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Climatic changes will influence the possibilities for agricultural production (e.g. longer growing season), agricultural management practices (e.g. changes in tillage, fertilization, increased use of fungicides) and runoff conditions, and thereby the losses of nutrients from agricultural fields to the environment. Nitrogen (N) is of particular interest in the Baltic Sea region because of its adverse effects on water quality. This paper gives an overview of the expected climatic changes in the Nordic–Baltic region, and the possible effects of these changes on runoff and N losses. Downscaled climate scenarios are used as a basis for evaluating the potential effects of climate change on hydrology, runoff and N losses. Examples from selected catchments in Nordic–Baltic water quality monitoring programmes, including data from extreme events, are presented and used for an assessment of the required adaptations. The analysis shows that there is a strong relationship between annual precipitation and runoff, and between runoff and N loss. The seasonality of precipitation, runoff and N loss indicate high losses outside the growing season. With climate change, increased precipitation is expected to occur mainly outside the growing season – in September–March – and result in increased runoff and thereby increased N losses. Existing data show that extreme events of precipitation have occurred in all seasons during the monitoring period, and have caused high runoff and high losses of N. With the expected increases in N losses, there is an urgent need for efficient measures to reduce N losses in order to fulfil the requirements of e.g. the EU Water Framework Directive (EU-WFD) and the Nitrates Directive and reduction of greenhouse gas emissions (GHG) from agriculture. [ABSTRACT FROM AUTHOR]

Nitrogen (N) transport and retention in streams are largely determined by hydrological characteristics (e.g. water runoff, baseflow index (BFI) and flashiness index (FI)) in the catchment. It is important to know the impact of catchment characteristics such as land use, subsurface drainage intensity, elevation difference and catchment size on the hydrological properties and N loss. This paper presents a comparison of the magnitude and variation of the baseflow and flashiness in streams in relation to the selected geographical and drainage characteristics for thirty studied agriculture dominated catchments in the Nordic and Baltic countries and the effects it can have on N loss. The analysis included measured data from the total discharge and nitrogen loss at the catchment outlets for the period from the beginning of 1993 to 2011, although there is variation in the length of periods among catchments and countries. The study revealed that the rate of subsurface drainage systems and drainage intensity (given as lateral tile drainage spacing) were statistically significant explanatory variables in explaining differences in hydrological characteristics between catchments. There is a considerable increase in the FI, almost by a factor of three, when using hourly discharge values instead of average daily values, indicating that large diurnal variation in discharge can occur, especially at higher FI values. The analysis also showed that there is a negative relation between FI and the BFI, i.e. a high BFI corresponding to a low FI and vice versa. In general, there seems to be a positive relationship between long-term average runoff and N loss, with the highest runoff and N loss occurring in the Norwegian catchments. However, flow path can have a significant influence on the N loss. [ABSTRACT FROM AUTHOR]