Longitudinal dispersion coefficient estimating

As described in equation (6.59), longitudinal dispersion coefficient has a 67% confidence interval that is a factor of 1.7 times the best estimate. If the distribution of multiplicative uncertainty is normal, the 95% confidence interval would be at a factor of 3.4 times the best estimate. The reaeration coefficient has are MME of 1.8 for the Thackston and Krenkel equation (equation (9.7)). Again, if the multiplicative distribution is normal, the MME is 0.4 times the 95% confidence interval. Then the 95% confidence interval is a multiplicative factor of 4.5. 

The t2 profile of Fig. 2-4 was measured 5 hr after a pulse injection of dye. What is the average river velocity if the maximum concentration is occurring 1025 m down the river from the pulse injection at this time Estimate the longitudinal dispersion coefficient for this river if the standard deviation in the longitudinal direction, crL, is approximately 350 m when the chemical has traveled a distance of 1975 m to L3. 

The longitudinal dispersion coefficient DL can then be estimated from Eq. [2-7] ... 

Estimate the longitudinal dispersion coefficient for the reach of stream between the proposed outfall and the measurement location. 

Estimate Longitudinal Dispersion Coefficient from Experimental Data... 

Longitudinal dispersion coefficients can be evaluated by injecting a flat pulse of tracer into the bed so that dC/dr = 0. The values of Dl can be estimated by... 

In the case of the longitudinal dispersion coefficient, Dl, stream velocity and width are important predictors. The following equation estimates the longitudinal dispersion coefficient within a factor of about four (Fischer et al., 1979) ... 

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