Water Table Depth Research Articles

Interplay between Selected Chemical and Biochemical Soil Properties in the Humus Horizons of Grassland Soils with Low Water Table Depth

Grasslands are the most carbon-rich of all agricultural ecosystems, but are also the most endangered. The global area of grassland decreased during the 20th century, mainly due to conversion to arable land, improper management, and abandonment. Due to ongoing climate change, maintenance of an adequate level of soil organic matter is of primary importance, not only to maintain the productive function of the soils, but also to ensure their role as carbon stores. The main aim of this study was to assess the linkages between selected chemical and biochemical soil properties in alluvial grassland soils, characterized by a low water table. The area under study was located in the Koło Basin, central Poland. Soil parameters, such as total organic carbon, total nitrogen, pH, phosphorus, magnesium, and potassium contents, as well as enzymatic activity and soil microbial structure were studied. Positive correlations were observed between total organic carbon content and the following enzymatic activities: dehydrogenase (r = 0.63), acid phosphatase (r = 0.69), and alkaline phosphatase (r = 0.86). There was a significant correlation between fungi abundance and phosphorus and potassium contents, and between actinobacteria abundance and total organic carbon content.

Monitoring Seasonal Shear Wave Velocity Changes in the Top 6 m at Garner Valley in Southern California With Borehole Data

AbstractSubsurface structures play important roles in seismic ground motion, crustal hydrology, stability of the built environment, and more. Constraining temporal changes of subsurface shear wave velocity (VS) can provide useful information to all these topics and the growing field of hydrological monitoring with seismic velocity. Using borehole records at Garner Valley, CA, we estimate seasonal subsurface VS variations from impulse response functions (IRFs) of earthquake data (2005–2018) along with IRFs and cross‐correlation of cross‐hole experiment data (2015–2018). The inferred VS variations are up to ∼25% in the top 6 m and ∼10% at 2–5 m in depth. The VS variations correlate strongly with the water table depth changes, suggesting that the changes are mostly due to fluctuations of pore pressure in the shallow material. The shallow velocity changes alter the near‐surface conditions, can affect seismic hazard estimation, and may be improperly attributed to deeper processes without careful analysis.

Local identification of groundwater dependent vegetation using high-resolution Sentinel-2 data – A Mediterranean case study

Groundwater dependent ecosystems (GDEs) are biodiversity hotspots and provide important ecosystem services. This study presents a novel multi-instrument concept for the local identification of groundwater dependent vegetation (GDV) in the Mediterranean. The concept integrates high-resolution Sentinel-2 remote sensing data with available geodata and requires in situ vegetation data for validation and calibration. The approach combines five criteria to identify GDV: 1) high vitality, and wetness during dry period, 2) low seasonal changes in vitality and leaf area, 3) low interannual changes in vitality, 4) high topographic potential of water accumulation and low water table depth, 5) high potential inflow dependency. Iso Cluster Unsupervised Classification (ICUC) was applied to identify GDV in the study area (Campania, Italy). Botanical field mapping was utilized for validating the remote sensing approach, as it exhibited significant differences between GDV and Non-GDV in terms of ecohydrological indicator values, leaf anatomy and phreatophyte coverage. According to a new simple ecohydrological rule set that considers phreatophyte cover and mean moisture value of non-phreatophyte species, 9% of vegetation plots are considered GDV and 33% likely GDV. 80% of all GDV derived from classification occur in hydrostratigraphic units (HSU) that are characterized by surficial groundwater circulation and low permeability. The overall accuracy of classifying likelihoods is 62.7%. For 14.6% of the plots, non-GDVs were classified as GDVs (false positives), and only one GDV plot has been classified falsely as non-GDV (false negative). Local results on GDV locations can be overlayed with aquifer use or aquifer reaction to climate change in order to identify GDV under threat and implement sustainable managements of groundwater resources.

