FOREST COVERAGE AND STREAMFLOW OF WATERSHEDS IN THE TROPICAL ATLANTIC RAINFOREST

Mendes, Natalia Gomes de Souza; Cecílio, Roberto Avelino; Zanetti, Sidney Sara

doi:10.1590/1806-90882018000200004

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Articles • Rev. Árvore 42 (2) • 2018 • https://doi.org/10.1590/1806-90882018000200004 copy

FOREST COVERAGE AND STREAMFLOW OF WATERSHEDS IN THE TROPICAL ATLANTIC RAINFOREST

COBERTURA FLORESTAL E VAZÕES DE BACIAS HIDROGRAFICAS DA MATA ATLÂNTICA

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The present study analyzed the average and minimum streamflow behavior of 11 watersheds located in the Atlantic Forest Biome, relating them to the changes in forest cover. The average minimum flow with seven days of duration (Q₇), the average annual flow (Q_ave), the total annual precipitation (P_a) and the percentage of forest cover (FC) for each watershed were determined. The joint correlation between the FC and the P_a with the flow for each watershed were analyzed by adjusting multiple linear regression equations. The partial correlation coefficient was also used to analyze whether the variation in the FC influenced the water flow when the effects of P_a are fixed. This study allowed us to identify significant associations between FC and P_a with Q₇ or Q_ave in only two of the watersheds. Disregarding the effects of P_a, the increase in the FC tended to result in a reduction in the Q_ave, and in turn increased the Q₇ in these two watersheds.

Keywords:
Water availability; Watershed management; Forest hydrology

Table 1 Streamflow stations and watersheds of the Itapemirim basin.

ANA Code	Station (Watershed)	River	Area (Km²)
57490000	Castelo (CAS)	Rio Castelo	975
57650000	Fazenda Cacheta (FCA)	Rio Muqui do Norte	481
57476500	Fazenda Laginha (FLA)	Rio Castelo	436
57420000	Ibitirama (IBI)	Rio Braço Norte Direito	342
57400000	Itaici (ITA)	Rio Braço Norte Esquerdo	1045
57360000	Iúna (IUN)	Rio Pardo	432
57450000	Rive (RIV)	Rio Itapemirim	2218
57370000	Terra Corrida Montante (TCM)	Rio Pardo	587
57350000	Usina Fortaleza (UFO)	Rio Braço Norte Esquerdo	196
57580000	Usina Paineiras (UPA)	Rio Itapemirim	5168
57550000	Usina São Miguel (USM)	Rio Castelo	1459

Table 2 Percentage of forest coverage (FC), average annual flow (Qave), seven days duration minimum flow (Q7) and annual rainfall depth (Pa) of each watershed in the Itapemirim river basin at each period of evaluation.

