Table 3.

The overall average composition (AA = absolute abundance—n. individuals, RA = relative abundance—%) and distribution of benthic macroinvertebrate communities in the Gurugoda Oya, above (sites F–E–D) and below (sites C–B–A) the weir (see Fig. 5).

Taxon		Sites above the weir						Sites below the weir
		Site F		Site E		Site D		Site C		Site B		Site A
		AA	RA	AA	RA	AA	RA	AA	RA	AA	RA	AA	RA
Oligochaeta	Aeolosoma sp.	0	0	6	1.9	5	1.2	1	0.7	0	0	2	0.5
Gastropoda	Pila sp.	840	75.3	217	68.2	316	76	33	22.2	200	80.6	368	91.3
	Gyraulus sp.	117	10.5	0	0	0	0	0	0	0	0	0	0
	Paludomus sp.	26	2.3	10	3.1	2	0.5	0	0	0	0	0	0
	Melanoides sp.	0	0	0	0	0	0	0	0	6	2.4	0	0
Bivalvia	Lamellidens sp.	15	1.3	21	6.6	22	5.3	0	0	0	0	0	0
Amphipoda	Caridina sp.	17	1.5	14	4.4	21	5	1	0.7	4	1.6	2	0.5
Decapoda	Paratelphusasp.	23	2.1	7	2.2	11	2.6	0	0	0	0	1	0.2
Coleoptera	Eubrianax sp.	0	0	5	1.6	2	0.5	0	0	0	0	1	0.2
Diptera	Tabanid larvae	23	2.1	2	0.6	16	3.8	4	2.7	0	0	0	0
Ephemeroptera	Mayfly nymphs	20	1.8	3	0.9	4	1	17	11.4	21	8.5	15	3.7
Odonata	Damselfly naiads	10	0.9	21	6.6	2	0.5	28	18.8	6	2.4	2	0.5
	Dragonfly naiads	2	0.2	10	3.1	13	3.1	13	8.7	1	0.4	6	1.5
Plecoptera	Stonefly nymphs	3	0.3	0	0	0	0	34	22.8	0	0	0	0
Trichoptera	Caddisfly nymphs	20	1.8	1	0.3	2	0.5	18	12.1	10	4	6	1.5
Hemiptera	Heleocoris bengalensis	0	0	1	0.3	0	0	0	0	0	0	0	0
Average total abundance		1116		318		416		149		248		403