Remote sensing of environment and disaster laboratory

Institute of Industrial Science, The University of Tokyo, Japan

Development of Groundwater Table Depth Estimation
Method for Tropical Peatland
Yuta Izumi
The University of Tokyo, JapanAbstract
Tropical peatlands, being important carbon sinks and stores, play a critical role in carbon cycling between the earth
surface and the atmosphere [1]. In Indonesia, especially in Kalimantan and Sumatra, a substantial amount of tropicalpeatlands has been deforested. Such a land transformation has resulted in a decrease of groundwater table depth over
the tropical peatland, increasing a peat fire risk and accelerating a carbon loss due to the microbial decomposition.
Therefore, spatio-temporal information of the groundwater table depth is of importance in managing and evaluating thetropical peatland as well as predicting the potential risk. In this background, this study aims to develop thegroundwater table depth estimating method for tropical peatland in Indonesia. Because this study is now ongoing, theresearch plan and expected outcomes are described in this poster.

Soil moisture estimation
Microwave remote sensing has a potential to offer thesurface soil moisture information over wide area. This study
utilizes synthetic aperture radar (SAR) and microwave
radiometer data to estimate the soil moisture with medium
resolution and accuracy (via downscaling algorithm).
Furthermore, this study aims to develop the soil moisture
estimation method incorporating vegetation cover usuallypresented over the tropical peatland.

Microwave transmit/receive

Vegetation scattering

Ground scattering

PeatlandGroundwater Table Depth Estimation Framework
Remote sensing DataSimulation(2) Initial parameter
estimation(1) Surface soil moisture
estimationMicrowave radiometer
resolution(3) Hydrological modelTranspiration
Rain fall

Initialparameter

Evaporation

infiltration

In-situ sensor
Peat
SAR resolution

Downscaling algorithm

p Soil moisture characteristic
parameters estimation
p Relationship bet. surface
moisture and GWT

GWT
runoffchannel

GWT flow model

22

Data assimilation

Optimized estimation(analytical value）

Update initial parameter

The proposed groundwater table depth
estimation framework is based on theintegration system of satellite remotesensing products and the numericalsimulation (hydrological model). The
hydrological behavior is modeled by theemployed groundwater flow model,describing the relationship between
surface soil moisture and groundwater.
The groundwater table depth is thenestimated through the model optimized
by data assimilation technique. Several
unknown parameters in the hydrologicalmodel is derived by in-situ sensors.

In-situ sensors
Several in-situ sensors, measuring
groundwater table depth, surface soil
moisture, and precipitation, areavailable over tropical peatland inIndonesia. Those information is used
to calibrate the hydrological model
One of the sensor installed In central and validate the result.
Kalimantan, Indonesia (image from [2])Data assimilation
Data assimilation technique assists to modify thenumerical simulation results by remote sensing
products and produce the optimal groundwater
depth estimation value.

Impact of this study
The spatio-temporal information of the groundwater table depth to be estimated in this study cann estimate the carbon dioxide emissions via the relationship between groundwater table depth and CO2 efflux [3]n support to predict the potential risk area of the peat firen evaluate the peatland restoration
References[1] O. Mitsuru et al. 2016. Peatland inIndonesia." In Tropical Peatland Ecosystems, 49-58. Springer.
[2] J. Widodo et al., “Application of SAR Interferometry Using ALOS-2 PALSAR-2 Data as Precise Method to Identify Degraded Peatland Areas Related to Forest Fire.” Geosciences, vol. 9, no. 11, 2019.
[3] T. Hirano et al., “Carbon dioxide emissions through oxidative peat decomposition on a burnt tropical peatland.” Global Change Biology, vol. 20, 555-565, 2014.

For further details, contact: Yuta Izumi, Ce-506, 6-1, Komaba 4-chome, Meguro, Tokyo 153-8505 JAPAN (URL: http://wtlab.iis.u-tokyo.ac.jp/ E-mail: yizumi@g.ecc.u-tokyo.ac.jp)