Surface water quality and geogenic process in the quillcayhuanca and shallap streams, huaraz-Peru

Abstract

This research developed because, given the evidence of previous studies, it is necessary to determine the chemical quality of the water in the Quillcayhuanca and Shallap streams, which surround the city of Huaraz on its way to the Santa River, on the western slope of the Cordillera Blanca in Peru. In this sense, the investigated area is located at altitudes between 3524 m.a.s.l. and 4174 m.a.s.l. Twenty-four surface water samples were collected and analyzed for anions, metal, and total cations at the INGEMMET laboratory, Geological, Mining, and Metallurgical Institute of Peru. Likewise, geological mapping was carried out to identify the mineralized and chemically altered areas, evidencing the significant presence of sulfides (pyrite). The waters of the streams have been characterized as magnesium calcium sulfate, with SO4= anion contents of up to 181.10 mg/L in the Quillcayhuanca stream and 78.8 mg/L in the Shallap stream. Likewise, for both streams, an oxidized acid environment has been determined. The oldest stratigraphic unit corresponds to shales and sandstones of the Upper Jurassic Chicama Formation. The igneous rocks are made up mostly of granodiorites and tonalites corresponding to the Batholith of the Cordillera Blanca from the Neogene-Miocene. The Quaternary is represented by glacial, glacial fluvial, morainic and fluvial deposits. Regarding the chemical quality of the water, some elements exceed the environmental quality standards (ECA) for "Surface water intended for the production of drinking water" such as Al, Fe, and Mn. These elements are due to geogenic factors, given the presence of sulfides in the exposed rocks in the upper parts of the ravine plus the alteration of aluminosilicates in the exposed rocks.