Stream water chemistry in Stream water chemistry in three meso-scale hydrologic three meso-scale hydrologic basins in Eastern Amazonianbasins in Eastern Amazonian

Ricardo de O. FigueiredoRicardo de O. Figueiredo11, Daniel Markewitz, Daniel Markewitz22, , Eric A. DavidsonEric A. Davidson33, Ewerton S. da Cunha, Ewerton S. da Cunha44, ,

Marysol A.E. SchulerMarysol A.E. Schuler44, and Patrício de S. Silva, and Patrício de S. Silva55

1. Embrapa Amazônia Oriental; 1. Embrapa Amazônia Oriental; 2. The University of Georgia; 2. The University of Georgia;

3. The Woods Hole Research Center;3. The Woods Hole Research Center; 4. Instituto de Pesquisa Ambiental da Amazônia; 4. Instituto de Pesquisa Ambiental da Amazônia; 5. Universidade do Estado do Pará / CNPq-CTHidro5. Universidade do Estado do Pará / CNPq-CTHidro

Main Objective and Previous StudiesMain Objective and Previous Studies

This work addresses the effects of land use This work addresses the effects of land use

change on stream water chemistry change on stream water chemistry

In previous studies, we showed:In previous studies, we showed: significantly lower soil nitrate concentration in significantly lower soil nitrate concentration in

pasture soils compared to forest soilspasture soils compared to forest soils significant leaching of cations from pasture soils significant leaching of cations from pasture soils

to the stream (larger concentrations at high to the stream (larger concentrations at high

flows)flows)

Streams (Igarapés):Cq = Igarapé Cinquenta e quatroSt = Igarapé do SetePj = Igarapé Pajeú

Three watersheds Three watersheds near Paragominas near Paragominas (Eastern Amazonia)(Eastern Amazonia) * * Landsat 1999 scenesLandsat 1999 scenes

Cq (130 kmCq (130 km22) - 18% forest ) - 18% forest St (150 kmSt (150 km22) - 34% forest ) - 34% forest

Pj (45 kmPj (45 km22) - 45% of forest) - 45% of forest

FField campaigns from ield campaigns from April/2003 to July/2004, April/2003 to July/2004,

from headwaters in remnant from headwaters in remnant mature forests, through mature forests, through

pastures, secondary forests, pastures, secondary forests, and agricultural fields.and agricultural fields.

headwaters in remnant mature forests

headwaters in an extremely explored forest

CropsPasture

IGARAPÉ DO SETE

IGARAPÉ PAJEÚ

A view of a farm area between two of the studied streamsA view of a farm area between two of the studied streams

Stream dammed up

flow completely interrupted

controled flow

A very typical streamwater use:A very typical streamwater use:water supply and electricity water supply and electricity

for the farmsfor the farms

Two distinct Two distinct downstream patternsdownstream patterns

Let’s see the Let’s see the first results …first results …

0

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Cq St Pj FL

ºC a

nd

FT

U

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7.0

pH

FTU ºC pH

Decrease in turbidity, temperature and pH related to decreasing in Decrease in turbidity, temperature and pH related to decreasing in percentual watersheds forested areas.percentual watersheds forested areas.

In this graph we also present values of an entire forested microbasin In this graph we also present values of an entire forested microbasin (FL) situated about 80 km from Paragominas.(FL) situated about 80 km from Paragominas.

4.20

4.40

4.60

4.80

5.00

5.20

5.40

St1 St2 St3 St4 St5 St6 St74.00

4.20

4.40

4.60

4.80

5.00

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5.40

5.60

Pj1 Pj2 Pj3

4.20

4.40

4.60

4.80

5.00

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5.40

5.60

5.80

6.00

6.20

6.40

6.60

6.80

Cq1 Cq2 Cq3 Cq4 Cq5

Sete - 34% forest Sete - 34% forest

Cinquenta e Quatro - Cinquenta e Quatro - 18%18% forest forest

Pajeú - 45% of forestPajeú - 45% of forest

downstream downstream

downstream

In the watershed where the In the watershed where the remmant forest has been extremely remmant forest has been extremely explored, pH is high at headwaters explored, pH is high at headwaters decreasing downstream. decreasing downstream.

