.San Pablo Reservoir and material balance. The San PabloReservoir is located about 5 km east of campus near the town of ElSobrante (see map, UC Berkeley is at the bottom left). Thereservoir holds 48 x 106 m3 of water when it is at maximumcapacity. Its surface area is approximately 3.5 x 106 m2. TheSobrante drinking water treatment plant, which treats water pumpedfrom the reservoir before it is delivered to customers, has acapacity of 100 x 103 m3/day. There are no other major outflowsfrom the reservoir, except 1 m/y of evaporation.

a. Estimate the characteristic residence time of a watermolecule in the reservoir, assuming the level of the reservoirstays constant. Remember to include both water use and evaporationin your estimate.

b. Due to a drought, the flow into the reservoir has decreasedby about 35%. Assuming the water use continues at the same rate,how long will it take to until the reservoir reaches 25% of itscapacity? Assume that the surface area of the reservoir stays thesame.1

c. Our local utility (EBMUD) operates the reservoir andtreatment plant and delivers treated customers in Berkeley and muchof the East Bay. To conserve water during this hypotheticaldrought, EBMUD asks their customers to reduce water use by 20%. Howmuch longer will it take for the reservoir to reach 25% capacity ifrationing is successful?

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