Properties of water equal to that of the hydrogen ion (), which gives a pH of 7 at 25 °C. Action of water on rock over long periods of time typically leads to weathering and water erosion, physical processes that convert solid rocks and minerals into soil and sediment, but under some conditions chemical reactions with water occur as well, resulting in metasomatism or mineral hydration, a type of chemical alteration of a rock which produces clay minerals. It also occurs when Portland cement hardens. Water ice can form clathrate compounds, known as clathrate hydrates, with a variety of small molecules that can
Water management in the Metropolitan Region of São Paulo developed from the Iguape river in the Ribeira valley 80 km to the south of MRSP. Furthermore, the efficiency of existing water use is expected to be increased through more reuse of treated wastewater and further reductions in water losses. The first modern water supply system for São Paulo was built by a private company, the Cantareira Water Supply and Drainage Company of the City of São Paulo, in the 1880s. The company built a pipeline from the Cantareira mountains in the North to São Paulo, which would become the first element of what would later become the Cantareira system