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Dynamics of negative hydraulic barriers to prevent seawater intrusion
- Pool, María, Carrera, Jesús
- Hydrogeology journal 2010 v.18 no.1 pp. 95-105
- aquifers, coasts, desalination, freshwater, models, pumps, remediation, saline water, saltwater intrusion, seawater, wells
- Negative hydraulic barriers that intercept inflowing saltwater by pumping near the coast have been proposed as a corrective measure for seawater intrusion in cases where low heads must be maintained. The main disadvantage of these barriers is that they pump a significant proportion of freshwater, leading to contamination with saltwater at the well. To minimize such mixing, a double pumping barrier system with two extraction wells is proposed: an inland well to pump freshwater and a seawards well to pump saltwater. A three-dimensional variable density flow model is used to study the dynamics of the system. The system performs very efficiently as a remediation option in the early stages. Long-term performance requires a well-balanced design. If the pumping rate is high, drawdowns cause saltwater to flow along the aquifer bottom around the seawater well, contaminating the freshwater well. A low pumping rate at the seawards well leads to insufficient desalinization at the freshwater well. A critical pumping rate at the seawater well is defined as that which produces optimal desalinization at the freshwater well. Empirical expressions for the critical pumping rate and salt mass fraction are proposed. Although pumping with partially penetrating wells improves efficiency, the critical pumping rates remain unchanged.