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Increased annual precipitation and more frequent episodes with heavy precipitation are expected in Norway due to climate change. The purpose of this paper is to use two case studies to investigate effects of precipitation on the amounts of faecal indicator bacteria and parasitic protozoa (Cryptosporidium and Giardia) loaded to surface waters from catchment areas exposed to different faecal sources.

In the first case study, the loads of faecal indicator bacteria and Cryptosporidium and Giardia, were investigated in relation to precipitation in a stream from a small valley where cattle and sheep are grazed. In the second case study, historical data (monthly values from 2004‐2009) regarding faecal coliforms and water flow in five tributaries (urban and rural) of a lake used as a drinking water source, were used for calculating loads of faecal indicator bacteria. These loads were evaluated in relation to historical data on precipitation. Additional sampling during/after rainfall, including analysis of samples for Cryptosporidium and Giardia, was performed.

The study visualises how heavy rainfall may increase the load of faecal microorganisms and potential pathogens in Norwegian water sources.

This study provides supplementary information about microbial contamination (including by parasites) of Norwegian surface waters during or after rainfall. This is useful input for decision making regarding protection of vulnerable water sources and for risk assessments. Data are also provided for evaluation of water treatment needs for Norwegian municipalities and waterworks responsible for providing safe drinking water under future climatic conditions.

The purpose of this paper is to investigate the effects of extreme weather conditions on runoff, nutrient, and soil loss from agriculture‐dominated catchments at different locations in Norway.

Four catchments have been selected to study the potential effects of climate change on runoff and nutrient loss. The catchments are part of the Agricultural Environmental Monitoring Programme in Norway (JOVA) and represent different climatological conditions, agricultural production systems/practices, and soil types. Different characteristics were calculated on the basis of existing measurements and evaluated with respect to climate change.

In four selected catchments, climate change is predicted to lead to an increase in runoff. Under similar land use and tillage methods, this will most likely lead to an increase in nutrient and soil loss. Milder winters as a consequence of climate change might lead to extreme runoff conditions and severe erosion, caused by a combination of frozen soil, snowmelt, and intense rainfall. Existing large diurnal variations in discharge have to be taken into consideration in the future design of hydrotechnical implementations. Information about the potential effects of climate change on runoff generation, the magnitude of the different hydrological flow paths, and their potential effects on nutrient and soil loss processes is necessary in choosing the right mitigation measures.

Long time series on runoff and water quality (such as those collected in small agriculture‐dominated catchments as part of the Agricultural Environmental Monitoring Programme in Norway (JOVA)) are rare, but indispensable in evaluating the potential effects of climate change on nutrient and soil loss.