Sources and Factors Affecting Dry Weather Flow

In order to determine the dimension of the sewer, we have to determine the quantity of water flow.The total wastewater flow is due to dry weather flow and storm weather flow.These flow of water is taking through wastewater carriage systems.

The difference between dry weather flow and wet weather flow is, dry weather flow is the flow through sewers only during non-rainfall periods and wet weather flow is combined flow of stormwater and domestic water from houses etc..

Here we are going to learn about factors affecting dry weather flow and sources of dry weather flow.


Sources of dry weather flow

  • Domestic sewage 
  • Industrial wastewater.
  • Wastewater from public facilities
  • Ground Water infiltrationdry weather flow


Dry Weather flow is the quantity of wastewater flow through in dry weather when no stormwater is in the sewer.The dry weather flow sometimes called sanitary sewage

What are the Factors affecting dry weather flow?

Rate of water supply

The main factors affecting dry weather flow is the rate of water supply.The quantity of wastewater generated depends upon the quantity of the rate of water supply per day.

The quantity of water entering sewer is less than the quantity of water supplied.This is due to water is lost due to domestic consumption.

Population growth

The sewage system is not only designed for the current population but also designed for the future generated.To find the future population of a region, we use these methods

  1. Arithmetic increase method
  2. Geometrical increase method
  3. Incremental increase method
  4. Decreased rate of growth method.
  5. Graphical Extension method.
  6. Graphical Comparison Method

Type of area served

The quantity of wastewater produced depends upon the area to be served is residential, commercial or industrial.If there is no infiltration facilities and no private source of supply, then the quantity of water entering into the sewer will be equal to 70 to 80 percent of the water supplied.

The amount of water generated from the industries depends upon the type of industries and process in the industries.

Infiltration of the subsoil

The last factor affecting dry weather flow is due to infiltration the quantity of flow through sewer increases, the exfiltration results decrease in the flow.

Read More

  1. Do you know how we get water?A complete guide to the hydrological cycle.

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