Example5
========

This example shows how to set up a simple groundwater model
in SWMM. It consists of a single 5 acre subcatchment that is
completely pervious and has a groundwater zone beneath it.

An Aquifer object is used to store the properties of the soil
in the groundwater zone. The zone is 6 feet deep with the initial
water table being 3.5 feet above the bottom of the zone and the
initial moisture content of the soil above that at 40 percent.

An outfall node at 4 feet elevation receives the lateral outflow
from the groundwater zone. The outflow rate is 10 percent of the
difference between the ground water level and the node elevation
(in cfs/acre). A 6-hour 2-inch rainfall with a triangular shaped
distribution is applied to the subcatchment.

After opening the file, view the properties assigned to the
Aquifer object and to the subcatchment's Groundwater property.
Then run the model and plot the subcatchment's runoff and
groundwater water flow along with the outfall node's total
inflow on the same time series graph. Create another time series
graph that plots the subcatchment's groundwater elevation on the
left axis and its soil moisture on the right axis.

Note how it takes 6 hours for the groundwater level to reach
the 4 foot elevation at which  groundwater flow can begin. Before
this time the outfall node see only surface runoff. Then it sees
combined surface and groundwater flow for another 3 hours
until surface runoff ceases. After that it sees all groundwater
flow. This flow keeps rising as the water table height increases
due to percolation from the upper soil zone until hour 19. After
that it begins to recede as the upper zone moisture content is
depeleted and the water table height drops.

See what effect changing the Aquifer's conductivity from 0.1
in/hr to 1.0 in/hr has on the groundwater's behavior.