scholarly journals The Use of Subsidence to Estimate Carbon Loss from Deforested and Drained Tropical Peatlands in Indonesia

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 732
Author(s):  
Gusti Z. Anshari ◽  
Evi Gusmayanti ◽  
Nisa Novita
Keyword(s):  
Water Table ◽  
Carbon Emission ◽  
Bottom Layer ◽  
Groundwater Table ◽  
Microbial Oxidation ◽  
Tropical Peat ◽  
Subsidence Rate ◽  
Tier 1 ◽  
Tropical Peatlands ◽  
Physical Changes

Drainage is a major means of the conversion of tropical peat forests into agriculture. Accordingly, drained peat becomes a large source of carbon. However, the amount of carbon (C) loss from drained peats is not simply measured. The current C loss estimate is usually based on a single proxy of the groundwater table, spatially and temporarily dynamic. The relation between groundwater table and C emission is commonly not linear because of the complex natures of heterotrophic carbon emission. Peatland drainage or lowering groundwater table provides plenty of oxygen into the upper layer of peat above the water table, where microbial activity becomes active. Consequently, lowering the water table escalates subsidence that causes physical changes of organic matter (OM) and carbon emission due to microbial oxidation. This paper reviews peat bulk density (BD), total organic carbon (TOC) content, and subsidence rate of tropical peat forest and drained peat. Data of BD, TOC, and subsidence were derived from published and unpublished sources. We found that BD is generally higher in the top surface layer in drained peat than in the undrained peat. TOC values in both drained and undrained are lower in the top and higher in the bottom layer. To estimate carbon emission from the top layer (0–50 cm) in drained peats, we use BD value 0.12 to 0.15 g cm−3, TOC value of 50%, and a 60% conservatively oxidative correction factor. The average peat subsidence is 3.9 cm yr−1. The range of subsidence rate per year is between 2 and 6 cm, which results in estimated emission between 30 and 90 t CO2e ha−1 yr−1. This estimate is comparable to those of other studies and Tier 1 emission factor of the 2013 IPCC GHG Inventory on Wetlands. We argue that subsidence is a practical approach to estimate carbon emission from drained tropical peat is more applicable than the use of groundwater table.

Edge effects on water table dynamics in tropical peatlands

2020 ◽  
Author(s):  
Alex Cobb ◽  
Surin Kumar Thamilselvam ◽  
Ramasamy Zulkiflee ◽  
Jeffery Muli Incham ◽  
Khalish Ideris ◽  
...  
Keyword(s):  
Water Table ◽  
Edge Effects ◽  
Water Level Fluctuations ◽  
Model Driven ◽  
Tropical Peat ◽  
Water Table Fluctuations ◽  
Water Tables ◽  
Tropical Peatlands ◽  
Practical Implications ◽  
Range Of Influence

<p>Water level fluctuations affect many ecosystem processes in tropical peatlands, and have important practical implications because low water tables cause decomposition and flammability.  In recent work, we showed that a simplified model driven by precipitation and evapotranspiration can work surprisingly well at predicting water table fluctuations in the interior of ombrotrophic tropical peatlands.  However, a model driven only by precipitation and evaporation cannot give accurate predictions of water table dynamics at the dome edge, where important fire and flood processes occur. Further, changing boundary conditions from tides and seasonal changes in river stage can drive fluctuations that propagate towards the dome interior.  Classic studies of how such fluctuations at edges propagate into the interior of a domain provide solid theory for simple aquifers with constant and uniform transmissivity or conductivity, but tropical peatlands are not described well by these models because of the much higher conductivity of peat near the surface. We explore how precipitation, evapotranspiration, and changes in river or channel stage interact to drive water table fluctuations in tropical peat domes using an exponential transmissivity model previously validated for a tropical peatland.  We discuss these "edge effects" and their frequency-dependent range of influence from fluctuations on diurnal, monthly, annual, and superannual time scales.</p>

scholarly journals Model-Based Analysis of the Link between Groundwater Table Rising and the Formation of Solute Plumes in a Shallow Stratified Aquifer

