Simulated Streamflow is Extremely Low

[jst...@up.edu.ph]

Hello!

I am currently modeling a small river basin with the following characteristics:

Drainage Area: 39.97 sq. km.

Annual Average Rainfall: >2000 mm

My problem is that the flo_out (daily and monthly) is extremely low despite having high precipitation and a high surface runoff coefficient.

The initial simulation resulted in the following average streamflows:

• simulated daily average: 1.96 cu. m/s
• simulated monthly average: 1.95 cu. m/s

In comparison, the observed data are:

• observed daily average: 7.91 cu. m/s
• observed monthly average:  22.28 cu. m/s

I have tried computing the estimated discharge using the rational formula for comparison. For example for October (wet season):

• observed daily rainfall is 104 mm
• observed streamflow is 26 cu. m/s
  

Assuming a runoff coefficient of 0.4, the average streamflow should be around 19.26 cu. m/s. However, the simulated average streamflow for this specific month is just 0.28 cu. m/s.

Basically, the model underestimates the total flow for all seasons (PBIAS>+_ 90) but it follows the same trend. Its r-square and Pearson correlation are above 0.80.

Hope someone can explain the possible cause and solutions.

Thank you very much!

*** Because I am still an undergraduate student, my knowledge of hydrology is limited ***

[Natalja C.]

Hello,

Well, this is not what your WB is showing. What output are you looking at? Do the following:

- make sure that you are printing the daily and the monthly output (print.prt)

- Re-run the model;

- make sure that you are comparing the right channel/reach/outlet

According to your WB picture, you should have huge streamflow

Best,

Natalja