|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 Projects and Themes
Understanding water fluxes in an emblematic headwaters watershed
The East River catchment is a representative headwater basin of the Colorado River, which in turn supplies the Southwest United States with water for energy, irrigation, and municipal use. Given that 85% of streamflow is generated in small, topographically-complex basins, more research is needed to understand nutrient and water cycling in these regions. The Maxwell group contributes to the larger Department of Energy Scientific Focus Area by developing and testing integrated models of the catchment at multiple scales and maintaining multiple meteorological towers to validate simulations. Our interdisciplinary team merges field observations, model development, and climate change studies to better understand water availability for the Western United States. Current work includes improving the snow formulation of the ParFlow-CLM model by comparing simulated results to observational networks and reconciling errors in the energy balance; exploring the importance of small-scale heterogeneity to controlling water and energy fluxes; and understanding how model resolution and other scale effects complicate predicted future water export from headwater basins.
Simulating hydrology and land-energy processes at the continental scale
Changes in water storage and supply is a growing global challenge with implications in human and environmental health. Recent literature suggests that expanding hydrologic studies across continental and even global scales may provide critical insight into nonlinear interactions between the water and energy budgets; help connect, explain and guide observations from the point scale to remote sensing; inform climate and weather models that operate at the mesoscale and above; and improve national water management by bridging water management scales, e.g. from local municipalities to inter-state water policies. The Maxwell group models hydrologic processes across the Continental US (CONUS) using an integrated surface-subsurface hydrologic model, ParFlow, to study the influence of climate variations on hydrologic processes. The ParFlow CONUS model is applied to a range of applications, including 1) topographic and climatic controls to continental-scale groundwater heterogeneity; 2) the influence of hydrofacies, hydraulic parameters and availability of hydrogeologic data on simulated surface energy fluxes; 3) groundwater storage controls on Budyko relationships; 4) anthropogenic-induced anomalies to recharge and their scale-dependent impacts to national groundwater resources; 5) land-atmosphere interactions, specifically the impact of terrestrial hydrology representation in the lower boundary condition of meteorological and climate modeling; and 6) interannual variability of groundwater anomalies and comparisons of major storage changes to the Gravity Research and Climate Recovery Experiment. Studying integrated hydrologic processes across a range of scales will improve our understanding of water storage, water depletion, and groundwater-land surface coupling, and will improve national water management.
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.
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.
Research Group News
Some nontechnical news articles about my group's research: