Hydrological Assessment of Water Resources in Bergen - Climate Change Impacts
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Bergen Waterworks is reliant on steady loads of precipitation to meet the drink- ing water demand. Accordingly, the system is vulnerable to drought events and seasonal changes in inflow. Climate change impact analysis, as part of water management design and operation, is advantageous for ensuring a reliable and economic development of the infrastructure. Consequently, adaptation strategies in terms of hydrological assessments ought to keep up with the scientific progress in climate research. This thesis provides a complete framework for evaluating cli- mate change impacts on drinking water resources in Bergen. A comprehensive hydrological assessment is conducted, including inflow data analysis, calibration of regional HBV model, and transferring of calibrated parameters to ungauged catchments. Projected changes in temperature and precipitation are obtained us- ing empirical-statistical downscaling of the global climate model, Nor-ESM1-M, and IPCC AR5 emission scenarios RCP2.6, RCP4.5 and RCP8.5. Climate change impacts are evaluated by comparing historical climate variables for the control pe- riod 1981-2010, with future projections for 2011-2040, 2041-2070 and 2071-2100. Changes in water supply capacity in Bergen are estimated using extreme drought event analysis and hydrological routing. The maximum supply capacity, while accounting for 100 % storage reliability, is confronted with projected changes in drinking water demand. The results convey seasonally inflow changes, connected to changes in the snow regime and increased evapotranspiration. More inflow is expected during winter and autumn, while less is expected in spring and sum- mer. Winter drought extremes are therefore likely to disappear, as opposed to summer drought extremes, for which an upturn is predicted. Within the time span of 2011-2100, all emissions scenarios reduce the maximum supply capacity of Bergen Waterworks. However, neither of the scenarios threaten the reliability of the drinking water supply, provided that leakages in the distribution system are reduced to 20 %.