What is lag time on a hydrograph?

Lag time – the time taken between peak rainfall and peak discharge. Rising limb – shows the increase in discharge on a hydrograph.

What does lag time indicate?

The lag time is the time difference between the peak precipitation and and the peak discharge. A long lag time indicates that it’s taking a long time for precipitation to enter the river. Conversely, a short lag time indicates that the precipitation is entering the river fairly quickly.

What is watershed lag time?

Lag time is a measure of the speed at which a watershed responds to a runoff-producing rain event; specifically, it represents the delay in time between the maximum rainfall and the peak discharge.

How do you calculate lag time in geology?

With certain annular volume, the lag time, normally expressed in minutes, can be determined by dividing the annular volume (bbls) by the flow rate (bbl/min). If there are changes in mud flow rate, the lag time figure will be changed as well.

What is lag time pharmacokinetics?

Lag time in pharmacokinetics corresponds to the finite time taken for a drug to appear in systemic circulation following extravascular administration. Failure to specify the lag time can lead to inappropriate or erroneous estimates of pharmacokinetic parameters.

Is lag time the same as time of concentration?

In hydrograph analysis, lag is the time interval be- tween the center of mass of the excess rainfall and the peak runoff rate (fig. 15–3). Time of concentration (Tc) is the time required for runoff to travel from the hydraulically most distant point in the watershed to the outlet.

How do you calculate lag time on a graph?

The lag time is obtained by taking the later points in the plot (when the plot is straight) and drawing a straight line through them, then extrapolating back to the horizontal axis intercept. The intercept will be the lag time.

What increases lag time?

The type of precipitation can also have an impact. The lag time is likely to be greater if the precipitation is snow rather than rain. This is because snow takes time to melt before the water enters the river channel. When there is rapid melting of snow the peak discharge could be high.

What is streamflow in hydrology?

Stream flow, or discharge, is the volume of water that moves over a designated point over a fixed period of time. The flow of a stream is directly related to the amount of water moving off the watershed into the stream channel. It is affected by weather, increasing during rainstorms and decreasing during dry periods.

What is absorption lag?

Absorption lag is the short fall of rate of water absorption over the rate of transpiration. It is due to high rate of transpiration.

What is lag time in a hydrograph?

Lag time in regards to a hydrograph, and in particular to a unit hydrograph, has a couple of different definitions, depending on what reference you use. Conceptually, it is a relation between the center of mass of the hydrograph and the center of mass of the hyetograph. However, it is generally not computed in that fashion.

What is the lag time of a watershed?

It depends only on the geography of the watershed. Lag Time ( t l ): It is the time from center of mass of excess rainfall to the center of mass of direct runoff hydrograph. It represents the position of runoff hydrograph w.r.t. the rainfall causing the runoff. One estimate of lag time as given by NRCS is: t l = 0.6 × t c

How do you calculate lag time in SCS?

Lag time = 0.6 * Tc The “SCS Lag” help topic is specific to the SCS Lag Tc method, not a general comment about the Tc (Time of Concentration). In general, the hydrology calculations in PondPack, SewerGEMS and CivilStorm always work with Tc, so if you’re entering a user defined Tc, you would enter the Tc, not the lag time.

What is the lag time on a unit storm hyetograph?

Because the duration of the unit hydrograph (the duration of the unit storm hyetograph) is generally small in comparison to the time to peak of the unit hydrograph, the difference between time to peak and lag time is often small enough to be ignored and lag time is treated as the time to peak.