Relationships between Agriculture, Riparian Vegetation, and Surface Water Quality in Watersheds

Broetto, Tiago; Tornquist, Carlos Gustavo; Campos, Ben-Hur Costa de; Schneider, Júlio Cézar

doi:10.1590/18069657rbcs20160286

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Revista Brasileira de Ciência do Solo

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Sumário

Division 3 - Soil Use and Management • Rev. Bras. Ciênc. Solo 41 (0) • 2017 • https://doi.org/10.1590/18069657rbcs20160286 copy

Relationships between Agriculture, Riparian Vegetation, and Surface Water Quality in Watersheds

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Agricultural land use and degradation of natural vegetation in riparian zones can impair water quality. This study was conducted in seven agricultural watersheds in Ibirubá, RS, Brazil, with the following objectives: identify relationships between concentrations of soluble phosphorus (P_sol) and nitrate (NO⁻₃) in surface water and agricultural use of soil and current vegetation in riparian zones, and assess the risk of eutrophication. Water samples from the main watercourses in each watershed were collected monthly from 10/2013 to 6/2014. Current land use was established by field surveys in the watersheds. The riparian zones of the watercourses were evaluated in terms of the condition of permanent preservation area (PPA) and access of the animals to the watercourses. The concentration of P_sol and NO⁻₃ were correlated with land use indicators obtained from geoprocessing tools. Agricultural use of PPA increases the risk of surface water degradation, which increases through application of manure on crops and free access of livestock to PPAs and to these watercourses for drinking water. Surface water samples obtained showed water P_sol concentrations that generate risk of eutrophication, whereas concentrations of NO⁻₃ were generally below critical levels.

environmental pollution; dairy cattle; manure; riparian zone

Watershed	Drainage				Kc	Kf	Drainage density	Sinuosity	Drainage gradient	Watershed area

	1^st order⁽¹⁾	2^nd order	3^rd order	Total
							km km^-2		%	ha
W1	3	1	0	4	1.20	0.45	1.50	1.18	2.22	348
W2	12	3	1	16	1.15	0.43	1.40	1.26	1.62	1201
W3	19	4	1	24	1.28	0.52	1.38	1.32	1.19	2731
W4	2	1	0	3	1.11	0.76	1.48	1.12	4.70	130
W5	1	0	0	1	1.10	0.75	1.25	1.07	4.57	68
W6	4	1	0	5	1.20	0.57	1.24	1.22	1.62	709
W7	2	0	0	2	1.07	0.59	1.02	1.17	2.14	328

Source of variation	DF	Type III SS	MS	F	p>F	DF	Type III SS	MS	F	p>F
	-------------------- P_sol --------------------					------------------ NO⁻₃ -----------------
Watershed	6	1473.7	245.6	260.2	<0.0001	6	2170.7	361.8	381.7	<0.0001
Sampling point	1	262.7	262.7	278.3	<0.0001	1	8.3	8.3	8.7	0.0036
Watershed × sampling point	24	31.6	1.3	1.4	0.12	24	32.6	1.4	1.4	0.0995
Sampling date	7	3439.6	491.4	520.6	<0.0001	7	900.9	128.7	135.8	<0.0001
Watershed × point × date	14	1483.3	106.0	112.3	<0.0001	27	1129.0	41.8	44.1	<0.0001

