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Headwaters of the Ngermeskang River, Palau

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Republic of Palau, Oceania, Ngeremlengui State

The Ngermeskang is the longes river in the Republic of Palau, with 20km of constant water flow emptying into Ngermendu Bay. Its headwaters lie in deeply-cut valleys, just below Palau’s highest mountain, Ngerchelchuus, between Ngeremlengui and Ngardmau State.

This is a pristine river, with little to no agricultural of domestic run-off, largely protected by national laws. It carves its way through the thick jungle, on a bed of volcanic gravel, smooth volcanic rocks, and fine red clay. It can only be accessed by foot, hiking down the steep jungle inhabited by reptiles, giant silk spiders, and fruit bat. The frequent rains can cause even the headwaters to dangerously swell in size and cause turbidity in the usually-clear waters (see my sad biotope underwater video). Even though saltwater crocodiles usually inhabit the lower reaches and mangrove areas, they have been observed in the deeper pools above falls, cascades, and rapids.

Submitted by
Rene Menz
Approved by
Greg Martin & Peter Unmack
GPS
7.5006361, 134.5455170
Geographical region
Southeastern Asia
Drainage Basin
Ngermendu Bay
River catchment
Ngermeskang River
Water body type
Hill streams
Water body name
Ngermeskang
Water body part
Rapids
Water body course
Headwaters
Water body: tributary of
River
Tributary name
Ngermeskang

Videos above and below water

Water Chemistry

Water information

Water type
Fresh water
Water color
Clear water
Water transparency
Medium
Concentration of sediments
Medium
Water temperature
24-30 °C
Water flow/curent
Very strong

Chemical parameters

pH
7.2
Conductivity
400
GH
7 mg/l
KH
7 mg/l
Dissolved Oxygen
7.5 %

Substrate in nature

Sand
Reddish
Pebble/Gravel
Orange
Stone
Mixed
Stone form
Irregular
Silt/Mud
Orange
Leaves
Many
Driftwood
Many
Submerged terrestrial vegetation
Yes

Aquatic Biotope

Date of collecting
11/04/2020
Collecting area
Above waterfall
Water depth
1,0m
Air temperature
29 °C
Sunlight
Filtered/dappled sun

Environment

Environment
Untouched
Surrounding area

Steep valley banks with dry pseudo-fern and Pandanus savannah drooping into the dense rainforest with too many species of plants to count, including numerous endemic orchids, trees, ferns, shrubs and mosses.

Underwater landscape

Fishes:

  • Stiphodon pelewensis (Sicydiinae) – Moderate Population
  • Stiphodon percnopterygionus (Sicydiinae) – Scattered Population
  • Sicyopus zosterophorus (Sicydiinae) – Dominant Population
  • Smilosicyopus fehlmanni (Sicydiinae) – Moderate Population
  • Redigobius bikolanus (Gobiidae) – Scattered Population
  • Giuris margaritaceus (Eleotridae) – One Pair in every deeper pool between cascades and falls
  • Anguilla marmorata (Anguillidae) – A population of frequent Visitors to the Headwaters

Shrimps:

  • Caridina variabilis (Atyidae) – Very large and dense population
  • Atyoida pilipes (Atyidae) – dense population in cascades and falls
  • Macrobrachium rosenbergii (Palaemonidae) – Moderatly dense population in deeper pools between cascades and falls
  • Macrobrachium sp. (Palaemonidae) – Scattered population in smaller pools between cascades and falls

Mollusks:

  • Neritina pulligera (Neritidae) – Dense population
  • Melanoides tuberculata (Thiaridae) – Abundant in the gravel and clay sediment

Aquatic plants/Mosses:

  • ?Monosolenium tenerum (Monosoleniaceae) – Abundant on volcanic rocks submerged in shallow water

Shallow cascades with aufwuchs-covered rocks, from pebble to boulder size on volcanic gravel mixed with clay, interrupted by deeper pools with fallen leaves, vegetation and muddy sediment.

Threats to ecology

Unlike this specific river in Palau, many similar waterway are threatened by agricultural, domestic and construction run-off. Many rivers have lost up to 70% of their biodiversity due to water quality degradation. In addition to the averse effects on freshwater aquatic inhabitants, which are poorly studied, this threatens the drinking water supply of Palau, which is completely dependent on surface water collection.

Riparian zone

Trees near the aquatic habitat
Many - Pandaus aimerikiiensis, Semecarpus venosa, Pininga insignis, Stemonurus ammui, Phlegmariurus phlegmaria, Cyathea spp., Terminalia catappa

Bibliography

  • A Fieldguide to Native Trees of Palau by Ann Hillman Kitalong, Robin Ann DeMeo and Tarita Holm
    ISBN ISBN 978-982-98016-4-7 1

Comment by the expert

Greg Martin: Well researched.

Peter Unmack: I really good level of details across the categories.