HS10.7

How to cite: Dadap, N., Cobb, A., Hoyt, A., Harvey, C., Feldman, A., Im, E.-S., and Konings, A.: Predicting climate change impacts to peatland soil moisture in Southeast Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10763, https://doi.org/10.5194/egusphere-egu22-10763, 2022.

The 16.5 million ha Cuvette Centrale peatland complex in the Congo Basin was described for the first time in 2017. However, a proper understanding of the entire hydrological functioning of this peatland complex is a challenge and large-scale land surface models (LSMs) are unlikely to accurately represent the circulation of water in this area. One of the major issues of large-scale LSMs is the quantification of the spatially- and temporally-variable lateral water input from rivers into peatlands.

In this research, we applied our recently developed tropical peatland-specific module PEATCLSM_Trop,Nat in a land surface modeling and assimilation scheme that uses L-band brightness temperature (T_b) data from the Soil Moisture and Ocean Salinity (SMOS) satellite mission. Despite the dense vegetation cover in tropical peatlands, preliminary results showed that the data assimilation improved the water level estimates at 4 evaluation sites over model-only simulations, with mean correlation coefficients of 0.46 for the model-only and 0.63 for the data assimilation estimates, and mean anomaly correlation coefficients of 0.02 for the model-only and 0.26 for the data assimilation estimates. To gain insight into the large-scale hydrology of the Cuvette Centrale peatland complex, we analyzed data assimilation diagnostics and found temporally autocorrelated positive and negative total water storage (tws) increments (=tws correction introduced via data assimilation) over periods of up to four months over the Cuvette Centrale peatlands. This is indicative of a temporarily suboptimal assimilation system, due to a shortcoming in the LSM. Since PEATCLSM_Trop,Nat does not simulate lateral water input and the positive autocorrelated periods of tws increments coincide with anomalies in river stages measured upstream, it suggests that lateral water input (=flooding) from upstream mineral areas into the peatlands of the Cuvette Centrale is an important but unmodelled process in its hydrology. This means that land use change and a climate change-induced precipitation reduction in upstream mineral areas will influence the local hydrology of the Cuvette Centrale peatland complex, making it even more vulnerable to external disturbances.

How to cite: Apers, S., De Lannoy, G., Cobb, A. R., Dargie, G. C., Reichle, R. H., and Bechtold, M.: River water input from upstream areas into the Cuvette Centrale peatland complex detected via SMOS data assimilation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7430, https://doi.org/10.5194/egusphere-egu22-7430, 2022.

Many upland headwaters of the UK drain areas of blanket peat, much of which has been degraded through atmospheric deposition of pollutants, vegetation change, peat extraction, artificial drainage and erosion. These areas are increasingly the focus of interventions to restore some of the multiple-benefits lost through degradation. Understanding their runoff generation processes underpins analysis of their wider benefits including their potential to mitigate downstream flooding.

Using a series of multivariate analysis techniques we examine controls on storm runoff in ten blanket peat catchments of 0.2-3.9 hectares all within 5 km of one another. We find that: 1) rainfall intensity is the dominant hydro-meteorological driver for both magnitude and timing of peak discharge for all ten catchments, with antecedent rainfall only relevant in small storms; 2) most of the inter-catchment variability in discharge predictability from rainfall can be explained by catchment characteristics, particularly catchment area; 3) runoff responses, particularly in small storms, are sensitive to scale even in an apparently homogenous and saturation-excess overland flow dominated peatland landscape; 4) peak discharge in large storms is strongly controlled by attenuation processes associated with the travel time distribution, and thus drainage network geometry; 5) peak discharge in smaller storms underlines the importance of hydrological connectivity at scales <1 hectare, perhaps due to depression storage driven (dis)connectivity.

