Water quality of the São Gonçalo channel, urban and agricultural water supply in southern Brazil

Albertoni, Edélti Faria; Palma-Silva, Cleber; Trindade, Claudio Rossano; Furlanetto, Leonardo Marques

doi:10.1590/2318-0331.011716082

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Scientific/Technical Article • RBRH 22 • 2017 • https://doi.org/10.1590/2318-0331.011716082 copy

Water quality of the São Gonçalo channel, urban and agricultural water supply in southern Brazil

Qualidade de água do canal São Gonçalo, manancial urbano e agrícola no sul do Brasil

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

São Gonçalo channel connects Patos and Mirim lagoons, in South Brazil. This ecosystem is 70 Km long, and is a major regional source of urban and agricultural water supply, mainly for the municipality of Rio Grande, with ca. 250 thousand citizens. This study aims to diagnose their water quality by measuring benthic invertebrates (Shannon-Wiener diversity index, richness and abundance), use of a BMWP biotic index, physical and chemical evaluation, and applying a trophic state index. The BMWP index showed predominance of taxa indicating altered conditions and polluted waters (Sarcodina and Hydracarina). The abiotic variables indicated eutrophicated waters, chlorophyll values characteristic of eutrophic environments (>2.9 µg. L^–1), low N:P rates in sediment and water, with nitrogen limitation during most periods studied. The results of trophic state indexes indicated mesotrophic and eutrophic conditions, reaching hipereutrophic periods. The highest TSI were in Piratini river, in April 2009 and February 2011, coinciding with rice crop leaching. These results regarding nutrient concentration, nitrogen and phosphorus stoichiometry and biotic index support the need to evaluate the occupation of the surroundings of this water supply.

Keywords:
TSI; BMWP; eutrophication; urban and agricultural water supply

*São Gonçalo Channel*

*Ponto*	Local	Station	Coordenate	Characteristics
1	Upstream of the sluice	LM 1.1	31°48. 592’ S 52°29.044’ W	Beggining of the barrier region to salt water mixture
1	Upstream of the sluice	RM 1.2.	31°48. 596’ S 52°23.547’ W	Beggining of the barrier region to salt water mixture
2	Downstream Piratini river	LM 2.1.	32°00.699’ S 52° 25.176’ W	Above river drainage area
2	Downstream Piratini river	RM 2.2.	32° 01.070’ S 52° 25 087 W	Above river drainage area
3	Piratini River	LM 3.1.	32° 00. 910’ S / 52° 25. 672’ W	End of river receptor body
3	Piratini River	RM 3.2.	32° 00.816’ S 52° 25.636’ W	End of river receptor body
4	Upstream Piratini River	LM 4.1.	32° 01.301’ S 52° 25.212’ W	Below river drainage area
4	Upstream Piratini River	RM 4.2.	32° 01.274’ S 52° 25.098’ W	Below river drainage area
5	CORSAN	LM 5.1.	32°02.375’ S 52° 24.730’ W	Catchment water to Rio Grande
5	CORSAN	RM 5.2.	32° 02.455’ S 52° 24.601’ W	Catchment water to Rio Grande
6	Ilha Grande	LM 6.1	32°04.144’ S 52°30.493’ W	Intermediate region with narrowing of the channel
7	Santa Isabel	LM 7.1	32°07.124’ S 52° 35.550’ W	Village near the entrance of Mirim lagoon
7	Santa Isabel	RM 7.2	32°07.207’ S 52° 35.550’ W	Village near the entrance of Mirim lagoon

Taxa	OTU	Point 1	Point 2	Point 3	Point 4	Point 5	Point 6
Sarcodina	11	65.3 (±29.0)	0.7(±0.6)	247.3(±44.7)	126.0(±117.3)	18.0(±8.5)	9.0(±15.6)
Bryozoa	1	14.0 (±9.6)	0.7(±0.6)	8.3(±3.1)	10.3(±7.6)	1.0(±0.0)	1.0(±1.0)
Nematoda	1	2.7(±3.1)	0.3(±0.6)	1.0(±1.0)	1.7(±2.1)	2.0(±2.0)	0.0(±0.0)
Oligochaeta	1	6.0(±4.6)	2.3(±1.5)	8.3(±5.7)	25.3(±21.4)	41.7(±8.1)	1.7(±2.9)
Hirudinea	1	0.0(±0.0)	0.0(±0.0)	0.3(±0.6)	0.7(±0.6)	2.7(±1.5)	0.0(±0.0)
Bivalvia	6	1.0(±1.0)	0.0(±0.0)	0.0(±0.0)	19.7(±18.9)	14.0(±7.8)	1.0(±1.0)
Gastropoda	8	1.3(±1.5)	1.3(±0.6)	1.0(±1.7)	14.0(±13.1)	16.0(±8.9)	11.7(±8.5)
Ostracoda	8	16.0 (±12.8)	0.3(±0.6)	8.3(±7.0)	13.7(±15.0)	3.3(±3.2)	1.0(±1.7)
Cladocera	1	0.0(±0.0)	0.0(±0.0)	0.7(±0.6)	0.0(±0.0)	0.0(±0.0)	0.0(±0.0)
Copepoda	2	1.0(±1.0)	0.3(±0.6)	0.3(±0.6)	0.3(±0.6)	0.3(±0.6)	0.0(±0.0)
Decapoda	1	1.0(±1.7)	0.0(±0.0)	0.0(±0.0)	0.0(±0.0)	0.0(±0.0)	0.0(±0.0)
Hydracarina	9	34.3(±7.0)	2.3(±2.1)	21.3(±7.8)	34.3(±31.3)	6.3(±1.5)	0.3(±0.6)
Ephemeroptera	2	0.3(±0.6)	0.0(±0.0)	0.3(±0.6)	0.3(±0.6)	0.0(±0.0)	0.0(±0.0)
Collembola	2	0.3(±0.6)	0.0(±0.0)	0.3(±0.6)	0.0(±0.0)	0.3(±0.6)	0.0(±0.0)
Trichoptera	2	0.0(±0.0)	0.0(±0.0)	0.0(±0.0)	4.3(±1.5)	3.3(±0.6)	0.0(±0.0)
Tabanidae	1	0.0(±0.0)	0.0(±0.0)	0.0(±0.0)	0.3(±0.6)	0.0(±0.0)	0.0(±0.0)
Chironomidae	3	51.0(±4.5)	4.3(±3.5)	72.3(±15.0)	133.0(±117.5)	29.3(±2.5)	0.7(±1.2)
Coleoptera	3	0.3(±0.6)	0.3(±0.6)	0.0(±0.0)	1.0(±1.0)	0.0(±0.0)	0.7(±1.2)