Watershed	Oct 28, 2013	Dec 4, 2013	Jan 4, 2014	Feb 4, 2014	Mar 7, 2014	Apr 11, 2014	May 2, 2014	Jun 4, 2014
	NO⁻₃ (mg L^-1)
	Midpoints
W1	0.88 ± 0.53 A	1.40 ± 0.11 AB	1.59 ± 0.22 A	1.57 ± 0.06 B	0.84 ± 0.04 B	1.43 ± 0.02 AB	1.42 ± 0.06 B	1.58 ± 0.01 B
W2	1.53 ± 0.34 A	1.47 ± 0.11 AB	2.20 ± 0.13 A	1.60 ± 0.04 B	0.93 ± 0.09 B	0.66 ± 0.03 BC	1.49 ± 0.02 B	2.04 ± 0.20 AB
W3	1.46 ± 0.53 A	0.75 ± 0.13 B	0.56 ± 0.04 B	0.49 ± 0.04 C	MS	0.37 ± 0.04 C	0.32 ± 0.02 C	0.37 ± 0.04 C
W6	1.00 ± 0.15 A	1.84 ± 0.03 A	2.06 ± 0.05 A	2.85 ± 0.04 A	2.37 ± 0.18 A	2.37 ± 0.05 A	2.86 ± 0.07 A	2.94 ± 0.06 A
W7	1.33 ± 0.80 A	1.59 ± AB	1.44 ± 0.04 AB	1.17 ± 0.06 BC	0.55 ± 0.22 B	0.86 ± 0.13 BC	0.90 ± 0.06 BC	1.49 ± 0.07 B
	Outlets
W1	0.77 ± 0.36 BCD	1.48 ± 0.09 AB	1.88 ± 0.06 AB	1.47 ± 0.09 AB	0.78 ± 0.02 A	1.07 ± 0.08 A	1.29 ± 0.11 ABC	2.10 ± 0.04 A
W2	1.78 ± 0.66 AB	1.48 ± 0.05 AB	2.17 ± 0.01 A	1.63 ± 0.01 A	0.99 ± 0.01 A	0.85 ± 0.08 A	1.63 ± 0.05 AB	1.94 ± 0.09 A
W3	0.42 ± 0.34 D	0.98 ± 0.06 B	1.11 ± 0.06 BC	0.94 ± 0.01 AB	0.34 ± 0.05 A	0.66 ± 0.04 A	0.64 ± 0.02 BC	0.91 ± 0.04 B
W4	2.24 ± 0.43 A	1.87 ± 0.03 AB	2.05 ± 0.12 AB	1.79 ± 0.09 A	1.14 ± 0.12 A	1.34 ± 0.08 A	1.57 ± 0.06 AB	2.13 ± 0.04 A
W5	0.70 ± 0.43 CD	1.09 ± 0.12 B	0.39 ± 0.05 C	0.50 ± 0.10 A	MS	0.72 ± 0.56 A	0.54 ± 0.08 C	1.82 ± 0.08 AB
W6	1.86 ± 0.26 A	2.35 ± 0.04 A	1.80 ± 0.06 AB	1.89 ± 0.13 A	0.97 ± 0.34 A	1.64 ± 0.05 A	1.87 ± 0.06 A	2.27 ± 0.01 A
W7	1.53 ± 0.30 ABC	1.84 ± 0.10 AB	1.56 ± 0.03 AB	1.68 ± 0.04 A	1.18 ± 0.04 A	1.50 ± 0.17 A	1.85 ± 0.32 A	2.79 ± 0.44 A
	P_sol (mg L^-1)
	Midpoints
W1	0.002 ± 0.001 B	0.009 ± 0.002 B	MS	MS	MS	0.015 ± 0.001 B	0.004 ± 0.000 C	MS
W2	0.017 ± 0.001AB	0.030 ± 0.007 A	0.009 ± 0.001 B	0.025 ± 0.001 B	0.019 ± 0.001 AB	0.029 ± 0.001 B	0.045 ± 0.007 A	0.025 ± 0.002 A
W3	0.019 ± 0.000	0.032 ± 0.001A	0.010 ± 0.000 B	0.010 ± 0.003 B	0.013 ± 0.000 B	0.031 ± 0.000 B	0.021 ± 0.000 BC	0.004 ± 0.001 A
W6	0.026 ± 0.001 A	0.037 ± 0.001 A	0.032 ± 0.000 A	0.050 ± 0.005 A	0.036 ± 0.000 A	0.095 ± 0.000 A	0.038 ± 0.001 AB	0.013 ± 0.001 A
W7	0.007 ± 0.000AB	0.022 ± 0.000	MS	MS	0.006 ± 0.001 B	0.023 ± 0.000	0.011 ± 0.000	MS
	Outlets
W1	0.066 ± 0.006 A	0.051 ± 0.011 AB	0.199 ± 0.003 A	0.046 ± 0.018 B	0.015 ± 0.004 BC	0.033 ± 0.002 BC	0.026 ± 0.003 B	0.016 ± 0.001 A
W2	0.024 ± 0.006 B	0.035 ± 0.006 BC	0.013 ± 0.003 B	0.023 ± 0.001 C	0.023 ± 0.001 BC	0.033 ± 0.003 BC	0.054 ± 0.002 A	0.012 ± 0.003 A
W3	0.022 ± 0.005 B	0.028 ± 0.002 C	0.014 ± 0.001 B	0.010 ±0.002 CD	0.015 ± 0.002 BC	0.042 ± 0.001 BC	0.024 ± 0.002 B	0.003 ± 0.000 A
W4	0.013 ± 0.002 B	0.015 ± 0.009 C	0.000 ± 0.000 B	0.001 ± 0.001 D	0.005 ± 0.000 C	0.026 ± 0.005 C	0.010 ± 0.000 B	MS
W5	0.016 ± 0.000 B	0.060 ± 0.020 A	0.001 ± 0.001 B	0.003 ± 0.002 CD	0.032 ± 0.003 AB	0.065 ± 0.002 A	0.013 ± 0.004 B	0.021 ± 0.004 A
W6	0.013 ± 0.000	0.020 ± 0.001 C	0.012 ± 0.001 B	0.007 ± 0.001 CD	0.014 ± 0.000 BC	0.053± 0.000 AB	0.023 ± 0.000 B	MS
W7	0.013 ± 0.000	0.028 ± 0.008 C	0.005 ± 0.001 B	0.078 ± 0.005 A	0.053 ± 0.003 A	0.035 ± 0.000 BC	0.025 ± 0.001 B	MS