Pollutants ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 66-86
Author(s):  
Simone Varisco ◽  
Giovanni Pietro Beretta ◽  
Luca Raffaelli ◽  
Paola Raimondi ◽  
Daniele Pedretti
Keyword(s):  
Water Table ◽  
Cost Effective ◽  
Groundwater Table ◽  
Monitoring Wells ◽  
Modeling Analysis ◽  
Contaminant Sources ◽  
Simultaneous Decrease ◽  
Pumping Rates ◽  
Agricultural Areas ◽  
T System

Groundwater table rising (GTR) represents a well-known issue that affects several urban and agricultural areas of the world. This work addresses the link between GTR and the formation of solute plumes from contaminant sources that are located in the vadose zone, and that water table rising may help mobilize with time. A case study is analyzed in the stratified pyroclastic-alluvial aquifer near Naples (Italy), which is notoriously affected by GTR. A dismissed chemical factory generated a solute plume, which was hydraulically confined by a pump-and-treat (P&T) system. Since 2011, aqueous concentrations of 1,1-dichloroethene (1,1-DCE) have been found to exceed regulatory maximum concentration levels in monitoring wells. It has been hypothesized that a 1,1-DCE source may occur as buried waste that has been flushed with time under GTR. To elucidate this hypothesis and reoptimize the P&T system, flow and transport numerical modeling analysis was developed using site-specific data. The results indicated that the formulated hypothesis is indeed plausible. The model shows that water table peaks were reached in 2011 and 2017, which agree with the 1,1-DCE concentration peaks observed in the site. The model was also able to capture the simultaneous decrease in the water table levels and concentrations between 2011 and 2014. Scenario-based analysis suggests that lowering the water table below the elevation of the hypothesized source is potentially a cost-effective strategy to reschedule the pumping rates of the P&T system.

scholarly journals Modelling effects of seasonal variation in water table depth on net ecosystem CO<sub>2</sub> exchange of a tropical peatland

2014 ◽  
Vol 11 (3) ◽  
pp. 577-599 ◽  
Author(s):  
M. Mezbahuddin ◽  
R. F. Grant ◽  
T. Hirano
Keyword(s):  
Seasonal Variation ◽  
Nutrient Uptake ◽  
Water Table ◽  
Water Table Depth ◽  
Hydrological Processes ◽  
Plant Nutrient ◽  
Predictive Capacity ◽  
Tropical Peatland ◽  
Tropical Peat ◽  
Dry Seasons

Abstract. Seasonal variation in water table depth (WTD) determines the balance between aggradation and degradation of tropical peatlands. Longer dry seasons together with human interventions (e.g. drainage) can cause WTD drawdowns making tropical peatland C storage highly vulnerable. Better predictive capacity for effects of WTD on net CO2 exchange is thus essential to guide conservation of tropical peat deposits. Mathematical modelling of basic eco-hydrological processes under site-specific conditions can provide such predictive capacity. We hereby deploy a process-based mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of a drainage affected tropical peat swamp forest at Palangkaraya, Indonesia. Simulated NEP suggested that the peatland was a C source (NEP ~ −2 g C m−2 d−1, where a negative sign represents a C source and a positive sign a C sink) during rainy seasons with shallow WTD, C neutral or a small sink (NEP ~ +1 g C m−2 d−1) during early dry seasons with intermediate WTD and a substantial C source (NEP ~ −4 g C m−2 d−1) during late dry seasons with deep WTD from 2002 to 2005. These values were corroborated by regressions (P < 0.0001) of hourly modelled vs. eddy covariance (EC) net ecosystem CO2 fluxes which yielded R2 > 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEP from 2002 (−609 g C m−2) to 2005 (−373 g C m−2) with decreasing WTD which was attributed to declines in duration and intensity of dry seasons following the El Niño event of 2002. This increase in modelled NEP was corroborated by EC-gap filled annual NEP estimates. Our modelling hypotheses suggested that (1) poor aeration in wet soils during shallow WTD caused slow nutrient (predominantly phosphorus) mineralization and consequent slow plant nutrient uptake that suppressed gross primary productivity (GPP) and hence NEP (2) better soil aeration during intermediate WTD enhanced nutrient mineralization and hence plant nutrient uptake, GPP and NEP and (3) deep WTD suppressed NEP through a combination of reduced GPP due to plant water stress and increased ecosystem respiration (Re) from enhanced deeper peat aeration. These WTD effects on NEP were modelled from basic eco-hydrological processes including microbial and root oxidation-reduction reactions driven by soil and root O2 transport and uptake which in turn drove soil and plant carbon, nitrogen and phosphorus transformations within a soil-plant-atmosphere water transfer scheme driven by water potential gradients. Including these processes in ecosystem models should therefore provide an improved predictive capacity for WTD management programs intended to reduce tropical peat degradation.

