Research

Below I summarize current and future research, as well as some of the key research projects that I have done in the past, and I list some of the key findings from past projects. I present them in reverse chronological order, with the most recent first. While the study sites have varied geographically (Antarctica, Niger, Ethiopia and Vermont could hardly be more different), the common thread connecting all of these projects is climate change impacts. I have always been interested in how climate change translates into societal and ecological impacts.

Summit-to-shore snow sensing and modeling (2022-2025):

This research project, funded by the Cold Regions Research and Engineering Lab (CRREL), aims to improve monitoring and modeling of snow at multiple elevations, aspects, and canopy conditions in Vermont. For this project, we installed 22 new meteorological stations with snow depth sensors in a transect spanning the shore of Lake Champlain in South Burlington, over Mount Mansfield (which hosts a high density of stations), and ending in the Sleeper’s River watershed in northeastern Vermont. Four of the stations also measure snow water equivalent using scales. With these data, we aim to learn about the dependence of snowpack characteristics on a number of meteorologic and environmental determinants, which is important in a region seeing rapid changes in the winter.  For example, results from this study will allow detailed analysis of changing conditions that are increasing the risk of rain-on-snow flooding. A significant rain-on-snow flood occurred in December 2023 during the project period, underscoring the need for such research in this region.

Bridge-Stream interactions, Vermont (2018-2021):

This research project, funded by the Vermont Agency of Transportation, explored the response of river hydraulics to alterations of bridges and associated embankments under extreme event scenarios. Using the 2-dimensional HEC-RAS river hydraulics model, we simulated alterations to bridges and the impacts on both upstream and downstream peak water levels and peak flows during extreme events. We began by studying Otter Creek, a low-gradient river that drains the central Green Mountains and flows north into Lake Champlain, removing or widening bridges in the model. Some of the bridges showed pronounced impact both upstream and downstream, and some showed very little impact, depending on the original dimensions and whether there was an elevated grade on either side as is typical of railroad bridges. We later shifted attention to the Mad River in central Vermont, a higher-gradient stream. MS students Rachel Seigel and Matthew Trueheart worked on this project.

Research on Adaptation to Climate Change (RACC) and Basin Resilience to Extreme Events (BREE) projects (2011-2021):

These two projects were funded by NSF EPSCoR as RII Track 1 awards, for a total of $40 million over ten years (two separate five-year grants). I was involved with these highly successful projects from inception to finish. I began as a team lead for hydrological systems, then became Associate Director, and later became director and principal investigator in 2018 until the end of the NSF funding period in late 2021.

The research projects were highly interdisciplinary studies of Lake Champlain watersheds as social-ecological systems, seeking to understand the basic social and biogeochemical drivers of harmful algal blooms that recur in certain parts of the lake, as well as the social, hydrological and climatic processes that can affect the transport of excess nutrient leading to harmful algal blooms. The project involved people from multiple disciplines working closely together, such as geologists, environmental engineers, social scientists, computer scientists, climatologists, and others. A key outcome of the project was the development of an Integrated Assessment Model (IAM) that simulates various disciplinary processes together as a tightly coupled system (from climate to lake water quality outcomes). This necessitated close collaboration of the diverse participants which was highly rewarding to all involved. Many graduate students and postdocs worked on this project.

Malaria and land use, Ethiopia (2009-2010):

During my first two years at the University of Vermont, I worked to expand hydroclimate/malaria research by establishing field research at a site in southwestern Ethiopia, near Jimma. Together with my first graduate student Jody Stryker, we set up a meteorological and hydrological observation system in a region that had seen a dramatic upswing in malaria in recent years. It was possible that climate change played a direct role through warming (higher temperatures cause mosquitoes that acquire malaria parasite to become infectious more quickly) but there are also good reasons to believe that land use change affected hydrology leading to more runoff collecting in pools, and other processes. For example, we integrated with a research group from Bentley University and Harvard University that had been studying the site for many years, and they had good data indicating that local farmers switching from growing the traditional teff to maize crops increased mosquito longevity because they had more nutrition from the wind-blown maize pollen that was recently planted. This could be a clear link with malaria increases. Our goal in Ethiopia was to tease apart these various causations, including hydroclimate variability, and improve understanding of malaria trends in Ethiopian highlands. Our research yielded some insights into the hydrological controls of malaria in the region, but unfortunately research at the site was discontinued because I could not get the project funded. PhD student Jody Stryker worked on this project.

