Spatiotemporal streamflow variability in a boreal landscape : Importance of landscape composition for catchment hydrological functioning

• Main Author: Karlsen, Reinert Huseby
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Uppsala universitet, Luft-, vatten- och landskapslära 2016
• Subjects: streamflow; catchment hydrology; boreal; water balance; spatiotemporal variability; landscape analysis; climate change; recession curve; Oceanography; Hydrology and Water Resources; Oceanografi; hydrologi och vattenresurser; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302400

The understanding of how different parts of a landscape contribute to streamflow by storing and releasing water has long been a central issue in hydrology. Knowledge about what controls streamflow dynamics across landscapes can further our understanding of how catchments store and release water, facilitate predictions for ungauged catchments, and improve the management of water quality and resources. This thesis makes use of data from the Krycklan catchment in northern Sweden. Streamflow data from 14 catchments (0.12 - 68 km2) with variable landscape characteristics such as topography, vegetation, wetland cover, glacial till soils and deeper sediment soils were used to investigate spatial patterns and controls on runoff. The differences in specific discharge (discharge per unit catchment area) between nearby catchments were large at the annual scale, and have the same magnitude as predicted effects of a century of climate change or the observed effects of major forestry operations. This variability is important to consider when studying the effects of climate change and land use changes on streamflow, as well as for our understanding of geochemical mass balances. Streamflow from different catchments was strongly related to landscape characteristics. The distribution of wetland areas had a particularly strong influence, with an annual specific discharge 40-80% higher than catchments with high tree volume on till soils. During drier periods, catchments with deeper sediment soils at the lower elevations of Krycklan had a higher base flow compared to both forested till and wetland catchments. This pattern was reversed at high flows. The storages releasing water to streams in downstream sediment areas were able to maintain base flow for longer periods and were less influenced by evapotranspiration compared to the more superficial till and wetland systems. The results of this thesis have led to a better understanding of the landscape wide patterns of streamflow during different seasons and time scales. The strong ...