scholarly journals Modelling effects of seasonal variation in water table depth on net ecosystem CO<sub>2</sub> exchange of a tropical peatland

2013 ◽  
Vol 10 (8) ◽  
pp. 13353-13398
Author(s):  
M. Mezbahuddin ◽  
R. F. Grant ◽  
T. Hirano
Keyword(s):  
Seasonal Variation ◽  
Water Table ◽  
Co2 Exchange ◽  
Water Table Depth ◽  
Hydrological Processes ◽  
Transfer Scheme ◽  
Predictive Capacity ◽  
Tropical Peatland ◽  
Tropical Peat ◽  
Dry Seasons

Abstract. Seasonal variation in water table depth (WTD) determines the balance between aggradation and degradation of tropical peatlands. Longer dry seasons together with human interventions (e.g. drainage) can cause WTD drawdowns making tropical peatland C storage highly vulnerable. Better predictive capacity for effects of WTD on net CO2 exchange is thus essential to guide conservation of tropical peat deposits. Mathematical modelling of basic eco-hydrological processes under site-specific conditions can provide such predictive capacity. We hereby deploy a mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of an Indonesian peatland. We simulated lower NEPs (~ –2 g C m–2 d–1) during rainy seasons with shallow WTD, higher NEPs (~ +1 g C m–2 d–1) during early dry seasons with intermediate WTD and again lower NEPs (~ –4 g C mm–2 d–1) during late dry seasons with deep WTD during 2002–2005. These values were corroborated by regressions (P < 0.0001) of hourly modelled vs. eddy covariance (EC) measured net ecosystem CO2 fluxes which yielded R2 > 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEPs from 2002 (−609 g C m–2) to 2005 (−373 g C m–2) with decreasing WTD which was corroborated by EC-gap filled annual NEP estimates. These WTD effects on NEP were modelled from basic eco-hydrological processes including microbial and root oxidation-reduction reactions driven by soil and root O2 transport and uptake which in turn drove soil and plant C, N and P transformations within a soil-plant-atmosphere water transfer scheme driven by water potential gradients. This modelling should therefore provide a predictive capacity for WTD management programs to reduce tropical peat degradation.

scholarly journals Minimizing carbon loss through integrated water resource management on peatland utilization in Pulau Burung, Riau, Indonesia

2020 ◽  
Vol 200 ◽  
pp. 02019
Author(s):  
Nurul Ihsan Fawzi ◽  
Annisa Noyara Rahmasary ◽  
Ika Zahara Qurani
Keyword(s):  
Water Management ◽  
Resource Management ◽  
Water Resource ◽  
Water Table ◽  
Water Resource Management ◽  
Peat Soil ◽  
Carbon Loss ◽  
Integrated Water Resource Management ◽  
Subsidence Rate ◽  
Yearly Average

