A 5 km2 lake does not have a defined input but receives runoff from its watershed (25 km2). The area receives 60 cm/yr in precipitation. Evaporation from the lake surface is 10 cm/yr with watershed evapotranspiration of 20 cm/yr. Infiltration from the watershed transfers 20 cm/yr to groundwater while seepage contributes 10 cm/yr from the groundwater to the lake.
If the lake and the watershed are at stead-state and no other inputs/outputs exist, estimate:
a. The runoff from the watershed into the lake (in cm/yr),
b. The runoff coefficient, and
c. The outflow from the lake (in cm/yr).