PIAHSProceedings of the International Association of Hydrological SciencesPIAHSProc. IAHS2199-899XCopernicus PublicationsGöttingen, Germany10.5194/piahs-377-3-2018A multi-approach and multi-scale study on water quantity and quality changes in the Tapajós River basin, AmazonA multi-approach on water quantity and quality changes in the Tapajós River basinNóbregaRodolfo Luiz Bezerrar.nobrega@reading.ac.ukhttps://orcid.org/0000-0002-9858-8222LamparterGabrieleHughesHaroldGuzhaAlphonce ChenjerayiAmorimRicardo Santos SilvaGeroldGerhardDepartment of Physical Geography, Faculty of Geoscience and Geography, University of Göttingen, Göttingen, GermanyUSDA Forest Service, International Programs, c/o CIFOR, World Agroforestry Center, Nairobi, KenyaDepartment of Soil and Agricultural Engineering, Federal University of Mato Grosso, Cuiabá, MT, Brazilnow at: Department of Geography & Environmental Science, University of Reading, Reading, UKRodolfo Luiz Bezerra Nóbrega (r.nobrega@reading.ac.uk)16April2018377377June20176November201715November2017This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/This article is available from https://piahs.copernicus.org/articles/377/3/2018/piahs-377-3-2018.htmlThe full text article is available as a PDF file from https://piahs.copernicus.org/articles/377/3/2018/piahs-377-3-2018.pdf
We analyzed changes in water quantity and quality at different spatial scales
within the Tapajós River basin (Amazon) based on experimental fieldwork,
hydrological modelling, and statistical time-trend analysis. At a small
scale, we compared the river discharge (Q) and suspended-sediment
concentrations (SSC) of two adjacent micro-catchments (< 1 km2)
with similar characteristics but contrasting land uses
(forest vs. pasture) using empirical data from field measurements. At an
intermediary scale, we simulated the hydrological responses of a sub-basin of
the Tapajós (Jamanxim River basin, 37 400 km2), using a hydrological
model (SWAT) and land-use change scenario in order to quantify the changes in
the water balance components due to deforestation. At the Tapajós' River
basin scale, we investigated trends in Q, sediments, hydrochemistry, and
geochemistry in the river using available data from the HYBAM Observation
Service. The results in the micro-catchments showed a higher runoff
coefficient in the pasture (0.67) than in the forest catchment (0.28). At
this scale, the SSC were also significantly greater during stormflows in the
pasture than in the forest catchment. At the Jamanxim watershed scale, the
hydrological modelling results showed a 2 % increase in Q and a 5 %
reduction of baseflow contribution to total Q after a conversion of 22 %
of forest to pasture. In the Tapajós River, however, trend analysis did
not show any significant trend in discharge and sediment concentration.
However, we found upward trends in dissolved organic carbon and NO3-
over the last 20 years. Although the magnitude of anthropogenic impact has
shown be scale-dependent, we were able to find changes in the Tapajós
River basin in streamflow, sediment concentration, and water quality across
all studied scales.
Introduction
Southern Amazonia was the first region of Brazil's Amazon area to be exposed
to intensive conversion to agricultural lands (Fearnside, 2016). The Tapajós River, an important
tributary of the Amazon River, lost in this basin ca. 30 % of forest
cover (ca. 500 000 km2) by 2016, mainly due to the
establishment of agro-industrial farms. The forest loss in this river basin
is projected to reach approximately 65 % by 2050 (Soares-Filho et al., 2006).
The understanding of small areas is essential to propose solutions to
maintain tropical forest services, such as water and nutrient cycling, in
the Amazon (Vedovato et al., 2016). These areas can be well
assessed by experimental catchment studies. For example,
Bleich et al. (2016) studied 10 small pristine streams in the Tapajós River basin and argue
that in case measures of conservation of small catchments are not taken,
environmental impacts on regional streams in South Amazonia are expected to
increase. Impacts at regional scales have been the concern of the scientific
community with regards to the role of tropical forests in the global climate
systems, especially the effects of the Amazon deforestation in large scales
(Ometto et al., 2011). Lima et al. (2014) argue that
large-scale deforestation triggers complex non-linear interactions between
the atmosphere and biosphere, which may impair important ecosystem services
such as water for agriculture and hydroelectric power generation.
