Our research is focused within the hydrological sciences, but often extends into the ecological sciences and occasionally has sociopolitical implications. Some selected projects are briefly described below.
Controls on Water Quality and Associated Harmful Algal Blooms
Water-quality degradation is a “wicked problem,” a challenge that is difficult to overcome because of incomplete or contradictory understanding, the number of factors involved, the large economic burden of the possible solutions, and the interconnected nature of terrestrial and aquatic environments, which are commonly studied separately. The problem is rooted in how water and contaminants are routed from “ridge-to-reef’, with myriad natural and anthropogenic forcings and feedbacks. These projects are designed to address these complex matters, bringing together scientific expertise and stakeholder partners under a set of common thematic questions. View media coverage of a recent award related to this research focus: - A Collaborative Approach to Harmful Algal Blooms in Florida's Largest Lake
Funding has been provided by the U.S. Environmental Protection Agency, the Florida State Department of Environmental Protection, and the Fred L. and Helen M. Tharp Endowed Scholarship Fund.
Reorganization of the Waterscape by Wetland Loss and Drainage Network Extension
The conterminous United States lost more than half of its wetland area between European settlement and the late 1980s. Recently, the trend has changed nationally, with wetland area in the conterminous United States remaining approximately constant in recent years. However, the trend has not changed in coastal watersheds on the Atlantic and Gulf of Mexico coasts, where wetland area continues to decrease. Net gains in wetland area, where they have occurred, can be largely attributed to both created or restored wetlands and other waterbodies (e.g., stormwater ponds). Concomitantly, ditching and draining has extended the natural drainage network and increased drainage efficiency. The subsequent rearrangement of the waterscape has been done incrementally in a series of one-off decisions, with no coherent, watershed-wide guidance or plan. This represents a large-scale shift in ecosystem functions, and the ecosystem services they provide, a massive experiment with no controls and unknown and/or unconsidered consequences.
Funding has been provided by the Tampa Bay Estuary Program, as flow-through from the U.S. Environmental Protection Agency, and St. Lucie County, Florida, and the Fred L. and Helen M. Tharp Endowed Scholarship Fund.
Ranking Inundation Potential of Wetlands in the Northern Tampa Bay Area
Following cutbacks in groundwater pumping at well fields operated by Tampa Bay Water, thousands of wetlands in the Northern Tampa Bay area showed evidence of hydrologic recovery. Few of these wetlands are monitored and many seasonal streams entering and exiting the wetlands have not been mapped. As a result, we currently have little information on the hydroperiod of these wetlands or their potential to contribute to down gradient streamflow and possible flooding. The objectives of this study are to use a combination of field data and remote sensing to map and characterize the stream flow entering and exiting each wetland and to rank wetlands across this region in terms of their inundation potential.
Funding has been provided by Tampa Bay Water.
Hydrological Connectivity Between Geographically Isolated Wetlands and the Broader Hydrological Landscape, Including Downgradient Wetlands and Waterbodies
Hydrological flowpaths connect landscapes in four dimensions—longitudinally, laterally, vertically, and through time. This four-dimensional hydrological connectivity, operating at local to landscape scales, is a basic tenet of freshwater ecology. Hydrological flowpaths are dynamic, expanding and contracting through seasons and storms, which results in headwater wetlands and streams being connected to downstream wetlands and waterbodies along a continuum controlled by watershed wetness, at various times and places disconnected, connected by slow groundwater flows, or connected by surface-water flows. Especially when and where the latter occurs, headwater wetlands and streams can be fully integrated into the surface-water flow network and serve as significant sources of water and water-borne materials for downgradient wetlands and waterbodies.
Funding has been provided by U.S. Geological Survey, the National Science Foundation, the U.S. Department of Justice, and the Pebble Limited Partnership.
Geological Control of Ecological Structure and Function in Sandhill Wetlands
Sandhill wetlands are wetlands embedded in imperiled sandhill communities. They exhibit a characteristic hydrology which can vary widely over days, seasons, or decades. This distinction is due to their karst origin, xeric setting, and dependence upon a shallow water table. In west-central Florida, the shallow water table is that of the Upper Floridan aquifer, part of the massive Floridan Aquifer System which spans all of Florida and parts of four southeastern states. Wetland hydrologic control by the water table of a regional water-supply aquifer is not well documented and has important implications for natural resource management, public water-supply and regulation.
Funding has been provided by the Southwest Florida Water Management District.
