Simulação de modelo de cobrança pelo uso da água subterrânea: estudo de caso aquífero Barreiras, Maceió - AL

Abstract

Groundwater is of great importance in Brazil's water supply. Because of this, this resource has been undergoing overexploitation, since there is still no effective application of management tools to inhibit unrestrained use. The best-known and most widely used tool is water allocation, but, in many cases, its implementation alone is insufficient to preserve water resources. Another management tool that has been disseminated throughout the country, and whose implementation is foreseen by law, is the charging for the use of water, which has the objective of guaranteeing the availability and quality of water. To ensure the implementation of charging there are laws, such as 9.433/1997, which establishes the National Water Resources Policy (PNRH), and the State Laws N° 7.094/2009 and N° 5.965/1997, which refer to the preservation of groundwater and the institution of the State Water Resources Policy, respectively. In regions where the charging tool is implemented, the same model is often adopted for surface and groundwater, not taking into account important characteristics of aquifers, such as: type of confinement, vulnerability, availability, etc. Therefore, this work aims to propose a charging model for groundwater use in order to consider aquifer peculiarities and their demands, performing a case study in the Barreiras aquifer. As a method, it was carried out research related to charging for water use in Brazil and in the state of Alagoas, focusing on the situation regarding the implementation of the models already proposed; from this survey it was carried out an analysis of the characteristics and the hydric balance of the Barreiras aquifer to subsidize the suggestion of criteria and conditioning factors in the model proposition. With this, the proposed model is represented by the following equation: 𝑉𝐶 = 𝑄𝑜𝑢𝑡𝑜𝑟𝑔𝑎𝑑𝑎 𝑥 𝑃𝑃𝑈𝑐𝑎𝑝 𝑥 𝐾𝑢𝑠𝑜 𝑥 𝐾𝑐𝑜𝑛𝑓𝑖𝑛𝑎𝑚𝑒𝑛𝑡𝑜 𝑥 𝐾𝑣𝑢𝑙𝑛𝑒𝑟𝑎𝑏𝑖𝑙𝑖𝑑𝑎𝑑𝑒 𝑥 𝐾𝑑𝑖𝑠𝑝𝑜𝑛𝑖𝑏𝑖𝑙𝑖𝑑𝑎𝑑𝑒, where Qoutorgada is the value of the flow rate granted for a given well, PPUcap refers to the unit public price, and Kuso, Kconfinement, Kvulnerability and Kdisposability are the type coefficients of aquifer use, confinement, vulnerability and availability, respectively. The case study was divided into two parts, first ten wells were used to observe in detail the application of the model and its variations, and after the criteria were defined, the model was applied to all the wells in the study area. A comparison was also made for the same region with a model proposed by SEMARH, in order to evaluate the impact on revenue with the change in criteria. The result was an annual revenue of approximately R$ 200 thousand for the wells contained in the Barreiras aquifer that are in effect (230) and an estimated revenue of about R$ 700 thousand per year for the entire state, which would be invested in actions to protect the aquifers and improve their conditions. It is understood that the work presented the expected results and some suggestions can improve the model, as is the case of the change of the authorized flow rate for measured flow rate, which would represent a fairer value and the charging of a minimum value of R$ 120,00 for water catchment.