Avaliação da dinâmica hídrica da sub-bacia hidrográfica do rio Paramirim no estado da Bahia, Brasil.

Abstract

To assess the water dynamics of the Paramirim River Watershed Sub-Basin (SBHRP), predominantly located in the Caatinga Biome, hydrological data from the period 1977 to 2019 were used. The SBHRP is a tributary of the right bank of the São Francisco River basin, belonging to the Water Planning and Management Region XX of the state of Bahia, entirely located in the Bahian semi-arid region, in the so-called Drought Polygon. The sub-basin covers an area consisting of twenty-four municipalities, with its mouth located in the municipality of Morpará, and its source in the municipality of Érico Cardoso, with a total area of 17,942 km². The climate of the study area varies from semi-arid to sub-humid. Temperatures fluctuate, on average, between 19ºC and 25ºC. Rainfall tends to concentrate between spring and summer, with annual precipitation ranging from 800 to 500 mm in the driest areas. The methodology called Advanced and Experimental Hydrology (HAE) proposed by Gonçalves (2004) was used, which presents itself as a new alternative for observing flows in a watershed by associating them with precipitation, allowing for an integrated evaluation with the Mean Lag Time (TRM), expanding the basic use of usual concepts of lag time, concentration, or delay, as they are known, and allowing the interaction between surface and groundwater. The results demonstrated the effectiveness of using this methodology in identifying the influence of precipitation and the aquifer on the composition of flow formation in this sub-basin and confirming the importance of climatic and physiographic factors in flow formation. Based on the classification of the watershed using the Mean Lag Time (TRM) <30 days or ≥30 days, we can classify watersheds into two typologies: impermeable basin or permeable basin. The Mean Lag Time (TRM) is of paramount importance for hydrological analysis studies; these data provide information that enables better management and planning of water resources in the SBHRP. Knowing flow data allows identifying periods of high and low flow and thus maintaining water volume with greater availability for riparian populations and surrounding areas. The possible use of Paramirim River water, especially water from the Zabumbão dam for a project to supply other downstream cities, may generate new conflicts over water use, mainly among farmers living near the dam, as in case of a water crisis, human supply and animal watering take priority. Conclusions about the experienced parameters reveal that the Paramirim River Watershed Sub-Basin could be classified as permeable, with TRM