Peatlands develop in specific hydrological settings and react sensitively to changes in climatic and hydrological boundary conditions. The hydrology of peatlands is fundamental to their function and development. Soil hydrological properties can change drastically after human interventions such as drainage, causing challenges for both model parameterization and re-wetting measures. Pristine peatlands offer and regulate many ecosystem services such as biodiversity, carbon storage, and nutrient retention. Hydrology is a key control for a number of these services. Furthermore, the effects of peatlands (both pristine and disturbed) on flood retention and regional climate are much debated. As hydrological and biotic processes in peatlands are strongly coupled, estimating the eco-hydrological response of peatlands under climate change and linking it to vegetation development and greenhouse gas emissions is a demanding task for modelers.
This session focuses on:
(1) hydrological processes operating in all types of peatlands (pristine, disturbed, degraded, drained, managed, rehabilitated or re-wetted) in northern and tropical latitudes, and
(2) the first-order control of peatland hydrology on all kinds of peatland functions.
We aim to boost knowledge transfer across spatial/temporal scales and methods; from the pore to the global scale, including laboratory, field, remote sensing, and modeling studies on hydrological, hydrochemical, biogeochemical, ecohydrological or geophysical topics, as well as ecosystem service assessments.
vPICO presentations: Thu, 29 Apr
Representing peatlands in global Earth System Models (ESMs) is a major challenge, but a crucial one since peatlands represent a significant component of the global carbon cycle.
Here we present the first ESM implementation of peat accumulation and degradation that integrates both organic and mineral soils in a single formulation, implemented in JULES - the land-surface component of the UK Earth System Model (UKESM). In this scheme, the soil column is able to expand with the addition of new organic material and to subside as this material decomposes, with variable organic layer thickness, which means that peat can appear and disappear within the landscape without a need for a prescribed peatland fraction.
Thermal and hydraulic characteristics of the soil are dynamically updated depending on the organic matter content and its level of decomposition, using relationships derived from observations. This scheme captures important feedbacks within the soil, such as the way that peatlands - once formed - can be self-sustaining even under conditions where they would not form today. It also captures the loss of carbon and soil structure when peatlands are drained. We demonstrate this behaviour in the model.
This provides a new approach for improving the simulation of organic and peatland soils, and associated carbon-cycle feedbacks in ESMs.
The key remaining challenges for simulating global peatlands are to realistically distribute water around the landscape, in order to represent topographically-controlled peatlands, and to develop appropriate peatland vegetation types.
How to cite: Chadburn, S., Burke, E., Gallego-Sala, A., and Smith, N.: A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2200, https://doi.org/10.5194/egusphere-egu21-2200, 2021.
A basic and universal characteristic of peatlands is that the water table frequently rises near the surface of the soil profile. Surface peat is naturally loose and open-structured, and often has microtopographic features; the water table frequently rises above the level of local depressions. Therefore, water table fluctuations in peatlands cause rapid changes in the permeability and effective porosity of the medium through which flow occurs. We use a simple model based on Boussinesq's equation to explore the challenges that arise from these basic and universal physical aspects of peatland hydrology. We show that simulation of water table fluctuations in peatlands requires precipitation data with a high temporal resolution, and careful attention to the time derivative for accuracy of the mean water tables and correct water balance for two reasons. First, large vertical gradients in specific yield can result in large mass balance errors analogous to errors from naive discretization of the Richards equation; a change of variables from water table elevation to water storage can eliminate these errors and also speed up calculations by allowing larger time steps. Second, large vertical gradients in permeability near the peat surface cause a strongly nonlinear response to precipitation, so that time-averaged precipitation data or neglect of diurnal cycles of evapotranspiration results in erroneously high water levels, and careful time stepping is required around rain storms. Consideration of these features of peatland hydrology results in efficient hydrologic models that can be used to predict spatial and temporal patterns in greenhouse gas uptake and emissions in peatlands.
How to cite: Cobb, A. and Harvey, C.: General considerations for modeling water table dynamics in peatlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-759, https://doi.org/10.5194/egusphere-egu21-759, 2021.
In wetlands, the water budget is traditionally quantified by measuring the hydrologic components including precipitation, evapotranspiration and surface water-groundwater inflows and outflows. However, the reliability of measurements is often questioned due to the difficulty of rigorously monitoring all components of the water budget. Quantifying the rainfall event to water table response ratio is an alternative approach with minimal need for data commonly collected in peatland studies. However, the method has been used only in a limited number of biophysical settings including different microforms, hydroclimatic and hydrogeological settings. The objectives of this study are to quantify the reactivity of the water table to precipitation for different pristine peatlands located in different hydroclimatic conditions and to provide quantitative assessments of water storage of as many peatlands as possible. To do so, site-specific hourly water table and precipitation measurements was collected from northern peatlands worldwide. In total, data from more than 30 sites were retrieved from 8 research groups. For all peatlands, water-table depths varied between 80 cm below the peat surface and 10 cm above the peat surface. The results highlight that the hydrology of all peatlands is characterized by a shift from an environment that can store water to an environment that contributes to rapid outflow, and this is a uniform feature across sites. However, for peatlands with the lowest water storage capacities, this shift occurs during relatively moderate rainfall events (40 mm) or successive small rainfall events. Blanket peat bog best embodied this type of hydrological response. For peatlands with the highest water storage capacity, this shift occurs following multiple moderate to large precipitation events (40 mm – 80 mm) and it is strongly enhanced by the shift from high to low evaporative periods. The peatlands with the highest storage capacity are raised bogs with deep water-table. These conditions are best observed in peatlands located in geographical settings with high evaporation rates. Among all the peatlands, maximum water storage capacity for given rainfall events was equal to ≈150 mm. These analyses also confirm that the water table rise caused by precipitation events contain sufficient information to constrain water storage variations around monitored wells peatlands for a wide array of biophysical settings.
