An exact solution for a constant-strength line-sink satisfying the modified Helmholtz equation for groundwater flow

► We present an exact solution to the modified Helmholtz equation for a line-sink of constant strength. ► We demonstrate its use for two cases of groundwater flow: Semi-confined and transient flow. ► Limits on the numerical evaluation do not affect the practical application of the solution. ► We also present an exact calculation of flow across a poly line, important for Neuman boundaries.