Scenarios for Sand Mining Activity in Guaíba Lake, South of Brazil

Abstract

Guaíba lake, located near the Metropolitan Region of Porto Alegre, is the main source of raw water for the nearby municipalities. In the last decades, the bottom sediment was exploited to provide sand to the region's construction market. However, the mining activity was paralyzed after complaints of environmental damage. Therefore, the continuity of the activity was conditioned to the previous Guaíba Lake zoning. The present study intends to contribute to this zoning proposal, structuring spatial information about Guaíba Lake and later, using InVEST ecosystem models - Integrated Valuation of Ecosystem Services and Tradeoffs to propose the modeling of distinct zoning scenarios for sand mining activity. The different scenarios considered, in different levels of restrictiveness, physical and environmental aspects of the lake. Points that attract human activities were inserted into the model as Hotspots. To evaluate the overlapping use, we obtained maps of the Frequency of Overlapping Use and Use Importance. In view of the developed scenarios, the areas with no restrictions and with lower degrees of importance for human activities were considered more suitable for mining activity. Scenario A, or Conservationist, presented mining restrictions in 76% of the study area. Scenario B, Developmental, resulted in 28% of mining restrictions. And, finally, Scenario C, Management, resulted in 50.1% of mining restriction. The results present in an integrated way the main aspects to be observed in the proposition of a mining zoning for Guaíba Lake, supporting the decision-making process.