How to cite: Bourgault, M.-A., Bechtold, M., Holden, J., Blundell, A., Dettman, U., Garneau, M., Howson, T., Jutras, S., Kløve, B., Larocque, M., Marttila, H., McKendrick-Smith, K., Menberu, M., Ronkanen, A.-K., Roulet, N., and Tiemeyer, B.: The quantification of water storage capacity of peatlands across different hydroclimatic settings using a simple rainfall event to water-table response ratio method, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9918, https://doi.org/10.5194/egusphere-egu21-9918, 2021.
Fens belong to the most threatened ecosystems in Europe. Maintaining a high water table through rewetting is an effective measure to rehabilitate many of their ecosystem functions. However, the impact of meteorological factors such as relative humidity, precipitation and air temperature on water storage and its dynamics is still unclear especially for rewetted fens in the temperate regions. Here, we quantify the impact of meteorological factors on water table dynamics comparing a drained and a rewetted fen in North-East Germany, using multiple linear regression with data from continuous high-resolution (temporal) water level monitoring and weather stations. We found that a 1-degree rise in daily maximum air temperature causes a drop of about 4 mm in the water table in the drained and degraded fen but only a drop of around 2 mm at the rewetted site, mainly through evapotranspiration. Higher minimum relative humidity limits evapotranspiration and is, thus, negatively associated with water table elevation at both sites. Precipitation contributes to recharge, causing the water table to rise almost six times higher at the drained site than at the rewetted site. We attribute the differential impacts of meteorological factors on water table dynamics to (1) differences in vegetation, which acts as surface control and (2) differences in soil properties. We found that for the depths at which the groundwater fluctuates, the peat of the rewetted fen has a higher specific yield compared to the drained fen, causing the water table to rise or recede at smaller rates. A period of 20 years of rewetting was sufficient to form a new layer of organic matter with a substantial fraction of macropores providing water storage capacity and thereby changing water table response. Our study underlines the importance of long-term rewetting and meteorological factors for peatland restoration. Continuous monitoring of water table and vegetation development in rewetted fens is advisable to ensure long-term success, especially under climate change conditions.
The updated versions of the papers on which this abstract is based can be found at (1) https://www.frontiersin.org/articles/10.3389/feart.2021.630469/abstract and (2) https://www.sciencedirect.com/science/article/pii/S0048969720351007
How to cite: Ahmad, S., Liu, H., Alam, S., Günther, A., Jurasinski, G., and Lennartz, B.: Long-term rewetting of fen peatlands alters the response of water tables to rainfall and temperature, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10938, https://doi.org/10.5194/egusphere-egu21-10938, 2021.
Peatland hydrology forms, together with vegetation cover and carbon dynamics, a sensitive interconnected three-pillar system, which furnishes essential ecosystem services from the local (specific biodiversity, interaction with the watershed) to the global scale (carbon and fresh water storage). The present study focuses on the hydrological function of the Frasne peatland, and especially investigates how restoration of water supplies can be used to mitigate climate change effects on peatland hydrology and sustainability.
In this perspective, the Forbonnet bog, belonging to the Frasne peatland complex (300 ha; French Jura Mountains; 46.826 N, 6.1754 E; 850 m a.s.l) is monitored in the framework of the French observatory of peatland (SNO Tourbières) since 2008. The site, restored in 2015 (European program "Life Tourbières"), is located in a wide karstifed syncline overlain by moraine deposits. Between 2009 and 2019, mean annual precipitation and air temperature were respectively 1618 mm and 7 °C.
In order to identify and model water supply and transfers at the ecosystem scale, this study combines a range of hydrological, geochemical and reservoir modeling approaches. This enabled us to propose a conceptual scheme of the hydrological functioning that implies a nested organization of 3 water origins:
(1) The superficial reservoir (acrotelm) featuring a low mineralization, has a fast (daily) reactivity to precipitation, suggesting a strong dependence to direct atmospheric inputs. In addition, the outlet discharge shows a complex relation with the water level of this layer, highlighting a threshold effect where the saturation degree of the acrotelm seems to be involved.
(2) Five years of outlet discharge and electrical conductivity (EC) monitoring highlight a seasonal pattern. During low flow periods (June-Oct.) EC is positively correlated with rainfall recharge of the previous winter (Nov.-May). Furthermore, the bog water budget is loss-making when only considering the topographical watershed. Considering the geological context, these elements argue for groundwater inflows from the surrounding karst aquifer likely occurring at the base of the bog, throughout the permeable or discontinuous moraine layers. Vertical EC profiles show that these inflows supply the mineralized water deep reservoir of the bog.
