Proposta conceitual para a regionalização de vazões / Conceptual proposal for the hydrologic regionalization

Renata del Giudice Rodriguez

The knowledge water availability through hydrographic net is fundamental to management water resources concession use rights. Normally this knowledge is restrict to the places where exist fluviométrica measurement station. Hydrologic regionalization is a technical tool to supply lack of information where there are few or no data availability. From a socio- political point of view, the San Francisco basin is Brazils most important river basin, as it covers the Southeast, Center- West, and Northeast regions. A better understanding of water availability along the hydrography net will help to smooth the political decision-making process. However, some specific difficulties need to be considered in order to implement the hydrologic regionalization, for example: reservoir effects in river flow, decrease discharges discontinuity when change from an homogenous hydrologic environment to another, river drying in some seasons of the year and contribution variation in tributaries in both side of the main river. The importance of hydrologic regionalization technique to know the water availability it is one of the most important tool to water management in this basin. The objectives this work are: to develop and to apply to the San Francisco basin a new conceptual framework for the regionalization of average and minimum discharges; to evaluate the use of minimum discharges variables throughout the year to characterize water availability; and to evaluate the differential impact of natural discharges with respect to observed discharges for the Paracatu basin. The regionalization was built on average long term discharges (Qmld), minimum discharge with ten years return period (Q7,10), discharges related with permanence of 90% (Q90) and 95% (Q95) and this Q95 related with the month of the largest water availability (January) (Q95jan) that was applied to all São Francisco basin. Two methods of regionalization were used: traditional and conservation of masses (MCM). The variables independent were drainage area, equivalent discharge relate to rain volume and the equivalent discharge to rain volume taking in account the decrease of hydrological inertia 700 mm (Peq700) and 750 mm (Peq750) (which consist of the annual average precipitation less the hydrological inertia of 700 or 750 mm multiplied by the area becoming m3 s-1. The regionalization model selection was base on the analysis of the relative residues, runoff coefficient (C) in the case of the average discharges regionalization, and the minimum specific flow in the case of the minimum discharges regionalization. Where possible, an evaluation of the relationship between Q95jan and Q95 was conducted. The impact of the use of natural flows in the Paracatu basin was estimated for the average long-term discharges and the minimum discharges. The results show that: a) the traditional method best represents the behavior of average and minimum discharges in the San Francisco basin; b) the physical limits for Qmld (CE) and for the minimum discharge (minimum specific discharge) showed to be possible to reduce the risk of the extrapolation of the equations of regionalization; c) regionalization equations for the average long-term discharges and minimum discharges (Q90; Q95; Q7,10) which consider average annual rainfall less the hydric inertia are more precisely estimated in most of the San Francisco sub-basin; d) the hydrologic regionalization, considering different interactions in the sub- basins and in the San Francisco river, allowed the reduction of the current discharge discontinuity of the individualized analysis of each homogeneous hydrological region; e) the comparison of the regionalization between Q95jan and Q95 shows the potential of variable discharges along the year for better characterization of the water availability; and f) the impact of the use of natural discharges in place of observed discharges in the Paracatu basin are insignificant in the estimation of average long-term discharges and are reasonably significant in the estimation of minimum discharges.

Proposta conceitual para a regionalização de vazões / Conceptual proposal for the hydrologic regionalization

AUTOR(ES)

DATA DE PUBLICAÇÃO

RESUMO

ASSUNTO(S)

ACESSO AO ARTIGO

Documentos Relacionados