Step 1: Drainage Coefficient Formula.
The drainage coefficient (D) is calculated using the formula:\[D = \frac{Q}{A}\]Here, \(Q\) represents the discharge in m³/s and \(A\) denotes the area in hectares.
Step 2: Discharge Calculation.
Given a discharge \(Q = 2.5 \, \text{m}^3/\text{s}\) and an area of \(1500 \, \text{hectares}\), and a drainage coefficient of 3 cm, the discharge through the drain is computed.
Step 3: Result.
Following the formula application and calculation, the resulting discharge is \(0.33 \, \text{m}^3/\text{s}\).
Final Answer: \[ \boxed{0.33 \, \text{m}^3/\text{s}}\]