Together these results suggest a switching in rainfall-runoff behavior within these catchments where peak discharge is controlled by: catchment storage, connectivity and antecedent conditions in small storms; but runoff attenuation, travel time and thus and network structure and scale in larger storms. In the context of Natural Flood Management, our findings suggest that enhancing depression storage by creating distributed shallow peatland pools in addition to existing restoration methods could raise the threshold storm size below which catchment storage, antecedent conditions and connectivity remain important. However, changes in surface roughness and other measures that target runoff velocities are likely to be more effective in the largest (and thus most flood relevant) storms.

How to cite: Edokpa, D., Milledge, D., Allott, T., Holden, J., Shuttleworth, E., Kay, M., Johnston, A., Millin-Chalabi, G., Scott-Campbell, M., Chandler, D., Freestone, J., and Evans, M.: Controls on storm runoff behavior in a gullied blanket peatland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10081, https://doi.org/10.5194/egusphere-egu22-10081, 2022.

Thawing discontinuous permafrost in subarctic peatland-dominated landscapes is increasingly recognized as an indicator of a warming climate and potentially shifting these landscapes from atmospheric carbon store to source. Furthermore, in certain discontinuous permafrost landscapes (e.g., northwest Canada) the thaw of permafrost peatlands leads to a reorganization of near-surface flow paths as permafrost-free peatlands expand, connect, merge, and drain. Collectively, these permafrost-thaw-driven landcover and hydrological changes have increased runoff and altered biogeochemical cycles threatening natural resources and critical infrastructure in Indigenous peoples’ traditional territories along with aquatic and terrestrial wildlife habitat. Owing to the region’s remote position and vast scale, comparatively less is known about the landcover and hydrological impacts of permafrost thaw in the Hudson Plains, the world’s third largest peatland region (370,000 km²) and southern most extent continental permafrost. For this study, we assign specific hydrological functions to individual peatland types based on their form, to then infer hydrological flux and storage processes within and between peatlands un a circuitry analog, at the scale of the peatland complexes and peatland complex regions. We analyze several remotely sensed data, including high-resolution lidar, historical air photographs, and recent panchromatic and multispectral satellite imagery along a latitudinal transect to evaluate peatland form, complex, and regional patterns. We then summarise these results and interpretation to present an initial vulnerability map of peatland complexes in the Hudson Plains to permafrost-thaw-driven hydrological change.  

How to cite: Mack, M., Quinton, W., McLaughlin, J., and Hopkinson, C.: Vulnerability of peatland complexes in the Hudson Plains, Canada to permafrost-thaw-driven hydrological change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10949, https://doi.org/10.5194/egusphere-egu22-10949, 2022.

Sphagnum moss, lichen and peat are widely present in arctic regions, covering millions of km² in permafrost-dominated regions. This multi-component low vegetation strata plays a key role in surfaces fluxes in these areas, as they are the most widespread interface between the atmosphere and the geosphere. Therefore, characterizing their transfer properties such as hydraulic and thermal conductivities is crucial for climate change impacts forecasting in arctic regions. In this work, 12 samples were collected in a discontinuous permafrost arctic area (Khanymey Research Station, Russian Federation) and dried to ensure their conservation. Collected samples have been digitally reconstructed by X-ray scanning. After having assessed morphological and hydraulic properties using numerical analysis of the obtained 3D digital tomographies (Cazaurang et al, submitted), we aim here at developing and using both experimental and numerical methodologies to characterize thermal properties of these samples of Sphagnum, lichen and peat.

This new study consist in comparisons of numerically and experimentally estimated thermal properties for contributing to the existing knowledge on Sphagnum, lichen and peat transfer properties. Experiments consist of a steady-state thermal conductivity estimation using a hot plate source on real arctic vegetation cover samples. For this purpose, samples are placed in a confined thermal atmosphere and a constant heat flux is applied at sample base. Thermal conductivity is then retrieved with the resolution of Fourier’s heat conduction law. Similarly, numerical computations are conducted on the same digital reconstructions than those used for hydraulic properties determination. Simulations consist of a numerical reproduction of previously described experiments, allowing to strengthen the analysis of the experimental data. Additionally, the definition of representative elementary volumes of the studied samples is also undertaken using the numerical results.

