Observations and analysis of snow cover and runoff in boreal catchments

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa, auditorium L10

Topic of the dissertation

Observations and analysis of snow cover and runoff in boreal catchments

Doctoral candidate

MSc Leo-Juhani Meriö

Faculty and unit

University of Oulu Graduate School, Faculty of Technology, Water, Energy and Environmental Engineering

Subject of study

Water resources and environmental engineering

Opponent

Professor Hjalmar Laudon, Swedish University of Agricultural Sciences

Custos

Assistant Professor Hannu Marttila, University of Oulu

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Snow cover impact on boreal headwaters runoff

Snow conditions in the boreal region are changing, mainly due to climate change. Changes in snowmelt are expected to have drastic changes in water storage conditions and streamflow in rivers through spring and early summer, especially in headwaters. The measurement of snow cover variability is a challenge using current techniques, and the connections between environment, climate conditions, and hydrology are still not completely understood. This thesis aims to develop and test new robust and cost-efficient observation methods to quantify snow cover variability and to improve understanding of the factors controlling snow hydrology in the boreal landscape.

This work applies two approaches for measuring snow cover: in-situ, using low-cost temperature loggers; and remote sensing, using drones. The high temporal-resolution data from temperature loggers, with the algorithm developed, provided reliable data on spatiotemporal variations in snow cover ablation in different boreal landcover types. With drones, the snow depth variability could be determined with a very high spatial resolution in the boreal landscape, enabling the identification of interactions between snow and vegetation.

To analyze the factors controlling snow hydrology, data from a spatially well-represented Finnish headwaters research network was used to calculate low flows and catchment storage indices. The findings suggest that the changes in summer low flow related to snow conditions will be pronounced in certain snow-to-precipitation ratio thresholds in a warming climate. In Finland, this threshold zone was in and between Northern Ostrobothnia and North Karelia.

The developed measurement methods can be used in measuring snowpack variations in ungauged or remote basins. Especially the data from drones showed potential in extending snow course measurements and improving distributed catchment-scale snow models. The improved understanding of the factors controlling snow hydrology can be used to guide water resource and land-use management in boreal and high-latitude regions, where rapid climate change is projected.
Last updated: 11.11.2021