(3) The monitoring of the restoration effects (by backfilling of drainage channels) through panpipe piezometers suggests that lateral seepage from the neighboring wooded, more elevated and mature peatlands supplies a transitional peat reservoir.
Moreover, spatial (horizontal and vertical) and temporal EC variability argue for advective water transfers through the bog.
This work supports the interest in monitoring over the long-term (several and contrasted hydrological years) for constraining hydrological processes. The three water supplies delineated could have contrasted responses to climate change and then impact both biological and carbon cycles. This work also highlights the importance to integrate hydrological processes beyond the ecosystem scale, to consider climate change and anthropogenic pressure effects on the regional hydrology that probably interact with peatlands in mountainous environments. In this perspective, the current hydrological monitoring is nowadays combined with isotopic (δ18O and δ2H) evaluation to refine this conceptual scheme and quantify the contribution of the 3 identified water flow paths.
How to cite: Lhosmot, A., Collin, L., Magnon, G., Steinmann, M., Bertrand, C., Stefani, V., Binet, P., Toussaint, M.-L., Boetch, A., and Bertrand, G.: Characterization of nested water supplies in a mid latitude/altitude peatland using long-term monitoring data before and after restoration. The case study of the Frasne peatland (Jura Mountains, France), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1302, https://doi.org/10.5194/egusphere-egu21-1302, 2021.
Hydrophysical soil properties play an important role in regulating the water balance of peatlands and are known to be a function of the status of peat degradation. The objective of this study was to revise multiple regression models (pedotransfer functions, PTFs) for the assessment of hydrophysical properties from readily available soil properties. We selected three study sites, each representing a different state of peat degradation (natural, degraded and extremely degraded). At each site, 72 undisturbed soil cores were collected. The saturated hydraulic conductivity (Ks), soil water retention curves, total porosity, macroporosity, bulk density (BD) and soil organic matter (SOM) content were determined for all sampling locations. The van Genuchten (VG) model parameters (θs, α, n) were optimized using the RETC software package. Macroporosity and the Ks were found to be highly correlated, but the obtained functions differ for differently degraded peatlands. The introduction of macroporosity into existing PTFs substantially improved the derivation of hydrophysical parameter values as compared to functions based on BD and SOM content alone. The obtained PTFs can be applied to a wide range of natural and degraded peat soils. We assume that the incorporation of macroposity helps to overcome effects possibly resulting from soil management. Our results suggest that the extra effort required to determine macroporosity is worth it, considering the quality of parameter estimates for hydraulic conductivity as well as the soil hydraulic VG model.
How to cite: Wang, M., Liu, H., and Lennartz, B.: Effect of Macroporosity on Physical Property Estimates for Peat Soils, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5238, https://doi.org/10.5194/egusphere-egu21-5238, 2021.
Globally peatlands are degrading due to drainage and intensified land use e.g. for forestry, agriculture and peat extraction. Peatland restoration can recover biodiversity of the threatened habitats, reestablish the natural hydrological role of the peatland as retaining water and nutrients and diminish greenhouse gas emissions.
Restoration monitoring for peatlands is urgent in order to reveal the peatland hydrological recovery and ecological succession after restoration, needs for corrective actions and to enable further method development. Restoration monitoring with conventional approaches is laborious, time-consuming and does not cover large areas. Visual evaluation is biased, and the traditional systematic methods give only focused information while conditions for most of the site remain hidden.
Unmanned Aircraft Systems (UAS) imaging produces large coverage information on restoration success in high spatial resolution. Aerial perspective with superior resolution alone extends the monitoring aspect together with the photogrammetric high-precision digital elevation models (DEMs) allowed by the Structure from Motion (SfM) technology.
Additionally, external instruments such as thermal cameras attached in the drone allow revealing temperature anomalies and moisture patterns. We used thermal infrared (TIR) imaging to monitor changes at a boreal rewetted peatland site. The uncalibrated thermal data alone turned out to be useful showing near-surface flow routes recovered in restoration. We further applied a variety of processing methods for the data to explore their applicability on boreal peatlands. The results show the thermal UAS imaging to have great potential in monitoring the hydrological changes due to peatland restoration in high spatial resolution.
How to cite: Ikkala, L., Marttila, H., Ronkanen, A.-K., Ilmonen, J., Rehell, S., Kumpula, T., and Klöve, B.: Thermal UAS Imaging to Monitor Restored Peatlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10582, https://doi.org/10.5194/egusphere-egu21-10582, 2021.
