Impact Assessment of Hydrologic Attributes and Slope Instability - Semi-quantitative Approaches for Landslide Assessment and Prediction - page 101

Table 3.3 Monthly evapotranspiration (after Penman 1963 and Jensen et al. 1990 )
Month parameters Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

T (in ° C) 9.50 10.80 14.06 17.88 18.45 19.81 20.03 20.33 19.16 17.65 14.90 11.56

(kPa/ ° C) 0.08 0.09 0.11 0.14 0.14 0.15 0.15 0.16 0.15 0.13 0.11 0.09

Δ

P (kPa) 88.22 88.22 88.22 88.22 88.22 88.22 88.22 88.22 88.22 88.22 88.22 88.22

k (MJ/kg) 2.48 2.48 2.47 2.46 2.46 2.45 2.45 2.45 2.46 2.46 2.47 2.47

(kPa/ ° C) 0.06 0.06 0.05 0.05 0.05 0.06 0.06 0.06 0.05 0.05 0.05 0.05

c

e s 1.15 1.25 1.65 2.00 2.07 2.26 2.29 2.33 2.17 1.96 1.65 1.32

e d 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11

D
Dþ c

0.57 0.60 0.69 0.74 0.74 0.71 0.71 0.73 0.75 0.72 0.69 0.64

c
Dþ c

0.43 0.40 0.31 0.26 0.26 0.29 0.29 0.27 0.25 0.28 0.31 0.36

s

R so (MJ m − 2
day − 1 )

18.75 22.68 26.64 29.95 31.89 32.77 32.31 30.35 27.22 23.51 19.59 17.42

R s (MJ m − 2 day − 1 )

8.16 12.23 17.94 20.35 16.41 17.07 12.68 13.21 12.02 13.39 14.38 10.03

R n 4.75 6.84 9.74 11.28 9.96 10.34 8.37 8.32 7.39 7.17 6.44 4.83

λ ET o (MJ m − 2
day − 1 )

2.88 4.66 8.52 11.08 10.23 11.21 9.76 9.61 8.25 7.59 6.10 3.88

ET (in -mm) 21.74 51.36 93.89 122.12 112.74 109.81 119.51 123.56 90.92 83.64 67.22 42.76

Rainfall (mm) 12.57 16.67 43.76 94.85 302.8 728.4 995.5 783.9 587.9 183.3 12.3 21.9

Difference − 9.17 − 34.69 − 50.13 − 27.27 190.06 618.59 875.99 660.34 496.98 99.66 − 54.92 − 20.86