Watershed indicator	P_sol	NO⁻₃
Area	-0.22	-0.41
Agricultural area in the watershed	0.32	-0.53
Fraction of remaining PPA (30 m)	-0.61	0.48
Fraction of remaining PPA (5 m)	-0.49	0.60
Fraction of PPA to undergo restoration	0.32	-0.60
Fraction of PPA receiving PS	-0.05	-0.33
Fraction of agricultural area receiving PS	-0.07	-0.31
Number of beef/dairy cattle	0.13	0.01
Number of pigs	0.87 ^***	0.00
Density of beef/dairy cattle	0.06	-0.74 ^**
Density of beef/dairy cattle in the agricultural area	0.23	-0.47
Density of pigs	0.87 ^***	-0.01
Density of pigs in the agricultural area	0.87 ^***	-0.01
Density of pigs in the agricultural area receiving PS	0.89 ^***	0.02
Fraction of watershed with beef/dairy cattle	0.54	-0.08
Fraction of drainage ways to which beef/dairy cattle have free access	0.37	0.73 ^**

Sampling point	Oct 28, 2013	Dec 4, 2013	Jan 4, 2014	Feb 4, 2014	Mar 7, 2014	Apr 11, 2014	May 2, 2014	Jun 4, 2014
	--------------------------------------- mg L^-1 NO⁻₃ ---------------------------------------
	W1
Outlet	0.77 ± 0.53 A	1.48 ± 0.09 A	1.88 ± 0.06 A	1.47 ± 0.09 A	0.78 ± 0.02 A	1.07 ± 0.08 A	1.29 ± 0.11 A	2.10 ± 0.04 A
Midpoint	0.88 ± 0.22 A	1.40 ± 0.11 A	1.59 ± 0.22 A	1.57 ± 0.06 A	0.85 ± 0.04 A	1.43 ± 0.02 A	1.42 ± 0.06 A	1.58 ± 0.01 A
	W2
Outlet	1.78 ± 0.66 A	1.48 ± 0.05 A	2.17 ± 0.01 A	1.63 ± 0.01 A	0.99 ± 0.01 A	0.85 ± 0.08 A	1.63 ± 0.05 A	1.94 ± 0.09 A
Midpoint	1.53 ± 0.34 A	1.47 ± 0.11 A	2.20 ± 0.13 A	1.60 ± 0.04 A	0.93 ± 0.09 A	0.66 ± 0.03 A	1.49 ± 0.02 A	2.04 ± 0.20 A
	W3
Outlet	0.42 ± 0.34 B	0.98 ± 0.06 A	1.11 ± 0.06 A	0.94 ± 0.01 A	0.34 ± 0.05	0.66 ± 0.04 A	0.64 ± 0.02 A	0.91 ± 0.04 A
Midpoint	1.46 ± 0.53 A	0.75 ± 0.13 A	0.56 ± 0.04 A	0.49 ± 0.04 A	MS	0.37 ± 0.04 A	0.32 ± 0.02 A	0.37 ± 0.04 A
	W4
Outlet	2.24 ± 0.43	1.87 ± 0.03	2.05 ± 0.12	1.79 ± 0.09	1.14 ± 0.12	1.34 ± 0.08	1.57 ± 0.06	2.13 ± 0.04
	W5
Outlet	0.70 ± 0.43	1.09 ± 0.12	0.39 ± 0.05	0.50 ± 0.10	MS	0.72 ± 0.56	0.54 ± 0.08	1.82 ± 0.08
	W6
Outlet	1.86 ± 0.26 A	2.35 ± 0.04 A	1.80 ± 0.06 A	1.89 ± 0.13 A	0.97 ± 0.34 B	1.64 ± 0.05 A	1.87 ± 0.06 A	2.27 ± 0.01 A
