|Reed M. Maxwell Selected Research Topics
My research is interdisciplinary in nature and is focused on a range of water-related questions. My emphasis is usually the development and application of numerical models to study interfaces in hydrology, but there is also a significant field component to my work. My interests span a variety of hydrology, water resources and water quality topics including: surface water and the terrestrial hydrologic cycle; interactions of the land-surface, surface water and groundwater, and the atmosphere; human health risk assessment; and reactive contaminant transport and geochemical cycling.
The application of numerical models to water resources problems, with their inherent complications, is difficult. Because of this, my group develops models that draw on novel numerical methods and parallel or high-performance computing. My work is collaborative and I pursue lines of inquiry that transcend scientific and disciplinary boundaries by using models to understand and bridge scales and processes. I have a fantastic research group and they are critical to the projects the reason for the successes you see here.
Research Group News
Some nontechnical news articles about my group's research:
Coupled Terrestrial Hydrologic Cycle
The hydrologic cycle is composed of a number of coupled processes, yet it is seldom treated as such. Often models are developed in a compartmentalized manner that follows scientific and disciplinary boundaries and ignores important process interplay. In an effort to provide a more integrated approach, I have led the development of a suite of unique, fully coupled models of the hydrologic cycle. These models simulate the cycling and movement of water and contaminants at watershed and larger scales. This has involved coupling land surface models, which have traditionally been highly parameterized, with more so-called process-based vadose and groundwater models. Relaxing some of the more limiting assumptions involved in the parameterizations in land surface models necessitated the development of a whole new class of coupled models. Additionally, I have led the development of fully-coupled groundwater-to-atmosphere models. These efforts have resulted in a number of models (ParFlow, PF.CLM, PF.ARPS, PF.WRF) that more accurately represent fluxes of water in the terrestrial environment. Model results have shown significant interplay between groundwater and land-surface energy processes that persist into the lower atmosphere. These simulation platforms can be combined with my Lagrangian transport code to simulate watershed transport and residence times which may be used to understand watershed scaling. They may also be used to diagnose watershed response and feedbacks to a changing climate or to understand management practices on the hydrologic cycle. Recent work in my group has characterized feedbacks due to groundwater pumping and/or irrigation on land-energy feedbacks.
References: Maxwell and Miller JHM 2005; Kollet and Maxwell AWR 2006; Maxwell et al. AWR 2007; Kollet and Maxwell WRR 2008; Kollet and Maxwell GRL 2008; Maxwell and Kollet AWR 2008; Maxwell and Kollet NGeo 2008; Ferguson and Maxwell WRR 2010; Rihani et al.WRR 2010; Maxwell VZJ 2010; Maxwell et al MWR 2011; Ferguson and Maxwell ERL 2011; Atchley and Maxwell Hydrogeol 2011; Meyerhoff and Maxwell Hydrogeol 2011; Ferguson and Maxwell ERL 2012; Maxwell AWR 2013.
Groundwater-Driven Human Health Risk Assessment
Subsurface heterogeneity imparts uncertainty on the spatial distribution of contaminants in groundwater. This uncertainty interacts with the variability in human behavioral and physiological parameters. Inclusion of this joint uncertainty and variability creates a different, more realistic picture of the exposure and health risk. This work has created a better assessment of the risk to human health and provided guidance for managing contaminated groundwater resources. This methodology has also been used probabilistically quantify the reduction in human health risk due to a pump-and-treat remediation scheme. This work was highlighted in two National Research Council reports [NRC, 1999, Environmental cleanup at Navy facilities: risk-based methods. Washington, DC: National Academy Press; NRC, 2003, Environmental Cleanup at Navy Facilities: Adaptive Site Management. Washington, DC: National Academy Press].
Two members of my group along with collaborators in Prof. John McCray's group are currently funded to work on the health risks associated with leakage of CO2 into groundwater. These projects are funded through the EPA and the DOE. References: Maxwell et al. WRR 1998; Maxwell and Kastenberg, SERRA 1999; Maxwell et al. WRR 1999; Maxwell and Kastenberg, SERRA 1999; Maxwell et al. EG 2008; Siirila et al AWR 2012; Siirila and Maxwell WRR 2012; Siirila and Maxwell STOTEN 2012; Atchley et al ES&T 2013.
