# How much time does water takes to reach to the ground?

I want to understand the phenomena where water droplets after precipitation reaches to the ground.

How much time does it take to become ground water or in other words how much time is taken by water to recharge the ground after rain.

I am assuming the water droplets falls in the plain having no concrete human constructions.

• You are asking for a rough order of magnitude for the time passing? It considerably depends on the soil and on the final depth of the ground water. May 23, 2016 at 12:59
• It's highly dependent on conditions, some water in the Great Artesian Basin of Australia is estimated to have fallen as rain 2 million years before it is discharged.
– Siv
May 23, 2016 at 19:08

It depends upon the hydraulic conductivity, the degree of saturation, and the depth to water table. Generally, water seeping down in the unsaturated zone moves very slowly. Assuming a typical depth to water table of 10 to 20 metres, the seepage time could be a matter of minutes in the case of coarse boulders, to months or even years if there is a lot of clay in fine sediment. Under saturated conditions, the water might move a lot faster. Other factors include the configuration of the wetting front, the unsaturated storage, temperature, and the hydraulic gradient. So basically, there is no simple answer - it's all a matter of the local hydrogeology.

There is no substitute for local measurement - water levels in an observation bore, in the case of water table conditions, or tensiometry in the case of the unsaturated zone.

Your question is difficult to answer because many factors will affect ground water recharge:

• Soil porosity, which will be affected by soil pore space volumes, soil cohesion (the distribution of clay & sand etc. within the soil matrix) and the presence of hydrophobic soil grains and minerals
• Soil moisture content
• Depth of the soil
• The presence or absence of water impervious strata, such a clays
• The presence or absence of ground fissures, faults or other discontinuities that can allow water to be channelled through them
• The amount of rain that falls and surface evaporation rates
• The depth of the ground water table
• Drought affected soil may have soil grains that may need to be hydrated, by absorbing some water, prior to letting surplus water pass by them
• Could you include a rough order of magnitude in this answer (or a range thereof)?
– cr0
May 23, 2016 at 22:16