Midpoint	1.00 ± 0.15 A	1.84 ± 0.03 A	2.06 ± 0.05 A	2.85 ± 0.04 A	2.37 ± 0.18 A	2.37 ± 0.05 A	2.86 ± 0.07 A	2.94 ± 0.06 A
	W7
Outlet	1.53 ± 0.30 A	1.84 ± 0.10 A	1.56 ± 0.04 A	1.59 ± 0.04 A	1.18 ± 0.04 A	1.50 ± 0.17 A	1.85 ± 0.32 A	2.79 ± 0.44 A
Midpoint	1.33 ± 0.80 A	1.59 ± 0.04 A	1.44 ± A	1.68 ± 0.06 A	0.55 ± 0.22 A	0.86 ± 0.13 A	0.90 ± 0.06 A	1.49 ± 0.07 B

Watershed	Oct 28, 2013	Dec 4, 2013	Jan 4, 2014	Feb 4, 2014	Mar 7, 2014	Apr 11, 2014	May 2, 2014	Jun 4, 2014
	--------------------------------------- mg L^-1 P_sol ---------------------------------------
	W1
Outlet	0.066 ± 0.006 A	0.051 ± 0.011 A	0.199 ± 0.003	0.046 ± 0.018	0.015 ± 0.004	0.033 ± 0.002 A	0.026 ± 0.003 A	0.016 ± 0.001
Midpoint	0.002 ± 0.001 B	0.009 ± 0.002 B	MS	MS	MS	0.015 ± 0.001 A	0.004 ± 0.000 B	MS
	W2
Outlet	0.024 ± 0.006 A	0.035 ± 0.006 A	0.013 ± 0.003 A	0.023 ± 0.001 A	0.023 ± 0.001 A	0.033 ± 0.003 A	0.054 ± 0.002 A	0.012 ± 0.003 A
Midpoint	0.017 ± 0.001 A	0.030 ± 0.007 A	0.009 ± 0.001 A	0.025 ± 0.001 A	0.019 ± 0.001 A	0.021 ± 0.001 A	0.044 ± 0.007 A	0.025 ± 0.002 A
	W3
Outlet	0.022 ± 0.005	0.028 ± 0.002 A	0.014 ± 0.001 A	0.010 ± 0.002 A	0.015 ± 0.002 A	0.042 ± 0.001 A	0.024 ± 0.002 A	0.003 ± 0.000 A
Midpoint	0.019 ± 0.000	0.032 ± 0.001 A	0.010 ± 0.000 A	0.010 ± 0.003 A	0.013 ± 0.000 A	0.031 ± 0.000 A	0.021 ± 0.000 A	0.004 ± 0.001 A
	W4
Outlet	0.013 ± 0.002	0.015 ± 0.009	0.000 ± 0.000	0.001 ± 0.001	0.005 ± 0.000	0.026 ± 0.005	0.010 ± 0.000	MS
	W5
Outlet	0.016 ± 0.000	0.060 ± 0.020	0.001 ± 0.001	0.003 ± 0.002	0.032 ± 0.003	0.065 ± 0.002	0.013 ± 0.004	0.021 ± 0.004
	W6
Outlet	0.013 ± 0.000	0.020 ± 0.001 A	0.012 ± 0.001 A	0.007 ± 0.001 B	0.014 ± 0.000 B	0.053 ± 0.000 B	0.023 ± 0.000 A	MS
Midpoint	0.026 ± 0.001	0.037 ± 0.001 A	0.032 ± 0.000 A	0.050 ± 0.005 A	0.036 ± 0.000 A	0.095 ± 0.000 A	0.038 ± 0.001 A	0.012 ± 0.001
	W7
Outlet	0.013 ± 0.000	0.028 ± 0.008	0.005 ± 0.001	0.078 ± 0.005	0.053 ± 0.003 A	0.035 ± 0.000	0.025 ± 0.001	MS
Midpoint	0.007 ± 0.000	0.022 ± 0.000	MS	MS	0.006 ± 0.001 B	0.023 ± 0.000	0.011 ± 0.000	MS

