Presented by Azwar Ma’as, Professor at the Faculty of Agriculture, Gadjah Mada University, at "Online Workshop Series:Exploring Criteria and Indicators for Tropical Peatland Restoration", on 2 Sep 2020. In this session Prof. Ma’as shared insights from hydrology and water balance standpoint. These biophysical factors are important for the development of criteria and indicators for peatland restoration, particularly ensuring appropriate consideration for the water balance of each PHU.

1. Water Balance of Peatland Hydrological Unit
Azwar Maas
Senior Lecturer in Soil Science Department,
Faculty of Agriculture. Gadjah Mada University.
Yogyakarta

2. The natural condition of Tropical peatland and disturbed by Human Activities
• Closed nutrient cycles
• Varies vegetation/flora growth and production
adapted to wet, thicker by time to form Dome
• Varies fauna growth and developed
• Always wet, shallow ground water through water
balance (hydrophilic)
• Human live ajusted to the natural resources
• Converted Peatland to monoculture dryland tree
vegetations
• Lost of peat formation
• Oxidation, speed up decomposition by releasing
carbon dioxide and DOC
• Subsidence
• Bare peat surface, even GWL <0.4m the peat surface can
become hydrophobic --> potential burning
Important: Utilization of peatland creates negative impact to the environment
sooner or later

3. Water Balance in Nature of Peatland Hydrological Unit (PHU)
• Eroded soil mineral particles from
upstream rivers,
• sedimented to the swamp until
shalow enough for the aquatic
plants to grow
• The trees adapted to wet
condition for growth
• Infilling woody remnant to shallow baseline
mineral sedimentation in swampland
• Topogeneous peatland is formed
• Inflow from rain, river, sea tidal,
upland border
• Outflow to river, sea, and
evapotranspiration, interception
plant canopy
• Ombrogeneous peatland is formed
above Topogeneous peatland
• Inflow: rain
• Outflow: to the river, sea,
evapotranspiration, Interception
plant canopy
Picture Source: Noor, 2001, quoted van de Meene, 1984).
Important:
More attention to Water Balance in Ombrogeneous type of PHU

4. Water Management (Water Balance) in the Peat Hydrological Unit (PHU/KHG)
• Tertiary Drain Canal does not
touch the secondary channel
above it
Ideal Sharing water
KHG/Sub-KHG
Border drainage of sub KHG (Outflow)
An example water management
KHG Batanghari Air Hitam Laut,
Jambi. Individual concession,
independent à no sharing water
Remark:
Sharing water in existing water
management individual concesion, difficult
to adjust the ideal water sharing

5. Case Study : Tebing Tinggi Peatland
• Tebing Tinggi area is an island peatland, Surrounding by sea, The
only source of frest water is rain
• PP 71/2014: At least 30% of KHG in dome and surounded area being
conservation areas with peat thickness 6m up to 12 m
• 30% x 138.000 ha = sekitar 42.000 ha, BD 0.1ton/m3
• Potential water storage in the peat thickness (assume as landscape) in
average of 2.5 m being used for conservation:
42.000.x100x100x2.5x0.9 ton of water = 904 milion ton of water.
• This potential water with subsurface slow moving water able to keep
the surface peatland still in hydrophillic status at least if no rain 2
months consequtively if still in natural forest and good eco-hydro
system. The utilization function should have good canal blocking.
Source: Besri Nasrul Dissertation 2019

6. Concluding remarks
• Semi-detailed peat depth mapping and detailed topography for
each PHU are main parameters to divide at least 30% of
conservation/protected zone and utilization zone, especially for
Ombrogeneous PHU
• The existing condition, water sharing among stakeholders in one
PHU or sub-PHU dificult to implement. Non-technical aspect also
factor to be considered for future restoration action
• Restoration planning for rewetting of PHU by sharing water with
water balance concept. Stakeholders in both government and
consession, local settlers must be involved in planning up to
implementation, especially for those who are not used to the
concept of sharing water

7. THANK YOU