Question

Identify what the difference in volume is between effective precipitation and the volume under the hydrograph that is the response to that precipitation. Show how to calculate each.

Please type out.

Answer 1

Hydrograph

In case of response to precipitation the discharge contains both effective precipitation and base flow ( base flow is the discharge which joins the stream after a long period)

Effective precipitation or Direct runoff hydrograph

In this case the base flow is removed. This represents the discharge after satisfying the losses,

The volume in the both cases is calculated by Trapezoidal formula

For hydrograph

Volume = 1/2*[O1+O9 + 2( O2+O3+O4+O5+O6+O7+O8)]*delta T

(delta T is time period between each ordinate, for example 1 hr)

For effective precipitation

Assume base flow = 30 m^3/s

The effective precipitation ordinates are calculated as follows

O1' = O1-30 m^3/s

O2' = O2- 30 m^3/s so on

  Volume = 1/2* [O1'+O9'+ 2( O2'+O3'+O4'+O5'+O6'+O7'+O8')]* delta T

see below figures for reference

* Discharge mols time (brs) hydrograph Base flow e Discharge mi?l's Co to io time (hus) Direct runoff hydrograph Scanned with CamScanner