Fluctuations of water table depth (WTD) affect many processes in peatlands, such as vegetation development and emissions of greenhouse gases. Here, we present the OPtical TRApezoid Model (OPTRAM) as a new method for satellite-based monitoring of the temporal variation of WTD in peatlands. OPTRAM is based on the response of short-wave infrared reflectance to the vegetation water status. For five northern peatlands with long-term in-situ WTD records, and with diverse vegetation cover and hydrological regimes, we generate a suite of OPTRAM index time series using (a) different procedures to parametrise OPTRAM (peatland-specific manual vs. globally applicable automatic parametrisation in Google Earth Engine), and (b) different satellite input data (Landsat vs. Sentinel-2). The results based on the manual parametrisation of OPTRAM indicate a high correlation with in-situ WTD time-series for pixels with most suitable vegetation for OPTRAM application (mean Pearson correlation of 0.7 across sites), and we will present the performance differences when moving from a manual to an automatic procedure. Furthermore, for the overlap period of Landsat and Sentinel-2, which have different ranges and widths of short-wave infrared bands used for OPTRAM calculation, the impact of the satellite input data to OPTRAM will be analysed. Eventually, the challenge of merging different satellite missions in the derivation of OPTRAM time series will be explored as an important step towards a global application of OPTRAM for the monitoring of WTD dynamics in northern peatlands.
How to cite: Burdun, I., Bechtold, M., Komisarenko, V., Lohila, A., Humphreys, E., Desai, A. R., Nilsson, M. B., Sagris, V., Mander, Ü., and De Lannoy, G.: Monitoring of water table dynamics in peatlands with OPTRAM: Towards globally applicable algorithms in Google Earth Engine using Landsat and Sentinel-2, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4698, https://doi.org/10.5194/egusphere-egu21-4698, 2021.
Storing up to 70 kg of carbon per cubic meter, peatlands are among the most carbon-dense environments in the world. If in pristine conditions, peatlands support a number of ecosystem services as for example water retention and mitigation of droughts and floods, water purification, water availability to wildlife. Their preservation is one of the main goals of the EU policy and of other initiatives around the world.
Despite their importance, Alpine peatlands have been rarely studied and their presence is not even included in the EU maps, as for example the JRC Relative Cover of Peat Soils map, and only some sites are included in the Corine Land Cover map. The precise localization of peatland sites and the assessment of their extent is the first fundamental step for the implementation of adequate conservation policies. To this end, satellite remote sensing is the ideal instrument to provide adequate spatial resolution to detect and characterize Alpine peatlands at the regional scale. In this study, we use Sentinal-2 satellite data combined with 2m spatial resolution digital elevation model (from LiDAR data) to detect and quantify the extent of peatlands in the Trentino - Alto Adige region, an area of about 12,000 sq km located in the heart of the Italian Alpine region. Ground truth data include 71 peatlands that cover a total surface of more than 2,000 sq m. Field campaigns and lab analyses on some selected sites show that, on average, the sampled peatlands have depth of about 1m, Bulk Density of 0.128 g cm-3 and LOI of 63%, hence indicating that the organic carbon content by soil volume is high, being on average 0.04 g cm-3. Satellite data analysis allowed us to detect a large number of peatland sites with high accuracy, thus confirming the importance of Alpine peatlands as carbon stock sites for the region. Moreover, thanks to the correlation between two indices (NDVI and NDWI) we could characterize the water content of these sites, hence analyzing its seasonal variation and inferring possible future scenarios linked to climate change effects.
How to cite: Silvestri, S. and Borgia, A.: Characterization of Alpine peatlands based on remote sensing of vegetation and water content, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16196, https://doi.org/10.5194/egusphere-egu21-16196, 2021.
Peatlands represent the largest natural terrestrial carbon store and provide a multitude of ecosystem services. Many peatlands across the world have been intensively used for centuries either for peat extraction, agricultural usage or forestry. Drainage and removal of the peat layer have led to a disruption of respective ecosystem functioning caused by falling water levels, altered microbial activity and the shrinkage or depletion of the peat layer. Lately, some areas have been restored and brought back to a semi-natural state by prohibiting their use and closing drainage ditches to raise the water table. All these activities have resulted in very heterogeneous peatlands composed by severely degraded, less disturbed or successfully rehabilitated patches. The respective state of peatlands affects not only the hydrology and the typical shrinkage and swelling of peat known as mire breathing, it also determines the role of peatlands as carbon sink or source and is thus of high relevance for climate change mitigation.
Through the application of interferometric Synthetic Aperture Radar (InSAR) time series to several rewetted semi-natural pre-alpine bogs south of the city of Munich, Germany, it was possible to monitor the surface deformation of the peat layer caused by mire breathing for the period 2016-2020. An experimental InSAR data set was used where both the Persistent Scatterer Interferometry (Ferretti et al. 2001) as well as the distributed scatterers technique (Ansari et al. 2018) were applied to satellite images from the Sentinel-1A and B platforms. The use of distributed scatterers allows to obtain a good coverage over semi-natural peatlands.
The seasonal height fluctuations peatlands are naturally subject to are clearly visible from the time series. The overall trend for the observation period shows a subsidence for the largest part of the test sites of up to 2 cm. Throughout the year 2018, a stronger negative trend, expectedly related to the extremely dry conditions in 2018 in this part of Europe, was observed, which caused the peat layer to dry out and to shrink. Furthermore, the combination of persistent and distributed scatterers captures spatial differences in the sign and intensity of the surface movement. Such deviations might be related to former uses, the degree of degradation and the implementation of restoration measures which have affected the hydrology, soil chemistry and vegetation cover of the bogs.