How is the Everglades Landscape Likely to Change in Response to Restoration and Climate Change?
As a low-lying coastal wetland, the Everglades is extremely sensitive to shifts in freshwater availability and influxes of seawater, which will be inevitable in future decades due to changes in rainfall, increased evapotranspiration, sea level rise, and restoration. We have provided the first landscape-scale simulations of ecological responses to a range of climate scenarios for the Everglades National Park which offered glimpses of vastly different future outcomes (Flower et al., 2017). This screening-level study revealed important data gaps and opportunities to develop new modules that integrate FCE long term data sets to answer important questions as to subsequent impacts on consumer dynamics, periphyton, and soil, and which restoration activities provide more ecosystem resilience in the face of the changes to come. Our scenarios modeling will help inform the Comprehensive Everglades Restoration Plan, to build resilience to climate change and sea level rise.
Funding has been provided by the National Science Foundation.
Collaborative Tool Development for Promoting Resilient Groundwater Resources and Holistic Watershed Management on the Kenai Peninsula, Alaska
Groundwater discharge plays a critical role in maintenance of temperature and nutrient supply for salmon-bearing stream on the Kenai Peninsula. Effective management of these systems requires knowledge of the distribution and extent of groundwater recharge and discharge sites, but this information has largely been lacking in this remote region. We will be integrating diverse datasets with GIS tools to develop a predictive model to map likely locations of groundwater recharge and discharge sites. This effort will include ground-truthing as well as model development.
- StoryMap & Animation - GPS: Groundwater, People, and Salmon
- Seminar - Groundwater Subsidies to Salmonid Streams: A Decade+ of Collaborative Science and Outcomes in Alaska
Funding has been provided by the National Estuarine Research Reserve System Science Collaborative and by the Margaret A. Davidson Graduate Fellowship fund.
The Role of Groundwater in Supporting Juvenile Salmonid Habitat, Kenai Peninsula, Alaska
This is a multi-project, collaborative effort that brings together principle investigators in various combinations from Alaska Department of Fish & Game/Kachemak Bay Research Reserve, Smithsonian Environmental Research Center, Baylor University, the University of Alaska-Anchorage, and the University of South Florida. There are many dimensions to this effort, with ours focused specifically on how groundwater discharge contributes to the physical (e.g., temperatures) and chemical (e.g., nutrient concentrations) characterisitcs of summer or winter habitats.
Funding has been provided by the U.S. Environmental Protection Agency, the National Estuarine Research Reserve System Science Collaborative, the Alaska Department of Fish & Game, the Alaska Sustainable Salmon Fund, and the National Center for Ecological Analysis and Synthesis.
Mobilization of Arsenic During Aquifer Storage and Recovery
Aquifer storage and recovery (ASR) is a strategy in which water is injected into an aquifer when it is plentiful and pumped from the aquifer when water is scarce. An impediment to ASR in Florida is leaching of naturally-occurring arsenic from limestone of the Upper Floridan Aquifer System (UFAS) into stored water. The concentration of arsenic in surface water, which serves as the recharge water for many ASR systems, and native groundwater is usually much less than 3.0 µ/L. However, data from ASR wells in Florida show that arsenic in recovered water frequently exceeded the 10 µg/L maximum contaminant level (MCL) established by the Environmental Protection Agency and were as high as 130.0 µg/L. The cause of elevated arsenic concentrations is displacement of reduced native groundwater with oxygenated surface water that dissolves arsenic-bearing pyrite in limestone. Although arsenic can be removed from recovered water during final treatment, mobilization of arsenic in the aquifer at levels that exceed the MCL is problematic under federal regulations.
Funding has been provided by the Southwest Florida Water Management District.
The Role of High Elevation Wetlands (Páramos) to Water Security in the Colombian Andes
Water security requires a sufficient quantity and quality of water be delivered at the appropriate time. Imported water can come from three possible sources: surface water, groundwater, or desalinated sea water. Of these, surface water is the most readily available and cost-effective and therefore the preferable source in less developed nations. Headwater wetlands can play a particularly important role in water storage and generation of streamflow, because they are topographically and geologically predisposed to store water and therefore play important roles in how streamflow is both generated and distributed in time. These issues are particularly salient for urban and agricultural socioecosystems that flank the Colombian Andes. However, these headwater wetlands (páramos) are increasingly at risk due to climate change and development pressure, particularly grazing, logging, and mining. In an effort to assist with water resource planning, we quantified the contribution of páramos to flow generation in the Tuluá River. Like many rivers with headwaters in the Andes, the Tuluá River serves as the primary water source for a community situated in a fertile valley below.