Although it has been reported that deforestation leads to changes in the
water cycle in this region (Davidson et al.,
2012), the effects of forest clearing on the concentrations of suspended and
dissolved materials that are usually seen in small streams are difficult to
be detected in larger streams and rivers (Thomas et al., 2004). However, the chemistry
of the large rivers in the Amazon that remained relatively unaltered until
2000 was compromised because of the upcoming growing of area occupied by
pastures (Neill et al., 2001). Additionally, analyses of
land-use change impacts that were usually limited to small plots or
experimental catchments are now possible to be applied to larger scales,
such as river basins, due to recent improvements in data collection,
archiving and distribution (Eshleman, 2004). New evidence shows
that the conversion of forest to pasture is manifested in systematic changes
in the hydro-climatology cycle with increase in river discharge in large
catchments in the Amazon (Souza-Filho et al., 2016).
In this study, we examined the impact of the land-use change on the
streamflow and water quality of the Tapajós River basin using different
spatial scales and approaches. Our objective is to identify what signatures
from the land-use change are possible to observe within and across these scales.
Area of study
Our study focus on the Tapajós River basin (ca. 500 000 km2),
which is the fifth largest sub-basin of the Amazon
River and covers 7 % of the total Amazon basin (Pavanato et al., 2016). This basin
includes 7 of the 41 municipalities where Brazilian Environmental
authorities concentrate anti-deforestation efforts due to their high
incidence of forest clearing (Bragança, 2015). In order to
estimate the impacts of scale, we integrated to our study a sub-basin of the
Tapajós, the Jamanxim River basin (37 400 km2), and a
pair of micro-catchments (< 1 km2) with contrasting
land uses (forest vs. pasture) located in the municipality of Novo
Progresso, in the Brazilian state of Pará (Fig. 1). The climate in this
area is humid tropical with a rainy season from November to May and a dry
season that extends from June to October. Mean annual precipitation averages 1900 mm.
Area of study.
MethodsExperimental micro-catchment study
We compared the streamflow of the micro-catchments by using empirical data
from field measurements from 2013 to 2014. At the catchment outlets, we
installed rectangular weirs and a DS 5X multiparameter sonde (OTT, USA) to
measure water level and to quantify streamflow. We quantified the runoff
coefficient as the ratio of total streamflow to total precipitation, and the
baseflow index as the ratio of total baseflow to total streamflow following
Nóbrega et al. (2017). In these catchments, we
also collected 1 L water samples during stormflow events for suspended
sediment concentration (SSC) analysis following the method of
ASTM (2000). More details on the catchments' characteristics and
instrumentation setup can be found in Guzha et al. (2015).
(a) Land-use distribution in 2011, and (b) Land-use
scenario (22 % of deforestation) for the year 2030 following a business as
usual approach (Gollow et al., 2017).
Jamanxim River basin modelling
We simulated the hydrological behavior of the Jamanxin River basin using the
SWAT eco-hydrological model (Arnold et
al., 2012). For the setup, calibration and validation of SWAT, we used a
gradual land-use change parameterization, field assessments, and available
regional data, and then simulated a land-use change scenario in order to
quantify the changes in the water balance components due to deforestation.
The model parameterization, calibration and validation details can be found
in Lamparter et al. (2016). The land-use change scenario
used in this study (Fig. 2) suggests a rapid pasture expansion according the
study of Gollnow et al. (2017).
Tapajós River basin analysis
We investigated trends in Q, sediments, and hydrochemistry and geochemistry,
i.e. pH, DOC, Mg, K, HCO3-, Si, NO3- and Ca, in the
Tapajós River using available data from the HYBAM Observation Service
(http://www.ore-hybam.org, station code 17730000). We used Mann-Kendall test for
detecting either an upward or downward trend in the data series with a
significance threshold set at .05. The data were also used to quantify
fluxes of nitrate and total dissolved carbon (DOC) using mean discharge and
concentration in 5-year periods from 1996 to 2015.
Results and discussion
Figure 3 shows the streamflow comparison between the two micro-catchments.
The pasture catchment has a higher runoff coefficient (0.67) than the forest
catchment (0.28). Baseflow indices were 0.76 and 0.88 for the pasture and
forest catchments, respectively, showing a higher baseflow contribution in
the forest catchment. At this scale, the SSC were also significantly higher
during stormflows in the pasture (mean of 579.7 mg L-1, n= 37) than
in the forest catchment (mean of 81.8 mg L-1, n= 50). The geometric
mean and 75th percentile for the SSC in the pasture and forest catchments were
47.2 and 26.1 mg L-1, and 886.0 and 147.8 mg L-1, respectively.
