A coastal watershed has a total surface area of 387 km 2 . The land area is 381

Question

A coastal watershed has a total surface area of 387 km2. The land area is 381 km2 and the area of the rivers is 6 km2. A water budget for the watershed has the following long-term average annual values (all rounded to the nearest integer):              [20]

precipitation: 80 cm                            baseflow: 13 cm

evapotranspiration: 49 cm                  stream flow: 21 cm

runoff: 8 cm                                        ocean seepage: 10 cm

ALL values are normalized, meaning they represent the depth of water if spread out over the entire 387 km2 area. For all questions below, assume there are no long-term changes in storage.

A. What is the total volume of water recharged to the groundwater each year?

(report as m3)

B. What is the average discharge from the watershed through stream outflow?

(report as m3/s)

Note: If fractional values need to be considered, either calculate or show why they can be ignored.

Explanation / Answer

A. Total volume of water recharged to the ground water each year

R=2.0(P-15)0.4

Where R is the Recharge

p is the precipitation in inches

p=80cm=31.49608

R=2.0(31.49608-15)0.4

R=2.0(16.49608)0.4

R=2.0*3.0687

R=6.1374 inches

R=0.0159

recharge of ground water per year=0.0159m

surface area=387km2

volume of water=194*194*194*0.0159

                       =1.1383 m3

B. Discharge Q=QS + Qg = P - E - ds/dt

                                      =80-49-8

                                      =23cm

                                    =0.23m/s

average discharge from the watershed=1.1383*0.23=0.2618 m3 /s

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