Webpages with more detailed information.
Thesis, CO2 adsorption/emissions
Land Classes and Areas
Impact, including CO2 emission
Problems, including CH4 emissions
Water Management System
Model Areas (size 100 ha) are used
to develop Operation & Maintenance activities in cooperation with Farmers and Farmer
Groups. This includes institutional organization for maintenance of the water control
system, involving Water User's Associations. On this WebPage the emphasis will be put on
the operation of the system. Each type of operation of the water control system depends on
its physical environment of the command area. A particular problem are the areas
with high toxic ferrous iron levels in the groundwater.
Conditions of O&M Model Area of Pamusiran, Jambi Province
||There is no Tidal
Irrigation possible in the O&M Model area of Pamusiran. Water supply for rice mainly
depends on rainfall. The control gates can only maintain water levels in canals below land
||Drainage is possible throughout
the year for 40 cm below land surface and more. (Except during very high flood levels of
the Batang Hari river for one or two days only.
||Without the on-farm water
management system and recommended water control the rice plants suffer in this area during
short dry spells when capillary rise of toxic groundwater harms the plant when it is still
in the first month after planting.
||There is pyrite in the soil at
70 cm depth. There is oxidation of pyrite every long dry season. This can not be
controlled by gate operation in the canals. This means new acids are formed each dry
season. This acid must be leached out from the rootzone to be able to grow rice on a
sustainable basis. The soils in Pamusiran became in the recent past acid and extremely low
yielding, because not sufficient leaching occurred for many years. The situation further
deteriorated during the three El Niņo's of 1991, 1994 and 1997.
||One rainfed rice crop is
possible when there is sufficient leaching applied. There is also a very positive effect
when surface soil dries out during the dry season. This must be followed by lots of
leaching at the beginning of the rainy season and during planting and early growth of the
rice plant. In later stages of the rice growth, the plant is more robust and strong enough
to overcome more toxic conditions.
||The planting of dryland crops
as a second crop is still difficult as the soil is still too acid for most dryland crops,
except some acidity resistant pulses and sweet potato. In the near future it is expected
that conditions for the topsoil will improve and maize and soybean would be possible.
||Yields will improve when land
preparation by two-wheel tractor will be applied and land will be irrigated by pumping
during land preparation. Presently we recommend pump irrigation only during land
preparation and during early growth of the rice plant as long the soil is too porous and
too acid. In future a second pump irrigated rice crop might be an alternative when acids
are completely leached out and the topsoil becomes less porous
Gates in Tertiary canals for Model area Pamusiran
See for lay-out: (Example SK7)
Wet season from November-February
- First :determine if rainfall >50 mm in last 24 hours.
Objective operation: Maximum drainage.
Open gate for 24 hours. If less rainfall: go to step 2.
- Second: determine if rainfall is >25 mm in last 5 days.
Objective operation: Controlled
Drainage. Try to keep the water level at the 90 cm level for gauge TC 7 or 40 cm below
land level. Provide water supply from the SPD side through the culvert near the village
area. During springtide (one time in 14 days) open the gate for one full day (at least for
24 hours) and close the gate again at the 90 cm gauge level or higher. If rainfall < 25
mm: go to step3.
- Third : rainfall will be less than 25 mm in last 5 days.
Objective operation: Maximum retention
and water supply. Check everyday
if there is no smell of H2S of groundwater at piezometer: 50 cm deep. If there
is a strong bad smell: open gate 5 hours before low tide and close the gate again at high
tide (slack water condition) when there is no flow anymore. The water level near the gate
should be at about 100 cm at the gauge of TC 7 or about 30 cm below land level. When there
is no bad smell : supply every day water by opening the gate 2 hours before the
expected high tide and close again at high tide and keep the water level at 100 cm near
Remaining part of the year
- Objective of operation: Controlled
drainage; Try to keep the water level at the 70 cm level for gauge SK7 or 60 cm below land
level. Apply supply from the SPD side through the culvert near the village area.
Rainfall, Leaching and Water Levels in SK7
Explanation of Chart:
The Blue line shows the percolation (positive) and infiltration (negative) in meters drop
(percolation) or rise (infiltration) of water levels in the soil. This means that 6 cm
drop of waterlevel in one day (Corrected for rainfall and evapotranspiration) equals
6 mm percolation. (drainable pore space=10% by volume). The purple lines shows the average
groundwater level in Tertiary Unit SK7 in meter below land surface. The green line
shows the water levels in the tertiary canal below average land level. The yellow line
shows the water level in the secondary canal (SDU side). Note that the groundwater level
drops below the canal water levels during the dry month of August. Apparently the
Macro-Micro system can not maintain water levels above the pyrite layer.
Leaching/percolation at the beginning of the planting
season is every year essential. Leaching/percolation occurred sufficiently
during October by applying controlled drainage. But there was insufficient
leaching/percolation from November-January, caused by a gate operation too much focussed
on water retention. The result was that farmers who planted in October found good yields,
but later planting suffered from toxicity. Apparently the rice planted in October was
already strong enough to resist the toxic conditions from November-January.
On the left this field has been planted in late
November and suffered during early growth. Better conditions in February did not improve
the crop. The field in the middle has been planted in October with good results as it
found lots of leaching during early growth. (Note the oxidized iron in the rootzone; only
reduced iron will harm the plant). The best field in Pamusiran
was found in SK 4, planted in October (photo on the right). This farmer uses pump
irrigation during land preparation only and uses also always a two-wheel tractor for land
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