Measurement of groundwater flow by the dilution method using dye tracing under natural hydraulic gradient conditions

The method of measuring groundwater flow locally by dilution of dye introduced into a portion of a screened well under natural hydraulic gradient conditions, is easy to use, However the determination of the discharge from the resulting experimental curves is not immediate. Using a same scale mock-up, a parametric study was conducted for a range of dilution discharges close to that found under field conditions. A physical conceptualization of the system is proposed, i.e. an arrangement of simple flow models, such as plug flow and a perfectly agitated tank. The mass balance law applied to this arrangement leads to a system of equations that is solved in the Laplace domain. An analytical solution is obtained, and two fitting methods with respectively two and four unknowns are examined.