Vol
14 No 1
Water
Regime Management
Bird Ringing 2006
Shorebird counts (2000-2006)
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Water Regime Management
at Sungei Buloh Wetland Reserve
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By James Gan
Senior Conservation Officer
Jeremy
Ang
Conservation
Officer
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 Have
you ever visited Sungei Buloh and seen the two brackish water ponds
in front of the Main Hide filled with water? And at other times found
that one pond has exposed mudflats while the other is completely filled
with water and vice versa regardless of the tide? What is the rationale
for this water level regime?
The idea of managing the water levels in a wetland began with the
desire to increase the number of migratory shorebirds that make use
of Sungei Buloh. You see, historically and currently, Sungei Buloh
acts as both a high tide roost site and a feeding ground for shorebirds
but mainly as a high tide roost. When the tides are low across the
northern coast of Singapore, these birds fly out from Sungei Buloh
and forage on the tidal mudflats for polychaetes and mollusc. A few
hours later when the water rolls in and submerge these mudflats at
high tide, the birds need to find a roost to wait out the tides. Sungei
Buloh serves to provide them this roost site within the ponds that
have low water levels. And this is possible in Sungei Buloh, a forested
mangrove area because of the network of existing bunds that have created
ponds whose water levels can be regulated through the use of sluice
channels and sluice gates.
 Water
levels in three brackish water ponds within the wetland are currently
managed as a system on a fortnightly cycle generally between the shorebird
migratory months of July and April. Outside of the migratory months,
the water levels are generally not regulated and natural tidal influences
are maintained. At no point in time are any of the three ponds mudflats
submerged for more than four days (or left exposed to dry out for
also more than four days). For perspective, there are five other brackish
water ponds in the wetland whose water levels are not regulated at
all and are subject only to natural tidal influence.
What might happen to shorebirds should the water levels in all the
ponds be left to natural tidal influences? The first effect would
be the loss of valuable exposed mudflats for shorebirds to roost (and
to a lesser degree, feed) on during high tide. These birds will have
to find other areas to roost since the northern coastal flats of Singapore
as well as Sungei Buloh would be submerged under water. And this will
directly affect the number of shorebirds that are present (and can
be observed) at Sungei Buloh during the high tide period. Should the
shorebirds be unable to find alternative high tide roosts within close
proximity to their feeding grounds, there is a possibility that the
entire high tide roost cum feeding ground system (that is Sungei Buloh
– Singapore north coast mudflats) may be abandoned for more suitable
alternative systems in the region.
 Are
there detrimental effects to the regulation of water levels in the
three ponds? Over the years, we have found that leaving the ponds
at low water level for periods of more than a week result in the drying
out of the mud with consequent die off of the mud invertebrates. When
two or three ponds are carefully operated with minimal drying out
periods of four days or less, the benefits of water level regulation
are evident.
The bottom line – Has the number of shorebirds in Sungei Buloh increased,
decreased or remained stable over all these years? Analysis of the
shorebird census data for Sungei Buloh has been made for the wetland’s
seven most abundant shorebird species over a period of seven years
(from 2000 to 2006).
The trends discerned are as follows:
Common Greenshank, Common Redshank, Pacific Golden Plover and Whimbrel
– Increasing numbers during both southward and northward migration
Marsh Sandpiper – Stable numbers during both southward and northward
migration
Mongolian Plover – Steady recovery in numbers during the southward
migration after a dramatic and steep decrease observed in 2002 and
2003. Avoidance of the wetland during the northward migration since
the spring of 2003.
Curlew Sandpiper – Erratic numbers during the southward migration.
Avoidance of the wetland during the northward migration since the
spring of 2001.
In summary, the current water regime management at Sungei Buloh serves
its purpose.
Overall, the absolute number of shorebirds counted at Sungei Buloh
is at its highest over the last seven (and even ten) years. More can
be done to further improve the conservation management of the wetland’s
biodiversity and in particular the shorebirds that make use of Sungei
Buloh.
We invite concerned and interested people to contribute to the improvement
of Sungei Buloh as a wetland thriving with biodiversity. Opportunities
are available for volunteers in areas as diverse as research, guiding,
educational outreach, photography and documentation. Interested? Call
67941401 or email at info@sbwr.org.sg |
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wetlands