Compiling these assessments of transfer properties will represent essential information to simulate the dynamics of the permafrost underneath the arctic bryophytic layers with a devoted catchment-scale permafrost models. For instance in the framework of the HiPerBorea project (hiperborea.omp.eu), this approach will be used to forecast the impacts of climate warming on boreal permafrost-dominated catchments.

How to cite: Cazaurang, S., Marcoux, M., Pokrovsky, O. S., Loiko, S. V., Lim, A. G., Audry, S., Shirokova, L. S., and Orgogozo, L.: Arctic vegetation cover seen as a porous media : Numerical assessment of hydraulic and thermal properties of Sphagnum moss, lichen and peat from Western Siberia., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5810, https://doi.org/10.5194/egusphere-egu22-5810, 2022.

This study addresses the effects  of  future  climate-induced permafrost thaw  on  the distribution of land cover in the discontinuous permafrost zones of Northwest Territories (NWT) of Canada. The rapid transition from  a landscape dominated by peat plateaus to one dominated by connected wetlands (fens) and isolated wetlands (bogs) is intricately connected to permafrost thaw. To be able to predict and estimate the potential long-term evolution of these three dominant land covers, we developed a machine learning-based time series land cover change model (TSLCM). The TSLCM is trained on a set of spatio-temporal variables as driving factors of change including: the estimated summertime land surface temperature anomaly (LST), the distance to land cover interfaces, time intervals between observations, time-accumulated land surface temperature, and classified land cover maps from 1970-2008. The TSLCM is used to capture  spatial patterns of change, replicate historical land cover change, and generate reasonable estimates of future land cover evolution over time. The output of TSLCM model is the spatial distribution of fen, bogs, and peat plateaus consistent with a default 50\%\ threshold applied on the predicted probability maps. 
We here use the TSLCM to simulate land cover change under multiple plausible futures scenarios by using the most recent set of climate model projections. The simulation of the TSLCM under different scenarios helps us to:

    1: visualize the spatial pattern of change
    2: calculate the pace of evolution over time and compare results between climate scenarios
    3:  explore the sensitivity of the model to driving factors of change

 
In addition to examining uncertainty due to climate uncertainty, a probabilistic approach is used to sample the threshold value to generate a range of land cover realizations. 

How to cite: Akbarpour Safsari, S. and Craig, J.: A machine-learning model to predict uncertainty in permafrost thaw-induced land cover transition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6665, https://doi.org/10.5194/egusphere-egu22-6665, 2022.

Water table depth (WTD) is one of the key factors that affect the carbon balance in peatlands. Optical remote sensing can detect WTD indirectly through the estimation of surface moisture. In peatlands, WTD and surface moisture conditions are closely related through the strong capillary connection in the topmost peat layer. We took advantage of this strong connection and calculated the OPtical TRApezoid Model (OPTRAM) that relies on the assumption that short-wave infrared reflectance represents the surface moisture conditions. OPTRAM was calculated based on Sentinel-2 MSI and Landsat 8 OLI over selected northern peatlands in Finland, Sweden, Canada, the USA, and Estonia. This is the first study in which the advantages and shortcomings of OPTRAM estimation from Sentinel-2 MSI and Landsat 8 OLI data were discussed. We calculated OPTRAM in two ways: (i) using a manual parametrisation and (ii) utilising a recently developed automatic parameterisation in Google Earth Engine. Further, we analysed the impact of these two parameterisations on OPTRAM performance in various peatlands. Our findings provide an important insight into the global applicability of OPTRAM for monitoring moisture conditions in northern peatlands.

How to cite: Burdun, I., Bechtold, M., Komisarenko, V., Lohila, A., Humphreys, E., Desai, A. R., Nilsson, M. B., Tuittila, E.-S., De Lannoy, G., Uuemaa, E., and Rautiainen, M.: Water table depth dynamics derived from optical remote sensing data in northern peatlands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11300, https://doi.org/10.5194/egusphere-egu22-11300, 2022.

