Nutrient transport scenarios in a changing Stockholm and Mälaren valley region, Sweden

Abstract

Norrström catchment, west of Stockholm, covers most of the Mälaren valley. Provision of drinking water from Lake Mälaren is an absolute precondition for continued growth in the region. Stockholm County's population is expected to increase by 600,000 people before 2030. Current climate change predictions anticipate significant temperature and precipitation increases. We implement the PolFlow model embedded in PCRaster for quantifying water and substances fluxes on the catchment scale over a 30-year time horizon. We formulate scenarios for changes in water quality and quantity due to climate change and population development. Results indicate a mild impact from climate change on surface flow rates but substantial effects on sub-surface residence times. Population development slightly affects nutrients loads. Using source apportionment and sensitivity analysis, we identify a number of critical parameters/processes to be further studied, in order for future results to be more reliable and usable in a water resources management context.

Hypoxia-Related Processes in the Baltic Sea

“…To decrease future overall nutrient loading to the Baltic Sea a much larger effort than anticipated may be necessary to achieve reductions in diffuse source loading (78). Projected population changes and increased meat production are expected to increase nutrient loading even with concurrent nutrient reduction strategies (81). To improve future prospects, it is therefore important to eliminate the gaps in our understanding so that the uncertainties in determining future nutrient loading to the Baltic Sea are diminished.…”

Quantification of advective solute travel times and mass transport through hydrological catchments

“…The advective travel time distributions that have been used in most previous studies have been approximated by assuming some common type of probability density function (e.g., log-normal, inverse Gaussian), which can be fully parameterized based on knowledge of only the possible mean and variance of solute travel times in the considered transport system. In this study, we adopt the Lagrangian advective travel time-based approach and extend it to quantify and investigate entire distributions of advective solute travel times in the two Swedish catchment cases and their different water subsystems, by the use of the flow and mass transport results that have already been modeled, tested against all available monitoring data and reported in a series of previous published studies of these catchment areas [19][20][21][22][23][24][25][26][27][28].…”

“…Furthermore, the previously reported flow and transport modeling of the specific two Swedish catchment cases considered in this study certainly include soil properties and processes [19][20][21][22][23][24][25][26][27][28]. The main reason and motivation for the present primary focus on quantifying and linking the groundwater and stream network travel times is that the soil depth of quaternary deposits above the bedrock is generally small (around 1-2 m, up to maximum 5 m) in both these catchment areas, with the groundwater table being on average about one meter below the soil surface.…”

“…In this paper, we investigate the possible quantification of solute travel time distributions in catchments, by the use of reported results on catchment-scale hydrological flow and mass transport modeling in two well-investigated, coastal Swedish catchments areas ( Fig. 1): the Norrström drainage basin [19][20][21][22][23][24] and the Forsmark catchment area [25][26][27][28]. In particular, we investigate here the role of different possible groundwater system representations for the quantification of solute travel times through catchments.…”

Diffuse hydrological mass transport through catchments: scenario analysis of coupled physical and biogeochemical uncertainty effects

“…-the spatiotemporal configuration, variability and historic-to-future development and change of driving forces and conditions that determine source inputs, such as human activities, weather, climate and land cover/use conditions (Darracq et al, 2005;Hagemann and Jacob, 2007;Jacob et al, 2007;Edwards and Withers, 2008;Kyselý and Beranová, 2009;Bergknut et al, 2010) -the transport pathways from the sources to the downstream observation points and receiving water environments, and the variability of water flow and mass transport velocities and travel times among and along these pathways (e.g. McGuire et al, 2005;Destouni et al, 2010;Beven, 2010;McDonnell et al, 2010) -the variability of biogeochemical processes and their combination and cross-correlation with the physical mass transport along the different flow and transport pathways (e.g.…”