The main objective of the Diagnostic Project on Hydrographic Basins in the Municipality of Viamao for an Integrated Management of Micro-basins is to gather information in cartographic databases that can be used by the Municipality as tools to plan and manage, by considering hydrographic micro-basins as basic working units.

The Municipality of Viamao, that covers an area of 1.494,2 km2, is located in the south-east Metropolitan Region of Porto Alegre, State of Rio Grande do Sul (Brazil). The Municipality’s watercourses are divided into three main basins: the Gravatí River Basin (RG), the Guaíba Lake Basin (LG), and the Laguna dos Patos Basin (LP). Their landscape ranges from granite hills to the west, smooth hills in the central strip and broad wetlands to the north and south-east. With a population of 226.669 inhabitants (IBGE, 2000), 93% concentrate in a little industrialised urban area, where low-income dwellings are predominant. The rural area includes small farming areas, vacation resorts, large extensions dedicated to rice fields and cattle-breeding stations.

The bibliographic collection by different entities oriented and enabled the generation of some of the thematic maps on the basis of existing material. The digital cartographic database was created from 9 scale sheets 1:50.000 (MI 2970-1, 2971-3, 2971-4, 2987-2, 2988-1, 2988-2, 2987-4, 2988-3 and 2988-4) of the Geographic Services of the Army, and the first six have already been digitised by Metroplan. With the help of AutoCad 14 software it was possible to upgrade all information concerning the network of roads, rivers, topography and municipal boundaries. To this end, existing maps were compiled, field observations conducted and stereograms used. The maps on this cartographic base, according to the equipment available, have been plotted with the 1:60.000 scale.

The borders of the Environmental Protection Area of the Banhado Grande and the State Park of Itapuá were digitised. These are preservation units that will become compulsory information on the municipal official maps generated by this work.

According to this project, the sub-division of the hydrographic network indicates a total of 16 micro-basins as follows: Banhados dos Pachecos (RG01), Pesqueiro Stream (RG02), Fiúza Stream (RG03), Alexandrina Stream (RG04), Estancia Grande (RG05), Aguas Belas Stream (RG06), Feijó Stream (RG07), Dilúvio Stream (LG01), Taquara Stream (LG02), Varejao Stream (LG03), Xambá-Estância (LG04), Itapuá (LG05), Capao da Porteira (LP01), Lagoa do Mato (LP02), Costa do Oveiro (LP03) and Lagoa Negra (LP94).

The map on the use of the soil and vegetation was prepared by the Ecology Centre of the UFRGS through the classification of a Landsat satellite image with the help of IDRISI software which resulted in classes of water, wetlands, shrubs, re-forestation, reeds/xerophilous shrubs, humid areas, dry lands, agriculture requiring irrigation, rice fields, exposed soils, sand, low, medium and high-density urbanisation.

The geological map, produced on the basis of the unpublished existing one, has been rasterised and vectored although it has not yet been possible to incorporate it to the adopted cartographic base.

The map showing mineral extraction areas, industries and disposal of sewage effluents was prepared on the basis of existing information at the Municipal Prefecture, the analysis of air photos and field observation. The mineral extraction points include quarries of all kinds as well as sand extraction sites, divided into regular and irregular legal exploitations, identified according to their DNPM registration number or owner.

Industries were identified according to their permanent addresses in the Prefecture’s registry and due to field knowledge on the part of Environmental Department inspectors. Among the most outstanding industries within the Municipality some specific industries and services were chosen, as their activities represent a higher potential contamination risk, as is the case of plastic, acrylic and fibre industries; metal production and beverage industries; dairy and sausage industries; cereal processing plants and pump stations.

The plots were delimited according to the chart blueprints. In addition to the boundaries of the individual plots, the road grid, the level curves and the plant cover and soil use charts, it was possible to determine segments of watercourses located inside the most densely populated areas. This information, together with the Municipality control reports allowed us to define and chart the segments of watercourses polluted by effluents from local sewage.

The chart of the sectors studied was made by the Ecology Centre of the UFR (RG) with data provided by IBGE. The task consisted of providing a geo-reference of the census units and setting up a database with the socio-economic data of the IBGE for each unit.

Also, as part of the present project, it was possible to obtain through a grant by Corsan a digital cartographic base in a 1:10.000 scale better suited to work in the urban milieu. It shows the hydrography, road grid, and 5 metre distant level curves. As in the 1:50.000 chart base it was necessary to standardise the symbols, make corrections and to update the road network.

The green areas of the urban zone were identified by the Department of the Environment in a 1:20.000 scale map and digitised to a cartography base 1:10.000 scale. Also drawn in this scale are maps of the Participatory Budget regions, master plan and waste collection routes.

Among the first materials produced we must point out, according to the objectives of this project, those of the Integrated Programme for the Recovery of Degraded Areas being implemented in the Feijó Stream Hydrographic Micro-basin. In this specific micro-basin the location of all green areas and schools is already part of the cartographic database whose products have been used to plan, discuss and proceed with environmental education activities that schools use as strategic units for dissemination; for example, the selective waste collection campaign, preparation of tree seedlings, and cleanup activities in public squares and riverbanks. According to the growing demand for information generated, this work has been highly accepted and acknowledged, and has demonstrated it can be an essential tool in municipal public administration decision-making processes and in involving the community through dissemination of knowledge on natural resources of the Municipality and their condition.

The implementation of the project is the result of an agreement between the Municipal Prefecture of Viamao, the Ecology Centre of the UFRGS and the Itapuá State Park Commission in their struggle to make this park effective. It also received help in the way of funds granted by the International Development Research Centre of Canada.