Reducing greenhouse gas emissions from degraded, agriculturally used peatlands is a vital contribution to meeting the German climate protection targets by 2050. It requires an understanding their closely coupled hydraulic and geochemical processes, which is the basis of sustainable land and water management on these sites. Hydraulic modelling of the fluxes in a soil profile was done to characterise the hydraulic state of a degraded peatland site with spatially and temporally high resolution. The basis of the model were measurements from groundwater lysimeters in a site with three horizons in Spreewald wetland, Germany. The model was implemented in the one-dimensional hydraulic modelling software Hydrus-1D. The first step was the determination of initial soil hydraulic properties using soil physical properties and the ROSETTA tool based on pedotransfer functions, which is integrated in Hydrus-1D. Two model variants were set up that differed in their lower boundary condition – either the measured pressure head (representing groundwater level) or the measured flux at the lower boundary of the lysimeter. The modelled volumetric water contents, pressure heads and groundwater table (variant 1) or fluxes at lower boundary (variant 2) were validated with the measured lysimeter data. In a second step, the soil hydraulic parameters were inversely optimised based on measured time series data, for both variants. To further improve the model results, dual porosity type flow was implemented in the upper two horizons. The different steps were able to continuously improve the model. The choice of lower boundary condition had an effect on the quality of the model results: The use of groundwater table as lower boundary condition improved the modelled volumetric water contents and pressure heads, but yielded deviating fluxes at the lower boundary in comparison to the measurements. The application of flux as a lower boundary condition produced deviations in the modelled groundwater table, the water contents and the pressure heads, especially after heavy rainfall events. The integration of preferential flow (dual porosity) into the model improved the vadose zone pressure head and water content results significantly.

How to cite: Davies, M., Dietrich, O., and Merz, C.: Modelling water fluxes in a soil profile of a degraded peatland site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2242, https://doi.org/10.5194/egusphere-egu22-2242, 2022.

To meet the sustainable development goals and enable protection of peatlands, there is a strong need to plan and align land-use management with the needs of the environment. The most critical tool to succeed in sustainable spatial planning is accurate and detailed maps. Here we present a novel approach to map mineral and peat soils based on a high-resolution digital soil moisture map. This soil moisture map was produced by combining LIDAR-derived terrain indices and machine learning to model soil moisture at 2 m spatial resolution across the Swedish landscape with high accuracy (Kappa = 0.69, MCC = 0.68). We used field data from about 20,000 sites across Sweden to train an extreme gradient boosting model to predict soil moisture. The predictor features included a suite of terrain indices generated from national LIDAR digital elevation model and other ancillary environmental features, including surficial geology, climate, land use information, allowing for adjustment of soil moisture maps to regional/local conditions. As soil moisture is an important control on peat formation, we investigated if this map can be used to improve the mapping of peatlands. In this study, we included a total of 5 479 soil pit data for organic layer thickness from the Swedish Forest Soil Inventory. Peat was defined as organic layer thickness > 50 cm. The data was split into a calibration dataset and a validation dataset using a randomized 50% split. An empirical relationship between the thickness of the organic layer and the continuous SLU soil moisture map (R² = 0.66, p < 0.001) was used to generate both a categorical map (of mineral soil and peat) and continuous map (of organic layer thickness) to demonstrate how these two mapping approaches can be useful for different management objectives. The peat coverage on the new categorical map, the quaternary deposits map and topographical map was 17.3%, 14.1% and 13.5%, respectively. Map quality measures from the evaluation dataset showed that the newly developed peat map had higher recall and MCC (80.4, 0.73) than quaternary deposits map (68.5, 0.65) and topographical map (49.8, 0.61). The continuous map of the organic layer ranged 6-95 cm with an RMSE of 4 cm.