Station	Variable	^______Base years^______
		1987	1991	1995	1999	2003	2007	2011
Castelo	FC (%)	32	36	34	35	35	30	37
	Q₇ (m³ s^-1)	4.1	7.6	2.9	2.4	2.1	2.0	2.7
	Q_ave (m³ s^-1)	18.6	12.3	13.7	13.0	12.2	19.8	18.6
	Pa (mm)	1525	1354	1249	1363	1268	1510	1540
Fazenda Cacheta	FC (%)	24	36	23	20	21	18	21
	Q₇ (m³ s^-1)	1.1	1.6	0.3	0.8	1.1	1.3	2.0
	Q_ave (m³ s^-1)	6.6	4.0	5.2	6.8	4.1	7.4	7.8
	Pa (mm)	1275	1202	1239	1211	1186	1534	1433
Fazenda Laginha	FC (%)	37	40	42	43	46	39	47
	Q₇ (m³ s^-1)	2.4	2.7	1.2	1.1	0.8	1.3	1.7
	Q_ave (m³ s^-1)	8.1	6.7	7.1	7.4	6.5	9.1	7.6
	Pa (mm)	1553	1350	1205	1356	1268	1460	1495
Ibitirama	FC (%)	30	31	34	32	36	33	36
	Q₇ (m³ s^-1)	2.0	3.7	1.4	1.9	1.9	2.1	2.3
	Q_ave (m³ s^-1)	12.5	10.6	11.6	12.0	11.6	15.7	13.6
	Pa (mm)	1549	1424	1311	1472	1427	1760	1723
Itaici	FC (%)	18	20	19	20	23	16	20
	Q₇ (m³ s^-1)	5.2	8.7	4.0	4.1	4.2	5.9	6.4
	Q_ave (m³ s^-1)	22.0	15.0	18.6	20.0	17.6	24.9	20.7
	Pa (mm)	1397	1352	1166	1453	1327	1535	1555
Iúna	FC (%)	12	14	12	15	19	12	12
	Q₇ (m³ s^-1)	3.0	6.1	1.9	3.2	2.4	3.5	4.0
	Q_ave (m³ s^-1)	9.8	6.3	12.4	8.0	7.6	9.2	8.5
	Pa (mm)	1361	1351	1167	1418	1373	1512	1552
Rive	FC (%)	19	23	19	20	21	17	20
	Q₇ (m³ s^-1)	10.8	16.9	8.2	10.9	10.8	13.0	14.8
	Q_ave (m³ s^-1)	49.7	32.8	38.2	43.9	38.9	55.2	48.3
	Pa (mm)	1473	1360	1248	1412	1339	1635	1635
Terra Corrida	FC (%)	13	16	14	16	19	13	14
	Q₇ (m³ s^-1)	3.7	5.0	2.3	3.5	3.3	4.1	5.2
	Q_ave (m³ s^-1)	12.4	7.8	9.8	11.4	10.4	13.1	12.4
	Pa (mm)	1357	1349	1172	1416	1367	1516	1554
Usina Fortaleza	FC (%)	28	27	29	28	35	26	32
	Q₇ (m³ s^-1)	0.9	1.9	1.6	0.8	0.7	0.8	1.1
	Q_ave (m³ s^-1)	4.9	4.2	5.3	5.3	4.0	5.6	4.3
	Pa (mm)	1437	1369	1096	1357	1295	1514	1515
Usina Paineiras	FC (%)	26	31	24	24	25	21	25
	Q₇ (m³ s^-1)	19.5	42.0	15.4	17.2	19.2	20.1	25.3
	Q_ave (m³ s^-1)	93.4	69.0	76.7	84.2	71.5	118.0	102.0
	Pa (mm)	1480	1359	1286	1387	1296	1601	1603
Usina São Miguel	FC (%)	36	41	37	37	38	33	39
	Q₇ (m³ s^-1)	6.8	9.3	7.5	4.8	3.9	4.8	6.2
	Q_ave (m³ s^-1)	25.8	18.8	24.4	20.6	17.5	30.4	26.1
	Pa (mm)	1524	1384	1307	1381	1273	1552	1571

Table 3 Partial correlation coefficient (Rp) between streamflow and forest coverage, maintaining the effects of annual rainfall constant for all watersheds of the present study.

Watershed	Q_ave		Q₇
	R_p	P-value*	R_p	P-value*
Castelo	-0.65	0.16	0.35	0.50
Fazenda Cacheta	-0.46	0.36	0.59	0.22
Fazenda Laginha	-0.40	0.43	-0.45	0.37
Ibitirama	0.09	0.87	-0.31	0.54
Itaici	-0.76	0.08	-0.01	0.99
Iúna	-0.68	0.14	-0.08	0.88
Rive	-0.90	0.02	0.82	0.05
Terra Corrida	-0.58	0.23	0.00	1.00
Usina Fortaleza	-0.68	0.14	-0.43	0.40
Usina Paineiras	-0.89	0.02	0.93	0.01
Usina São Miguel	-0.77	0.08	0.59	0.22

Table 4 Multiple linear equations representing the association of streamflow with forest coverage (FC, in %) and annual rainfall (Pa, in mm) for the watersheds where correlation was statistically significant.

Watershed	Adjusted equation	R²	P-value*
			FC	Pa
Average annual flow (Q_ave) in m³ s^-1
Rive (RIV)	Q_ave = 44.74 - 2.37 FC + 0.03 Pa	0.94	0.02	0.01
Usina Paineiras (UPA)	Q_ave = -11.30-2.12 FC + 0.11 Pa	0.97	0.02	0.01
Average minimum flow with seven days of duration (Q₇) in m³ s^-1
Rive (RIV)	Q₇ = -36.07 + 1.30 FC + 0.01 Pa	0.74	0.05	0.05
Usina Paineiras (UPA)	Q₇ = -85.86 + 2.91 FC + 0.03 Pa	0.87	0.01	0.14

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