Landscape controls on lake-peatland-forestland hydrology within the Boreal Plains

Leader, Samantha Nicole (2022). Landscape controls on lake-peatland-forestland hydrology within the Boreal Plains. University of Birmingham. Ph.D.

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Abstract

Shallow lakes provide the world’s richest bird communities, and provide major critical habitat in the adjacent wetlands, forests and downstream ecosystems that they support. Their resilience is strongly linked to stability of water levels, yet shallow lakes are diminishing in the face of climatic warming and local land use pressures, which will modify hydrological connectivity and negatively impact vital habitats. However, the patterns and controls on shallow lake water levels are poorly understood in relation to their hydrogeoclimatic setting and long-term weather cycles. This PhD thesis investigates how climate, geology, landcover and landscape position interact to control spatiotemporal variability of shallow lake water depth. Findings are used to inform a conceptual framework for defining landscape controls on boreal hydrology based upon mechanistic understanding within a complex heterogenous hydrogeoclimatic Boreal Plains (BP) setting. This is achieved through empirical and numerical evidence of the patterns and controls on 20 years of lake, peatland and forestland water tables in 26 study catchments. The primary research outcomes are: (1) BP lake water levels exhibit low synchronicity as high and spatially variable landscape storage of water produces high interannual variability; (2) surficial geology incorporates important landscape parameters that define the source, magnitude, and continuity of hydrological connectivity and interactions with land cover and lake geometry further modify lake water level patterns; (3) spatiotemporal variation in landscape memory of climate, driven by differences in storage and antecedent conditions, can cause wet or dry climatic conditions to propagate into extreme events; (4) reduced-complexity modelling founded upon HRAs and HUs provide sufficient functionality to accurately simulate multi-decadal, interannual and seasonal lake-peatland-forestland connectivity and water table patterns, and provides a valuable tool to transpose knowledge to ungauged catchments and evaluate spatial variability of hydrological sensitivity to climate. This research provides significant new knowledge of the dominant controls on boreal lake, peatland and forestland hydrological interactions of diverse hydrogeoclimatic settings. It characterises spatial differences in lake water level responses to seasonal and decadal climate cycles and demonstrates the role of storage-driven landscape memory in driving asynchronous spatiotemporal variability. Empirical and simulated results have strengthened conceptual understanding of the HRA-HU framework for defining hydrologic landscapes and yields crucial insights and model development for evaluating hydrological sensitivity to climate.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):