Using Sweden as a test case, this study provides a guide to improved mapping of mineral and peat soils from Lidar data in other boreal forest regions for effective ecosystem management. The map of organic soils was developed to support the need for land use management optimization by incorporating landscape sensitivity and hydrological connectivity into a framework that promotes the protection of soil and water quality. The organic soil map can be used to address fundamental considerations, such as;

• guiding the restoration of drained wetlands;
• designing riparian protection zones to optimize the protection of water quality and biodiversity as the new map also include riparian peats.

How to cite: Ågren, A. M., Hasselquist, E., Stendahl, J., Nilsson, M. B., and Paul, S. S.: Delineating the distribution of mineral and peat soils in the northern boreal regions – Transition from discrete classification to continuous maps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1731, https://doi.org/10.5194/egusphere-egu22-1731, 2022.

The UK supports 15% of the world’s blanket peat cover but much of this vital resource is significantly degraded. Damaged peatlands lose their hydrological integrity, depressing water tables and exacerbating downstream flooding as water is quickly evacuated from hillslopes across bare peat surfaces and through erosional gullies. The restoration of damaged peatlands is a major conservation concern, and landscape-scale restoration by revegetation and damming of gullies is extensive in areas of upland Britain. There is increasing evidence that the restoration techniques can raise water tables and significantly slow the flow of water in addition to providing other ecosystem service benefits. More recently, focus has shifted from stabilising eroding surfaces to reintroducing Sphagnum moss as part of multi-benefit restoration initiatives, but to date there is limited empirical data to evidence its impacts.

This paper reports the results of long-term post-restoration monitoring on the Kinder Plateau in the southern Pennines, UK. Two sites were revegetated using lime-seed-fertiliser-mulch in 2011 and one of these sites was also gully blocked in 2012 and had a further phase of restoration in the form of intensive Sphagnum planting in 2015. A third unrestored control site was also monitored. We present post-intervention trajectories spanning 10 years showing the long-term recovery of vegetation, water tables, runoff generation, water quality, and sediment production.

The trajectories of recovery for different functions differ in form and rate. At both treatment sites, vegetation cover and diversity increased rapidly then expansion slowed as full cover was approached. Sediment production was quickly reduced to levels comparable to intact peatlands within two years and bare peat cover became negligible after ~7 years. Key runoff metrics (e.g. peak discharge and lag time) showed similar immediate step changes as a result of increased surface roughness from the rapid vegetation expansion, followed by more gradual improvements as species richness developed through time.  The addition of gully blocking enhanced the short-term impacts of re-vegetation, amplifying the step change, but on longer timescales there were no additional benefits relative to the revegetation only site. Water tables recovered gradually at a constant rate and there is no sign of this slowing after 10 years. Water quality (DOC and colour) was highly variable throughout the study period and the long-term impact of restoration is inconclusive. The introduction of Sphagnum provided additional hydrological benefits, most notably through further increases in lag times and attenuation of runoff. There is also preliminary evidence that the Sphagnum provides resilience to surface drying.

This study provides the first evidence that the reintroduction of Sphagnum in degraded headwater peatlands can provide additional natural flood management (NFM) benefits compared to standard restoration techniques aimed at stabilising eroding surfaces. We also show that water table recovery does not counteract the benefits of flow attenuation. We emphasise the critical importance of control in assessing the impact of restoration interventions and the need for investment in longer-term (>10 year) monitoring to better understand the hydrological recovery of restored peatlands.

How to cite: Shuttleworth, E., Allott, T., Edokpa, D., Evans, M., Goudarzi, S., Howson, T., Johnston, A., Kay, M., Milledge, D., Pilkington, M., Rees, J. L., Ritson, J., and Spencer, T.: A ten-year trajectory of hydrological recovery in a restored blanket peatland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10042, https://doi.org/10.5194/egusphere-egu22-10042, 2022.