Evaluation of a geospatial liquefaction model using land damage data from the 2016 Kaikōura earthquake

The paper uses two geospatial liquefaction models based on (1) global and (2) New Zealand specific variables such as Vs30, precipitation and water table depth to estimate liquefaction probability and spatial extent for the 2016 Kaikōura earthquake. Results are compared to observational data, indicating that the model based on global variables underestimates liquefaction manifestation in the Blenheim area due to the low resolution of the input datasets. Furthermore, a tendency for underprediction is evident in both models for sites located in areas with rapidly changing elevation (mountainous terrain), which is likely caused by the low resolution of the elevation-dependent variables Vs30 and water table depth leading to incorrect estimates. The New Zealand specific model appears to be less sensitive to this effect as the variables provide a higher resolution and a better representation of region specific characteristics. However, the results suggest that the modification might lead to an overestimation of liquefaction manifestation along rivers (e. g. Kaikōura). An adjustment of the model coefficients and / or the integration of other resources such as geotechnical methods can be considered to improve the model performance. The evaluation of the geospatial liquefaction models demonstrates the importance of high resolution input data and leads to the conclusion that the New Zealand specific model should be preferred over the original model due to better prediction performance. The findings provide an overall better understanding on the models’ applicability and potential as a tool to predict liquefaction manifestation for future hazard assessments.

Water table dynamics of dune slacks in an arid zone

In this study, a characterisation is undertaken of the humid dune slacks water table situated in the arid transgressive coastal dune field of the Maspalomas Special Area of Conservation, ES701007 (Gran Canaria, Canary Islands, Spain). Humid dune slacks are listed as a European Union Habitat (EU Habitat 2190 humid dune slacks) in Annex I of the EU Habitats Directive. This water table is relatively stable throughout the year, with a 41 cm maximum oscillation. The annual dynamics of the flow pattern and water table level depend on the climate conditions. At the end of the hydrological dry season the mean water table drops (ca. 11 cm) and water flows to the lagoon. After rains, the mean water table level rises (ca. 4 cm) and flows towards the Maspalomas beach. The distribution of plant communities (associated to EU Habitat 2190) in the Maspalomas humid dune slacks depends on water table depth, pH and salinity. The knowledge acquired in this study of the water table dynamics has enabled a better understanding of the spatial distribution patterns of the vegetation of these slacks, in particular with respect to the relationship between the water table flux toward the coast during the dry season and the distribution of plant communities in the slacks closest to the coast. The study of the dynamics of the water table of the slacks and the associated vegetation has allowed us to better understand the characteristics of the Maspalomas humid dune slacks and potentially improve their management as EU Habitat. This is especially significant considering that the only European arid climate dune field where this habitat can be found is in Maspalomas.

Subsurface mobility of land applied greenhouse nutrient feed water and environmental implications

Greenhouse nutrient feedwater (GNF) discharge is considered a potential contributor to eutrophication issues in Lake Erie, Ontario. Land application of GNF is an accepted legislated management response to mitigate the impact of such nutrient loads. To assess the potential environmental impacts of this management practice, field infiltration experiments were conducted at four different greenhouse operations near Leamington, Ontario. Over a three-year study, GNF was applied on agricultural land adjacent to the greenhouse operations in the fall during the first year, and along with a bromide tracer in the summer and fall in Years 2 and 3, respectively. The GNF was applied at the maximum allowable rates as defined in legislation. Chemical constituents (nutrients, metals and the conservative tracer bromide) were monitored within the soil profile matrix and pore water above the water table. The results showed that, even with the GNF being applied at the highest permissible rates, the species of interest remained within the unsaturated soil zone at low concentrations over three to six months sampling intervals. The bromide tracer test demonstrated that highly mobile species could move through permeable soils to the water table depth in a potential worst-case application scenario. However, considering the low initial concentrations, long vadose zone residence time and the low mass flux, it would appear that land application of GNF, when applied in accordance with Ontario's Regulations, is a feasible and environmentally reasonable treatment option for managing GNF.

Secondary succession in swamp gallery forests along 65 fallow years after shifting cultivation

