7.1

A lake of modest size is the subject of study as the start of a water supply design project. The surface area of the lake is approximately 380 acres (640 acres = 1 mi ²). The data from a part of this study are presented in Exhibit 7.1. Tabulated are the monthly precipitation P, the monthly average inflow and outflow rates to and from the lake, and the water surface elevation WSE at the beginning of each month. The local geology suggests that subsurface seepage from the lake may be neglected.

1. The largest of the monthly evaporation amounts from this lake is most nearly

   1. 220 acre-feet

   2. 300 acre-feet

   3. 450 acre-feet

   4. 550 acre-feet

2. An alternative to the collection of these data is to base the determination of monthly lake evaporation on U.S. Weather Bureau pan evaporation data. Which of the following statements about the pan evaporation procedure is least correct?

   1. The value of the pan coefficient is 0.70.

   2. The value of the pan coefficient is dependent on location.

   3. The value of the pan coefficient is seasonally dependent.

   4. Pan evaporation is always larger than lake evaporation.

7.2

A rainfall hyetograph is presented...