1. Drainage areas within each of the isohyetal lines for a storm are tabulated for a watershed. Use the isohyetal method to determine the average precipitation depth within the basin for the storm. Make a conceptual sketch including (a) the watershed boundaries, (b) the isohyetal lines, and (c) labels for the isohyetal lines and the drainage areas in acres. Isohyetal interval (in.) Area (acres) 0-2 2700 2-4 1900 4-6 1000 6-8 0