Hydrology of malaria, Niger (2005-2009):

Malaria modeling using hydrology: My PhD research investigated the role of hydrology in seasonal malaria transmission, in areas where water availability is the limiting factor (remembering that malaria-transmitting Anopheles mosquito larvae need water to breed). This took me to Niger, a country whose Sahel region bridges the Sahara desert to the north and the equatorial forests to the south. The Sahel has a large human population, and these people are exposed to malaria by mosquitoes multiplying following rainfall, but are also dependent on the rain for subsistence farming. The region shows pronounced seasonal and interannual rainfall variability, with a rainy season from June through September. However, the northern extent of the intertropical convergence zone, which brings with it the summer rains, varies from year to year. This can lead to both famine if there is not enough rain, and malaria epidemics if a lot of rain falls (especially when the previous year had little rain and immunity has waned). The population dynamics of mosquitoes depends on the presence of small, turbid pools favored by the dominant malaria-transmitting mosquitoes, Anopheles gambiae. This means that hydrology is a necessary intermediate linking climate variability to malaria risk where water availability limits mosquito abundance. I developed the very high resolution hydrologic models that link climate with malaria, simulating overland flow of water and collection into the muddy puddles which are favored by Anopheles gambiae mosquitoes. The hydrologic models allowed a number of modeling experiments to be run, including simulations for the impacts of climate change, abrupt climate shifts of the type that have occurred there in the past, interannual climate variability, larviciding (see below) and environmental management by altering the land surface. Moreover, the highly detailed agent-based structure of the model yielded some novel insights. For example, in previous studies the correlation of rainfall to malaria in the Sahel has been surprisingly poor. The expectation that amount of monthly (or seasonal) rain could explain mosquito abundance did not hold particularly well in major previous work (such as the Garki Project in the Sahel zone of northern Nigeria), which was puzzling. However, using the detailed model I was able to show that the interplay of temporal rainfall patterns (the time elapsed between storms) with topographic variability can explain much of the observed variance in mosquito abundance. If the time between storms is longer than the time needed for a pool to dry out, then an entire cohort of mosquitoes in that pool is lost resulting in a nonlinear connection between rain and mosquitoes. This effect is not captured when using long rainfall integration periods, like monthly totals. The model was also able to show that the abundance of larvae in a particular water body does not necessarily indicate the pool’s danger to the community. The proximity of peoples’ houses to water bodies is a much better indicator of the relative importance of a pool in the local transmission.

Sustainable larvicide, Niger and Ethiopia (2006-2010):

I spent seven months straight in the field in 2005-2006, taking repeat field measurements in two Niger villages. During that time, I witnessed an extensive insecticide-treated-bed net deployment taking place in the country. It struck me how malaria control initiatives relied upon these expensive, logistically difficult international efforts that are almost certain to lead to insecticide resistance in mosquitoes at some point and cannot control how well bed nets are used. I wondered if there might be a local natural source of insecticide that could help the situation and get away from reliance on the bed nets manufactured far away from these poor, remote villages. After some research, I found references to the neem tree having such properties, and neem is the most common tree in Niger Sahel villages. People prize the trees for shade and wood and they are hardy in the arid climate.  There had been some observations documented in Sudan of locust swarms decimating almost all vegetation in certain villages, but leaving the neem trees untouched. This led those researchers to cunduct investigations on the properties of the neem tree, resulting in the identification of a cocktail of 99 active chemicals in neem. This was highly promising to get around the problem of insecticide resistance in bed nets, and promised an abundant source directly at the target site. We just had to test the harvesting and application to mosquito breeding in the field. With two student colleagues, we demonstrated the efficacy of neem at combatting larval stage Anopheles gambiae mosquitoes, without the need for outside aid, and without the threat of the emergence of resistance. This positive result was documented in our 2008 Malaria Journal paper (see publications tab, reference number 5). For this effort, our team won an MIT IDEAS award in 2007 which was enough to fund the trial.

Field hydrology, Antarctica (1998-1999): 

In this project I investigated the impacts of hydroclimatic variability on the water balance of closed-basin lakes in the Dry Valleys of Antarctica. This was a particularly exciting start of my research career. It was the perfect combination of rugged adventure and earth science, which is exactly what I was looking for. I had a wonderful experience working under my advisor Diane McKnight in the Dry Valleys, based out of a camp on the shores of Lake Fryxell (our camp was called F6 back then, which no longer exists). The towering mountains with polar glaciers provided an impressive backdrop for field investigations into the glacial meltwater streams that feed into a series of closed-basin lakes. Helicopter flights across the McMurdo sound and in the 15,000-foot Transantarctic Mountains, and other adventurous aspects of the job such as frequent long hikes with gear greatly colored this experience. Daily work entailed measurement of stream flows, which are triggered by the low-angled sun striking the vertical sides of nearby glaciers. These measurements were then used to calibrate automated stream gauges at multiple sites surrounding three lakes (Fryxell, Hoare, and Bonney). The site is part of the LTER (Long Term Ecological Research) network, with diverse research projects going on simultaneously. One of the primary reasons for stream gauging is to measure the nutrient fluxes entering the closed basin lakes, because those nutrients feed extremophile ecosystems characterized by diverse algae living with very low light and nutrient. The stream gauging data observations could also be used for climate change studies. Lake Bonney has a two-lobed shape. The distance across the narrow strait between the two lobes was actually measured back in 1903 by a party from Robert Scott’s Antarctic expedition seeking the magnetic south pole. Combined with modern-day bathymetry measurements, this measurement from Scott’s diary allowed retrospective Monte Carlo simulation of water balance (and therefore lake level) in the lake assuming current climate conditions, which could be compared to the actual lake level backed out by the 1903 measurement. The conclusion was that the recent water balance has favored more meltwater input, either through less cloud cover or through warmer temperatures or both. My journal articles numbered 1 and 2 under the publications tab above describe this research.