Watersheds and Climate of Tabin Wildlife Reserve

RIVERS & STREAMS

The entire area of Tabin is interlaced a network of perennial streams and rivers that mainly run north and south carrying water from its interior highlands to its lower lying periphery (see map right).

No rivers flow into Tabin so water-borne pollution is not carried in from surrounding plantations. Water-dependent species are well provided for throughout the reserve. The Tabin watershed provides water to the plantations and settlements that surround it. The retention of appropriate vegetation cover protects the water catchment area and that is an important function of the reserve.

Tabin contains several watersheds from which rivers flow outwards over all the reserve boundaries except the eastern one that is not crossed by any major water course. The north-western quarter of the reserve is drained by three major river Systems arising in high land in the heart of Tabin and flowing northwards into the Segama river. These include the Urit, Tagas-Tagas Kecil and Tagas-Tagas Besar river systems.

The entire central highlands are drained by the very extensive Sungai Tabin system, some tributaries of which originate near the southern reserve boundary. The main river arises in the south-western watershed while other portions of the Tabin system drain the western and northern parts of the core area. The main tributary of the Tabin River flows in a deep gorge below the western flank of Mount Hatton then proceeds on a meandering course toward the north-west to cross the reserve’s northern boundary about 2 km west of Kampong Dagat.

The eastern sector of the core area is drained by the Lumpongon river system. The main river flows north through lowlands and crosses the northern reserve boundary shortly after receiving water from the Baklayan. The Lumeru, arises in the south-eastern corner of the reserve, drains the eastern boundary lowlands and flows north to cross the boundary a few kilometres east of the Lumpongon.

The south-eastern fringe of the peninsular portion of Tabin is drained by the Sungai Libong whilst its south-western corner drains into the Silabukan river. The range of mountains in the south-western quarter of Tabin forms a watershed with rivers to the north (Tagas-Tagas Besar and Tabin) south (Matamba and Matambabula) and west. The western system is the Lipad River that flows past the Tabin Wildlife Resort.

CLIMATE

Records from weather stations in the vicinity of Tabin indicate an average annual total ranging between 150-300 cm. per annum. There are three separate categories for rainfall levels in Tabin with an increasing gradient from south to north. The south-western portion of the reserve, including the peninsula portion, falls within the 150 cm rainfall band along typical of the southern coast of the Dent Peninsula and the District town of Lahad Datu. These areas are within the rain shadow of the high land in central Tabin during the northeast Monsoon. The central portion of Tabin which includes mostly mountainous terrain falls within the 200 cm. band, while the largely low lying northern part of the reserve receives the highest annual average and is within the 250 cm. band. This relatively high rainfall reflects the exposure of the northern area to the northeast monsoon during the early and late months of the year. For southerly areas of the reserve mean monthly rainfall is fairly evenly distributed with highest means in the November-March period. There is a slight peak in July-August but June is generally the driest month. In northerly areas a larger proportion of the annual total falls during the months of December and January. There is a slight peak in May-June and October and the driest month is April.

The fact that humidity remains relatively high in Tabin throughout all months of the year is undoubtedly one of the factors responsible for a comparative absence of fire in the reserve. Evidence of fire has only been found in the north-western area of Tabin (WWFM, 1987).

Mean daily temperatures in the Tabin resort area range from a maximum of 32^oC to a minimum of 22^oC (Thomas et al, 1976). The hottest month tends to be May when mean daily temperatures of more than 32oC have been observed. The coolest month tends to be February when mean daily temperatures as low as 20oC have been encountered.

The collection long-term climatic data is an important function now being carried out at the Reserve headquarters on a regular basis.

The hilly, forested nature of most sites in Tabin mean that there is usually protection from the wind. As a rainforest area Tabin gets it share of rain but temperatures are tropical and comfortable shelter is near at hand so Tabin can be enjoyed through rain or shine by the properly equipped observer.