ABSTRACT
For the purpose of illustration, we can apply these two equations in order to estimate the flow deficit of the Corbassière watershed (Haute-Mentue, Switzerland). For the year 1998, the following data is available: P = 1170 mm, Q = 604 mm and ET = 620 mm. The flow deficit is therefore D = P – Q = 566 mm. Knowing that the annual average temperature for 1998 was 7.28 °C, calculating the flow deficit using Turc’s equation gives us 464 mm while Coutagne’s equation produces a flow deficit of 455 mm. (Equation 2.14 is used because the conditions for using Equation 2.13 are not satisfied.) There is a difference of about 25% between the measured and calculated values of the flow deficit. This difference is due to the fact that the watershed studied is small and has specific hydrological characteristics.