The findings show that peatlands respond to dry periods in a spatially heterogeneous manner. In the light of climate change, such InSAR time series can be used to monitor surface changes over long time frames to assess the long-term vulnerability of semi-natural peatlands and to indicate whether and which restoration measures prove successful.
The work presented here is part of the KliMoBay project, funded by the Bavarian State Ministry for the Environment and Consumer Protection through the European Regional Development Fund (ERDF).
Ansari, H.; De Zan, F.; Bamler, R. (2018): Efficient Phase Estimation for Interferogram Stacks. In: IEEE Trans. Geosci. Remote Sensing 56 (7). 4109-4125.
Ferretti, A.; Prati, C.; Rocca, F. (2001): Permanent scatterers in SAR interferometry. In: IEEE Trans. Geosci. Remote Sensing 39 (1). 8-20.
How to cite: Huber García, V., Klatt, J., Schlaipfer, M., De Zan, F., Ludwig, R., and Marzahn, P.: InSAR time series over rewetted bogs highlight spatially heterogeneous surface deformation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9038, https://doi.org/10.5194/egusphere-egu21-9038, 2021.
As part of the EU-funded MoorLIFE2020 project, we assessed the impact of pipe blocking on the hydrological responses at pipe and stream level in a heavily degraded blanket bog in the Peak District of northern England. The study catchment, Upper North Grain, has a blanket peat cover up to four meters thick at places, with a branching network of deep gullies that incise into the bedrock. Earlier survey work has shown piping to be ubiquitous to the site, with 346 pipe outlets found and a mean frequency of 22.8 km-1 gully bank. Topographic position was an important control on the size and depth of pipe outlets. Pipe outlets on streambanks with signs of headward retreat (head pipes) were significantly larger and closer to the peat surface compared to pipe outlets that issued onto uniform streambank edges (edge pipes). In the context of peatland restoration, managers are keen to understand how these pipes contribute to hydrological responses of streams and associated export of fluvial carbon borne away in stream waters. However, little is known about pipe-to-stream connectivity and whether blocking methods used to impede flow in open ditch networks and gullies also work on pipe networks. Results will be presented on a before-after-control-intervention experiment in which we investigated: 1) whether impeding drainage from pipe networks alters the streamflow response at the catchment outlet; 2) how such intervention affects the hydrological functioning of the pipe network and the surrounding peat; 3) the scale of fluxes of particulate organic carbon (POC) and dissolved organic carbon (DOC) from a head pipe before and after pipe outlet blocking; and 4) whether pipe outlet blocking alters DOC and POC export in streams. Four blocking methods were trialed: peat-plugs, peat and stone, wooden planks, and plastic pilling. Results show that pipe outlet blocking led to new pipe outlets appearing or seepage around blocks within 90 days of blocking. Over a period of 17 months, four individual pipe outlets (2 head and 2 edge) produced 11.3 % of streamflow. Head pipes produced significantly larger peak flows and storm contributions to streamflow compared to edge pipes. A distinctive distance-decay effect of the water table around pipe outlets was observed, with deeper water tables around the outlets of edge pipes. To avoid further erosion in gully edge zones, we propose that future pipe blocking efforts prioritize increasing the residence time of pipe water by forming surface storage higher up in the pipe network. Further results will be presented from ongoing analyses of the effect of pipe blocking on the export of particulate and dissolved organic carbon from pipes and streams.
How to cite: Regensburg, T., Chapman, P., Pilkington, M., Chandler, D., Evans, M., and Holden, J.: Impairing pipe-to-stream connectivity in a heavily degraded blanket bog: the results of a pipe outlet blocking trial, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5252, https://doi.org/10.5194/egusphere-egu21-5252, 2021.
One of the most important benefits of natural and restored peatlands in boreal ecosystem is their critical role in storing water and consequently reducing flood peaks at the basin outlet. Compared to forests, peatlands have been suggested to have different hydrological behaviors altering the water transit time, flood peaks and runoff volumes, but the science underpinning such statements are largely lacking. This is problematic, as peatland restoration to regain landscape hydrological functioning has become high on the management agenda. However, if it is true that peatlands behave differently they can help mitigate the impacts of both extreme flooding and drought conditions by storing large volumes of water that will delay runoff and keeping streams and rivers flowing during low flow conditions. Accordingly, an accurate estimation of potential and available volume of catchment water storage with different physical characteristics would help us to choose the best peatland management strategies for reducing flood and drought risk in the future. However, the direct estimation of water storage requires an extensive amount of field observations. Hydrological models provide an indirect estimation of water storage and allow us to compare several catchments over a wide range of spatiotemporal scales.
Here, we tested the role of peatlands by using data from 14 nested sub-catchments within a 68 km2 boreal forest landscape in Northern Sweden and then classified them into four different groups (forest on till, forest on sediment, peatlands, and mixed land cover) based on their landscape characteristics. We focused on the “dynamic storage” of catchment which directly controls the catchment streamflow generation. The simple bucket-type hydrological model, HBV-light, with a calibration period of 7 years (2010 to 2017) was deployed to simulate catchments storage dynamics. The calibration trials were repeated 100 times to assess the uncertainty of simulated results. The evaluation of model performance carried out using the coefficient of efficiency, ranged from 0.76 to 0.87. The relationship between storage characteristics and physical catchment properties such as soil depth, peatland percentage, elevation, and area were then analyzed using Spearman rank correlation.