Understanding the resilience of ecosystems to different land uses is critical to elucidate the mechanisms underlying regeneration processes and plan more sustainable land-use systems. While these relationships are well understood in continuous tropical forests, they are still poorly comprehended in forest formations embedded in a savanna matrix, even though these forest systems are critical for conserving savanna biodiversity and water resources. We assessed the time and capacity of swamp gallery forests to recover after shifting cultivation, in the Cerrado (Brazilian savanna), investigating the role of environmental factors in community recovery. This shifting cultivation system uses slash and burn techniques and establishes drained fields of 0.3–1.2 ha which are cultivated for 10 years, then left fallow for 10–65 years. To assess the resilience of these communities, we analyzed a chronological sequence of 28 secondary forests (1–65 years) and compared them with four old forests (reference ecosystems). We evaluated the trajectory and recovery time of community diversity, composition, and structure (height, canopy coverage, density, basal area, and biomass) as a function of fallow time, water table depth, and soil characteristics using multiple linear models. Forest fragments were considered recovered when their attributes reached the mean values of the reference forests. Most attributes are projected to reach the mean reference values of old-growth forests within nine decades, except for the proportion of non-pioneer species, canopy cover, and biomass. Water table depth influenced the trajectory and time required for recovery species richness and floristic composition. Soils with higher pH and higher nutrient availability positively influenced the recovery of non-pioneer species composition, while soils with lower pH and high organic carbon availability favored an increase in canopy height throughout succession. The disturbances generated by this shifting cultivation system do not prevent the recovery of at least 80 percent of the assessed community attributes in 65 years, suggesting that the resilience of secondary forests was not lost. Considering disturbance at similar scales, we recommend that these ecosystems be left fallow for at least 90 years to complete the recovery of ecological attributes.

Machine-learning-based downscaling of modelled climate change impacts on groundwater table depth

Abstract. There is an urgent demand for assessments of climate change impacts on the hydrological cycle at high spatial resolutions. In particular, the impacts on shallow groundwater levels, which can lead to both flooding and drought, have major implications for agriculture, adaptation, and urban planning. Predicting such hydrological impacts is typically performed using physically based hydrological models (HMs). However, such models are computationally expensive, especially at high spatial resolutions. This study is based on the Danish national groundwater model, set up as a distributed, integrated surface–subsurface model at a 500 m horizontal resolution. Recently, a version at a higher resolution of 100 m was created, amongst others, to better represent the uppermost groundwater table and to meet end-user demands for water management and climate adaptation. However, the increase in resolution of the hydrological model also increases computational bottleneck. To evaluate climate change impacts, a large ensemble of climate models was run with the 500 m hydrological model, while performing the same ensemble run with the 100 m resolution nationwide model was deemed infeasible. The desired outputs at the 100 m resolution were produced by developing a novel, hybrid downscaling method based on machine learning (ML). Hydrological models for five subcatchments, covering around 9 % of Denmark and selected to represent a range of hydrogeological settings, were run at 100 m resolutions with forcings from a reduced ensemble of climate models. Random forest (RF) algorithms were established using the simulated climate change impacts (future – present) on water table depth at 100 m resolution from those submodels as training data. The trained downscaling algorithms were then applied to create nationwide maps of climate-change-induced impacts on the shallow groundwater table at 100 m resolutions. These downscaled maps were successfully validated against results from a validation submodel at a 100 m resolution excluded from training the algorithms, and compared to the impact signals from the 500 m HM across Denmark. The suggested downscaling algorithm also opens for the spatial downscaling of other model outputs. It has the potential for further applications where, for example, computational limitations inhibit running distributed HMs at fine resolutions.

GIS-Based Simulation for Landfill Site Selection in Mekong Delta: A Specific Application in Ben Tre Province

The aim of this research is to develop a GIS-based simulation for selecting the most suitable site of solid waste landfill which could help to minimize harmful impacts to the environment and society in the extreme sensitive and complex delta by an integration of geographic information system (GIS) and analysis hierarchy process (AHP) and nine criteria (distance from surface water; depth of ground water table; distance from residential area, land use, distance from main roads, geo-environmental and geotechnical characteristics, distance from historical and tourism sites, and distance from industrial zones). Different from most of the previous studies on the landfill site selection, geology-related criteria including soil types/lithology, soil permeability, and soil depth/soil thickness (soil-structure), which are called geo-environmental and geotechnical characteristics in this research, will be carefully considered, integrated, and evaluated. The AHP was employed to determine the weight of each criterion based on pair weight comparison and its matrix, while a land suitability index (LSI) score was calculated to determine the most suitable site. Moreover, the suitability map was also created which indicated very advantageous, advantageous, rather advantageous, and disadvantageous areas in the study area for landfill siting. Finally, the developed model could be used for supporting planners, managers, policy makers, and local government to make decisions on suitable and effective planning strategies for landfill site selection and could be applied anywhere and especially in other deltas around the world.

Evidence for older carbon loss with lowered water tables and changing plant functional groups in peatlands.