For the Jamanxim River basin, simulation results show a 2 % increase in
discharge (Q) and a 5 % reduction of baseflow contribution to total Q
after a 22 % conversion of forest to pasture (Fig. 4 and Table 1). Our
results are in accordance to Davidson et
al. (2012); they state that even though basin-scale impacts of land use may
not yet surpass the magnitude of natural hydrological variability and
biogeochemical cycles, there are some signs of a transition to a
disturbance-dominated regime, which include changes in the water cycle in
the Southern and Eastern regions of the Amazon basin.
Q results with SWAT for the land-use distribution and scenario.
Streamflow and rainfall in the forest and pasture micro-catchments.
Calibration and validation with land-use update for the Jamanxim catchment.
Nitrate and total dissolved carbon fluxes.
At the scale of the Tapajós River basin, however, trend analysis did not
show any significant trend in discharge and sediment concentration.
Hydrological changes due to land-use change are known to be primarily
manifested at smaller scales. Therefore, we ascribe the absence of visible
trend at a large scale to the fact that most of the deforestation in the
Tapajós River basin has occurred in its upper portion, which produces
hydrological signatures that may be buffered along the river until its
outlet. The analyses of the outflow fluxes over the last 20 years in the
Tapajós River revealed upward trends in dissolved organic carbon and
NO3-, which have reached an up to 10-fold increase (Fig. 5).
Conclusions
Effects of deforestation on large rivers of the Amazon basin were relatively
unknown due to the low degree of connection between large rivers and land
uses in these basins (Neill et al., 2001). We were able to
find changes in the Tapajós River basin in river discharge, sediment
concentration, and water quality across all studied scales. In this context,
our study adds to an increasing body of literature showing that although the
magnitude of anthropogenic impact has shown to be scale-dependent, some
changes are detectable in both small and large rivers in the Amazon.
The data used in this study for the micro-catchments and Jamanxim are
available from the Open Science Framework (10.17605/OSF.IO/UCDE7) and the Spatial Data Infrastructure of the
Carbiocial Project (http://gdi.carbiocial.de/). Time series used for the
trend analysis are available from the HYBAM Observation Service
(http://www.ore-hybam.org), and discharge data used to calibrate and validate the
hydrological model are available from the HydroWeb platform of the National
Water Agency of Brazil (http://hidroweb.ana.gov.br/, station code: 2650000).
The authors declare that they have no conflict of interest.
This article is part of the special issue “Water quality and
sediment transport issues in surface water”. It is a result of the IAHS
Scientific Assembly 2017, Port Elizabeth, South Africa, 10–14 July 2017.
Acknowledgements
This research was feasible thanks to the support of the
Bundesministerin für Bildung und Forschung (BMBF) through its grant to
the CarBioCial project (grant number: 01LL0902A). The authors also
acknowledge the data availability of HYBAM Observation Service and the
National Water Agency of Brazil (ANA).
Edited by: Akhilendra B. Gupta
Reviewed by: Jagdish Kumar Bassin and one anonymous referee
ReferencesArnold, J. G., Moriasi, D. N., Gassman, P. W., Abbaspour, K. C., White, M. J.,
Srinivasan, R., Santhi, C., Harmel, R. D., van Griensven, A., Van Liew, M. W.,
Kannan, N., and Jha, M. K.: SWAT: Model Use, Calibration, and Validation,
T. ASABE, 55, 1491–1508, 10.13031/2013.42256, 2012.
ASTM: Standard Test Methods for Determining Sediment Concentration in Water
Samples: D3977-97, West Conshohocken, PA, 2000.Bleich, M. E., Mortati, A. F., André, T., and Piedade, M. T. F.: Structural
Dynamics of Pristine Headwater Streams from Southern Brazilian Amazon, River
Res. Appl., 32, 473–482, 10.1002/rra.2875, 2016.Bragança, A.: Prices, land use and deforestation: Evidence from the Tapajós
basin, Rio de Janeiro, available at: http://www.inputbrasil.org (last
access: 15 May 2017), 2015.Davidson, E. A., de Araújo, A. C., Artaxo, P., Balch, J. K., Brown, I. F.,
Bustamante, M. M., Coe, M. T., DeFries, R. S., Keller, M., Longo, M., Munger,
J. W., Schroeder, W., Soares-Filho, B. S., Souza, C. M., and Wofsy, S. C.: The
Amazon basin in transition, Nature, 481, 321–328, 10.1038/nature10717, 2012.Eshleman, K. N.: Hydrological Consequences of Land Use Change: A Review of the
State-of-Science, in: Ecosystems and Land Use Change, edited by: Defries, R. S.,
Asner, G. P., and Houghton, R. A., American Geophysical Union, Washington, D.C.,
10.1029/153GM03, 2004.Fearnside, P. M.: Brazil's Amazonian forest carbon: the key to Southern Amazonia's
significance for global climate, Reg. Environ. Chang., 10.1007/s10113-016-1007-2, in press, 2016.Gollnow, F., Göpel, J., deBarros Viana Hissa, L., Schaldach, R., and Lakes,
T.: Scenarios of land-use change in a deforestation corridor in the Brazilian
Amazon: combining two scales of analysis, Reg. Environ. Chang., 10.1007/s10113-017-1129-1, in press, 2017.Guzha, A. C., Nobrega, R. L. B., Kovacs, K., Rebola-Lichtenberg, J., Amorim,
R. S. S., and Gerold, G.: Characterizing rainfall-runoff signatures from
micro-catchments with contrasting land cover characteristics in southern
Amazonia, Hydrol. Process., 29, 508–521, 10.1002/hyp.10161, 2015.
