Thermal and hydraulic characteristics of landscapes and their rivers

Abstract

Landscapes and riverscapes are hydrologically interconnected through the four dimensions of space and time. While we have some understanding of local scale processes and global scale cycles, at the landscape and riverscape scales we have yet to truly solidify an understanding of interconnectedness. This dissertation examines the hydrological interconnectedness between landscapes and rivers using temperature as a tracer, and the spatial arrangement of aquatic habitats of rivers and wetlands. It was found that geology and specifically bedrock transmissivity exerts an apparent primary control on hydrological processes and river thermal regimes across the New Brunswick region. In areas with high conductance geology, topographic incisions (valleys) generated groundwater discharge which modified river flow and temperature. Inversely, topographic incisions in low conductance geology lacked groundwater discharge, and river flow and temperatures were more tightly coupled to climate. Upland wetlands on a high conductance geologic formation were associated with a lack of groundwater discharge and warm river temperatures, indicating potential recharge points. Winter satellite imagery can accurately delineate groundwater discharges in frozen rivers. Groundwater plume extent was observed to differentiate between summer and winter. High-resolution aerial imagery (30 cm) coupled with field calibration data was effective at modelling river bathymetry and hydraulics across a large catchment (> 1,000 km²). Applying these data to a machine learning algorithm revealed that low flow, aquatic habitats in the Little Southwest Miramichi broadly follow pool-riffle-slack water sequences. Earth's abiotic and biotic systems are tightly interwoven. Changes within each reverberate through space-time moving towards a dynamic equilibrium. While some changes occur at scales that override our ability to observe them, commonalities exist across Earth's ecosystems, and these fuel adaptation and evolution. My thesis illustrates the interconnectedness of landscapes, wetlands that lie upon them and rivers that flow through them. I conclude by presenting a concept to guide future research direction, 'the waterscape continuum concept' (WCC). The continuum unifies surface water, soil and rock moisture, and groundwater. Applying the WCC, scientists, researchers, and practitioners are required to learn about climatic, geologic, and geomorphic processes - inherently leading to better experimental designs, and will reveal new findings of Earth system processes.