2016 GMekong Forum - S08 - Macro-invertebrate Sampling on the Nam Ou

MACRO-INVERTEBRATE SAMPLING ON THE NAM OU RIVER Peter-John Meynell WLE Forum 10 November 2016

November 11, 2016

MACRO-INVERTEBRATE SAMPLING ON THE NAM OU RIVER

Carried out during field work for developing the Nam Ou River Basin Profile

January/February 2016

Eight case study villages to develop mini-profiles of the river and its use •  Two villages per zone •  One on mainstream and one on a

tributary

November 11, 2016

Ban Nagnao

Ban Phoumuang/Homsang

Ban Pakban

Ban Sopnao

Ban Buamsom

Ban Sopkhong

Ban Pak Nga

Ban Pak Ou

Sampling with nets along banks and shallow gravel/rock boTom

Using simple Southern African Scoring System

IdenUfy macroinvertebrates according to group, not species

10 sites sampled, but some sites could not be sampled because of high or fluctuaUng water levels

QUICK KEY TO IDENTIFY MACRO-INVERTEBRATE GROUPS

SCORE SHEET TO RECORD PRESENCE OF GROUPS

MACRO-INVERTEBRATE SAMPLING RESULTS

Date Description Flatworms

Worms

Leeches

Crabsandshrimps

Stoneflies

Minnowmayflies

Othermayflies

Damselflies

Dragonflies

BugsandBeetles

Caddisflies

Trueflies,Diptera

Molluscs

Megaloptera

Tadpoles

Fish

Totalscore

Average

Score 3 2 2 6 17 5 11 4 6 5 9 2 4 901-Feb NamOusource 17 11 6 5 9 2 x x 50 8.302-Feb NaturalsitebetweenSourceandGnotOutown 6 17 11 6 5 9 4 9 67 8.302-Feb BridgebelowGnotOutown 17 5 11 6 5 4 x 48 8.003-Feb BanPhoumouangboatlanding Biosurveynotdonebecauseriverisnowpartofreservoir05-Feb Pakban Biosurveynotdonebecauseattimeofsamplingthewaterlevelhadrisenby1mbetweenamandpm08-Feb BanSopkongFCZDOprofile 6 11 6 5 9 4 x x 41 6.830-Jan BanPakNga 6 11 5 4 x 26 6.508-Jan BanHatkhe 6 5 9 4 x 24 6.029-Jan IslandnearBanVangle 6 11 5 4 x 26 6.5

Tributaries31-Jan NamKor-fastwater 6 5 11 6 5 9 2 4 x 48 6.0

slowwater 6 5 11 5 4 9 x 40 6.231-Jan ConfluenceofNamKorandNamPhak 6 5 11 6 5 9 2 4 48 6.006-Feb BanSopNao 5 11 6 5 9 36 7.2

ColourcodeforrockytyperiversUnmodified(Naturalcondition) >7.9Largelynatural/fewmodifications(Goodcondition) 6.8-7.9Moderatleymodified(Faircondition) 6.1-6.8Largelymodified(Poorcondition) 5.1-6.1Seriously/criticallymodified(VeryPoorcondition) <5.1

NATURAL CONDITION, LARGELY UNMODIFIED

GNOD OU BRIDGE SAMPLING SITE

Natural conditions according to macroinvertbrates, but river weed growth showing signs of eutrophication

RIVER HABITAT SURVEY

• Study Google Earth images and topographic maps of the area

• Use river habitat survey observaUon on: •  River features – width, flow rate, rapids, riffles, pools, narrows, channels,

midstream rocks, sandbars, in channel bushes and shrubs, tributary joining •  Presence and character of islands – small, medium sized, large,

vegetated or cultivated, with houses •  River bed – rocks and boulders, pebbles, gravel, sand, mud •  River bank - rocks and boulders, pebbles, gravel, sand, mud, man-made,

structures •  Aquatic vegetation – submerged water weed, floating plants, emergent

plants, bushes and shrubs in the river, trees growing in the river •  River bank vegetation – reeds and grasses, bushes and shrubs, large

trees •  People using the river – fishers, river bank gardeners, NTFP harvesters,

small scale gold panners

PAK OU ROAD BRIDGE – DEEP POOL (20 M)

BUILDING RIVER HABITAT MAPS – UPSTREAM FROM PAK OU

CHALLENGES AND CONSTRAINTS

1.  Macro-invertebrate sampling appeared to be effecUve in showing river health especially when used with other observaUons e.g. water quality and habitat surveys

2.  Easier to carry out in smaller, shallower rivers

3.  Larger rivers are oeen deep and fast flowing, with steep banks – safety issue

4.  Important to select the best habitats to sample •  Gravel and rocky river beds with shallow, gently sloping banks are best •  Slower moving reaches with water weeds •  Sand bars tend to be rather poor substrates

5.  Recent and rapid changes (increase and decrease) in water level tends to depress macro-invertebrate populaUons, e.g. from recent rain storms, beginning of wet season, and flow changes from hydropower.