HYDROLOGICAL DROUGHTS IN SWEDEN: Mapping of historical droughts and identificationof primary driving climate variables andcatchment properties

• Main Author: Rudebeck, Hugo
• Format: Bachelor Thesis
• Language: English
• Published: Uppsala universitet, Institutionen för geovetenskaper 2018
• Subjects: hydrological droughts; drought propagation; drought indices; SSI; threshold index; SPI; catchment properties and drought events; hydrologisk torka; propagering av torrperioder; torkindex; tröskelvärdes index; avrinningsområdesegenskaper och torrperioder; Oceanography; Hydrology and Water Resources; Oceanografi; hydrologi och vattenresurser; Engineering and Technology; Teknik och teknologier; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-350520

This study investigated the relationship between hydrological, and to some extent, meteorological droughts, and meteorological variables and catchment characteristics in 235 Swedish catchments between 1983 and 2013. This was done in order to investigate what factors affect the drought sensitivity in Swedish catchments and to map the occurrence of droughts in Sweden between 1983 and 2013. There have been studies about which meteorological phenomena and catchment characteristics that promote hydrological droughts, but for Sweden this is relatively unexplored. To investigate droughts during the study period three indices were used: the Standardized Precipitation Index (SPI), which is an index for meteorological droughts, the Standardized Streamflow Index (SSI), which predicts hydrological droughts and a threshold index for streamflow droughts. These indices were used to identify the number of drought events and the total number of drought days. For the majority of the 235 Swedish catchments there were no significant trends for the number of drought events or the total number of drought days during the 30-year period. The SPI and the SSI were found to correlate best in time when adding a one-month lag period to the SSI time series. The correlations between the indices and the meteorological variables and the catchments properties varied depending on how the catchments were grouped according to latitude or elevation. For example, the number of drought events was positively correlated to the mean elevation of the catchments in north and central Sweden when using the SSI while there were no significant correlations with elevation in southern Sweden. Another example is that it was almost only in northern Sweden where significant correlations between the percentage of bedrock and drought characteristics were identified. The percentage of bedrock can be used as an indication for how much groundwater a catchment can store. The correlations also look different for the different indices. For example, when looking at all ...