The objective of this work is to present the methodology used in the project “Vulnerability Mapping and Groundwater Pollution Risk in the State of São Paulo, Brazil”, implemented by the DAEE, CETESB and Institute of Geology, and intended to be a risk assessment procedure to evaluate the threat of groundwater quality deterioration using existing data. Such method is based on the interaction between the natural aquifer vulnerability and an imposed contaminant load generated by human activities, and aims to identify critical areas to prioritize the adoption of control measures and more intensive quality monitoring. This paper describes the principles used in the assessment of the contaminant load generated by industries, solid waste disposal and mining activities in the State. More than 500 industries were identified as important groundwater potential pollution sources, and a criterion of ranking their capability to generate contaminant loads to the aquifer was|established.
In 1984, in Taubaté County, Brazil, a study was carried out to identify the groundwater pollution due to land disposal of chemical industrial wastewater. After characterization of the wastes, some analytical parameters were selected for a monitoring programme: TOC, COD and electrical conductivity. This programme was started after a network of 39 monitoring wells was installed. The water level was determined monthly and four times a year samples from the groundwater were collected for chemical analysis. The data were interpreted by a computer program (SYMAP) which produced hydrochemical and isopotential maps. The interpretation of these maps shows groundwater pollution due to wastewater infiltration and the limit of the pollution plume was the adjoining stream. In addition to determining the horizontal trend of pollution into the aquifer, research is necessary to verify vertical pollution, in order to evaluate the degree the aquifer has been compromised.
The geomorphological map of the Lake Tana basin (15,077 km2, Nile basin, Ethiopia) presented in this paper was prepared from fieldwork data, maps and satellite data that were processed with a geographic information system (GIS). It contains four major components: (i) hydrography, (ii) morphology and morphometry, (iii) materials and (iv) processes at a scale of 1:500,000. The geomorphological setting of the basin consists of lavas that erupted from fissures or (shield) volcanoes during the Tertiary and Quaternary eras, were uplifted and eroded primarily by water. Lake Tana emerged through a combination of a lava barrier blocking the Blue Nile to the south and by epirogenetic subsidence. When the lake reached its maximum extent, extensive lacustrine plain (e.g. Fogera and Dembia plains) were created, river valleys and basins were filled with sediment and higher lying topography was eroded. Today, the lake plays a lesser role in landscape formation because of a decreased extent (3041 km2) compared to the ancient maximum (6514 km2). Dominant processes today are fluvial and subaerial. Recent (1886–2010) changes in the lake coastline are small with the exception of the delta formed by Gilgel Abay, which has increased disproportionally over the last 15 years. This indicates a large input of sediment which is mainly due to rivers flowing through Quaternary lavas. The recent sediment input increase is most probably related to human induced land-use changes.
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