4-3. A 4,000-km² watershed receives 102 cm of precipitation in one year. The average flow of the river draining the watershed is 34.2 m³/s. Infiltration is estimated to be 5.5 × 10−7 cm/s and evapotranspiration is estimated to be 40 cm/y. Determine the change in storage in the watershed over one year. The ratio of runoff to precipitation (both in cm) is termed the runoff coefficient. Compute the runoff coefficient for this watershed.

Fig: 1