The upper and lower bounds on the level curve were estimated numerically by solving Equations (16) and (17), and assuming for simplicity (although other assumptions are possible) α₁ = α₂ = ɛ/2, with ɛ = 0.05. The upper and lower bounds are denoted as B₁ and C₁, respectively, in Figure 7. It is found that the bounds are close to the horizontal asymptote (i.e., w₇ = 61.49 × 10⁸ m³ for T= 1,000 and w₇ = 50.23 × 10⁸ m³ for T= 200) and vertical asymptote (i.e., q_p = 22,800 m³/s for T= 1,000 and q_p = 19,300 m³/s for T= 200) due to the small value assumed for the probability level ɛ. The upper and lower bounds were also calculated by the boundary identification method proposed by Volpi & Fiori (2012). The results are also presented in Table 5 and the derived bounds are denoted as B₂ and C₂, as shown in Figure 7. It is shown that the bounds estimated by the proposed method and that proposed by Volpi & Fiori (2012) are very similar.