microorganisms that decompose the peat, resulting in subsidence of the ground
surface. There are reports of subsidence rates as high as 1.5 m in the first 5 years
after drainage (Hooijer et al. 2012). The management of peatlands must follow new
concepts to prevent peat degradation and to grow commodity crops while also
preventing peat fires. Principally, a key to peatland management is to not base it
on drainage but on how to keep groundwater constant throughout the year. Although
drainage directly to the river on the slopes of the peat domes have been observed in
peatlands (gravity drainage), such drains should be blocked with several dams to
prevent water from flowing from top to bottom. However, such canal blocking alone
is not sufficient to maintain high-water levels during the dry season, and even in
natural forests, the water level during the dry season is 1–1.5 m below the ground
surface. That is, canal blocking has a limited impact on GWL (Ritzema et al. 2008).
2.6.2 Innovative Water Management (WM) of Tropical
Peatland (Stock-Based WM)
It is necessary to develop branch canals along contour lines so that the water can flow
throughout the dome (Ritzema and Wösten 2002). For this purpose, high-precision
topographic maps, with a 0.5-m contour interval, are required (Fig. 2.4, left).
Therefore, the main canal would be dammed at 0.5–1-m intervals.
Another major challenge is the availability of water in the dry season, especially
when there is no rain for more than 50 days. The water stored in the peat dome is
obtained by precipitation. When precipitation is absent for an extended time, the
GWL can drop by more than 1 m, even in its natural state. Moreover, the peatland
soil managed by conventional drainage, i.e., Drainage-based WM, methods becomes
significantly drier because GWL is lowered beyond the natural state. With Drainagebased WM, fires are more likely, and they can burrow underground and become a
peat fire that is difficult to extinguish. The primary way to prevent this is to dam up
the main canal with several dams to prevent the water from flowing into the river by
gravity. In addition, the gently sloping or flattened areas above the dome should be
preserved, and a large amount of water should be stored underground as a reservoir.
This allows the water to flow slowly from the reservoir to the entire dome when the
dome slope dries up in the dry season.
A peat dome has a water reservoir function in supplying water to the entire
peatland area in the dry season. Since the entire peatland area can be considered a
system that depends on the peat dome, water management of peatland must be
conceptualized as one continuous topographic sequence from upstream (peat dome)
to downstream (edge of peatland), which is called Stock-based WM. The details of
the Stock-based WM system are as follows.
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T. Kato et al.
surface. There are reports of subsidence rates as high as 1.5 m in the first 5 years
after drainage (Hooijer et al. 2012). The management of peatlands must follow new
concepts to prevent peat degradation and to grow commodity crops while also
preventing peat fires. Principally, a key to peatland management is to not base it
on drainage but on how to keep groundwater constant throughout the year. Although
drainage directly to the river on the slopes of the peat domes have been observed in
peatlands (gravity drainage), such drains should be blocked with several dams to
prevent water from flowing from top to bottom. However, such canal blocking alone
is not sufficient to maintain high-water levels during the dry season, and even in
natural forests, the water level during the dry season is 1–1.5 m below the ground
surface. That is, canal blocking has a limited impact on GWL (Ritzema et al. 2008).
2.6.2 Innovative Water Management (WM) of Tropical
Peatland (Stock-Based WM)
It is necessary to develop branch canals along contour lines so that the water can flow
throughout the dome (Ritzema and Wösten 2002). For this purpose, high-precision
topographic maps, with a 0.5-m contour interval, are required (Fig. 2.4, left).
Therefore, the main canal would be dammed at 0.5–1-m intervals.
Another major challenge is the availability of water in the dry season, especially
when there is no rain for more than 50 days. The water stored in the peat dome is
obtained by precipitation. When precipitation is absent for an extended time, the
GWL can drop by more than 1 m, even in its natural state. Moreover, the peatland
soil managed by conventional drainage, i.e., Drainage-based WM, methods becomes
significantly drier because GWL is lowered beyond the natural state. With Drainagebased WM, fires are more likely, and they can burrow underground and become a
peat fire that is difficult to extinguish. The primary way to prevent this is to dam up
the main canal with several dams to prevent the water from flowing into the river by
gravity. In addition, the gently sloping or flattened areas above the dome should be
preserved, and a large amount of water should be stored underground as a reservoir.
This allows the water to flow slowly from the reservoir to the entire dome when the
dome slope dries up in the dry season.
A peat dome has a water reservoir function in supplying water to the entire
peatland area in the dry season. Since the entire peatland area can be considered a
system that depends on the peat dome, water management of peatland must be
conceptualized as one continuous topographic sequence from upstream (peat dome)
to downstream (edge of peatland), which is called Stock-based WM. The details of
the Stock-based WM system are as follows.
78
T. Kato et al.