Mudanças no uso e cobertura do solo e resposta hidrológica da bacia do rio Piracicaba

Abstract

Land use/land cover changes and hydrological response in the Piracicaba river basin This study aimed at to evaluate the effect of changes in land use and land cover over the last 37 years (1972 to 2008) on the hydrological response in the Piracicaba river basin, SP. The main changes in the land use and land cover in the basin over that period were the increase in the urban area, decrease in the pasture area, and increase in the sugarcane plantations. Moreover, the basin has a peculiarity, which is the presence of the Cantareira System, which diverts water to the metropolitan region of São Paulo (RSMP), since 1974. We used a hydrological model of Great Basin (MGB), which has the advantage of evaluating in the distributed form, the variation of the land use/land cover, besides the flow propagation. The model was adjusted to the Piracicaba river basin (12,245 Km 2 in area) to simulate daily streamflow. Daily data, from 1972 to 2008, were used for the process of model fitting, from 12 streamflow stations, 61 rainfall and 20 meteorological, digital terrain model, maps of soils and land use and land cover (for the years 1978, 1983, 1985, 1997 and 2003), and parameters that are important to differentiate soil types and uses and land cover. The process of simulation of the streamflow was carried out in two stages: calibration of parameters (from 1972 to 1990) and verification (1991 to 2008). To assess the quality of fitting it was considered the visual analysis of the hydrographs (observed and calculated streamflows) and the values of objective functions (R2, Rlog and ∆V). We performed a sensitivity analysis of each parameter, in order to verify the influence of each one. The results showed a good fitting between the daily observed and calculated streamflows. The best results of the objective functions were obtained for the sub-basins of larger drainage area. The Cantareira System strongly influences the simulation of daily streamflow. Sensitivity analysis of parameters revealed that the simulation results of the model are extremely sensitive to variations of the parameters: soil water storage capacity (Wm), form parameter of the relationship between storage and saturation (b), parameters of drainage underground (K BAS) and subsurface (K INT), albedo and surface resistance (r S). Alternative scenarios for changes in the land use and land cover were tested and compared the simulation of the scenario actual of Piracicaba river basin in the period between 1972 and 2008. Comparing the scenario with no changes in the basin since 1972 to the actual scenario, a reduction in streamflow was detected: maximum of 2,5 m 3 /s, minimum of 2,1 m 3 /s, and an average of 1,9 m 3 /s. Other scenarios were tested and compared to the actual scenario, and it was detected an increase of the mean streamflow of 17,2 m 3 /s for scenario 100% of agriculture, and a decrease of the mean streamflow of 3,9 m 3 /s for the scenario of conversion from agriculture into pasture.

Deforestation impact on discharge regime in the Doce River Basin

“…The results suggest a rise in flood possibilities due to deforestation processes, which are consistent with the results found by Bayer (2014) and Andreassian (2004). On another hand, deforestation process results in the reduction of the annual minimum flows, also are in agreement with the previous papers (Caram, 2010;Beserra, 2016). The increase in floods caused by deforestation can be attributed to the hydrological role of surface water absorption forests and the regularization of liquid flows, avoiding floods.…”

“…This result indicates a decrease in annual mean flows in deforestation scenarios, which is in agreement with the average behavior of the results obtained in experimental basins (Bosch and Hewlett, 1982;Collischonn, 2001). However, Caram (2010) and Beserra (2016), when performing hydrological simulations using MGB-IPH in watersheds located in the Brazilian Southeast region, as well as in the Doce River Basin, also found results contrary to the average behavior observed in experimental basins. Additionally, during long drought periods, the average flow tends to suffer more influence from the base flow, which reduced the average annual discharge.…”

“…The Large Basin Model (MGB-IPH) is a hydrological model that has been applied to determine the impacts of changes in land use on the hydrological regime in different types of climate and vegetation. Caram (2010), Bayer (2014) and Beserra (2016) conducted studies on the impacts of changes in land use in watersheds using MGB-IPH.…”

Análise do albedo da superfície e índices de vegetação por sensoriamento remoto na bacia hidrográfica do rio Pacoti/CE

“…Há relatos de que áreas com cana-deaçúcar apresentam albedo na faixa de 0,16 a 0,20 (Gomes, 2009). No entanto, também podem ser observados valores entre 0,18 a 0,22, os quais podem representar pastagens, áreas com grande densidade de plantio e agricultura (SILVA et al, 2005;CARAM, 2010).…”

Dynamic modeling of native vegetation in the Piracicaba River basin and its effects on ecosystem services

“…The examples presented here are clear current topics of great importance in the State of São Paulo, Brazil and especially in the Atlantic Forest region TEIXEIRA et al, 2009;CARAM, 2010;DA SILVA, 2012;FARINACI;BATISTELLA, 2012;FERRAZ et al, 2014).…”