Organic matter and nutrient export from drained peatlands is affected by complex hydrological and biogeochemical interactions. Here partial least squares regression (PLSR) was used to relate various ...soil and catchment characteristics to variations in chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations in runoff. Peat core samples and water quality data were collected from 15 peat extraction sites in Finland. PLSR models constructed by cross‐validation and variable selection routines predicted 92, 88, and 95% of the variation in mean COD, TN, and TP concentration in runoff, respectively. The results showed that variations in COD were mainly related to net production (temperature and water‐extractable dissolved organic carbon (DOC)), hydrology (topographical relief), and solubility of dissolved organic matter (peat sulfur (S) and calcium (Ca) concentrations). Negative correlations for peat S and runoff COD indicated that acidity from oxidation of organic S stored in peat may be an important mechanism suppressing organic matter leaching. Moreover, runoff COD was associated with peat aluminum (Al), P, and sodium (Na) concentrations. Hydrological controls on TN and COD were similar (i.e., related to topography), whereas degree of humification, bulk density, and water‐extractable COD and Al provided additional explanations for TN concentration. Variations in runoff TP concentration were attributed to erosion of particulate P, as indicated by a positive correlation with suspended sediment concentration (SSC), and factors associated with metal‐humic complexation and P adsorption (peat Al, water‐extractable P, and water‐extractable iron (Fe)).
Key Points
Partial least squares regression models were developed to link biogeochemical and hydrological variables to runoff water quality
Chemical oxygen demand (COD) and nutrient concentrations in runoff could be predicted from relatively few soil and catchment characteristics
Peat sulfur concentration was inversely related to water‐extractable DOC and mean runoff chemical oxygen demand concentrations in catchments
The Skjønhaug constructed wetland (CW) is a free surface water (FSW) wetland polishing chemically treated municipal wastewater in southeastern Norway and consists of three ponds as well as trickling, ...unsaturated filters with light weight aggregates (LWA). Fluxes of nitrous oxide (N(2)O) and methane (CH(4)) have been measured during the autumn, winter and summer from all three ponds as well as from the unsaturated filters. Physicochemical parameters of the water have been measured at the same localities. The large temporal and spatial variation of N(2)O fluxes was found to cover a range of -0.49 to 110 mg N(2)O-N m(-2) day(-1), while the fluxes of CH(4) was found to cover a range of -1.2 to 1900 mg m(-2) day(-1). Thus, both emission and consumption occurred. Regarding fluxes of N(2)O there was a significant difference between the summer, winter and autumn, with the highest emissions occurring during the autumn. The fluxes of CH(4) were, on the other hand, not significantly different with regard to seasons. Both the emissions of N(2)O and CH(4) were positively influenced by the amount of total organic carbon (TOC). The measured fluxes of N(2)O and CH(4) are in the same range as those reported from other CWs treating wastewater. There was an approximately equal contribution to the global warming potential from N(2)O and CH(4).
•We modeled hydrology of the entire European continent with SWAT.•We included river discharge and nitrate loads as well as crop yield in the model.•We provide a protocol for calibration of ...large-scale models with uncertainty analysis.•We modeled blue and green water resources of Europe at subbasin level.•We improved SWAT-CUP to include parallel processing and visualization.
A combination of driving forces are increasing pressure on local, national, and regional water supplies needed for irrigation, energy production, industrial uses, domestic purposes, and the environment. In many parts of Europe groundwater quantity, and in particular quality, have come under sever degradation and water levels have decreased resulting in negative environmental impacts. Rapid improvements in the economy of the eastern European block of countries and uncertainties with regard to freshwater availability create challenges for water managers. At the same time, climate change adds a new level of uncertainty with regard to freshwater supplies. In this research we build and calibrate an integrated hydrological model of Europe using the Soil and Water Assessment Tool (SWAT) program. Different components of water resources are simulated and crop yield and water quality are considered at the Hydrological Response Unit (HRU) level. The water resources are quantified at subbasin level with monthly time intervals. Leaching of nitrate into groundwater is also simulated at a finer spatial level (HRU). The use of large-scale, high-resolution water resources models enables consistent and comprehensive examination of integrated system behavior through physically-based, data-driven simulation. In this article we discuss issues with data availability, calibration of large-scale distributed models, and outline procedures for model calibration and uncertainty analysis. The calibrated model and results provide information support to the European Water Framework Directive and lay the basis for further assessment of the impact of climate change on water availability and quality. The approach and methods developed are general and can be applied to any large region around the world.
