Hi there:

I am working kaplan book. And one hydrograph problem have the 'Base flow separation' draw it out so can subtract from the Qtotals to find the Qstorm. How do you determine Base flow, I dont see there is any info in the problem indicate base flow. All I see just a line draw on the bottom of the hydrograph and read out point. Can someone be able to answer my question?

tsli001

In the CERM pg. 20-7 it discusses taking out the base flow. Method #1 states, 'In the straight line method, a horizontal line is drawn from the start of the rising limb to the falling limb. All of the flow under this horizontal line is considered base flow'.

I'd just read that today. thanks. Let hope we all got the assumption is right

For base flow I believe they give you the flow at t=0 being greater than 0 and that is the start of the base flow, ie the flow prior to the rain event.