Date	W1	W2	W3	W4	W5	W6	W7
	--------------------------------------- mg L^-1 NO⁻₃ ---------------------------------------
	Midpoints
Oct 28, 2013	0.88 ± 0.53 A	1.53 ± 0.34 AB	1.46 ± 0.53 A	-	-	1.00 ± 0.15 C	1.33 ± 0.80 AB
Dec 4, 2013	1.40 ± 0.11 A	1.47 ± 0.11 AB	0.75 ± 0.13 AB	-	-	1.84 ± 0.03 BC	1.59 ± 0.04 A
Jan 4, 2014	1.59 ± 0.22 A	2.20 ± 0.13 A	0.56 ± 0.04 AB	-	-	2.06 ± 0.05 AB	1.44 ± 0.04 AB
Feb 4, 2014	1.57 ± 0.06 A	1.60 ± 0.04 AB	0.49 ± 0.04 AB	-	-	2.85 ± 0.04 A	1.17 ± 0.06 AB
Mar 7, 2014	0.84 ± 0.04 A	0.93 ± 0.09 B	MS	-	-	2.37 ± 0.18 AB	0.55 ± 0.22 B
Apr 11, 2014	1.43 ± 0.02 A	0.66 ± 0.03 B	0.37 ± 0.04 B	-	-	2.37 ± 0.05 AB	0.86 ± 0.13 AB
May 2, 2014	1.42 ± 0.06 A	1.49 ± 0.02 AB	0.32 ± 0.02 B	-	-	2.86 ± 0.07 A	0.90 ± 0.06 AB
Jun 4, 2014	1.58 ± 0.01 A	2.04 ± 0.20 A	0.37 ± 0.04 B	-	-	2.94 ± 0.06 A	1.49 ± 0.07 AB
	Outlet
Oct 28, 2013	0.77 ± 0.36 C	1.78 ± 0.66 ABC	0.42 ± 0.34 A	2.24 ± 0.43 A	0.70 ± 0.43 B	1.86 ± 0.26 AB	1.53 ± 0.30 B
Dec 4, 2013	1.48 ± 0.09 ABC	1.48 ± 0.05 ABC	0.98 ± 0.06 A	1.87 ± 0.03 AB	1.09 ± 0.12 AB	2.35 ± 0.04 A	1.84 ± 0.10 AB
Jan 4, 2014	1.88 ± 0.06 AB	2.17 ± 0.01 A	1.11 ± 0.06 A	2.05 ± 0.12 AB	0.39 ± 0.05 B	1.80 ± 0.06 AB	1.56 ± 0.03 B
Feb 4, 2014	1.47 ± 0.09 ABC	1.63 ± ABC	0.94 ± 0.01 A	1.79 ± 0.09 AB	0.50 ± 0.10 B	1.89 ± 0.13 AB	1.68 ± 0.04 B
Mar 7, 2014	0.78 ± 0.02 C	0.99 ± 0.01 BC	0.34 ± 0.05 A	1.14 ± 0.12 B	MS	0.97 ± 0.34 B	1.18 ± 0.04 B
Apr 11, 2014	1.07 ± 0.08 BC	0.85 ± 0.08 C	0.66 ± 0.04 A	1.34 ± 0.08 AB	0.72 ± 0.56 B	1.64 ± 0.05 AB	1.50 ± 0.17 B
May 2, 2014	1.29 ± 0.11 ABC	1.63 ± 0.05 ABC	0.64 ± 0.02 A	1.57 ± 0.06 AB	0.54 ± 0.08 B	1.87 ± 0.06 AB	1.85 ± 0.32 AB
Jun 4, 2014	2.10 ± 0.04 A	1.94 ± 0.09 AB	0.91 ± 0.04 A	2.13 ± 0.04 A	1.82 ± 0.08 A	2.27 ± 0.01 A	2.79 ± 0.44 A

