Relação da variabilidade climática e os índices de seca com a qualidade da água em reservatórios de abastecimento público na bacia hidrográfica do Rio Paraíba

Abstract

In the last decades, the process of environmental degradation has intensified, especially in different regions of the planet, causing deforestation, disorderly practices in crops, fires, irregular irrigation and pollution by chemical derivatives in plantations that provide contamination in water, underground and altering the physical-chemical parameters of the water. Therefore, such factors favor the increase in temperature and irregularity of precipitation, putting the wild flora and fauna at risk. Therefore, it is necessary to evaluate the effect between the climatic variability of the Paraíba River Basin (BHRPB) and the Drought Indexes with the physicochemical quality of the water and the presence of cyanobacteria in some reservoirs of public supply of the BHRPB, in the state of Paraíba. In the development of this research, monthly rainfall data from the Superintendence for the Development of the Northeast, the National Institute of Meteorology and the Executive Agency for Water Management of Paraíba were used. The temperature and relative humidity data used in this study were made available by a joint project between the University of Texas (USA) and the Federal University of Espírito Santo (Brazil). From the correlation between the following drought indices: Normal Percentage Index (IPN), Decis Method (MD) and Rainfall Anomaly Index (IAC), it was proposed to create a new index called Drought Severity Indices. (ISS). The statistical methods served in several aspects, initially to fill in gaps that existed in the rainfall data in some years in the municipalities. According to the results obtained, the proposed new IS proposition, streamlining the IAC, IPN and MD methods, contributed to the simplicity of the analysis of the rainfall characteristic in the region. Being the IAC method, presenting more representative results in the annual scale, and the MD in the monthly scale. Thus, using the annual scale on the ISS, it was possible to show 26 dry years and 14 wet years, ranging from ES to EU. In addition, it is noteworthy that the variables "S and U" occurred in more than 57.5% for the BHRPB, "MS and MU", together presented 25%, while the years of "ES and EU" presented 17.5 %. However, it is in these contexts that greater attention is needed on the part of the management of water resources. Regarding the monthly ISS, six months were characterized as "EU and ES", three months as "MS and MU" and three months as "S and U". Therefore, it was noted that extreme values are more likely to occur in the monthly analysis than annual, since its intensity and characteristics in the sum form the annual scale. It was possible to verify that in relation to the ISS and cyanobacteria, the Borborema and Acauã reservoirs demonstrate that the largest amount in the dry period, in the reservoirs of Gavião and Massaranduba, is present in the rainy season.Finally, the species that predominate in this region are Cylindrospermopsis raciborskii and Pseudanabaena catenata, present in all reservoirs.