A small imbalance in plant productivity and decomposition accounts for the carbon (C) accumulation capacity of peatlands. As climate changes, the continuity of peatland net C storage relies on rising primary production to offset increasing ecosystem respiration (ER) along with the persistence of older C in waterlogged peat. A lowering in the water table position in peatlands often increases decomposition rates, but concurrent plant community shifts can interactively alter ER and plant productivity responses. The combined effects of water table variation and plant communities on older peat C loss are unknown. We used a full-factorial 1-m3 mesocosm array with vascular plant functional group manipulations (Unmanipulated Control, Sedge only, and Ericaceous only) and water table depth (natural and lowered) treatments to test the effects of plants and water depth on CO2 fluxes, decomposition, and older C loss. We used Δ14 C and δ13 C of ecosystem CO2 respiration, bulk peat, plants, and porewater dissolved inorganic C to construct mixing models partitioning ER among potential sources. We found that the lowered water table treatments were respiring C fixed before the bomb spike (1955) from deep waterlogged peat. Lowered water table Sedge treatments had the oldest dissolved inorganic 14 C signature and the highest proportional peat contribution to ER. Decomposition assays corroborated sustained high rates of decomposition with lowered water tables down to 40 cm below the peat surface. Heterotrophic respiration exceeded plant respiration at the height of the growing season in lowered water table treatments. Rates of gross primary production were only impacted by vegetation, whereas ER was affected by vegetation and water table depth treatments. The decoupling of respiration and primary production with lowered water tables combined with older C losses suggests that climate and land-use-induced changes in peatland hydrology can increase the vulnerability of peatland C stores.

Modeling and evaluation of NAPL-impacted soil vapor intrusion facilitated by vadose zone breathing

The water table fluctuations can cause a reciprocating advection of soil gas in the vertical direction, known as vadose zone breathing. In this study, we developed a vadose zone breathing-facilitated vapor intrusion (VI) model and applied it to evaluate the influence of NAPL (non-aqueous phase liquid)-impacted soils. The developed model was first validated with data from previously conducted sand tank experiments and then used to simulate VI scenarios involving different fluctuation amplitudes and periods of the water table, soil types, building structures, and source depths. Our results suggest that within one month of vadose zone breathing (amplitude of 0.5 m and period of 4 d), the indoor pollutant concentration varies by approximately seven orders of magnitude, and the averaged concentration is nearly nine times larger than the steady-state concentration. The results also show that with the increase of mean soil particle size, the indoor pollutant concentration tends to increase and becomes more sensitive to vadose zone breathing; compared to the basement foundation, buildings with a slab-on-grade foundation are less susceptible; when the source depth exceeds 10 m, the source depth plays an insignificant influence. Our findings highlight that vadose zone breathing can promote the VI risks of buildings with a basement foundation at sites with shallow water tables, significant groundwater fluctuations, and coarse-textural soils.

Estimation of Daily Evaporation from Shallow Groundwater Using Empirical Models with a Temperature Coefficient

Abstract Shallow groundwater evaporation (Eg) is a major component of the hydrological cycle, especially in semiarid and arid locations. Empirical methods are commonly used to estimate Eg. However, most of these methods can only weakly represent Eg variations along the soil depth and do not consider the energy driver. In this paper, a temperature coefficient was proposed and incorporated into two preferred empirical models to characterize the impacts of soil temperature and air temperature lags on Eg. The method was evaluated using in situ daily data obtained from nonweighing bare soil lysimeters. The results indicated that the models that considered the temperature gradient variable (T) conformed to the changes in the actual Eg values with depth more appropriately than the original models, accompanied by 4.3%–8.8% accuracy improvements overall. Shallow groundwater evaporation Eg was found to be influenced by the water table depth (H), T, and pan evaporation (E0) in descending order, and strong interactions were found between H and T. Moreover, the impact of precipitation on Eg was investigated; measurements from dry days without precipitation revealed the actual Eg process, the relative errors in the cumulative Eg values derived at different depths demonstrated a positive relationship with infiltration recharge, and the errors related to precipitation induced 6.7%–8.3% Eg underestimations. These results contribute to a better understanding of evaporative losses from shallow groundwater and the typical Eg situation that occurs simultaneously with recharge, and they provide promising perspectives for corresponding integrated hydrologic modeling research.

