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UBC Theses and Dissertations

Land use effects on green water fluxes in Mato Grosso, Brazil Lathuillière, Michael Jacques


The blue water - green water paradigm has been increasingly used to describe water resources. Blue water represents liquid flows in rivers or aquifers, while green water (GW) represents vapour exchanges with the atmosphere either as evaporation from soil or as transpiration from plants. This study assesses the impacts of land use change on GW fluxes in the Brazilian state of Mato Grosso, an ideal candidate for the study of GW in light of recent deforestation for pasture and soybean expansion, and the near complete reliance of its agricultural land base on precipitation as the GW source. Fluxes were estimated for 2000-2009 by combining the MODerate Resolution Imaging Spectroradiometer (MODIS) evapotranspiration product with forest cover change from Brazil’s National Institute of Space Research (INPE), as well as guidelines from the Food and Agriculture Organization (FAO) to model soybean, maize, sugar cane, cotton and pasture GW. In 2000, forest cover represented one third of the state’s land base and returned half of the state’s water vapour to the atmosphere. Annual total GW volumes decreased by 10 % between 2000 and 2009 at a rate of 16.2 km³y⁻¹ per year. Deforestation explained up to 27 % of variance in annual total volumes while agricultural expansion, as cropland and pasture, explained up to 20 %. Cropland GW doubled within the study time period, 75 % to 83 % of which constituted soybean GW. Pasture GW was 5 times larger than soybean GW and offset the increase in cropland GW. The greatest uncertainty lies in the role played by residual land use GW fluxes which were attributed to Brazilian savanna (cerrado), the Pantanal wetland, as well as unaccounted agricultural land left as fallow.

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