Funding has been provided by the Fred L. and Helen M. Tharp Endowed Scholarship Fund.
Mangrove and Mangrove-Fringe Wetlands in Ostional, Nicaragua: Current Conditions and Pathways Forward
Mangrove forests have traditionally protected the coastline of Ostional, a rural Nicaraguan fishing village, from degradation of fishery habitat and onshore effects of storm surge. Swaths of mangrove were converted to agricultural use before the ecological role of these mangroves was understood. We assessed the soils, hydrology, and vegetation of the intact mangrove and adjacent converted mangrove to inform a nonprofit conservation agency (Paso Pacifico) regarding the potential for ecosystem function restoration in this landscape.
Funding has been provided by the Paso Pacifico, as flow-through from the World Bank.
Urban Development, Power Relations and Water Redistribution as Drivers of Wetland Change in the Tampa Bay Urban Socioecosystem
Urban ecosystems are heterotrophic entities, and their reliance on external inputs is central to an emerging theory of urban ecology. However, the drivers and consequences of this redistribution of resources remain poorly understood. The Tampa Bay Urban Long-Term Research Area (Tampa Bay ULTRA) is designed to investigate how social organization and distribution of power in a socioecosystem drive resource redistribution, and thus modify social and ecological structures and functions at scales beyond that of a built city. Water limits urban development in the Tampa Bay Region Socioecosystem (TBRS). The TBRS obtains water from within the TBRS boundary by way of ground-water pumping in wellfields adjacent to and even within the urban core. Ground-water pumping results in water-table drawdown, which drains wetlands within the urban-to-rural continuum. The regional water authority, recognizing threats to wetland ecosystem services, has sharply redcued pumping over the past two decades. This dynamic offers an opportunity to investigate environmental perceptions, behavior, and empowerment across a spectrum of social groups and institutions. Three core questions are being investigated: (1) What variability exists across a rural-to-urban continuum in perceptions and values of ecohydrological change? (2) How does the distribution of social and political power result in particular outcomes of water redistribution? (3) How do forested wetlands respond to ground-water withdrawal and the urban growth it facilitates?
Funding has been provided by the National Science Foundation.
Development of a Coordinated Watershed Approach for Linking Compensatory Mitigation and Tampa Bay Habitat Restoration Goals
The Tampa Bay Estuary Program (TBEP) has applied considerable research and collective wisdom to develop the idea of "restoring the balance" of freshwater wetlands and deep-water habitats in the Tampa Bay watershed. The most recent update to the Tampa Bay Habitat Master Plan has a goal of shifting future efforts to restoration and protection of habitats in ratios that were historically present. This will require an appreciation for the state of these habitats historically and currently, and skill in generating useful data that accurately represents conditions at different points in time. In addition, TBEP wishes to better apply market forces to accomplish targeted restoration goals. As part of this effort, we are quantifying the wetlands lost over the past 50 years, performing a rapid conditional assessment on the existing wetlands, performing an economic analysis of the land on which the existing wetlands are located, and using this information to prioritize wetland restoration in the Tampa Bay watershed and to help coordinate a linakages between these priorities and ongoing compensatory mitigation efforts.
Funding has been provided by the Tampa Bay Estuary Program, as flow-through from the U.S. Environmental Protection Agency.
Water Sources and Hydrodynamics of Closed-Basin Depressions, South-Central Alaska
Wetland and deep-water habitats cover >50 percent of the land surface in Alaska. Among the most prevalent wetland and deep-water habitats are depressions, which often occur as moraine, ice-scour, or dead-ice depressions on undulating, low-permeability terrain. Many of these depressions are closed-basin depressions, where surface-water inflows and outflows are negligible. Such closed-basin depressions are particularly common in south-central Alaska, where numerous glacial advances have left complex, low-permeability surficial deposits. The broad objective of the study was to quantify the water sources and hydrodynamics of these closed-basin depressions, particularly with respect to the role they play in ground-water recharge.
Funding has been provided through a number of private-sector partnerships.
The Role of Hydrological Processes in Maintaining Ecosystem Structure and Function in Mangroves
This is a multi-project, collaborative effort that brings together principle investigators in various combinations from many universities and resource and regulatory agencies. Currently, our work is focused along the Indian River Lagoon in east-central Florida and in the Florida Coastal Everglades. The latter is in collaboration with the Florida Coastal Everglades Long-Term Ecological Research (FCE-LTER) Program.
