One of my coauthor s s JANEN has uploaded two article in RG related this those will be useful to you pl

Hello Saravan,

Where I can find these articles? can you send me the links? I have discharge data, rainfall data of the watershed and plus I have the watershed area. I am trying to show that a storm water wetland can hold ( rentention) water to reduce the flooding in the river and the streams.

Srilanka is doing great in the Asia Cup..

Best regards

Nadeem

If your constructed wetland is already built, you can confirm the retention time using simple tracer experiments. Rhodamine dye can be measured using a fluorometer, or you can use a simple salt tracer and measure conductivity. Vegetation in the constructed wetland will also play a role in the retention time.

Retention Time = (Area * depth)/Flow per day

Flow is average of daily inflow and outflow

unit of area (acre), depth (ft) must match with flow (ac-ft). units will cancel and "day" will be left

To Wossenu, the computation is theoretically for retention time, and the experiment ways mentioned by Matthew is preferred and more reliable.

Please see the attached publication that compares two options for a constructed wetland for processing stormwater. One option considered in the paper was developed to maximize the retention time for stormwater. This was to enhance nutrient removal from the stormwate entering the constructed wetland. The methods used in thi paper may help you calculate retention time for your situation.

thanks , There is one constructed wetland for wastewater in Jakarta and I can read up their analysis regarding their retention period.

thanks

nadeem

Field measurements using traces will be superior to calculations, but if in the design phase you will need to calculate the retention time from inflow rate and volume. It is important to spread out the influent however to reduce short-circuiting.

It is work about measurment the retention time in constructed wetlands.

Conley L.M., Dick R.L., Lion L.W. 1991. An assessment of the root zone method of wastewater treatment. Research Journal WPCF, 64 (3),239-247.

Http://www.jstor.org/discover/10.2307/25043987?uid=3738840&uid=2&uid=4&sid=21103657607613

Analysis should start by studying the cross-section of the constructed wetland system (which must include the inlet/s and outlet/s).

the retention time can be correctly measured by the equation

HRT=nLWD/Q

n=porosity of the substrate, L=length of the cell, W= width of the cell, D= effective depth of the cell, Q= average flow rate of the wastewater.

Q (average)= (Average Inlet flow+Outlet flow)/2

Outlet flow can be measured by calculating the evapotranspiration rate of the constructed wetland.

For more details you can further contact to me.

Using seasonal/ annual data & Estimates for a watershed in the Water Balance Equation

Retention = Rain - Surface Runoff - Evaporation - Transpiration - Surface storage

= Ground Water (Inflow - Out flow)

Retention time for a constructed wetland is given as porosity multiplied by the effective volume divided by the designed inflow rate. The unit is given in days.