How is the ratio of runoff to precipitation expressed?

The ratio of runoff to precipitation is expressed as a coefficient in decimal form. This expression allows for a straightforward comparison of the amount of water that runs off a surface compared to the total amount of precipitation that occurs. By using a decimal, the ratio can easily reflect values between 0 and 1; for example, a runoff coefficient of 0.3 would indicate that 30% of the precipitation turns into runoff. This method of expressing the ratio is particularly useful in hydrological modeling and stormwater management because it provides a clear and quantifiable measure of runoff potential relative to precipitation, which is crucial for designing effective drainage systems and managing water resources.

In contrast, expressing this ratio as a percentage adds an extra conversion step, while volume and linear measurements do not directly convey the relationship between the runoff and precipitation effectively. Volume measurements focus on specific quantities of water without contextualizing them relative to the amount that has fallen, and linear measurements do not adequately address the ratios involved in hydrology. Thus, using a decimal coefficient is the most effective method for expressing the ratio of runoff to precipitation.