Groundwater-surface water interaction between an esker aquifer and a drained fen

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Hydraulic and physical properties of managed and intact peatlands : application of the van Genuchten-Mualem models to peat soils

Key Points: • Land use such as agriculture and peat extraction alter the physical and hydraulic properties of the peat more strongly than other land uses • The top 30 cm peat depth was most affected by agriculture and peat extraction, as indicated by the bulk density, specific yield, and porosity values • The van Genuchten-Mualem soil water retention model was applied successfully to different layers of peat under different land useUndisturbed peatlands are effective carbon sinks and provide a variety of ecosystem services. However, anthropogenic disturbances, especially land drainage, strongly alter peat soil properties and jeopardize the benefits of peatlands. The effects of disturbances should therefore be assessed and predicted. To support accurate modeling, this study determined the physical and hydraulic properties of intact and disturbed peat samples collected from 59 sites (in total 3,073 samples) in Finland and Norway. The bulk density (BD), porosity, and specific yield (Sy) values obtained indicated that the top layer (0–30 cm depth) at agricultural and peat extraction sites was most affected by land use change. The BD in the top layer at agricultural, peat extraction, and forestry sites was 441%, 140%, and 92% higher, respectively, than that of intact peatlands. Porosity decreased with increased BD, but not linearly. Agricultural and peat extraction sites had the lowest saturated hydraulic conductivity, Sy, and porosity, and the highest BD of the land use options studied. The van Genuchten-Mualem (vGM) soil water retention curve (SWRC) and hydraulic conductivity (K) models proved to be applicable for the peat soils tested, providing values of SWRC, K, and vGM-parameters (α and n) for peat layers (top, middle and bottom) under different land uses. A decrease in peat soil water content of ≥10% reduced the unsaturated K values by two orders of magnitude. This unique data set can be used to improve hydrological modeling in peat-dominated catchments and for fuller integration of peat soils into large-scale hydrological models

Influence of forest management changes and reuse of peat production areas on water quality in a northern river

In Northern Finland, the most significant land use challenges are related to bioenergy production from peat extraction and forest biomass. Increasing societal demand for bioenergy may increase production rates. However, environmental impacts of peat extraction are of increasing concern, which has led to a decline in production, thereby freeing up these areas for other uses. Using storylines for different societal futures and process-based models (PERSiST and INCA), we simulated the effect of simultaneous land use change and climate change on water quality (phosphorus, nitrogen and suspended sediments concentration). Conversion of peat extraction areas to arable land, together with climate change, may pose a risk for deterioration of ecological status. On the other hand, continuous forestry may have positive impacts on water quality. Suspended sediment concentrations in the river do not exceed water quality requirements for salmonids, but nitrogen concentrations may exceed threshold values especially during high flows. A storyline emphasizing sustainable development in energy pro-duction led to the best outcome in terms of water protection

After-use of peat extraction sites – A systematic review of biodiversity, climate, hydrological and social impacts

After drainage for forestry and agriculture, peat extraction is one of the most important causes of peatland degradation. When peat extraction is ceased, multiple after-use options exist, including abandonment, restoration, and replacement (e.g., forestry and agricultural use). However, there is a lack of a global synthesis of after-use research. Through a systematic review of 356 peer-reviewed scientific articles, we address this research gap and examine (1) what after-use options have been studied, (2) what the studied and recognized impacts of the after-use options are, and (3) what one can learn in terms of best practices and research gaps. The research has concentrated on the impacts of restoration (N = 162), abandonment (N = 72), and replacement (N = 94), the latter of which consists of afforestation (N = 46), cultivation (N = 34) and creation of water bodies (N = 14). The studies on abandonment, restoration, and creation of water bodies have focused mostly on analyzing vegetation and greenhouse gas (GHG) fluxes, while the studies assessing afforestation and cultivation sites mostly evaluate the provisioning ecosystem services. The studies show that active restoration measures speed-up vegetation recolonization on bare peat areas, reduce GHG emissions and decrease negative impacts on water systems. The most notable research gap is the lack of studies comparing the environmental and social impacts of the after-use options. Additionally, there is a lack of studies focusing on social impacts and downstream hydrology, as well as long-term monitoring of GHG fluxes. Based on the reviewed studies, a comparison of the impacts of the after-use options is not straightforward. We emphasize a need for comparative empirical research in the extracted sites with a broad socio-ecological and geographical context

