Application of the quality border delineation for sustainable protection of groundwater resources, qanats, against contamination using meshless numerical method

Abstract

As sustainable groundwater resources that provide a safe and clean water supply, qanats should be protected from pollution. For this purpose, this article introduces a new concept called the “quality border” or “quality harim.” This concept acts as a boundary and determines the safe area around the qanat system in terms of contamination risk. Construction or any other activities in this area that produce pollution can enter the groundwater and get into the qanats' water, polluting it. Therefore, it is necessary to delineate this area for all qanats and prevent construction or other activities inside it. In this study, with the meshless local Petrov-Galerkin numerical method, the quality harim is determined for two qanats in the Birjand aquifer. These two qanats are selected according to the DRASTIC index map, which shows high contamination vulnerability for these qanats. Haji-Abad and Nasr-Abad are the two selected qanats with flow rates of 50 l/s and 5 l/s, respectively. The meshless local Petrov-Galerkin numerical method is then used to simulate groundwater flow in this aquifer. In the next step, to obtain the quality harim, the transport equation is solved by this numerical method in the Birjand aquifer. There are two time steps considered: 5 years (2016) and 11 years (2022). The results show that the quality harim in 2022 for the two qanats is wider than in 2016 due to groundwater drawdown and urbanization. The findings also state that both quality harims are influenced by construction, and this increases the contamination risk for both.