Subsurface Microbial and Geochemical Reactive Transport
I have developed and applied numerical models of virus and pathogen transport in spatially-variable subsurface media. These numerical models have been used to compare different theoretical models of particle filtration to understand the management implications of using imported and tertiary-treated surface water to recharge groundwater. They have also been used to reinterpret a bacterial transport field experiment at the Cape Cod site using a stochastic approach. These studies demonstrate how transport models can bridge scales and integrate processes. These methods can be used to connect colloid/bacterial/virus filtration at the laboratory scale (derived from and using column-scale data) to predictions of migration at the field scale in real-world conditions with subsurface heterogeneity and complicated flow paths. In addition, this work used modeling to connect surface and groundwater quality in a setting with potentially serious human health implications with direct application to two important water resource areas: riverbank filtration and wastewater reuse.
References: Maxwell et al. AWR 2003; Maxwell et al. ES&T 2007; Bearup et al ES&T 2012; Atchley et al AWR 2013; Navarre-Sitchler et al AWR 2013; Atchley et al JCH 2014.
Some Examples of Current Projects:
WSC-CATEGORY 2 Collaborative: Water quality and supply impacts from climate-induced insect tree mortality and resource management in the Rocky Mountain West (CSM WSC) It is currently estimated that over 4 million acres of forests in Colorado and Wyoming are dying due to the ongoing mountain pine beetle (MPB) infestation. The visual impact of dying and dead forests is stunning, but the invisible changes to the water cycle in vital watersheds in the Rocky Mountain west, including the Platte and Colorado River headwaters, may be a longer-lasting legacy of the MPB. The objective of this work is to determine potential water resource changes resulting from the MPB epidemic by defining and quantifying feedbacks between changes in climate, forested ecosystems altered by MPB impacts, biogeochemical processes and resource management practices. Our highly interdisciplinary research team at CSM and CSU will merge field observations, laboratory experiments, integrated hydrologic models, and high-performance computing to increase our understanding and predictive capabilities for a critical problem facing society: changes to water availability and quality from an unprecedented change to our forests. References: Mikkelson et al NCC 2013a; Mikkelson et al EcoHydro 2013b; Mikkelson, Bearup et al BioGeo 2013; Bearup et al NCC 2014; Engdahl and MaxwellAWR 2014; Bearup et al STOTEN 2014.
Interoperable Design of Extreme-scale Application Software (IDEAS) The IDEAS Project is intent on improving scientific productivity by qualitatively changing scientific software developer productivity, enabling a fundamentally different attitude to creating and supporting computational science and engineering (CSE) applications. Here at CSM we are leading Use Cases 1 and 3 to better understand scaling of hydrologic processes to enable better integrated hydrologic models.
Re-inventing Urban Water Infrastructure: Stormwater Harvesting and Urban Water Management (ReNUWIt ERC) Stormwater represents a dynamic component of the urban water cycle that requires careful mitigation for beneficial outcomes. Stormwater typically consists of various contaminants that can threaten human and ecosystem health. To minimize adverse impacts of stormwater on surface water systems, practitioners have embraced various approaches for capturing and infiltrating stormwater using low impact development (LID) or green infrastructure. Effective LID design requires further research into the effects of distributed stormwater infiltration on the urban water cycle, the transport of contaminants in stormwater via infiltration into the subsurface, and the improvement of stormwater quality during Infiltration and storage.
The water sector is growing in importance worldwide as water utilities cope with problems ranging from inadequate supply to increasing costs of service, and a need to address growth and deferred maintenance of infrastructure. The aim of this project is to develop integrated hydrologic-economic-engineering models for evaluating water resource investments. The models will be developed at various scales ranging from neighborhoods to hydrologic regions. References: Condon and Maxwell AWR 2013, Condon and Maxwell ERL 2014 and Condon and Maxwell WRR 2014.