Sustainable utilization of peatland is required for balancing production and conservation efforts. On peatland, one of the main components to examine sustainability is understanding the carbon balance. This research was conducted in Pulau Burung, Riau, Indonesia, which has a long history of peatland utilization for agriculture. The sets of utilized data included historical data of water management on peatland represented by water table and subsidence rate, next to carbon density of peat soil. The results showed the function of integrated water resource management made the yearly average water table depth is 48 and 49 cm in 2018 and 2019, respectively. The range water table is between 31cm to 72 cm due to season variability and crop requirement. Consequently, the rate of annual subsidence is averaging at 1.7 cm with cumulative subsidence in 32 yr is 54.1 cm. Since the water never drained since the establishment, the subsidence rate of the first five years is averaging only at 3.3 cm yr–1. Low subsidence rates minimize annual carbon loss during the peatland utilization around (30 to 200) Mg CO2 ha–1 yr–1. In 32 yr, the water management in peatland utilization in Pulau Burung has prevented 2 000 Mg CO2 ha–1 to 4 925 Mg CO2 ha–1 loss compared to other cultivated areas in peatland. Further, this paper discusses the practice that resulted in low emission of coconut agriculture in Pulau Burung as one of sustainability dimensions, which support the other sustainability aspects, that is the thriving local livelihood.

Design of a hydrodynamic leachate containment system

1989 ◽  
Vol 16 (5) ◽  
pp. 615-626 ◽  
Author(s):  
M. D. Haug ◽  
D. J. L. Forgie ◽  
S. L. Barbour
Keyword(s):  
Contaminant Transport ◽  
Water Table ◽  
High Water ◽  
Groundwater Table ◽  
Cutoff Wall ◽  
Transport Modelling ◽  
High Water Table ◽  
Cutoff Walls ◽  
A Site

This paper presents the design concept for a case study sanitary landfill on a site that would not normally have been approved owing to the presence of a high water table. In this design, the base of the landfill was intentionally placed below the water table. A massive 2.5 m wide, 2.5 m high cutoff wall and a 0.3 m thick liner with hydraulic conductivities of approximately 5 × 10−10 m/s were constructed of recompacted glacial till to limit both groundwater intrusion into the landfill and leachate migration out of the landfill. In this case study, the landfill base was placed below the water table to (i) provide a relatively inexpensive source of cover material and (ii) use the hydrodynamic gradient from the high water table to help contain the leachate. Finite element modelling of the seepage and contaminant transport, for alternate designs for lined and unlined landfills placed above and below the groundwater table, is shown to confirm a previous, less-sophisticated, estimation that placing a lined landfill below the groundwater table has definite advantages in reducing both leachate seepage and contaminant transport. Key words: landfill, leachate, hydrodynamic containment, liners, compacted earth cutoff walls, seepage and contaminant transport modelling.

scholarly journals Scalar Simulation and Parameterization of Water Table Dynamics in Tropical Peatlands

2019 ◽  
Vol 55 (11) ◽  
pp. 9351-9377 ◽  
Author(s):  
Alexander R. Cobb ◽  
Charles F. Harvey
Keyword(s):  
Water Table ◽  
Tropical Peatlands

Post-fire carbon emissions from degraded tropical peat swamp forests in Brunei

2020 ◽  
Author(s):  
Massimo Lupascu ◽  
Hasan Akhtar ◽  
Thomas E.L. Smith ◽  
Rahayu S. Sukri
Keyword(s):  
Organic Carbon ◽  
Water Table ◽  
Ecosystem Respiration ◽  
Hot Spot ◽  
Tropical Peat ◽  
Brunei Darussalam ◽  
Peat Swamp ◽  
Physico Chemical ◽  
Significant Difference ◽  
Tropical Peat Swamp