The results of this study shows not only high differences in dynamic storage values among the sub-catchments but also the differences in locations of dynamic storage within the soil layers of peatland dominated catchments. The variations become even greater as we aggregate the storage amounts in shorter temporal scales. The magnitude and variability of total storage change calculated using water balance method was much higher than the dynamic storage estimated by HBV, indicating that not all the water stored in the catchments were available for draining to the stream. We also found that the total amount of dynamic storage in peatland dominated catchments were higher than the amount stored in forest on till and mixed characteristics catchments. Moreover, in peatlands, the proportion of water stored in the upper zone reservoir was much higher than the estimated amounts in other catchments (Spearman rank correlation r=0.73, p < 0.05), which also shows the ability of HBV in capturing the hydrological function of peat soils.
How to cite: Karimi, S., Seibert, J., Maher Hasselquist, E., Bishop, K., Huseby Karlsen, R., and Laudon, H.: Hydrological contrast between peatlands and forests: Implications on extreme flow in the boreal landscape , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13002, https://doi.org/10.5194/egusphere-egu21-13002, 2021.
This study investigates potential effects of wetland restoration on storm flow dynamics in a mainly waterlogged low mountain range catchment located in SW-Germany. Here, wetland drainage networks are being sealed, aiming to achieve rising soil water tables and reestablished peat vegetation. With the help of hydrograph separation, multiple linear regression (MLR) and covariance analysis (ANCOVA), runoff-governing storm properties and sealing influences were analyzed. Results show, that not only natural storm parameters (precipitation sum, rainfall intensity, antecedent precipitation and temperature) exert influence on storm-runoff, but sealings also led to significantly altered processes: On the one hand, storm-runoff coefficients increased in sealed catchments, resulting most likely from more saturated soils, providing a smaller infiltration capacity. This is a desired effect of rewetting but coincidently a downside regarding storm flood prevention. On the other hand, lag times, meaning the timespan between rainfall occurrence and the hydrograph starting to rise, were noticeably prolonged. This effect can be potentially beneficial when it comes to storm flood prevention. Overall, statistical models including sealings showed more satisfactory results describing stormflow variance compared to models without sealings. Therefore, sealings do exert – statistically proven – an effect on storm runoff. The heterogeneity of the results, representing a dense gauge network spread over an investigation area of roughly 7.5 km² shows, that a high-resolution sampling, both spatially and temporally, is vital. That is since runoff processes in waterlogged low mountain range catchments are still poorly understood.
How to cite: Zemke, J.: Storm-runoff processes in a mainly waterlogged low mountain range catchment in the national park Hunsrück-Hochwald, SW-Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13389, https://doi.org/10.5194/egusphere-egu21-13389, 2021.
Submarine groundwater discharge (SGD) is an important pathway for water and compounds within the land-ocean transition zone that can impact coastal environments and marine life. Although SGD research from sandy shorelines has rapidly advanced in recent years, there is very little understanding of coastal areas dominated by coastal peatlands, where the prevailing soils are characterized by a low hydraulic conductivity. Peatlands, the world’s most efficient carbon storage, could be a potential source of carbon, nutrients, and trace metals via the SGD pathway. The objective of this study was to determine the magnitude and location of SGD in a coastal peatland in northeast Germany. We wanted to understand the factors controlling terrestrial SGD from coastal peatlands through numerical modelling employing the HYDRUS-2D modeling package. Steady-state scenarios were simulated based on soil physical properties, hydraulic heads, and geological stratifications and structure. In the model set-up, emphasis was laid upon peat layers extending from land into the sea. Our results show that terrestrial SGD occurs at a net discharge volume flux of 0.0803 m3 m-1 d-1 with seepage rates of 1.05 cm d-1 near the shore and 0.16 cm d-1 at a second discharge region above the submerged peat layer. Calculated seepage rates compare to observations from other SGD sites in the Baltic Sea region and other wetland environments. The upscaled SGD estimate for the 3-km coastal peatland is 240 m3 d-1, which is in correspondence to earlier estimates from the same site. Analysis of the model output reveals that magnitude and location of terrestrial SGD are mainly driven by the magnitude of hydraulic gradient and the hydraulic conductivity of both peat and mineral soils. Additional influencing factors are peat anisotropy, thickness of aquifer sands and peat layers, and peat elevation. Submerged peat layers extending into the sea can restrict SGD flow in deeper discharge regions but may be less critical in terms of volume flux as most SGD occurs near the shoreline. We conclude that coastal peatlands could be an essential source of carbon, nutrients, and other compounds via SGD and may influence local geochemistry budgets and marine ecosystems.
How to cite: Racasa, E. D., Lennartz, B., Ibenthal, M., and Janssen, M.: Submarine groundwater discharge from coastal peatlands of northeast Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12071, https://doi.org/10.5194/egusphere-egu21-12071, 2021.
