Application of indices for water resource systems stress assessment

ABSTRACT This paper aims to present a methodology to conduct a water stress assessment of water resources systems through indices. The proposed methodology was applied to Cantareira System, which is one of the most important water supply systems of São Paulo Metropolitan Region (SPMR). The authors used two indices to support this evaluation: Normalized Deficit Index (NDI) and Normalized Deficit Cumulated (NDC). Both of them consider only the natural flow as the renewable source of water (supply), and account for natural and anthropic uses of this water (demand) as a way to determine the dependence level that the area relies on endogenous and/or exogenous sources of water to meet its needs. To support this assessment, two meteorological drought indices were used as well: the Standardized Precipitation Index (SPI) and Drought Magnitude (DM). The diagnosis of a water supply system, a country, region or even district, based on indices that represent the local water risk, is extremely important not only to bring a better understanding of extreme events, such as droughts and floods, but also to support strategic decision-making process regarding water resources management. This sort of assessment is a useful tool, for instance, in indicating eventual necessity of water storage, such as large reservoirs, or interbasin water transfers, which could improve the water security levels of the study unit.