One cumec-day is equal to : - Solved MCQ | Agrigyan

Gross storage capacities of these reservoirs at Full Reservoir Level (FRL):

• Nagarjunasagar (Krishna River): $\sim 11,560\text{ Mm}^3$
• Ukai (Tapi River): $\sim 7,414\text{ Mm}^3$
• Sriramsagar / Pochampad (Godavari River): $\sim 3,172\text{ Mm}^3$
• Koyna (Koyna River): $\sim 2,797\text{ Mm}^3$
• Idukki (Periyar River): $\sim 1,996\text{ Mm}^3$

• (A) is false: Sandy soils are dominated by macropores which drain rapidly by gravity; thus their water holding capacity is low.
• (B) is true: Silt loam and silty soils have a balanced pore size distribution with high available water holding capacity.
• (C) is false: Clay soils possess high microporosity and large specific surface area, giving them the highest total water holding capacity.
• (D) is true: Clay soils have small micropores that restrict gas diffusion and percolation, leading to poor aeration and drainage.
• (E) is true: Texture and organic matter are the two primary determinants of water retention.

The relationship between Duty ($D$), Delta ($

\Delta$), and Base period ($B$) is given by: \[ D = \frac{8.64 \times B}{\Delta} \]

Where:

• $D$ = Duty in $\text{ha/cumec}$
• $B$ = Base period in days = $90\text{ days}$
• $\Delta$ = Total depth of water in meters = $70\text{ cm} = 0.70\text{ m}$

Substituting the values:

\[ D = \frac{8.64 \times 90}{0.70} = \frac{777.6}{0.70} = 1110.857 \approx 1111\text{ ha/cumec} \]