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#11474 Da Nhong Stream, Phuoc Binh National Park, Vietnam

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Educated by Nature

Viet Nam, Ninh Thuan Province, Bac Ai District, Phuoc Binh National Park

The waterfall section of the Da Nhong headwater stream is a tributary of the Cai Phan Rang River, located within Phước Bình National Park, Bác Ái District, Ninh Thuận Province, Vietnam.

This lotic ecosystem is a high-gradient waterfall habitat within the Da Nhong headwater stream, a mountain tributary of the Cai Phan Rang River. The biotope is characterised by pristine, oligotrophic torrential waters (pH 6.8, conductivity 35 µS/cm) flowing over yellow-brown granite boulders, iron-stained pebbles, and quartz sand.

A dense canopy of Feoniella lucida shelters the riparian zone, where Ficus pumila and Cyclosorus parasiticus colonise damp rock faces, while Fissidens moss stabilises the splash zones. The hydrodynamic conditions create distinct ecological niches: mixed-species schools of Rasbora daniconius and Rasbora paviana occupy open, fast-flowing water, whereas the cryptic Puntius brevis forages among benthic crevices at the base of the rocks.

Submitted by
Nguyễn Thành Khang
GPS
12.0045033, 108.7892532
Geographical region
Southeastern Asia
Drainage Basin
South China Sea
River catchment
Đồng Nai River
Water body type
Stream
Water body name
Da Nhong
Water body part
Waterfall
Water body course
Headwaters
Water body: tributary of
River
Tributary name
Cai Phan Rang

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Water Chemistry

Water information

Water type
Freshwater
Water color
Clear water
Water transparency
High
Concentration of sediments
Low
Water temperature
23-26 °C
Water flow/curent
Strong

Chemical parameters

pH
6.8
Conductivity
36
GH
35 mg/l
dGH
KH
20 mg/l
dKH
Dissolved Oxygen
98 %

Substrate in nature

Sand
Grey
Pebble/Gravel
Mixed
Stone
Mixed
Stone form
Irregular
Silt/Mud
None
Leaves
Few
Driftwood
Few
Submerged terrestrial vegetation
None

Aquatic Biotope

Date of collecting
15/3/2025
Collecting area
Below waterfall
Water depth
0,2m
Air temperature
26 °C
Sunlight
Filtered/dappled sun

Environment

Environment
Affected by human activity
Affected by human activity
Deforestation
Deforestation
Initial
Surrounding area

The Da Nhong headwater stream is located within the strictly protected core zone of Phước Bình National Park. This steep, rocky ravine habitat is surrounded by pristine tropical moist evergreen forest.

The surrounding landscape is dominated by large, mature canopy trees, particularly Dipterocarpus alatus. Their extensive root systems penetrate the underlying granite and ancient acidic igneous bedrock, helping to stabilise the steep banks against erosion during seasonal floods.

Along the riparian corridor, Ficus hispida forms part of the shaded vegetation cover. A few hundred metres downstream lies the park’s buffer zone, where ecotourism activities, small trekking campsites, and fruit orchards cultivated by the indigenous Raglai community create a limited, localised human influence on the surrounding ecosystem.

Underwater landscape

The underwater habitat represents a high-gradient torrent flowing over a hydrodynamically sorted substrate within the Cai Phan Rang River drainage basin. The strong current generated by the waterfall continually removes decaying organic matter, leaving a rugged streambed composed of weathered, rusty orange-brown igneous pebbles and gravel interspersed with dark grey granite boulders.

Fine, light yellowish-grey quartz sand accumulates only within flow-sheltered rock crevices and deep fissures beneath the vertical cliff face, forming localised mixed-substrate patches. The clear, low-TDS, highly oxygenated water creates distinct ecological zones: a fast-flowing channel where schools of Rasbora daniconius and Rasbora paviana continuously swim against the current, and calmer, shaded rock cavities where Puntius brevis finds refuge and grazes on microalgae away from the main torrent.

Fishes:

  • Rasbora daniconius (Cyprinidae) – Slender Rasbora – 4
  • Rasbora paviana (Cyprinidae) – Pavie’s Rasbora – 2
  • Puntius brevis (Cyprinidae) – Brevis Barb – 3

Aquatic vegetation

  • Limonia acidissima (Rutaceae) – Wood Apple
  • Cyclosorus parasiticus (Thelypteridaceae) – Parasitic Marsh Fern
  • Ficus pumila (Moraceae) – Creeping Fig
  • Vesicularia ferriei (Hypnaceae) – Weeping Moss
  • Microsorum pteropus (Polypodiaceae) – Java Fern
Threats to ecology

The primary ecological threat to this microhabitat stems from increasing pressure associated with unregulated ecotourism, trekking, and overnight camping along the riparian corridor of the Da Nhong Stream. During periods of high visitor activity, human presence and noise may disrupt the natural behaviour of native fauna, causing shy, cave-dwelling species such as Puntius brevis to remain hidden and reducing their natural foraging activity.

Recreational wading and foot traffic can also damage delicate epiphytic communities, including Fissidens moss, wild ferns, and Weeping Moss (Vesicularia ferriei), growing on weathered granite surfaces. Although the area currently experiences relatively low human impact, the gradual accumulation of microplastics and chemical residues from sunscreens and camping products represents a potential long-term threat to the pristine, low-TDS water chemistry of this headwater stream.

Riparian zone

Trees near the aquatic habitat
Few -

Bibliography