Groundwater-fed peatlands are a rare and vital ecosystem providing rich biodiversity, carbon storage and regulation of the hydrological cycle. Management of these species and carbon stores are essential for maintaining a healthy ecosystem. In parallel to this, groundwater aquifers are a common source of relatively clean drinking water, under pressure from population growth and climate change. Groundwater abstraction can lead to a reduction in groundwater levels within associated wetlands, affecting their condition, for example by facilitating tree encroachment. Therefore, sustainable water supply needs to balance water demand against other unintentional environmental impacts on the ecosystems. Greywell Fen is located in Southern England, situated above a chalk aquifer that is used to provide drinking water to the area. The fen has been designated a site of special scientific interest (SSSI) in recognition of its important flora. However, the critical vegetation species have been declining in recent decades in favour of extensive tree growth throughout the site. New management of the area has included the reintroduction of grazing and large areas of tree clearance. Our research concerns the impacts of groundwater abstraction and woodland management on the health of the fen. Extensive water level monitoring connected to different areas of tree growth and clearance is being used to determine if tree management is having an effect on water levels within the fen. In addition, peat cores have been sampled in the different areas to determine if tree management and/or water level changes are impacting peat properties, as an indication of drying and decline in fen health. Peat properties studied include pH, water content, C:N, and organic matter decomposition. The latter was performed using FTIR spectroscopy.  The results of this in-depth monitoring are presented here.

How to cite: Halliday, E., Clark, J., Verhoef, A., Macdonald, D., and Wilkinson, D.: How tree management affects water levels and peat properties in a groundwater fed peatland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5177, https://doi.org/10.5194/egusphere-egu22-5177, 2022.

Erosion gullies are a common feature of degraded blanket peatlands and in recent years gully blocking has been increasingly employed as a restoration approach. The stated aims of gully blocking are typically to stabilise eroding gullies and to rewet the adjacent peatland by raising water tables, but in recent years the potential benefits of gully blocking for natural flood management (NFM) have also been recognised. However, data on the hydrological effects of gully blocking and for different gully blocking techniques are sparse.

We report on a before-after-control-intervention (BACI) experiment of gully blocking in peatland micro-catchments (hectare scale) in the Peak District National Park, UK. Three different gully blocking interventions were made in March 2020: impermeable peat dams, permeable cobble dams, and peat dams with a restricted diameter bypass pipe. The first two interventions represent standard restoration techniques, whereas the piped peat dams are specifically designed to be optimal for natural flood management benefit. The micro-catchments were monitored for one year before and two years after gully blocking for: rainfall, discharge, depth to water table proximate to the gullies (within 2m) and depth to water table distal from the gullies (>10m away). Storm hydrograph data (peak discharges and lag times) were extracted for >120 storms from the rainfall-runoff data. All intervention data were analysed relative to data from a control micro-catchment.

After blocking for all interventions there were significant declines in median depth to water table proximate to the gullies, with the magnitude of the rewetting benefit in the following order: peat dams > piped peat dams > cobble dams. There were no significant changes in depth to water table at the distal locations. Peat dams led to a slight increase in storm peak flows but no change in hydrograph lag times. Stone dams led to no change in peak flows but increases in lag times. Piped peat dams resulted in the greatest changes to storm hydrographs, with substantial declines in peak flows and increases in lag times once the pipe diameter had been optimised to the discharge regime.

Peat dams maximise the rewetting benefits of gully blocking but appear to have limited NFM potential, whereas once optimised, piped peat dams provide maximum NFM benefit and greater water table recovery than stone dams.  These findings are important for restoration practitioners when making decisions on which gully blocking techniques to employ to balance the co-benefits of peatland restoration.

How to cite: Allott, T., Edokpa, D., Cummings, T., Evans, M., Shuttleworth, E., Milledge, D., Kay, M., Johnson, A., Howson, T., Rees, J., and Spencer, T.: Hydrological impacts of contrasting gully blocking techniques for peat restoration and natural flood management in a degraded blanket peatland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11220, https://doi.org/10.5194/egusphere-egu22-11220, 2022.