	Point 1	Point 2	Point 3	Point 4	Point 5	Point 6	Point 1
Water Temperature (°C)	21.8 (±4.4)	21.3 (±4.1)	21.5 (±4.0)	21.0 (±4.4)	21.5 (±4.5)	21.1 (±4.3)	20.5 (±4.4)
Dissolved Oxigen (mg.L^–1)	8.2 (±1.2)	8.7 (±1.4)	9.3 (±2.4)	9.0 (±2.1)	9.2 (±2.5)	9.1 (±2.1)	9.0 (±3.3)
pH	7.4 (±0.3)	6.9 (±0.8)	7.1 (±1.0)	7.3 (±0.4)	7.3 (±0.5)	7.3 (±0.4)	7.1 (±0.7)
Alcalinity (mg.L^–1)	551.9 (±87.1)	543.5 (±172.2)	594.3 (±192.5)	608.5 (±81.6)	635.3 (±115.0)	635.8 (±166.3)	654.4 (±192.7)
Eletric Conductivity (µS.cm^–1)	102.0 (±16.9)	87.2 (±26.0)	86.8 (±23.8)	103.2 (±14.7)	104.1 (±14.5)	103.3 (±16.8)	104.2 (±14.9)
Suspended Material (mg. L^–1)	32.2 (±17.7)	21.6 (±15.6)	34.1 (±22.0)	30.3 (±9.1)	34.9 (±28.1)	38.2 (±24.2)	34.9 (±16.6)
Chlorophyll-a (µg. L^–1)	8.3 (±3.7)	27.8 (±48.3)	5.2 (±5.0)	4.4 (±1.8)	4.4 (±3.1)	5.6 (±3.1)	5.1 (±4.6)
Phosphate (µM)	1.1 (±0.6)	1.2 (±1.4)	1.6 (±1.7)	1.3 (±1.3)	0.9 (±0.5)	0.8 (±0.8)	1.1 (±0.6)
Nitrite (µM)	0.2 (±0.1)	0.2 (±0.1)	0.2 (±0.1)	0.3 (±0.1)	1.1 (±1.8)	0.2 (±0.2)	0.3 (±0.2)
Total Phosphorus (µg. L^–1)	62.9 (±21.0)	68.0 (±17.2)	65.5 (±20.7)	88.2 (±51.9)	71.1 (±20.7)	64.8 (±15.7)	82.9 (±36.6)
Total Nitrogen (mg. L^–1)	0.5 (±0.4)	0.6 (±0.1)	0.5 (±0.2)	0.5 (±0.2)	0.7 (±0.1)	0.7 (±0.4)	0.7 (±0.2)
Turbidity (NTU)	135.4 (±96.1)	89.7 (±18.0)	90.7 (±22.5)	92.5 (±28.4)	135.5 (±113.1)	185.7 (±175.7)	161.3 (±154.5)

	P1	P2	P3	P4	P5	P6	P7
Organic Matter (g)	0.0499 (±0.003)	0.0344 (±0.017)	0.0979 (±0.065)	0.0739 (±0.025)	0.0448 (±0.014)	0.0933 (±0.074)	0.0373 (±0.022)
Organic Carbon (mmol.g^–1)	0.0019 (±0.0001)	0.0013 (±0.001)	0.0038 (±0.002)	0.0029 (±0.001)	0.001756 (±0.000569)	0.003653 (±0.0029)	0.0015 (±0.001)
Total Phosphorus (mmol.g^–1)	0.0041 (±0.001)	0.0039 (±0.0003)	0.0039 (±0.001)	0.0043 (±0.001)	0.005303 (±0.00129)	0.0057 (±0.0003)	0.0043 (±0.001)
Total Nitrogen (mmol.g^–1)	0.0982 (±0.048)	0.0941 (±0.017)	0.0784 (±0.037)	0.0869 (±0.012)	0.1576 (±0.160)	0.1459 (±0.078)	0.0874 (±0.040)

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