Groundwater drawdown in swale?
Groundwater drawdown in swale?
(OP)
Hello all,
I have been asked to estimate the extent of groundwater level drawdown for a proposed swale (2' deep) that extends through a wetland (presumed groundwater elevation 6" below grade). The regulator is asking for an area around the swale that will have a lowered water table elevation due to this feature.
I haven't found a set of equations that match my needs exactly, I have seen the Theis equation that determines the cone of depression for a water well, and thought my case could be approximated by this condition.
Has anyone else had experience in answering this question?
Regards,
- smm
I have been asked to estimate the extent of groundwater level drawdown for a proposed swale (2' deep) that extends through a wetland (presumed groundwater elevation 6" below grade). The regulator is asking for an area around the swale that will have a lowered water table elevation due to this feature.
I haven't found a set of equations that match my needs exactly, I have seen the Theis equation that determines the cone of depression for a water well, and thought my case could be approximated by this condition.
Has anyone else had experience in answering this question?
Regards,
- smm
Talk To Other Members
RE: Groundwater drawdown in swale?
http://armypubs.army.mil/eng/DR_pubs/DR_a/pdf/tm5_...
There's a parameter "L," which you can estimate using page 4-24. Please note that permeability on the equation of 4-24 is in units of 10-4 cm/sec.
The length of zero drawdown is a function of permeability. Get some grain-size data (or run a field test to evaluate). If using grain-size data, here's something that may help:
http://home.comcast.net/~fatt-dad/permeability_cor...
Please note on the graph that permeability is also shown in units of 10-4 cm/sec.
You may want to consider all flow-to-slot equations if 4-2 doesn't quite work. That reference is a great document.
f-d
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