19.2.2 Evapotranspiration in Peatland
Umeda and Inoue (1985) evaluated the effect of evapotranspiration on GWL in the
peatland in Hokkaido, Japan. Takada et al. (2009) compared the evapotranspiration
got by the hydrological method, which used daily change of GWL and soil moisture
from surface to 20 cm in depth, with the eddy correlation method in the sphagnum
mire, Northern Hokkaido, Japan. The results showed the amount of evapotranspiration acquired by two methods has linear regression with R
2
¼ 0.78. However, the
evapotranspiration acquired by the hydrological method was larger than that the one
obtained by the eddy correlation method when the groundwater level is deeper than
30 cm in depth. This result means the soil moisture in the unsaturated layer is
important to estimate the evapotranspiration in a sphagnum mire.
Evapotranspiration is the most important component in the water balance in the
tropical peat swamp forest. Takahashi (1999) estimated the daily evapotranspiration
from June to December in 1997 using hourly record of GWL in a tropical peat
swamp forest of the Sebangau River Catchment, which was similar to the former
report by Kayama et al. (2000). The results showed the daily evapotranspiration had
a linear relationship with daily total solar radiation and changed from 0.5 to
5.2 mm day
À1 during the observation (Fig. 19.4). The dry season in 1997 was
very long and the drought was very serious in Indonesia because of the largest El
Niño event in the twentieth century. Very dense haze covered the sky, daily solar
radiation declined, and resultantly, daily evapotranspiration also decreased.
Hirano et al. (2015) measured the heat balance at the three sites, i.e. undrained
forest UF, drained forest DF, and drained and burned forest DB for 8 years from
2002. The results showed that the mean evapotranspiration for 8 years was
4.4 mm day
À1 (66.9% of total rainfall) at UF; 4.2 mm day
À1 (63.4%) at DF; and
3.7 mm day
À1 (56.1%) at DB, respectively. The annual evapotranspiration at UF and
DF showed a linear relationship with the yearly minimum groundwater level at each
site (Fig. 19.5).
Table 19.1 Comparison between gross rainfall (Pg), throughfall (Pt), stemflow (Ps), and rainfall
interception loss (Pi) at any places; percentage of the total amount of Pt, Ps, and Pi is the percentage
of total Pg, respectively (Kayama et al. 2000)
Location
Pg
(mm)
Pt
(%)
Ps
(%)
Pi
(%)
Remarks
Peat swamp forest, Kalimantan,
Indonesia
494.5
85.4 1.6
13.0 1998/12/16-1999/2/7
Do
1465.5 77.5 –
–
1998/11/14-1999/4/3
Tropical rainforest, unlogged
2199
87.2 1.4
11.4 Asdak et al. (1998)
Kalimantan Indonesia, logged
3563
93.5 0.3
6.2
Asdak et al. (1998)
Natural secondary forest, Cunha Sao
Paulo
82.8 1.1
16.1 Fujieda et al. (1997)
Terra Firme (dryland) forest, Manaus
Amazon
2721
91.0 1.8
7.2
Lyoyd and Marques
(1988)
19 Principles of Hydrological Management of Tropical Peatland
541
Umeda and Inoue (1985) evaluated the effect of evapotranspiration on GWL in the
peatland in Hokkaido, Japan. Takada et al. (2009) compared the evapotranspiration
got by the hydrological method, which used daily change of GWL and soil moisture
from surface to 20 cm in depth, with the eddy correlation method in the sphagnum
mire, Northern Hokkaido, Japan. The results showed the amount of evapotranspiration acquired by two methods has linear regression with R
2
¼ 0.78. However, the
evapotranspiration acquired by the hydrological method was larger than that the one
obtained by the eddy correlation method when the groundwater level is deeper than
30 cm in depth. This result means the soil moisture in the unsaturated layer is
important to estimate the evapotranspiration in a sphagnum mire.
Evapotranspiration is the most important component in the water balance in the
tropical peat swamp forest. Takahashi (1999) estimated the daily evapotranspiration
from June to December in 1997 using hourly record of GWL in a tropical peat
swamp forest of the Sebangau River Catchment, which was similar to the former
report by Kayama et al. (2000). The results showed the daily evapotranspiration had
a linear relationship with daily total solar radiation and changed from 0.5 to
5.2 mm day
À1 during the observation (Fig. 19.4). The dry season in 1997 was
very long and the drought was very serious in Indonesia because of the largest El
Niño event in the twentieth century. Very dense haze covered the sky, daily solar
radiation declined, and resultantly, daily evapotranspiration also decreased.
Hirano et al. (2015) measured the heat balance at the three sites, i.e. undrained
forest UF, drained forest DF, and drained and burned forest DB for 8 years from
2002. The results showed that the mean evapotranspiration for 8 years was
4.4 mm day
À1 (66.9% of total rainfall) at UF; 4.2 mm day
À1 (63.4%) at DF; and
3.7 mm day
À1 (56.1%) at DB, respectively. The annual evapotranspiration at UF and
DF showed a linear relationship with the yearly minimum groundwater level at each
site (Fig. 19.5).
Table 19.1 Comparison between gross rainfall (Pg), throughfall (Pt), stemflow (Ps), and rainfall
interception loss (Pi) at any places; percentage of the total amount of Pt, Ps, and Pi is the percentage
of total Pg, respectively (Kayama et al. 2000)
Location
Pg
(mm)
Pt
(%)
Ps
(%)
Pi
(%)
Remarks
Peat swamp forest, Kalimantan,
Indonesia
494.5
85.4 1.6
13.0 1998/12/16-1999/2/7
Do
1465.5 77.5 –
–
1998/11/14-1999/4/3
Tropical rainforest, unlogged
2199
87.2 1.4
11.4 Asdak et al. (1998)
Kalimantan Indonesia, logged
3563
93.5 0.3
6.2
Asdak et al. (1998)
Natural secondary forest, Cunha Sao
Paulo
82.8 1.1
16.1 Fujieda et al. (1997)
Terra Firme (dryland) forest, Manaus
Amazon
2721
91.0 1.8
7.2
Lyoyd and Marques
(1988)
19 Principles of Hydrological Management of Tropical Peatland
541