Objective: To examine the concept of water harvesting, how
it is used, and how it impacts us.
Water harvesting is collecting and storing runoff water from
a catchment. Often the infiltration rate of the area is reduced
by the application of materials (wax, latex, rubber, plastic)
to the surface. Sometimes the surface is cleared of vegetation
and packed down to decrease infiltration. In other cases the
catchment is paved with asphalt or concrete. At still other
times the runoff that is harvested is that from house and
building roofs.
Runoff efficiency indicates the percentage of the precipitation
falling on the catchment that runs off it at the exit point.
This is where storage structures are typically placed. The
following calculator predicts the volume of water that might
be collected for a given size catchment with specific ground
treatments.
Typical values for runoff efficiency for specific surface
covers are:
First, select the units you want to use from the pull down
menus. Then enter the values on the left and the calculator
will give the value on the right.
Before written history people have devised methods for collecting
rainwater and storing it for use later. There are numerous
ideas that can be used. The basic concept is to collect rain
water (or snow melt) and store it so that it can be used later
when rain or water flow may not be available. The catchment
area for collecting the water ranges from the surface of the
land to the roof of a hut.