It is the opposite downstream It is the opposite downstream pattern of the other two watersheds pattern of the other two watersheds that have remnant mature forests that have remnant mature forests and larger percentual forested and larger percentual forested areas.areas.

4.06

6.43 6.306.51

5.73 5.906.236.20

8.77

8.01

8.93

7.53

8.52

10.18

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4.00

6.00

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12.00

IG7-1 IG7-2 IG7-3 IG7-4 IG7-5 IG7-6 IG7-7

O2

(mg

/L)

avg

max

dammed flowingflowing

flowing just after dam

dammed dammed dammed

Dissolved oxygen (mg LDissolved oxygen (mg L-1-1) decreases due to the low flow ) decreases due to the low flow caused by dams in the Igarapé do Sete.caused by dams in the Igarapé do Sete.

Temporal variation of Nitrate month means Temporal variation of Nitrate month means ((M LM L-1-1)) in in the 3 streams from April to July/2003.the 3 streams from April to July/2003.

1.54

1.75

1.91

0.17

y = -0.3081x3 + 1.8256x2 - 3.1148x + 3.1406

0.00

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1.00

1.50

2.00

2.50

apr may jun jul

NO

3 (u

M/L

)

* nitrate month averages in the 3 streams increase with rainy season and decreases sharply when stop raining. This fact may be related to the importance of superficial and subsuperficial flows as main sources of nitrate.

equation of the polynomial trendline

Nitrate means and range (Nitrate means and range (M LM L-1-1) for the first 4 months ) for the first 4 months (April to July/2003) in each station of the Igarapé Pajeú.(April to July/2003) in each station of the Igarapé Pajeú.

y = -3.8151Ln(x) + 4.9128

0.00

1.00

2.00

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5.00

6.00

7.00

8.00

Pj1 Pj2 Pj3

NO

3 (u

M/L

)

equation of logarithimic trendline

Pj1 - forested headwaters (flowing slowly)

Pj2 - pasture/capoeira (flowing just after dam)

Pj3 - capoeira/pasture/crops (flowing)

* trend of nitrate decreasing from forested headwaters

* denitrification in the lake formed by dam at Pj2 may be an important factor for nitrate decreasing

* secondary vegetation may function nitrate source at Pj3

Nitrate means (Nitrate means (M LM L-1-1) for the first 4 months (April ) for the first 4 months (April to July/2003) in each station of the Igarapé Pajeú.to July/2003) in each station of the Igarapé Pajeú.

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2.00

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6.00

apr may jun jul

NO

3 (u

M/L

)Pj1

Pj2

Pj3

forested headwaters (flowing slowly)

pastures/capoeiras (flowing just after dam)

capoeira/pastures/crops (flowing)

* Nitrate decreases when stop raining in July

* forests as nitrate sources are clear at these more preserved headwaters areas among studied catchments

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IG54-1 IG54-2 IG54-3 IG54-4 IG54-5

NO

3 (u

M/L

)

forested headwaters (dammed)

pasture (dammed)

pasture/sewage (flowing just after dam)

crops/pasture (flowing)

crops/pasture (flowing)Nitrate pattern (forests as N sources) has been affected by land use:

* after decreasing at dams (mainly at station 2) nitrate values are so much larger at 4 and 5, what may be due to crops (3 at dam is also affected by pastures and urbanization).

Nitrate means and range (Nitrate means and range (M LM L-1-1) for the first 4 months (April ) for the first 4 months (April to July/2003) in each station of the Igarapé Cinquenta e Quatro.to July/2003) in each station of the Igarapé Cinquenta e Quatro.