Blanket peat directly underlies between 11% and 13% of Ireland, with catchments containing more than 10% blanket bog coverage hosting the majority of Water Framework Directive High Status sites. Since 1998 approximately 40% of these sites have experienced a decline in status, with catchments having peat coverage greater than 40% experiencing disproportionate impacts. Declines in status have typically been accompanied by anthropogenic activities that have affected bog hydrology; these include planting / maturing of plantation forestry on deep peat (> 1 metre thick). Although our understanding of mechanisms driving aquatic ecosystem degradation in these areas immediately after planting and following felling has improved considerably in recent years, the impact of mature closed canopy forestry on runoff remains less well defined. Moreover, where research has been carried out, it has focused on sampling conditions during high (quick) flow, while base flow conditions have received less attention.
Comparison of runoff quality, in a stream draining a relatively intact blanket bog-covered catchment, with conditions further downstream, after it had flowed through a mature Sitka Spruce (P.sitchesnsis) plantation on deep peat, aimed to better characterise the impact of the forestry on the stream’s ecology. The study area selected for investigation receives approximately 1600 mm/yr of precipitation, occurring throughout the year (259 days with >0.2mm precipitation). Pairwise comparisons of runoff quality between areas draining open bog land and afforested areas further downstream failed to detect significant differences during high flow events. By contrast samples collected under drier conditions proved significantly more mineralised downstream, with water containing significantly higher levels of Calcium and Magnesium at the afforested area sampling point. Similarly, visual observations in forest drains feeding the stream revealed the presence of tufa mounds, which had developed following planting, and zones of focused iron oxyhydroxide-bearing groundwater upwelling; these features proved absent upstream of the forestry.
Screening for biotic status at the outlets of blanket bog and forested catchments, using the Irish biological quality rating system (Q-scores), suggested that the upstream sampling point was indicative of Good status (Q4), whilst the findings at the downstream forested site were more indicative of High status (Q4-5). However, more detailed analysis of the species sampled suggested that although the sampling point in the forested area (downstream monitoring point) had higher biodiversity and as such allowed for the improvement in Q-score, it had slightly lower species density through lower counts of certain species. This is consistent with findings elsewhere which have highlighted the capacity of aqueous iron oxyhydroxides to detrimentally impact sensitive species, such as freshwater pearl mussel (M. margaritifera). Study results provide further evidence of the capacity of plantation forestry to impact on the aquatic ecology of low order streams, while further highlighting the need for alternative ecological metrics when investigating the impacts from human activity on lower order streams draining blanket bog.
How to cite: Flynn, R., McConigley, C., O'Connell, G., Mackin, F., and Renou Wilson, F.: Ecological Impact of Plantation Forestry on Blanket Bog on a Low Order Stream, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2684, https://doi.org/10.5194/egusphere-egu21-2684, 2021.
The development, the alternative pathways for use of bioresources, can lead to plausible stressors in the future on forestry dominated catchments. It is needed to analyse the impact of regional future projections on different land system management (LSM) attributes. The catchment scale projections are downscaled from Nordic Bioeconomic Pathways (NBPs), the subsets of Shared Socioeconomic Pathways (SSPs). As a case study, the Simojoki catchment (3160 km2) in northern Finland has been considered where drained peatlands and forests dominate (53%) in the catchment. We integrated stakeholder-driven input, Finnish forest inventory model pathways (MELA) and hydrological catchment model (SWAT) to explore the future consequences of forest management practices for different NBP scenarios. We calibrated and validated water quality parameters in SWAT for the Simojoki catchment. Then, based on the output of MELA model of LSM attributes including stand management, catchment management strategy and fertilizer use, we used NBP scenario projections in SWAT model. We also included stakeholders’ evaluations of biomass removal at the time of harvesting at the Simojoki catchment. Additionally, climate imposing emission scenarios have been integrated into SWAT model to analyse longer perception of climate change (CC). The final outcomes of the proposed scenarios (NBP and/or CC) will portray the probable impacts on each LSM attribute in the Simojoki catchment, to adapt to the future forest management consequences.
How to cite: Bhattacharjee, J., Marttila, H., Juutinen, A., Tolvanen, A., Haara, A., Karhu, J., and Klöve, B.: Nordic Bioeconomic Pathways - catchment scale water quality impacts of various scenarios and projections , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5744, https://doi.org/10.5194/egusphere-egu21-5744, 2021.
The export of Dissolved Organic Carbon (DOC) and evasion of carbon dioxide (CO2) from inland waters is increasingly being recognized as a key part of the terrestrial carbon (C) cycle, with recent global estimates suggesting that the magnitude of the aquatic CO2 conduit is equivalent to global Net Ecosystem Productivity (2.0 Gt C yr-1; Tranvik et al., 2009). However, a major weakness in the carbon balance estimation of terrestrial ecosystems, such as peatlands, is the poor quantification of DOC and CO2 evasion fluxes associated with drainage waters. This has implications for conservation, land-use management and climate change mitigation. Whilst intact peatland systems typically sequester carbon, drainage reverts peatlands to being C sources due, primarily, to the degradation of organic peat soil. This study examines the export of C in fluvial pathways from relatively intact catchments to those that are heavily drained, and also from peatland sites undergoing restoration works. This research is being carried out parallel other linked studies that are quantifying the carbon gaseous emissions from directly from the different bogs in order to determine the comparative net carbon budgets.
