Avaliação temporal de variáveis limnológicas do reservatório Rodolfo Costa e Silva - RS, e o uso da terra na área de captação

Abstract

The relationship between man and environment initially happens in a natural way. After a while, there is an accelerated populational growth, and new technology comes, which intensifies the human actions both in the terrestrial environment and in the aquatic one, imposing, therefore, unbalance in the relation man-nature. Thus, quantitative and qualitatively, the water in the planet finds itself at risk due to pollution. Consequently, the hydrological resources conservation is an increasing concern among public and private organs. Studies and researches concerning the integration of terrestrial and aquatic ecosystems have outstood, aiming at protecting and preserving the environment. Hence, having an integrated approach of both terrestrial and aquatic ecosystems as an objective, prioritazing quality to the environment, this research identified the relation between the limnologic characteristics of Rodolfo Costa e Silva Reservoir - RS and the terrestrial ecosystem, according to the land use and the physical characteristics in the Reservoir dam up area. A geographical data bank was created in the SPRING applicative, which, making use of topographic maps, Satellite images CBERS-2 CCD and of LANDSAT-5 TM and GPS data, made it possible to elaborate thematic maps of declivity, land use, of permanent preservation areas (APP) and of environmental conflicts. From this data analysis result, it was identified that, concerning the use of land in the Reservoir dam up area, what predominated in the agricultural cycles, respectively, were the agriculture, the field and the forest. Regarding the APP located at the drainage marginal areas and around the springs and the Reservoir itself, according to the up-to-date federal environmental legislation, it was verified that the place presents more than 72% of the APP with environmental conflicts. As for the relief declivity classes, the study area is mainly represented by plain forms and some slightly wavy ones. About the Reservoir limnologic characteristics evaluation, the greatest differences happened in the variables total of solids in suspension (TSS), water transparency and hydrogen ion concentration (pH). Therefore, it can be inferred that the higher alterations presented by the limnologic variables from Oct. 20, 2005 through Sep. 26, 2006 are linked, in a general way, to the first (10/20/2005), second (11/18/2005), fourth (01/06/2006), seventh (03/25/2006) and thirteenth (09/26/2006) field collections, associated with the use of land destined to the agriculture classes (especially exposed soil) and field; and to the influence of the highest pluviosity registers occurred 26 and 7 days prior to the field collections. The differences in how to use the land provided distinct limnologic compartments, which points out to the influence of the terrestrial ecosystem in the aquatic one in the Reservoir.