Modelagem de efeitos das mudanças climáticas sobre o deflúvio e a qualidade de água em bacias hidrográficas do Estado de São Paulo

Abstract

Modeling the effects of climate change on streamflow and water quality of watersheds in the state of São Paulo Climate change and its effects on water resources have been discussed by many researchers and public authorities. These effects will manifest in a very long time scale, affecting the streamflow and water quality for the population. Such effects can be predicted using hydrological models and global climate models (GCM) that provide estimates about climate in the future, based on climate scenarios. This study aims to evaluate the effects of climate changes on the streamflow and water quality and to zoning the hydrological response of watersheds in the state of São Paulo. A regional mapping of the watershed response was generated and critical areas were identified for the stability of water production in the watersheds. Some watersheds will be negatively impacted by the climate, presenting a reduction of the streamflow, and other watersheds will be less affected by the climate, because their physical characteristics constitute a more relevant factor to the water yield. Therefore, it is necessary to give importance to the watersheds of the State of São Paulo due to the urban and industrial concentration in that region. The results provide subsidies to guide public policy and propose ways to manage the land use in watersheds.

How does land use cover change affect hydrological response in the Atlantic Forest? Implications for ecological restoration

“…The "m" values in the Atlantic Forest ecoregions (ranging between 1.2 and 3.6, with an average between 1.72 and 2.30) are compatible with those observed on a global scale by Zhou et al (2015), although these authors estimated "m" values above 4 in some coastal and northeastern regions of Brazil. For the southeast region of Brazil, including the Cerrado biome (Ogasawara, 2020) found "m" values ranging from 1.79 to 3.63 with an average of 2.95, showing that the results are similar. In general, the Atlantic Forest showed a pattern, with mean values of "m" lower than 2.5, demonstrating the hydrological sensitivity of these regions to the change in land use (Zhou et al, 2015).…”

“…Since it is a factor with strong influence on the hydrological response (Shao et al, 2012;Ogasawara, 2020), we chose only sampling points where the slope was lower than 20% in order to reduce its effect. The slope data used were extracted from the Digital Terrain Model (DTM) of the United States Geological Survey (USGS), a product created from the Shuttle Radar Topography Mission (SRTM) data, with a spatial resolution of 30 m (Farr et al, 2007;NASA JPL, 2020).…”

“…Because of this, data that were negative and equal to 0 were deleted from the dataset. Also, the sampling points in which this number of years with negative data was greater than nine were also excluded, so that for each sampling point there were at least 10 years of climatic and hydrological data (Ogasawara, 2020). After data filtering, precipitation, potential evapotranspiration and water surplus ranged from 738 to 1,885 mm, 1,144 to 1,814 mm and 201 to 1,062 mm, respectively, in the ecoregions (Supplementary Table 1).…”

“…Forested areas have higher evapotranspiration than areas with shorter vegetation, so the increase of forests would cause a decrease in water availability (Zhang et al, 2001;Zhou et al, 2015). On the other hand, in the other regions, which do not show this sensitivity to water limitation (lower values of "m"), the increase in forest cover can intensify hydrological processes or even reduce evaporation rates, resulting in increased water availability, which is also gradually amplified on a time scale, constituting hydrologically more resilient areas (Ning et al, 2019;Ogasawara, 2020). This is the case of the Evergreen broadleaved forest (EVER) ecoregion, where the largest natural reserves of the Atlantic Forest are located (Ribeiro et al, 2009), with lower relative variations in responsiveness due to the conversion of pasture to native forest, probably resulting from the high rainfall of the region.…”

Serviços hidrológicos em região de transição Cerrado-Mata Atlântica

“…Considerando que a restauração florestal tende a diminuir a disponibilidade de água local principalmente no período de maior crescimento da floresta (Filoso et al, 2017;Ning et al, 2019), os planos de restauração devem considerar o caráter compensatório entre a assimilação de carbono e o uso de água pelas plantas (produtividade x transpiração) (Jones et al, 2022;Sun et al, 2023). Conforme essas florestas se desenvolvem e atingem um estágio mais maduro, porém, ainda que o processo de evapotranspiração seja alto, a maior infiltração e armazenamento de água no solo moderam e sustentam as vazões em períodos de seca (Filoso et al, 2017;Jones et al, 2022), constituindo áreas hidrologicamente mais resilientes e com maior oferta de serviços hidrológicos (Ning et al, 2019;Ogasawara, 2020).…”