Limiar da variabilidade do escoamento: Estação Palmares/PE.

Abstract

In Brazil, Law 9,433/97 was instituted, which is based on decentralized and participatory water management, with the hydrographic basin being the planning and management unit, using five instruments, among them, the grant, which has a regulatory character, conditioning the user the right to use the water for a certain period. In view of the different modalities of uses, allocating the quantities of water in view of the water availability in a watershed is a complex activity, given the fulfillment of grant-free demands, the need to maintain ecological/environmental flow, in addition to the priority of demand: human supply and animal watering. It also integrates atypical climatological events that significantly increase riparian variability. Traditionally, granting criteria with a fixed reference value throughout the year are used in management systems. The study area includes the watershed of the river Una (Pernambuco/Brazil), through the daily fluviometric series of the Palmares station (Period: 01/01/1977 to 12/31/2014). The methodology uses the separation of flows, starting from the lower limit of fluvial variability and calculation of indices to measure the domain of delimited flows. The results indicated, in view of the historical series: an average variability of 23.01% in the months from May to August, focusing on the years with the greatest water abundance; and the average variability of 17.51%, also from May to August, in years with lower water load. The results are expected to support decision-making from two perspectives: using the proportion of such variability as a guarantee of the environmental flow; and in greater water security, offering values above the reference flow, respecting this threshold or greater proportion, making better use of water that, in some cases, normally cannot be captured/consumed, due to the limit imposed by the system.