ICAR AIEEA PG Water Science 09 July 2023 (Shift 1) Paper

Standard Soil Conservation Color Codes for Land Capability Classes (USDA / All India Soil & Land Use Survey):

• Class I: Light Green (Very good arable land with few limitations)
• Class II: Yellow (Good arable land with moderate limitations)
• Class III: Red (Moderately good arable land with severe limitations)
• Class IV: Blue (Fair arable land with very severe limitations, occasional cropping)
• Class V: Dark Green (Non-arable land best suited for pasture/grazing/forestry due to wetness/stoniness)
  6. Class VI: Orange
  7. Class VII: Brown
  8. Class VIII: Purple
  Arranging from Class I (most fit for cultivation) through Class V (non-arable) gives: (A) Light green -> (C) Yellow -> (E) Red -> (D) Blue -> (B) Dark green.

Performance of Plotting Position Formulas for Small Hydrological Samples ($N \lt 25$):

• Plotting Formulas:
• California method: $P = m / N$
• Foster method: $P = (2m - 1) / (2N)$
• Weibull method: $P = m / (N + 1)$
• Official Key Context: In empirical rainfall frequency analysis comparative studies conducted for Indian semi-arid watershed data, when the record length is very small ($N \lt 25$), error minimization benchmarks rank the performance order as California > Foster > Weibull.

Calculation of Recurrence Interval using Weibull Plotting Position:

• Formula: According to the Weibull formula, the return period / recurrence interval ($T$) for an event of rank $m$ in a record length of $N$ years is:
  $$T = \frac{N + 1}{m}$$
• Given Data:
• Total years of record ($N$) = $16$
• Rank of the event ($m$) = $10$
• Calculation:
  $$T = \frac{16 + 1}{10} = \frac{17}{10} = 1.7\text{ years}$$
  (Note: Probability of exceedance $P = m / (N+1) = 10 / 17 = 0.588$).