Identify the rainfall–runoff empirical relation: Q = P − K[1.8 T + 32], where Q is runoff (cm), P is annual rainfall (cm), T is mean annual temperature (°C), and K is a regional constant.

Introduction / Context:Empirical runoff–rainfall relations are used for preliminary water-resources assessments when detailed hydrometric records are sparse. Recognizing common forms helps select suitable starting points for catchment studies.

Given Data / Assumptions:

• Q = P − K[1.8T + 32], units in centimetres for P and Q; T in degrees Celsius.
• K is a catchment-specific constant.

Concept / Approach:The presence of the temperature term modified by 1.8T + 32 (conversion towards Fahrenheit scale) is characteristic of the English formula used historically in hydrology texts for annual runoff estimation.

Step-by-Step Identification:

Verification / Alternative check:Cross-reference with common lists of empirical relations that include Justin, Khosla, English, and Vermule forms; only the English formula uses this specific temperature conversion factor.

Why Other Options Are Wrong:Other named formulas use different variables or structures and do not include the 1.8T + 32 term.

Common Pitfalls:Forgetting the temperature component and confusing with simpler Q–P linear relations.

Final Answer:English formula