What conditions favor the influence of seasonally frozen ground on hydrological partitioning? : a systematic review

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

Metsätalouden pohjavesivaikutukset : MEPO-hankkeen loppuraportti 2021

Metsätalouden pohjavesivaikutukset (MEPO) hankkeen tavoite oli antaa tutkimustietoon perustuvia suosituksia pohjavesialueiden metsänhoitotoimenpiteisiin. Luokiteltuja pohjavesialueita on Suomen pinta-alasta 4 % ja metsätalous on alueiden merkittävin maankäyttömuoto. Metsätalouden toimia, joilla voi olla vaikutusta pohjaveteen, ovat hakkuut, maanmuokkaus, ojaston kunnossapito, kasvinsuojeluaineet, metsälannoitus sekä kulotus. Omana erityispiirteenään tarkasteltiin myös happamia sulfaattimaita. Tutkimustieto koottiin kirjallisuudesta sekä pohjavesiseurannoista. Pohjavesialueiden turvemaiden määrää, ojitusta, luontoarvoja ja metsänkäyttöä arvioitiin paikkatietomenetelmin. Lisäksi viimeisteltiin metsätalouden ojien kunnostuksen vaikutusten arviointiin kehitetty KUNNOS-työkalu. Hakkuut voivat nostaa pohjavedenpintaa ja lisätä purkautumista reuna-alueilla ja lähteissä. Hakkuutähteistä vapautuvat ravinteet kohottavat tyypillisesti pohjaveden NO3-N-pitoisuutta. Myös pohjaveden lämpötilan on joissakin tutkimuksissa havaittu kohoavan. Muiden toimenpiteiden vaikutusten osalta Suomesta ei ole tutkimus- ja seurantatietoja ja arvioissa on tukeuduttu kansainvälisiin tutkimustietoihin. Tärkeä jatkotoimenpide on seurannan kehittäminen. Hanke toteutettiin v. 2020–2021 yhteistyössä Suomen ympäristökeskuksen, Luonnonvarakeskuksen, Tapio Oy:n ja Oulun yliopiston tutkijoiden kanssa. Tärkeässä roolissa työkalujen kehittämisessä olivat WaterHope ja Gain Oy.Tämä julkaisu on toteutettu osana valtioneuvoston selvitys- ja tutkimussuunnitelman toimeenpanoa. (tietokayttoon.fi) Julkaisun sisällöstä vastaavat tiedon tuottajat, eikä tekstisisältö välttämättä edusta valtioneuvoston näkemystä

Hydrologic and hydraulic processes in northern treatment peatlands and the significance for phosphorus and nitrogen removal

Abstract The understanding of flow processes is a key to evaluating treatment efficiency in constructed wetlands. This work focuses on the effects of flow paths on phosphorus (P) and nitrogen (N)retention in four treatment wetlands constructed on pristine peatlands in Finland. Particular attention was paid to water residence time, effective flow area and effective flow depth. Both an artificial tracer test and a new method based on the analysis of stable oxygen and hydrogen isotope distributions were employed. Tracer tests were used to calibrate steady-state flow models created using a groundwater modelling MODFLOW code. Furthermore, concentrations of P, Al and Fe in the peat and concentration of N in the surface water were measured. Surface water tracer distributions showed overland flow to be the dominant flow process and it was divided into a preferential flow area and dead zones. Also, active channel formation was observed during the years of the study (2002–2005). The results indicate that the hydraulic performance might deteriorate drastically within a short period of time. The active flow areas in the peatlands comprised only about 40–48% in summer, meaning that large areas with potential for nutrient removal were left unused. Flow simulations showed that a more optimal length of the distribution ditch will create a larger effective flow area and possibly could prevent channel formation. The peat P concentration was 1.8±3.9 mg g-1, and P was accumulated in the preferential flow area. The peat P concentration correlated positively with Al in the Ruka peatland treating wastewater. The results indicate that precipitation chemicals increase the P retention capacity of peatland substantially and maintain P retention at a stable level despite variable P loads. Furthermore, the results indicate that the accumulation of P to peat via adsorption and chemical precipitation is the major P removal process even after 10 years of loading. In Ruka, calculated N concentrations in surface water obtained with a first-order area model, together with regression analysis of the rate constant, were in good agreement with observed N concentrations. If a removal of 70% is to be achieved, the NH4-N loading to the peatland should be below 0.10 mg m2 d-1