Nitrate means (Nitrate means (M LM L-1-1) for the first 4 months (April to ) for the first 4 months (April to July/2003) in each station of the Igarapé Cinquenta e Quatro.July/2003) in each station of the Igarapé Cinquenta e Quatro.

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9.00

apr may jun jul

NO

3 (u

M/L

)

IG54-1

IG54-2

IG54-3

IG54-4

IG54-5

Nitrate pattern (forests as N sources) has been affected by land use:

* nitrate clearly increases from April to June and decreases in july at stations 4 and 5, what is related to more intensive

agriculture practices.

forested headwater (dammed)

pasture (dammed)

pasture/sewage (flowing just after dam)

crops/pasture (flowing)

crops /pasture (flowing)

0.0

1.0

2.0

3.0

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6.0

IG7-1 IG7-2 IG7-3 IG7-4 IG7-5 IG7-6 IG7-7

NO

3 (u

M/L

)

fore

sted

hea

dwat

ers

dammed

cap

oeira

/pas

ture

flowing

past

ure/

capo

eira

flowingafter dam

past

ure/

capo

eira

dammed

past

ure/

capo

eira

dammed

past

ure/

crop

s

dammed

flowing

capo

eira

/cro

ps/p

astu

re

Nitrate means and range (Nitrate means and range (M LM L-1-1) for the first 4 months ) for the first 4 months (April to July/2003) in each station of the Igarapé do Sete.(April to July/2003) in each station of the Igarapé do Sete.

Dams also promoting nitrate decreasing in the Igarapé do Sete.

13.06

26.96

21.06

17.66

y = -3.6938x2 + 19.006x

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5.00

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30.00

apr may jun jul

Ca

(uM

/L)

* calcium month average in the 3 streams increases with rainy season and decreases when stop raining.

* we will continue to monitore this to check the assumption of the important contribution of soil surface processes to the stream chemistry (Markewitz et al., 2001)

equation of the polynomial trendline

Temporal variation of Calcium month means Temporal variation of Calcium month means ((M LM L-1-1)) in the 3 streams from April to July/2003.in the 3 streams from April to July/2003.

Calcium means (Calcium means (M LM L-1-1) for the first 4 months (April to ) for the first 4 months (April to July/2003) in the Igarapé do Pajeú.July/2003) in the Igarapé do Pajeú.

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apr may jun jul

Ca

(uM

/L)

Pj1

Pj2

Pj3

forested headwaters (flowing slowly)

pastures/capoeiras (flowing just after dam)

capoeira/pastures/crops (flowing)

* As observed in early studies calcium concentrations are larger during rainy season.

* Perhaps there is a signal of agriculture at Pj3. This must be investigated along a larger period of time.

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apr may jun jul

Ca

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/L)

IG54-1

IG54-2

IG54-3

IG54-4

IG54-5

* different temporal pattern at stations 2 may be related to the obstructed outflow (dam).

forested headwater (dammed)

pasture (dammed)

pasture/sewage (flowing just after dam)

crops/pasture (flowing)

crops/pasture (flowing)

Calcium means (Calcium means (M LM L-1-1) for the first 4 months (April to ) for the first 4 months (April to July/2003) in each station of the Igarapé Cinquenta e Quatro.July/2003) in each station of the Igarapé Cinquenta e Quatro.

An ongoing research work…An ongoing research work…

We are measuring: temperature, pH, conductivity, turbidity, alkalinity, O2, Ca2+, Mg2+, K+, Na+, NH4

+, NO3-, PO4

3-, Cl-, DOC, DIC, pCO2, stream discharge, and rainfall.

Since March 2004 we are also sampling runoff, soil solution and groundwater at these watersheds (transects across riparian zones).

In addition, storm events will be sampled four times on each stream during 2005 rainy season to evaluate hydrologic flow paths during storm events.

Because soils are relatively similar within the study area, we suspect land use conversion is an important factor affecting the observed trends in stream chemistry.