Regionalização do índice de estresse hídrico WSI para o nordeste brasileiro

Abstract

Both water scarcity models Water Stress Index (WSI) and AWARE, applied in the Life Cycle Impact Assessment (LCIA), were recommended for use in Brazil as long as a regionalization process is carried out to increase their sensitivity to regions with events of water scarcity, such as the northeastern region of Brazil. Previous work regionalized the AWARE model for the 449 State Hydrographic Units (SHUs) in Brazil defined by the National Water Agency (NWA). The objective of this work was to generate regionalized monthly and annual factors (WSI-BR-NE) for the 146 Northeastern SHUs of Brazil to enable a future sensitivity analysis of the results, considering the application of different models for the calculation of the impact caused in the water scarcity. For this, national hydrological data, hydrogeographic limits of the SHUs proposed by NWA and the aggregation of precipitation data from rainfall stations (RS) in SHUs were used. Qualitative comparisons were made to verify the difference between WSI and WSIBR-NE, and quantitative comparisons, using the Geometric Standard Deviation (GSD²), to verify the proximity of the results of the models WSI, WSI-BR-NE and AWARE-BR, in which the closer to zero, the closer the results are. As a result, annual and monthly WSI-BR-NE factors were obtained for the 149 SHUs. After analyzing the annual WSI-BR-NE, it was observed that 97 SHUs were categorized as Very High Water Stress (VHWS) and the regions that concentrate the largest number of these SHUs are in the state of Ceará and Rio Grande do Norte. Analyzing the monthly WSI-BR-NE, it was identified that October is the month with the most intense water scarcity, with 110 (75%) SHUs classified as VHWS. On the other hand, April was the mildest month, with 51 (35%) SHUs classified as Low Water Stress (LWS). In the qualitative comparison, it was observed that 112 SHUs rose from the category of water scarcity and 128 SHUs obtained greater factors in WSI-BR-NE. The biggest increase, of 9105%, was found for SHU Dos Frades, Buranhém and Santo Antônio (Bahia), while the biggest reduction (50%), in SHU Traipu (Alagoas). In addition, the use of the annual WSI resulted in 99.7% of the Northeast area classified as LWS, against 26% of the annual WSI-BR-NE. In the quantitative comparison between WSI and WSI-BR-NE, GSD² of 112 was obtained for the annual factors and 154 as the maximum value of the monthly factors. Between WSI-BR-NE and AWARE-BR-NE, the GSD² was 46 in the annual analysis and 113 as the maximum value in the monthly analysis. These results show that regionalization has generated factors more adjusted to the water scarcity experienced in the Northeast, and can be proven in a joint analysis with ANA reports and government mechanisms (Drought Monitor), in addition to scientific studies already carried out in the Northeast, being useful for use in public policies, research and decision making and reducing uncertainties in studies of water scarcity of products in Brazil.