This study will focus on three raised bog sites in the midlands of Ireland: one in near natural condition (Clara bog), one significantly drained and degraded due to peat extraction (Garryduff) and one undergoing rehabilitation following many years of peat extraction (Cavemount). Flumes and sondes, with fluorescent dissolved organic matter (fDOM), temperature/conductivity and turbidity sensors, have been installed on the sites. The fDOM measurements will be correlated to grab samples taken every two weeks to give half hour proxy measurements for DOC.
Preliminary results suggest that DOC flux from the heavily drained and mined peatland site is some 295 times higher than that from the catchment with minimal interference. In addition to this, drainage waters are super-saturated in CO2 and rapidly evades back to the atmosphere resulting in an additional C loss. Thus, C losses in the drainage systems of peatland catchment areas are significantly under-reported and a significant source of C in countries with significant peat land cover such as Ireland. This research is thereby addressing the magnitude of C losses in fluvial pathways, the associated effects on ecosystem biodiversity and the effectiveness of restoration activities on mitigating against net C loss in degraded systems.
How to cite: Cox, P., Gill, L., Regan, S., and Saunders, M.: Quantifying fluvial carbon losses from lowland peatland ecosystems across a drainage-impact spectrum , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15719, https://doi.org/10.5194/egusphere-egu21-15719, 2021.
Rainfall-induced landslides are difficult to forecast and often evolve into highly destructive flows, as such, they are one of the most dangerous natural hazards globally. While our understanding of peatland hydrology has improved greatly in the past two decades, there has been less focus on the response of peat hydrology following perturbations such as wildfires and landslides. Here we report on a new paired catchment experiment in Ireland. Our focus is to quantify the hydrological changes following peat landslides and further, to establish the short-term and longer-term impacts on local peatland hydrology, ecology and recovery.
The two paired sites are located in Co. Leitrim, Ireland, in two adjacent, small upland blanket bog catchments. The first peat catchment (0.2km2) is an area of a recent (June 2020) slope failure. According to preliminary estimates ~178,000 – 188,000 tonnes of peat were transported downstream during the peat slide event, resulting in a large landslide scar section (~0.059 km2) in a special area of conservation [SAC]. Preliminary impacts are assessed to include: habitat loss, decreased slope stability, impacts on hydrology and water quality, as well as increased local erosion.
This catchment is paired with an adjacent upland blanket peat catchment (0.11 km2) which is deemed to have been under the same anthropogenic pressures (grazing, upslope forestry plantation).
A hydrometric suite, including weather station, piezometers, and water level recorders to evaluate the surface and subsurface hydrology has been installed at both sites. In addition, we are monitoring the response of landslide deposits (e.g. rafted peat, some with still-standing sika spruce), ecology, soil structure, permeability and shear strength in both catchments.
Here we will report on the initial results of our monitoring.
How to cite: Halpin, R., Bourke, M., Long, M., and Trafford, A.: The impacts of peat slides on upland blanket peatland hydrology, ecology and soil structure. A paired catchment approach. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11942, https://doi.org/10.5194/egusphere-egu21-11942, 2021.
Wetlands are accounted as important providers of ecosystem services, which yield several functionalities such as the support of biodiversity, flood control, soil stabilization to reduce dust generation, natural treatment of surface waters, groundwater replenishment, climate regulation and economic benefits. Over the past decades, the impacts of anthropogenic manipulations amplified by climatic changes have threatened both the quantity and quality of wetlands, worldwide. A continuous monitoring of wetlands is thus necessary to protect them from further destruction, as well as to devise and assess the success of any rehabilitation plans. The conventional methods of water body monitoring chiefly include field surveying, which is time consuming, costly, and limited in extent. Alternatively, remotely sensed data have facilitated a much less expensive and more extensive monitoring of water bodies over a wide range of spatiotemporal resolutions. In this study, we implemented a learning-based classification framework fed by remote sensing data to evaluate the historical trends of the most important wetlands across Iran using the Google Earth Engine cloud computing platform. To this end, we used Landsat imagery between 2000 and 2020 to extract the water body of wetlands in dry seasons to consider the most critical condition. We also examined different spectral indices to identify the best combination giving the largest classification accuracy for each wetland, separately, based on their distinct conditions of water depth and vegetation cover. We then quantified the contribution of wetlands drying to the generation of dust storms via a frequency-intensity index given the annual number of dusty days and the Aerosol Optical Depth (AOD) provided by MODIS. According to the results, the majority of the studied wetlands show significant descending trends with the average loss of 31% in surface area. The aerosol analysis also witnesses the expansion of dust generation sources around most of the retreated wetlands, particularly in those years when the wetlands areas were smaller than the long-term average. The above observations point out a potential threat for the agricultural activities and highlight serious consequences for the health of nearby urban and rural residents.
Keywords: Wetland, Dust Storm, Remote Sensing, Environmental Monitoring, Ecosystem Protection
How to cite: Bayati, M., Bayat-Afshary, N., and Danesh-Yazdi, M.: Quantifying the contribution of wetlands drying to aerosol generation across Iran, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-306, https://doi.org/10.5194/egusphere-egu21-306, 2021.
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