Responses of Global Atmospheric Energy Transport to Idealized Groundwater Conditions in a General Circulation Model

Abstract The representation of groundwater dynamics in land surface models and their roles in global precipitation variations has received attention in recent years. Studies have revealed the overall higher soil moisture but rather diverse precipitation changes after incorporating the groundwater component in climate models. However, groundwater effects on large-scale atmospheric energy transport, the fundamental atmospheric variable regulating Earth’s climate, have not been explored thoroughly. In this study, a pair of idealized experiments corresponding to contrast globally fixed water table depths by AMIP-type simulations in the Community Earth System Model was conducted. In the wet (shallow water table) experiments, an increased meridional surface temperature gradient makes the mean meridional energy transports and Hadley circulation stronger than dry (deep water table) experiments over the tropics. Such energy transport changes are primarily attributed to the dynamic contribution (intensified Hadley circulation). The wet experiments make the simulated world be like an aquaplanet simulation with less land–sea temperature contrast and the enhancement (reduction) of mean meridional circulation (stationary eddies) energy transports. Furthermore, the South Asian monsoon circulation in the wet experiment shows a southward shift in the premonsoon season (April–June) and slight weakening in the mature phase (July and August). This study explores the impacts of the soil conditions caused by various water table depths on global energy transport and has further implications for climate model developments and experiment designs.

Advancing AI-based pan-European groundwater monitoring

The main challenge of pan-European groundwater (GW) monitoring is the sparsity of collated water table depth (wtd) observations. The wtd anomaly (wtda ) is a measure of the increased wtd due to droughts. Combining long short-term memory (LSTM) networks and transfer learning (TL), we propose an AI-based methodology LSTM-TL to produce reliable wtda estimates at the European scale in the absence of consistent wtd observational data sets. The core idea of LSTM-TL is to transfer the modeled relationship between wtda and input hydrometeorological forcings to the observation-based estimation, in order to provide reliable wtda estimates for regions with no or sparse wtd observations. With substantially reduced computational cost compared to physically-based numerical models, LSTM-TL obtained wtda estimates in good agreement with in-situ wtda measurements from 2569 European GW monitoring wells, showing r ⩾ 0.5, root-mean-square error ⩽1.0 and Kling-Gupta efficiency ⩾0.3 at about or more than half of the pixels. Based on the reconstructed long-term European monthly wtda data from the early 1980s to the near present, we provide the first estimate of seasonal wtda trends in different European regions, that is, significant drying trends in central and eastern Europe, which facilitates the understanding of historical GW dynamics in Europe. The success of LSTM-TL in estimating wtda also highlights the advantage of combining AI techniques with knowledge contained in physically-based numerical models in hydrological studies.

English

Vertical electrical sounding (VES) and 2D electrical resistivity tomography (ERT) employing the Schlumberger and Wenner configurations respectively were combined for groundwater exploration in parts of Enugu metropolis. The area is underlain by Enugu Shale and Mamu Formation. A total of twenty (20) VES and four (4) 2D ERT traverses were acquired in the study area. VES and 2D ERT data were processed and interpreted using INTERPEX 1X1D and RES2DINV respectively. Sounding curves shows dominant decrease in resistivity with depth while 2D ERT inverse model shows lateral variation in resistivity of the rock layers with lower resistivity at increasing depth. VES geoelectric layer sections show top sideritic clay - clay/shale sequence. Resistivity curve analysis also shows predominance of Q and K curve types. 2D map of aquifer layer resistivity, thickness and depth were constructed. Aquifer layer resistivity range from 2.00 to 190 ?m, while the thickness range from 10 to 75 m and a depth range of 23 to 150 m. The 2D ERT shows layer resistivity range of 0.1 to 250 ?m. Based on the combination of the two techniques for groundwater exploration in the study area, a water table depth of 18 m with a maximum drill depth of about 100 m was determined. However, it is recommended that the selection of point of drill should be on the low saturated regolith as observed on the 2D ERT sections.   Key words: Aquifer, groundwater, VES, 2D ERT, resistivity.

A globally robust relationship between water table decline, subsidence rate, and carbon release from peatlands

Peatland ecosystems are globally important carbon stores. Disturbances, such as drainage and climate drying, act to lower peatland water table depths, consequently enhancing soil carbon release and subsidence rates. Here, we conduct a global meta-analysis to quantify the relationship among water table depth, carbon release and subsidence. We find that the water table decline stimulated heterotrophic, rather than autotrophic, soil respiration, which was associated with an increase in subsidence rate. This relationship held across different climate zones and land uses. We find that 81% of the total annual soil respiration for all drained peatlands was attributable to tropical peatlands drained for agriculture and forestry and temperate peatlands drained for agriculture. Globally, we estimate that, drained peatlands release 645 Mt C yr–1 (401–1025 Mt C yr–1) through soil respiration, equivalent to approximately 5% of global annual anthropogenic carbon emissions. Our findings highlight the importance of conserving pristine peatlands to help mitigate climate change.

