Vulnerabilidade dos recursos hídricos na mesorregião metropolitana de Belém, Pará.

Abstract

The vulnerability of water resources (VRH) was analyzed under three different cartographic scales, applying remote sensing techniques on different sensor products, TM/Landsat-5 and 8 for cities, RapidEye for mesobacias and orthophotos for micro catchments. Through a hybrid approach, first, by the use of these images and, also, by the application of supervised classifi-cation techniques MaxVer and GeoBIA. One of the VRH study parameters derived from the results of these analyzes, which was the LUCC. The other parameter, the Anthropogenic Pres-sure. VRH was the result of map algebra of these two parameters. The multitemporal diagnosis of MRMB in the years of 1984, 1994, 2008 and 2017, showed the tendency of increasing the classes of land use, Non Forest (NF) and Anthropic Areas (AA), in general, with the decrease of the classes of land cover, Forest (FL) and Secondary Formations (SF), with emphasis on the period from 1994 to 2017, where FS decreased by 1,234.04 km2 and NF increased by 554.79 km2. Also, classes for the pressure parameter were defined, in order to associate them numerically with those of LUCC, where the algorithm of natural breaks was applied. It was identified the reduction of FL in the four micro catchments for the period from 2011 to 2015, reaching a quantitative of 35.21 km2 in the Caraparu river basin, 18.47 km2 for Guajará-Açu, 24.12 km2 for Tauá and 0.75 km2 for that of Apeú. In the watersheds, FL and AA were predominant, in which the Ariri and Maguari-Açu basins were most impacted, with 60.88% and 54.55%, respectively, of their territories occupied by AA. To justify such changes in the landscape, drivers of change were pointed out and discussed. The VRH study revealed that in the Mesobacias there was a decrease in areas of vulnerability with low degree and increase of moderate degree, with emphasis on the Apeú basin, where the first one decreased by 10.94% and the last in-creased by 12.21%. For the micro catchments, considering the sum of the classes of the High and Very High grades, Ariri presented 36.45% and Maguari-Açu 45.59%. Similarly, the groups of basins presented regions of higher degree of VRH closer to the smaller watercourses, up to 30 m, as well as their sources. The Complementary Analyzes contributed towards the visualization of the problem in another perspective, such as the increasing fragmentation of the forests, as well as the vulnerability of the surrounding areas of the rivers, the APP.