Funding has been provided by the Smithsonian Marine Station at Ft. Pierce and the National Science Foundation.
Hydrology of Clay Storage Areas
The phosphate industry owns or has mineral rights to more than 440,000 acres of land in northern and central Florida, approximately 25% of which are river or wetland habitats. Following mining, approximately 40% of the land is covered with clay settling areas, which are steep-sided, high-walled reservoirs as large as one square mile, filled with supersaturated clay separated from the phosphate and sand during processing. It takes decades for the clays to dewater sufficiently to support even light land uses. Therefore, clay settling areas are the most conspicuous and development-limiting landforms remaining after phosphate mining. The effects of the clay settling areas on water resources are largely unknown. To be sure, annual rainfall is captured by the clay settling areas. However, the fate of this rainfall and the original processing water still contained within the clay settling area is unclear. Does it recharge the underlying surficial aquifer and flow to nearby wetlands and streams? Does it recharge the underlying Floridan aquifer from which many Floridians derive their water? Or does it simply evaporate back to the atmosphere and not become available for any beneficial use? This project was designed to address these and other fundamental questions of hydrological and ecological importance in Florida and other phosphate mining districts around the world.
Funding has been provided by the Florida Institute of Phosphate Research.
The Role of Headwaters in Maintaining the Integrity of Downstream Waters
The goal of this effort has been to provide links between science and policy in the ongoing debate over the definition of "Waters of the United States" subject to federal regulation under the Clean Water Act. Two recent US Supreme Court rulings have called this definition into question. In 2001, the Court explored Clean Water Act protections for isolated, intrastate, non-navigable waters in Solid Waste Agency of Northern Cook County v US Army Corps of Engineers (2001) (SWANCC). Five years later, the Court further explored Clean Water Act protections for tributaries and adjacent wetlands in Rapanos v United States and Carabell v United States, which were ultimately consolidated into Rapanos v United States (2006) (Rapanos). Working in response to SWANCC and in parallel with Rapanos, Tracie-Lynn Nadeau and I co-edited and contributed to a Featured Collection of the Journal of the American Water Resources Association addressing the roles played by headwater streams and adjacent wetlands in maintaining the integrity of downstream navigable-in-fact waters. Specific issues raised in Rapanos remained unresolved due to the relative timing of the Featured Collection and the issuance of the Rapanos decision. Most important were the meanings of the so-called Scalia and Kennedy Standards, two suggested standards by which the geographic extent of "Waters of the United States" could be defined. Scott Leibowitz, Jim Wigington, Donna Downing, and I responded in a paper interpreting the Scalia and Kennedy Standards within the established scientific context, then proposing specific metrics by which the Scalia and Kennedy Standards could be assessed for a given water or class of waters.
These have been largely unfunded labors of love for all of us.
Geology of National Parks: Spreadsheets, Quantitative Literacy, and Natural Resources
This project is a follow-up project to Spreadsheets Across the Curriculum (SSAC), which seeks to "develop and pilot spreadsheet modules to enhance students' quantitative literacy skills" (http://www.evergreen.edu/washcenter/project.asp?pid=75). An underlying thesis of these efforts is that every course containing numbers provides an opportunity for context-based mathematics education. The sciences provide many such opportunities. Central to these efforts is the development of spreadsheet modules that deliver both teaching and exercise materials to the students. Spreadsheet modules consist of ~20 slides constructed in PowerPoint in which foundational mathematical concepts are taught through problem-solving exercises within the context of a particular discipline. In this follow-up project, we are developing a set of spreadsheet modules that would be part of the SSAC Library and would be available for use in Geology of National Parks courses taught throughout the US. We have partners at many National Parks, and will ultimately have ~30 spreadsheet modules, which will be published and available online as possible (http://serc.carleton.edu/sp/ssac/national_parks/index.html).
Funding has been provided by the National Science Foundation.
