A tracer test was performed in a small stream with NaCl. The concentration of NaCl was measured in g/L, and a plot of the concentration as a function of time at 20 m (x =20m) downstream is shown below. Based on the graph:

a. Estimate the stream velocity (v) in m/sec

b. Estimate the standard deviation (_L) of longitudinal dispersion. Report in meter and clearly label the graphical procedure on the diagram for full credit.

c. Estimate the longitudinal dispersion coefficient D_L (m²/sec)

d. Calculate how much NaCl in g was added to this stream for the tracer test at the beginning (x=0 m). The cross-sectional area of the stream is 3 m²

graph given:

⁵⁰⁰⁰

⁴⁰⁰⁰

³⁰⁰⁰

²⁰⁰⁰

¹⁰⁰⁰

^{.................100 200 300}

^{.................... t(sec)}