Hydrograph Separation

Question 1

Goal

Answer 1

Separation of total discharge Qtot into single flow components regarding genesis, flow paths, response time

Question 2

Hydrograph Separation types

Answer 2

(1) Continuously
separation of multi year hydrographs into flow components regarding subsystems in the catchment
(e.g. for nutrient balancing or model parameter estimation)

(2) Event based
Separation of flood hydrograph into base flow and direct runoff for flood modelling

Question 3

Classification of flow components can also be done according to response time TR or travel time TT

Answer 3

 Travel time TT is usually much larger than response time TR

 Separation acc. to. TR → models → focus water quantity

 Separation acc. To. TT → tracer → focus nutrients

Question 4

Continuous hydrograph separation:

important equation

Answer 4

k = Dt / DlnQ

k = retention constant

Question 5

Event based hydrograph separation:

Answer 5

a) Horizontal line connection between point at which surface runoff (RO)
starts and intersection with the recession limb.

b) The baseflow (RB) before RO starts is projected ahead to the time of peak. A straight line is connected from that point to the point on the recession limb at fixed time N after the peak.
c) RB before RO starts is projected ahead to the time of peak. RB after RO ceases is extrapolated backward to the time of the point of inflection. A straight line connects both endpoints.