Determination of Water Table Depth Using Geophysical Methods

Water table (WT) depth is an important parameter in engineering and environmental studies. This information can be easily obtained through drilling boreholes. Some geophysical methods can also contribute to indirectly determine the WT depth. The methods that are effective in achieving this goal are GPR (ground penetrating radar) and electrical resistivity (ER). Other methods, such as FDEM (frequency domain electromagnetic method), seismic refraction, and seismic reflection, can also be employed to measure WT depth. This article presents a discussion on the use of some geophysical methods to determine WT depth, based on a brief literature review and analysis of some data obtained by the author.

Hydropedological Characteristics of the Cathedral Peak Research Catchments

It has long been recognised that the role of soils is critical to the understanding of the way catchments store and release water. This study aimed to gain an understanding of the hydropedological characteristics and flow dynamics of the soils of three mountain catchment areas. Digital soil maps of the hydropedological characteristics of the catchments were interpreted and a conceptual response of these watersheds to precipitation was formed. This conceptual response was then tested with the use of site-specific precipitation and streamflow data. Furthermore, piezometers were installed in soils classified as the interflow hydropedological soil group as well as the saturated responsive hydropedological soil group and water table depth data for the three catchments were analysed. Climatic data indicated that there is a lag time effect in the quantity of precipitation that falls in the catchment and the corresponding rise in streamflow value. This lag time effect coupled with data obtained from the piezometers show that the various hydropedological soil groups play a pivotal role in the flow dynamics. Of importance is the unique influence of different wetland systems on the streamflow dynamics of the catchments. The drying and wetting cycles of individual wetland systems influenced both the baseflow connectivity and the overland flow during wetter periods. They are the key focus in understanding the connectivity between the hydropedological flow paths and the contribution of soil water to the stream networks of the three catchments.

The Effect of Salty Groundwater Levels on the Grass Yield of Some Pasture Crops and Soil Salinity

F. elatior, Puccinellia distans, Lotus strictus have been tested at 4 different water table depths which grow under natural conditions in salt-affected soils of arid and semi-arid regions. The trial was carried out for 3 years with split plots test design in randomized blocks. The salt concentration of the groundwater where irrigation has been made was between 3.1-4.4 dS m-1. The effect of water table depths on dry grass yields of the cultivars was found statistically significant in the first trial year (P

Oil palm (Elaeis guineensis) plantation on tropical peatland in South East Asia: Photosynthetic response to soil drainage level for mitigation of soil carbon emissions

While existing moratoria in Indonesia and Malaysia should preclude continued large-scale expansion of palm oil production into new areas of South-East Asian tropical peatland, existing plantations in the region remain a globally significant source of atmospheric carbon due to drainage driven decomposition of peatland soils. Previous studies have made clear the direct link between drainage depth and peat carbon decomposition and significant reductions in the emission rate of CO2 can be made by raising water tables nearer to the soil surface. However, the impact of such changes on palm fruit yield is not well understood and will be a critical consideration for plantation managers. Here we take advantage of very high frequency, long-term monitoring of canopy-scale carbon exchange at a mature oil palm plantation in Malaysian Borneo to investigate the relationship between drainage level and photosynthetic uptake and consider the confounding effects of light quality and atmospheric vapour pressure deficit. Canopy modelling from our dataset demonstrated that palms were exerting significantly greater stomatal control at deeper water table depths (WTD) and the optimum WTD for photosynthesis was found to be between 0.3 and 0.4 m below the soil surface. Raising WTD to this level, from the industry typical drainage level of 0.6 m, could increase photosynthetic uptake by 3.6 % and reduce soil surface emission of CO2 by 11 %. Our study site further showed that despite being poorly drained compared to other planting blocks at the same plantation, monthly fruit bunch yield was, on average, 14 % greater. While these results are encouraging, and at least suggest that raising WTD closer to the soil surface to reduce emissions is unlikely to produce significant yield penalties, our results are limited to a single study site and more work is urgently needed to confirm these results at other plantations.