Since i = a / (t + b), it follows that:
45 = a / (1 + b); and
20 = a / (2 + b).
Solving for a and b:
a = 36; b = -0.2. ANSWER.
Since at t = ∞, the final infiltration rate is 0.6 mm/h, then: fc = 0.6 mm/h. Therefore, from Eq. 2-13:
3.5 = 0.6 + (fo - 0.6) e -k; and
1.0 = 0.6 + (fo - 0.6) e -3k
Therefore:
fo - 0.6 = 2.9 ek
fo - 0.6 = 0.4 e3k
Dividing these two equations:
e2k = 7.25.
From which: k = 0.99 h-1
Then: fc = 0.6 mm/h; fo = 8.4 mm/h; and k = 0.99 h-1. ANSWER.
Try several likely values for φ. For instance, assume φ between 1 and 2 cm/h.
Therefore: 2 • (2 - φ) + 2 • (3 - φ) + 2 • (4 - φ) + 2 • (2 - φ) = 12.
Solving for φ: φ = 1.25 cm/h. Therefore the assumption of φ being between 1 and 2 cm/h was correct.
ANSWER.
Use C = 11 for a large lake.
The saturation vapor pressure at 70°F is 0.739 inches of Hg.
The partial vapor pressure of the air is: 0.739 × (60/100) = 0.4434 inches of Hg.
E = 11 × (0.739 - 0.4434) × [1 + (20/10)] = 9.75 inches in the month of July.