Linking Freshwater Transport and Quality: A New Frontier?

2017 Spring Cyberseminar Series

Presenter(s):
Antoine Aubeneau / Purdue University

Talk Description:

As freshwater flows from clouds to oceans, it carries and relocates the shedding of the earth. The byproducts of natural processes and human activities are loaded on a permanent conveyor belt and transported down rivers. The relocation of anthropogenic waste alters the quality of the water we use, jeopardizing ecosystems and economies alike. Fertilizer pollution leading to downstream eutrophication and hypoxia is an example of the global challenges affecting water resources. Inland agriculture releases plant food to coastal areas, where algal blooms and their eventual decay damage the ecosystems that tourists and fishermen rely on.

As rivers flush out the wastes of our cities, industries and farms, they also act as natural filters that restore water quality. Water treatment plants use biological processes; streams and rivers have them built in. The hyporheic zone, the region beneath the stream where surface water flows through the ground, is a river’s liver (Fisher 2005). This is where microorganisms strive, clinging onto rocks and organic substrates. This is also a region where flow is slow and biogeochemical reactions have time to proceed.

I will present research I conducted to better understand streams as natural filters. My investigations span three broad areas: the physical exchange of water between the surface and subsurface, the models and equations we use to describe riverine transport and the relationship between water travel times and water quality. I will present experimental, numerical and theoretical results pertaining to these three areas. Specifically, I will discuss results that show how the statistics of riverbed topography can help understand those of water residence time in a sand bed. I will also present results illustrating how benthic and hyporheic biofilms affect hyporheic exchange. Finally, I will look forward and illustrate ongoing efforts to understand nutrient leaching from agricultural fields and possible field scale remediation.

Biography:

Dr. Aubeneau received a B.S. and M.S. from University of Poitiers (France) in 2000. After teaching high school for a few years, he went to graduate school at Northwestern University where he received a Ph.D. in Civ. & Env. Eng. in 2013. He was a post doc at Notre Dame for two years in Civil before joining the faculty at the Lyles School of Civil Engineering at Purdue in the Hydraulics and Hydrology area. Dr Aubeneau's research focuses on water transport and quality, and ranges from laboratory and field experiments to theoretical and numerical studies.

CUAHSI's Spring 2017 Cyberseminar Series on Heterogeneity, Complexity and Anomalous Transport in Hydrologic Systems

Real hydrologic systems are heterogeneous and hierarchical, leading to transport processes occurring over disparate and broad ranges of spatio-temporal scales. Many classical models of transport, while undoubtedly powerful and useful, are built on assumptions that simply fail to recognize these complexities.  As such they are incapable of predicting many features commonly observed in real systems. These behaviors are often called “anomalous”. They include processes with very large spatial jumps where solutes or particles quickly travel much larger distances than expected. Similarly trapping events can occur that hold back solutes and particles for much longer times than anticipated. Both the long jumps and trapping events are commonly characterized by power laws, rather than more conventional exponential and Gaussian distributions. Despite the name, anomalous transport is anything but that and is increasingly recognized as the norm across many disciplines in the hydrologic sciences, including flow and transport in highly heterogeneous aquifers as well as in flowing surface waters with hyporheic exchange. Additionally, such behaviors arise in related disciplines such as geomorphology in the fields of surficial processes and sediment transport. To overcome the limitations of classical modeling efforts, new classes of models have and continue to emerge, which successfully capture these so-called anomalous features. This cyberseminar series will focus on these efforts with expert speakers coming from the disciplines of subsurface and surface hydrology and geomorphology to outline these processes in accessible ways to the broader hydrology community.

The series was hosted by Diogo Bolster (Notre Dame University).