Annual, seasonal and monthly variations in precipitation during the period 1911–2011 were evaluated using spatially interpolated monthly precipitation records at 165 stations with more than 30 years ...of data (of which 32 stations had 101 years of data referring to full length of study period). Historical trends and cyclic patterns of precipitation and links to teleconnection indices were analysed. The results show that annual precipitation in Finland increased by 0.92 ± 0.50 mm year−1 (p < 0.05) during the study period (1911–2011), and showed negative relationships with the East Atlantic/West Russia (EA/WR) teleconnection pattern (ρ = −0.41, p < 0.05) through the years 1950–2011. However, there were spatial (north–south/east–west) differences between regions. The time cycle (λ) for annual precipitation cycles was estimated to 149 years (R2=0.15), and 1964 was indicated as the turning point from a negative (dry) to a positive (wet) phase. Analysis of seasonal and monthly cycles showed larger variations, depending mainly on teleconnection effects. Analysis of seasonal precipitation determined increasing trends for winter (by 0.46 ± 0.19 mm year−1) and summer (by 0.32 ± 0.29 mm year−1), while no clear trend was found for spring and autumn precipitation (p > 0.05). Winter precipitation was most strongly correlated with the North Atlantic Oscillation (NAO) index (ρ = 0.55, p < 0.05), while the EA/WR pattern was the most significant teleconnection index for precipitation variations in spring (ρ = −0.33, p < 0.05) and summer (ρ = −0.49, p < 0.05); the precipitation variability during autumn was negatively associated with the Scandinavia (SCA) pattern (ρ = −0.40, p < 0.05). The results clearly indicate that Finland has experienced wetter climate than normal conditions during recent decades, and precipitation in the Fenno‐Scandinavian climate is controlled by a number of climate teleconnection indices, not just the NAO as previously assumed.
Abstract
The influence of seasonally frozen ground (SFG) on water, energy, and solute fluxes is important in cold climate regions. The hydrological role of permafrost is now being actively ...researched, but the influence of SFG has received less attention. Intuitively, SFG restricts (snowmelt) infiltration, thereby enhancing surface runoff and decreasing soil water replenishment and groundwater recharge. However, the reported hydrological effects of SFG remain contradictory and appear to be highly site- and event-specific. There is a clear knowledge gap concerning under what physiographical and climate conditions SFG is more likely to influence hydrological fluxes. We addressed this knowledge gap by systematically reviewing published work examining the role of SFG in hydrological partitioning. We collected data on environmental variables influencing the SFG regime across different climates, land covers, and measurement scales, along with the main conclusion about the SFG influence on the studied hydrological flux. The compiled dataset allowed us to draw conclusions that extended beyond individual site investigations. Our key findings were: (a) an obvious hydrological influence of SFG at small-scale, but a more variable hydrological response with increasing scale of measurement, and (b) indication that cold climate with deep snow and forest land cover may be related to reduced importance of SFG in hydrological partitioning. It is thus increasingly important to understand the hydrological repercussions of SFG in a warming climate, where permafrost is transitioning to seasonally frozen conditions.
Peatland-based treatment wetlands that purify incoming water by means of natural physical, chemical and biological processes belonging to the peatland ecosystem are widely used at Finnish peat ...extraction sites. They can comprise either undrained or drained overland flow areas (OFAs or DOFAs), with the OFAs representing the best available technology (BAT) for peat extraction. We analyse here the long-term treatment performance of these OFAs and DOFAs and factors affecting this performance. Data on 14 OFAs and DOFAs in different parts of Finland were taken from the extensive long-term environmental pollution control databases. Nearly half of these wetlands had been monitored for at least 4 years and seven for 8–23 years. The results indicated that peatland-based treatment wetlands purify drainage water as efficiently as other natural treatment wetlands on soils in general, the common challenge being phosphorus retention. Iron was also efficiently retained. The average reductions were highest in OFAs with good hydraulic function, and these also showed long-term water protection performance. An important factor affecting purification efficiency was the hydraulic loading rate. Important system design elements in this regard were the size of the wetland in relation to its catchment area, its gradient, the length of the water flow route within the wetland, and the efficient flow area of the wetland. The results regarding the latter two design elements strongly indicate that not all the areas potentially suitable in DOFAs for water purification are yet being used efficiently.
