Cone of Depression calculator

This tool can be used to calculate the groundwater cone of depression in potential acid sulfate soil areas.
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Preliminary assessment of the radial extent of the cone of depression and pumping rates and times for all dewatering operations is critical for assessing the risk of disturbing acid sulfate soils in potential acid sulfate soil areas.

Broad-scale acid sulfate soil risk maps for several coastal regions of WA are accessible via Data WA.

Empirical methods to calculate the radial extent of the groundwater cone of depression and pumping rates and times for dewatering operations are outlined in National Acid Sulfate Soils Guidance: Guidance for the dewatering of acid sulfate soils in shallow groundwater environments.



Length of excavation: metres
Width of excavation: metres
Drawdown required: metres
Aquifer thickness(1): metres
Hydraulic conductivity: metres/second


Effective pumping radius, Re :   metres
Cone of depression radius, Ro :   metres
Total pumping rate:   litres/second
Pumping time required:   hours

Tools for calculating the radius of influence and pumping rates and times for dewatered excavations

In the absence of site-specific hydraulic data, default hydraulic conductivity values (K) listed below for a variety of Western Australian soil types may be used (2).

Lithology Hydraulic conductivity (metres/day) Hydraulic conductivity (metres/second)
Very coarse to gravel 246 0.002847
Very coarse 204 0.002361
Coarse 73 0.000845
Medium to coarse (moderately sorted) 50 0.000579
Fine to gravel (poorly sorted) 10 0.000116
Medium 16.5 0.000191
Fine to medium 8.2 0.0000949
Fine 4.1 0.0000475
Fine to very fine 1.7 0.0000197
Very fine 0.8 0.00000926
Silty 4 0.0000463
Clayey 1 0.0000116
Clay 0.4 0.00000463
Sand and limestone: Ascot Formation 8 0.0000926
Limestone and calcarenite: Tamala Limestone 100–1000 0.001157 to 0.011574
Sapric peat (highly decomposed, few visible fibres) 0.00864 (approx.) 0.0000001 (approx.)
Fibric peat (least decomposed, lots of visible fibres) 1.728 (approx.) 0.00002 (approx.)


  1. In the absence of site-specific information, the saturated thickness of superficial aquifers may be obtained from Perth Groundwater Map for sites in the Perth metropolitan region.
  2. Adapted from Davidson, W.A., 1995, Bulletin 142: Hydrogeology and Groundwater Resources Of The Perth Region, Western Australia, Geological Survey Of Western Australia.
  3. Hemond,H.F. and Goldman, J.C., 1985, On non-Darcian water flow in peat. Journal of Ecology, 73, 578-584.