The Role of Reconnecting Channels and Floodplains in the Restoration of Hydrological and Ecological Structure and Function in Riverine Ecosystems
This project explores the role of reconnecting a channel and a floodplain in the restoration of hydrological and biological structure and function in a riverine ecosystem. The project site was Bear Creek and the adjoining meadow near Dana, California. In 1960, the Soil Conservation Service assisted the previous landowner in a channel improvement project to enhance grazing and farming of the meadow. This project abandoned approximately 3.5 km of existing stream channel, diverting flow into straitened main and secondary channels constructed near the edges of the meadow. Between 1960 and 1999, the straightened channel reaches incised as much as 5 m into the alluvium. The incision led to the near complete loss of floodplain water and sediment storage, a significant lowering of the ground water table, the loss of riparian and meadow plant communities, and the loss of in-stream spawning habitat. Channel incision also led to substantial increases in flood waves and sediment loads delivered to the Fall River. In 1999, the current landowner implemented a restoration and enhancement design. The restored and enhanced channel was constructed or restored by linking newly-created channel with remnant channel segments, therby linking tghe channel back to the historic floodplain. This study focused on quantifying the hydrological and ecological effects of this restoration, providing some of the best evidence to date that river restoration of this kind can provide important hydrological and ecological benefits to on-site and down-stream ecosystems.
Funding has been provided by the Peter and Nora Stent Fund of the Peninsula Community Foundation, the Cantara Trustee Council, and the Packard Foundation.
Geological Control of Ecological Structure and Function in Vernal Pool Wetlands
Vernal pools are depressional features that are inundated for portions of the wet season, then drain and dry in the late wet and early dry seasons. They occur as small, poorly-drained depressions perched above an impermeable or very slowly permeable soil horizon or bedrock. They represent small yet complete ecosystems that are aquatic islands surrounded by uplands. Vernal pools occur in southern Oregon, northern Baja California, throughout California, and in other Mediterranean-type climates of the world. Vernal pools are best known for the biological functions that they perform, with extremely high frequencies of endemism and rarity. Hydrology is the primary forcing function in most wetlands, and is particularly critical in vernal pools. It is therefore surprising that few studies of vernal pool hydrogeology and biogeochemistry have been conducted. This study was focused on vernal pools on hardpans and clay-rich soils, the most common types of vernal pool in the Central Valley of California. Broadly speaking, our findings show that geological processes determine hydrogeological, biogeochemical, and biological structure and function in vernal pools, meaning that geological processes operating over the course of hundreds of thousand to millions of years continue to control hydrological and ecological structure and function in these systems today.
Funding has been provided by the California Department of Transportation.
The Effects of Reservoir Operations on Shallow Groundwater and Vegetation Distributions in Reservoir-Fringe Ecosystems
Currently, there are more than 75,000 dams greater than six feet in height in the United States, and the reservoirs created by these dams cover approximately three percent of the nation’s land surface. Most reservoirs are managed exclusively for traditional purposes: municipal and irrigation water supply, hydroelectric power, flood control, and recreation. However, there is growing interest in managing these reservoir resources, at least in part, for the maintenance of plant and wildlife habitats. Virtually all of the discussion surrounding this management objective is centered on the downstream effects of reservoir operations on flow regimes, vegetation distributions in the near-channel area, and channel morphology and in-channel fish habitat. Thus, decommissioning reservoirs or otherwise restoring natural flow regimes has been the focus of many recent efforts. This approach, however, does not always clearly result in net ecosystem benefits. Reservoir construction often leads to the development of new habitats in reservoir-fringe areas such as emergent marshes, wet meadows, scrub-shrub wetlands, and riparian forests. These habitats can be regionally unique and, therefore, can serve as critical habitats for regionally uncommon plant and wildlife species. Decommissioning reservoirs or otherwise altering reservoir operations can restore some channel and floodplain functions but can degrade or eliminate these regionally unique reservoir-fringe ecosystems. Thus, reservoir-fringe ecosystems should be considered in the context of the maintenance of plant and wildlife habitats. This is particularly true for reservoirs that are unlikely to be decommissioned due to their socioeconomic importance and for reservoirs that are located directly upstream from reservoirs or otherwise impaired water courses.
This project explored surface water and groundwater origins and interaction and associated vegetation distributions in riverine and reservoir-fringe systems. The overall objective of this effort was to develop concepts and tools for the planning, implementation, and monitoring stages of river and reservoir management efforts. This project was organized into three linked efforts. In the first effort, the primary sources of the shallow groundwater were identified. In the second effort, the roles of stream discharge, regional groundwater discharge, and reservoir stage in controlling shallow groundwater were characterized. In the third effort, a linked groundwater and vegetation distribution model was presented and used to simulate groundwater and vegetation distributions under different reservoir operations.
Funding has been provided by the by a cooperative agreement between the United States Bureau of Reclamation, Ducks Unlimited, and the Peter and Nora Stent Fund of the Peninsula Community Foundation.