Lamparter, G., Nobrega, R. L. B., Kovacs, K., Amorim, R. S., and Gerold, G.:
Modelling hydrological impacts of agricultural expansion in two macro-catchments
in Southern Amazonia, Brazil, Reg. Environ. Chang., 10.1007/s10113-016-1015-2, in press, 2016.Lima, L. S., Coe, M. T., Soares Filho, B. S., Cuadra, S. V., Dias, L. C. P.,
Costa, M. H., Lima, L. S. and Rodrigues, H. O.: Feedbacks between deforestation,
climate, and hydrology in the Southwestern Amazon: Implications for the provision
of ecosystem services, Landsc. Ecol., 29, 261–274, 10.1007/s10980-013-9962-1, 2014.Neill, C., Deegan, L. A., Thomas, S. M., and Cerri, C. C.: Deforestation for
pasture alters nitrogen and phosphorus in small Amazonian streams, Ecol. Appl.,
11, 1817–1828, 10.1890/1051-0761(2001)011[1817:DFPANA]2.0.CO;2, 2001.Nóbrega, R. L. B., Guzha, A. C., Torres, G. N., Kovacs, K., Lamparter, G.,
Amorim, R. S. S., Couto, E., and Gerold, G.: Effects of conversion of native
cerrado vegetation to pasture on soil hydro-physical properties, evapotranspiration
and streamflow on the Amazonian agricultural frontier, PLoS One, 12, e0179414,
10.1371/journal.pone.0179414, 2017.Ometto, J. P., Aguiar, A. P. D., and Martinelli, L. A.: Amazon deforestation
in Brazil: effects, drivers and challenges, Carbon Manage., 2, 575–585,
10.4155/cmt.11.48, 2011.Pavanato, H. J., Melo-Santos, G., Lima, D. S., Portocarrero-Aya, M., Paschoalini,
M., Mosquera, F., Trujillo, F., Meneses, R., Marmontel, M., and Maretti, C.:
Risks of dam construction for South American river dolphins: A case study of
the Tapajós River, Endanger. Species Res., 31, 47–60, 10.3354/esr00751, 2016.Soares-Filho, B. S., Nepstad, D. C., Curran, L. M., Cerqueira, G. C., Garcia,
R. A., Ramos, C. A., Voll, E., McDonald, A., Lefebvre, P., and Schlesinger, P.:
Modelling conservation in the Amazon basin, Nature, 440, 520–523, 10.1038/nature04389, 2006.Souza-Filho, P. W. M., de Souza, E. B., Silva Júnior, R. O., Nascimento,
W. R., Versiani de Mendonça, B. R., Guimarães, J. T. F., Dall'Agnol,
R., and Siqueira, J. O.: Four decades of land-cover, land-use and hydroclimatology
changes in the Itacaiúnas River watershed, southeastern Amazon, J. Environ.
Manage., 167, 175–184, 10.1016/j.jenvman.2015.11.039, 2016.Thomas, S. M., Neill, C., Deegan, L. A., Krusche, A. V., Ballester, V. M., and
Victoria, R. L.: Influences of land use and stream size on particulate and
dissolved materials in a small Amazonian stream network, Biogeochemistry, 68,
135–151, 10.1023/B:BIOG.0000025734.66083.b7, 2004.Vedovato, L. B., Fonseca, M. G., Arai, E., Anderson, L. O., and Aragão, L.
E. O. C.: The extent of 2014 forest fragmentation in the Brazilian Amazon,
Reg. Environ. Change, 16, 2485–2490, 10.1007/s10113-016-1067-3, 2016.