In northern peatlands, near‐saturated surface conditions promote valuable ecosystem services such as carbon storage and drinking water provision. Peat saturated hydraulic conductivity (Ksat) plays an ...important role in maintaining wet surface conditions by moderating drainage and evapotranspiration. Peat Ksat can exhibit intense spatial variability in three dimensions and can change rapidly in response to disturbance. The development of skillful predictive equations for peat Ksat and other hydraulic properties, akin to mineral soil pedotransfer functions, remains a subject of ongoing research. We report a meta‐analysis of 2,507 northern peat samples, from which we developed linear models that predict peat Ksat from other variables, including depth, dry bulk density, von Post score (degree of humification), and categorical information such as surface microform type and peatland trophic type (e.g., bog and fen). Peat Ksat decreases strongly with increasing depth, dry bulk density, and humification; and increases along the trophic gradient from bog to fen peat. Dry bulk density and humification are particularly important predictors and increase model skill greatly; our best model, which includes these variables, has a cross‐validated r2 of 0.75 and little bias. A second model that includes humification but omits dry bulk density, intended for rapid field estimations of Ksat, also performs well (cross‐validated r2 = 0.64). Two additional models that omit several predictors perform less well (cross‐validated r2 ∼ 0.5), and exhibit greater bias, but allow Ksat to be estimated from less comprehensive data. Our models allow improved estimation of peat Ksat from simpler, cheaper measurements.
Key Points
We report skillful statistical models to estimate saturated hydraulic conductivity in northern peats from simpler measurements
Peat dry bulk density and humification (von Post score) are particularly powerful predictors
Our models represent an improvement over existing pedotransfer functions for peat saturated hydraulic conductivity
ABSTRACT
Annual and seasonal variations in surface air temperature (SAT) during the period 1961–2011 were analysed using daily mean temperature data sets from regular grid points (10 × 10 km2) ...throughout Finland. The Mann–Kendall nonparametric test was used to detect significant historical trends in SAT and Spearman's correlation coefficient (ρ) to test the relationships between SAT patterns and various atmospheric circulation patterns over the northern hemisphere. The results showed that mean annual SAT in Finland increased (p < 0.05) by 0.4 ± 0.2 °C per decade during the study period and that the SAT was significantly (ρ = 0.58, p < 0.05) positively correlated with the Arctic Oscillation (AO) index. However, there were spatial differences within Finland for both the trends and relationships with the atmospheric circulation. Analysis of seasonal mean SAT identified significant (p < 0.05) warming trends for both spring (by 0.4 ± 0.2 °C per decade) and summer (by 0.3 ± 0.2 °C per decade). Winter and spring mean SATs were most strongly (p < 0.05) correlated with the AO index (ρ = 0.72 and 0.42, respectively), while the most significant teleconnection pattern for mean SAT in summer was the East Atlantic (EA) pattern (ρ = 0.43, p < 0.05); and in autumn the EA/West Russia (WR) pattern (ρ = −0.59, p < 0.05). These results provide a detailed spatial picture of climate warming in Finland in recent decades and reveal that interannual variation of the SAT in Finland is closely linked with a number of atmospheric circulation patterns, not just the AO and North Atlantic Oscillation (NAO). Annual and cold‐season SAT are mainly influenced by the AO and NAO, whereas the EA, EA/WR, Scandinavia (SCA) and West Pacific (WP) patterns play an important role for warm‐season SAT.
ABSTRACT
Numerous studies have reported significant declines in snow resources in Finland and elsewhere during the 20th century. To identify the main climate factors controlling these declines in ...Finland, this study evaluated long‐term variations and trends in wintertime climate, snowpack hydrological processes (SHPs) and continuous snow cover duration (CSCD), and their links to atmospheric circulation patterns (ACPs). Analyses were conducted using observed daily climatological time series and simulated SHPs at three stations in southern (Kaisaniemi), central (Kajaani) and northern (Sodankylä) Finland with about 100 years of data. The Mann‐Kendall nonparametric test was used to detect significant trends, the Pearson's coefficient (r) to identify relationships within snow‐related variables, and Spearman's coefficient (ρ) to measure correlations of these variables with ACPs. Sensitivity of the snow‐related variables with projected changes in temperature and precipitation was assessed. The results showed increases in wintertime temperature only at Kaisaniemi, but decreases in wintertime precipitation, snowfall and snow water equivalent (SWE) and shorter CSCD at all stations. In general, variations in wintertime temperature were positively associated with the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO). However, wintertime precipitation showed significant relationships with the East Atlantic/West Russia (EA/WR), AO and West Pacific (WP) patterns in southern, central and northern Finland, respectively. SHPs and CSCD in southern Finland were associated with the same ACP influencing wintertime temperature (AO), and those in central and northern areas with the patterns influencing wintertime precipitation (EA, EA/WR and AO). Thus, declines in snow resources in Finland are mainly the result of reductions in snowfall owing to both wintertime warming and decreased precipitation at Kaisaniemi, while only to decreases in wintertime precipitation at Kajaani and Sodankylä stations. However, increase in precipitation (up to 30%) plays an important role in offsetting effects of temperature warming (up to 4 °C) on snow resource decline in Finland.
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