Date	W1	W2	W3	W4	W5	W6	W7
	--------------------------------------- mg L^-1 P_sol ---------------------------------------
	Midpoints
Oct 28, 2013	0.002 ± 0.001 A	0.017 ± 0.001 BC	0.019 ± 0.000	MS	MS	0.026 ± 0.001 CD	0.007 ± 0.000 A
Dec 4, 2013	0.009 ± 0.002 A	0.030 ± 0.007 AB	0.032 ± 0.001 A	MS	MS	0.037 ± 0.001 BC	0.022 ± 0.000
Jan 4, 2014	MS	0.009 ± 0.001 C	0.010 ± 0.000 BC	MS	MS	0.032 ± 0.000 BCD	MS
Feb 4, 2014	MS	0.025 ± 0.001 ABC	0.010 ± 0.003 BC	MS	MS	0.050 ± 0.005 B	MS
Mar 7, 2014	MS	0.019 ± 0.001 BC	0.013 ± 0.000 ABC	MS	MS	0.036 ± 0.000 BC	0.006 ± 0.001 A
Apr 11, 2014	0.015 ± 0.001 A	0.029 ± 0.001 ABC	0.031 ± 0.000 AB	MS	MS	0.095 ± 0.000 A	0.023 ± 0.000
May 2, 2014	0.004 ± 0.000 A	0.045 ± 0.007 A	0.021 ± 0.000 ABC	MS	MS	0.038 ± 0.001 BC	0.011 ± 0.000
Jun 4, 2014	MS	0.025 ± 0.002 ABC	0.004 ± 0.001 C	MS	MS	0.013 ± 0.001 D	MS
	Outlet
Oct 28, 2013	0.066 ± 0.006 B	0.024 ± 0.006 BCD	0.022 ± 0.005 ABC	0.013 ± 0.002 AB	0.016 ± 0.000 BC	0.013 ± 0.000	0.013 ± 0.000
Dec 4, 2013	0.051 ± 0.011 BC	0.035 ± 0.006 AB	0.028 ± 0.002 AB	0.015 ± 0.009 AB	0.060 ± 0.020 A	0.020 ± 0.001 B	0.028 ± 0.008 C
Jan 4, 2014	0.199 ± 0.003 A	0.013 ± 0.003 CD	0.014 ± 0.001 BC	0.000 ± 0.000 B	0.001 ± 0.001 C	0.012 ± 0.001 B	0.005 ± 0.001 D
Feb 4, 2014	0.046 ± 0.018 BCD	0.023 ± 0.001 BCD	0.010 ± 0.002 BC	0.001 ± 0.001 B	0.003 ± 0.002 C	0.007 ± 0.001 B	0.078 ± 0.005 A
Mar 7, 2014	0.015 ± 0.004 E	0.023 ± 0.001 BCD	0.015 ± 0.002 BC	0.005 ± 0.000 B	0.032 ± 0.003 B	0.014 ± 0.000 B	0.053 ± 0.003 B
Apr 11, 2014	0.033 ± 0.002 CDE	0.033 ± 0.003 ABC	0.042 ± 0.001 A	0.026 ± 0.005 A	0.065 ± 0.002 A	0.053 ± 0.000 A	0.035 ± 0.000 BC
May 2, 2014	0.026 ± 0.003 DE	0.054 ± 0.002 A	0.024 ± 0.002 ABC	0.010 ± 0.000 AB	0.013 ± 0.004 BC	0.023 ± 0.000 B	0.025 ± 0.001 CD
Jun 4, 2014	0.016 ± 0.001 E	0.012 ± 0.003 D	0.003 ± 0.000 D	MS	0.021 ± 0.004 BC	MS	MS

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[1] * Corresponding author: carlos.tornquist@ufrgs.br