these drinking water sources based on various technical, economic, social, and environmental factors. Data include an assortment of physical and social sources including focus group interviews, surveys, and water quality measurements. Additionally, the MCDA methods (multiple attribute value theory, analytic hierarchy process, ELECTRE I, and ELECTRE III) are informed by preferences from three stakeholders—locals, nongovernmental organizations, and environmental science academics—to ensure proper weighting of criteria for success. Across all MCDA methods, we find that rainwater harvesting is the most likely to succeed as a reliable drinking water source in the region. Conversely, MAR is the least preferred alternative. Sensitivity analyses suggest a robust ranking order that is relatively insensitive to model parameters, including water source performance score and stakeholder weighting, across all criteria categories. This case study demonstrates how decision modeling and alternative assessment can be the first step to reach sustainable solutions in complex water management problems. DOI: 10.1061/(ASCE)WR.1943- 5452.0001029. © 2019 American Society of Civil Engineers.
The uncertainty in methane (CH4) source strength of rice fields and wetlands is particularly high in South Asia CH4 budgets. We used satellite observations of CH4 column mixing ratios from Atmospheric Infrared Sounder (AIRS), Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and Greenhouse Gases Observing Satellite (GOSAT) to estimate the contribution of Bangladesh emissions to atmospheric CH4 concentrations. Using satellite-derived inundation area as a proxy for source area, we developed a simple inverse advection model that estimates average annual CH4 surface fluxes to be 4, 9, and 19 mg CH4 m−2 h−1 in AIRS, SCIAMACHY, and GOSAT, respectively. Despite this variability, our flux estimates varied over a significantly narrower range than reported values for CH4 surface fluxes from a survey of 32 studies reporting ground-based observations between 0 and 260 mg CH4 m−2 h−1. Upscaling our satellite-derived surface flux estimates, we estimated total annual CH4 emissions for Bangladesh to be 1.3 ± 3.2, 1.8 ± 2.0, 3.1 ± 1.6 Tg yr−1, depending on the satellite. Our estimates of total emissions are in line with the median of total emission values for Bangladesh reported in earlier studies.
In the polder region of coastal Bangladesh, shallow groundwater is primarily brackish with unpredictable occurrence of freshwater pockets. Delta building processes, including the codeposition of fresh-to-saline porewater and sediments, have formed the shallow aquifer. Impermeable clay facies and the lack of a topographical gradient limit the flow of groundwater and its mixing with surface water so controls on spatial variability of salinity are not obvious. By characterizing groundwater-surface water (GW-SW) interactions, this study attempted to identify areas of potable groundwater for the polder communities. We used transects of piezometers, cores, electromagnetic induction, and water chemistry surveys to explore two sources of potential fresh groundwater: (1) tidal channel-aquifer exchange and (2) meteoric recharge. Fresh groundwater proved difficult to find due to heterogeneous subsurface lithology, asymmetrical tidal dynamics, extreme seasonal fluctuations in rainfall, and limited field data. Geophysical observations suggest substantial lateral variability in shallow subsurface conductivity profiles. Piezometers show varying degrees of tidal pressure attenuation away from the channels. Nevertheless, the active exchange of freshwater appears to be limited due to low permeability of banks and surface sediments. Results indicate that pockets of fresh groundwater cannot be identified using readily available hydrogeological methods, so alternative drinking water sources should be pursued. By better understanding the hydrogeology of the system, however, communities will be better equipped to redirect water management resources to more feasible and sustainable drinking water options.
FARZANA'S JOURNEY: A BANGLADESH STORY OF WATER, LAND, AND PEOPLE
Farzana's Journey is a narrative about a young girl, who must walk a long distance to fetch her family's water. Her usual journey develops into an adventure as she meets animal characters, who relay a story about her ever-changing environment and the subsequent human adaptation. The book was written as part of Vanderbilt University's research on the coevolution of physical and human systems in southwest Bangladesh.