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Volume 377
Proc. IAHS, 377, 3-7, 2018
https://doi.org/10.5194/piahs-377-3-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Proc. IAHS, 377, 3-7, 2018
https://doi.org/10.5194/piahs-377-3-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

  16 Apr 2018

16 Apr 2018

A multi-approach and multi-scale study on water quantity and quality changes in the Tapajós River basin, Amazon

Rodolfo Luiz Bezerra Nóbrega1,a, Gabriele Lamparter1, Harold Hughes1, Alphonce Chenjerayi Guzha2, Ricardo Santos Silva Amorim3, and Gerhard Gerold1 Rodolfo Luiz Bezerra Nóbrega et al.
  • 1Department of Physical Geography, Faculty of Geoscience and Geography, University of Göttingen, Göttingen, Germany
  • 2USDA Forest Service, International Programs, c/o CIFOR, World Agroforestry Center, Nairobi, Kenya
  • 3Department of Soil and Agricultural Engineering, Federal University of Mato Grosso, Cuiabá, MT, Brazil
  • anow at: Department of Geography & Environmental Science, University of Reading, Reading, UK

Abstract. 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 ( < 1km2) 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, 37400km2), 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.

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We analyzed the impacts of deforestation on water quantity and quality in the Tapajós River, one of the main tributaries of the Amazon River. To that end, we used data from 2 years of fieldwork as well other state-of-the-art techniques in small and large areas of this study area. We found changes in water quality and quantity across small and large portions of this area. Our results show that some impacts of deforestation usually observed in small streams are also affecting the major river.
We analyzed the impacts of deforestation on water quantity and quality in the Tapajós River,...
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