Rainwater harvesting: TTT

From LID SWM Planning and Design Guide
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TTT.png

Subcatchment element as displayed in the TT menu
Storage element as displayed in the TTT menu

Once the size of cistern has been determined, it can easily be modeled in many open source and proprietary applications. For planning purposes, a RWH system can be integrated into a site plan as a storage element, using the TTT.

  1. Create subcatchment for harvesting rainwater.


Stage Storage


Stage Storage
Storage type No removal
Catchment In many scenarios this will be the roof area, delineated on the map as a 'subcatchment'.
? Lined
Underlying soil Any:This doesn't matter for RWH cistern systems
Evaporation factor 0
Suction head (mm) 0
Saturated conductivity (mm/hr) 0
Initial soil moisture deficit (fraction) 0
The dimensions of the rainwater cistern can be placed into the fields:
  1. Bottom elevation (m)
  2. Maximum depth (m)
  3. Initial water depth (m)

The Curves table is designed to accommodate ponds of roughly conical dimensions. A rainwater cistern is usually cuboid or cylindrical in shape, so that the area (m2) will remain the same throughout the depth.