The main goal of this paper was to investigate possible relations between water quality and land use in public water-supplying watersheds in the state of Goias. Thus, data from 174 catchments, operated by Saneamento de Goias were compiled, corresponding to January/2002 - December/2004. Annual, drought and flood season means for turbidity, apparent color, pH, chloride and total and fecal coliform indices (ICT and ICF) were reported and summarized by principal component analysis, into a water quality index (IQA), Based on the land cover map for Goias, at the 1:250,000 scale, and on a SRTM (Shuttle Radar Topography Mission) mosaic, 89 water-supplying watersheds were delimited, for which a normalized remaining vegetation index was calculated. Apparent color, turbidity, pH, ICT and ICF did not achieve the required legal standards in up to 62.43% of the catchment data analyzed, particularly in the flood season, when the worst IQA values are observed. Our results demonstrate that the IQA utilized is responsible for both the seasonal variations and apportion of sediments and organic matter, via superficial run-off. Likewise, this index is also slightly related to the regional NRVI variations. In order to better determine these relations, further studies are needed, taking into account other water quality parameters (e.g. nitrogen and phosphorous) and different landscape scales (e.g. riparian zone).
Land use; water quality and IQA