&lt;p&gt;Tropical peat swamp forests hold about 15&amp;#8211;19% of the global organic carbon (C) pool of which 77% is found in Southeast Asia. Nonetheless, these ecosystems have been drained, exploited for timber and land for agriculture, leading to frequent fires in the region. Fire alters the physico-chemical characteristics of peat as well as the hydrology, which may convert these ecosystems into a source of C for decades as C emissions to the atmosphere exceeds photosynthesis.&lt;/p&gt;&lt;p&gt;To understand the long-term impacts of fire on C cycling, we investigated C emissions in intact and degraded PSFs in Brunei Darussalam, which has experienced 7 fires over the last 40 years. We quantified the magnitude and patterns of C loss (CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4, &lt;/sub&gt;and Dissolved Organic carbon) and soil-water quality characteristics along with continuous monitoring of soil temperature and water table level from June 2017 to January 2019. To investigate the age and sources of C contributing to ecosystem respiration (R&lt;sub&gt;eco&lt;/sub&gt;) and CH&lt;sub&gt;4&lt;/sub&gt;, we used natural tracers such as &lt;sup&gt;14&lt;/sup&gt;C.&lt;/p&gt;&lt;p&gt;We observed a major difference in the physico-chemical parameters, which in turn affected C dynamics, especially CH&lt;sub&gt;4&lt;/sub&gt;. In burnt areas (7.8&amp;#177;2.2 mg CH&lt;sub&gt;4 &lt;/sub&gt;m&lt;sup&gt;-2&lt;/sup&gt; hr&lt;sup&gt;-1&lt;/sup&gt;) the CH&lt;sub&gt;4&lt;/sub&gt; emission was approximately twice compared to the intact peat swamp forest (4.0&amp;#177;2.0 mg CH&lt;sub&gt;4 &lt;/sub&gt;m&lt;sup&gt;-2&lt;/sup&gt; hr&lt;sup&gt;-1&lt;/sup&gt;) due to prolonged higher water table creating optimum methanogenesis conditions. On the contrary, R&lt;sub&gt;eco&lt;/sub&gt; did not show a significant difference between burnt (432&amp;#177;83 mg CO&lt;sub&gt;2 &lt;/sub&gt;m&lt;sup&gt;-2&lt;/sup&gt; hr&lt;sup&gt;-1&lt;/sup&gt;) and intact areas (359&amp;#177;76 mg CO&lt;sub&gt;2 &lt;/sub&gt;m&lt;sup&gt;-2&lt;/sup&gt; hr&lt;sup&gt;-1&lt;/sup&gt;). Further, radiocarbon (&lt;sup&gt;14&lt;/sup&gt;C) analysis showed an overall modern signature for both CO&lt;sub&gt;2 &lt;/sub&gt;and CH&lt;sub&gt;4&lt;/sub&gt; fluxes implying a microbial preference for the more labile C fraction in solution.&lt;/p&gt;&lt;p&gt;With frequent fires and more flooding in the future, these degraded tropical peat swamp forests areas may remain a hot spot of C emissions as suggested by our findings.&lt;/p&gt;

Carbon balance of tropical peat ecosystems in Borneo

2020 ◽  
Author(s):  
Takashi Hirano
Keyword(s):  
Oil Palm ◽  
Carbon Balance ◽  
Peat Soil ◽  
Human Disturbances ◽  
Swamp Forest ◽  
Tropical Peat ◽  
Increased Risk ◽  
Tropical Peatlands ◽  
Carbon Balances ◽  
Peat Fires

&lt;p&gt;Tropical peat swamp forest (PSF) is a unique ecosystem rich in carbon and water, which is widely distributed in Southeast Asia&amp;#8217;s coastal lowlands, mainly in Borneo, Sumatra and Malay Peninsular. The ecosystem has accumulated a huge amount of organic carbon in peat soil over millennia under the condition of high groundwater level. However, PSF has been reduced and degraded by logging, drainage and burning mainly because of land conversion to oil palm and pulp wood plantations during the last two decades. Such human disturbances potentially increase carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) emissions to the atmosphere through enhanced oxidative peat decomposition and the increased risk of peat fires. Thus, it is essentail to assess the current carbon status of tropical peatlands and quantify the effects of disturbance on the carbon balance to understand the role of tropical peatlands in the regional and global carbon balances. We have continuously measured ecosystem-scale eddy fluxes and soil fluxes of CO&lt;sub&gt;2&lt;/sub&gt; and methane (CH&lt;sub&gt;4&lt;/sub&gt;) in different tropical peat ecosystems, including a little drained PSF, a drained PSF, a burned ex-PSF and an oil palm plantation, in Central Kalimantan, Indonesia, and Sarawak, Malaysia, in Borneo. Based on the monitoring data, I&amp;#8217;ll talk about the carbon balance of tropical peat ecosystems, such as its seasonal variation and its relationship with groundwwater level, and the effect of disturbance due to human activities and ENSO drought on the carbon flux and balance.&lt;/p&gt;

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