Collaborative Research: The effects of river regulation on lateral and integrated longitudinal mass and energy transfers in coupled terrestrial-aquatic systems

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Collaborative Research: The effects of river regulation on lateral and integrated longitudinal mass and energy transfers in coupled terrestrial-aquatic systemsRivers and shallow groundwater are inter-connected and continuously exchange water; river water temporarily circulates through the beds and banks of rivers. The lateral exchange zone (LEZ) in the banks affects instream water quality since microbial communities in the LEZ consume water-borne nutrients and solutes. We know little about how local LEZ processes integrate to impact instream water quality for large rivers. Globally, 60% of major rivers are regulated by dams and some dam-regulated rivers are subject to periodic (daily) floods. This study will examine and understand how flow and dynamic biogeochemical regimes in regulated rivers impact nutrient and thermal energy transfers through the river corridor. It will lead to understanding of biogeochemical processes in human-impacted surface-subsurface hydrologic systems. Through field observations along a 90-km section of the 6-th order Lower Colorado River in Texas and through coupled numerical simulations of instream and LEZ processes, we will determine how the dynamic expansion/contraction of the LEZ during flooding/recession controls chemical reaction rates and heat transfer within the LEZ, and how this in turn impacts instream water quality and downstream delivery of solutes and energy.The study will generate knowledge that is useful for the management of dam-regulated rivers. Texas has the most dams amongst all states with many more planned as part of a recent state bill that allocates resources for water infrastructure. It is critical that the trade-offs and potential effects of river-regulation on LEZ processes, groundwater and instream water quality, and river ecology be understood. This has seldom been studied and this investigation will help fill this knowledge gap. Further, the study will train the next generation of hydrologic engineers and scientists and increase public awareness of the importance of river-groundwater interactions, particularly within the context of regulated rivers. Students from K-12, BS, MA/MS, to PhD level, and K-12 teachers will participate in the research. Field trips to the site will be organized for K-12 students. Outreach lectures will be presented to the public.