Water Table Depth Calculator
Free Water table depth Calculator for soil & sediment mechanics. Enter variables to compute results with formulas and detailed steps.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
Water Table Depth = Ground Elevation - Water Level Elevation
Water table depth is the vertical distance from the ground surface to the water table. Water column height equals well depth minus static water level depth. Drawdown is the difference between pumping water level and static water level. Available head for pumping equals the water column height minus drawdown.
Worked Examples
Example 1: Residential Well Assessment
Problem:Ground elevation 100m, water table at 95m elevation, well drilled to 20m depth, static water level at 5m below ground.
Solution:Water Table Depth = 100 - 95 = 5 m below ground\nWater Column = 20 - 5 = 15 m\nAvailable Head = 15 m\nDepth to water = 5/20 x 100 = 25% of well depth
Result:Depth to water: 5.0 m | Water column: 15.0 m | Good availability
Example 2: Pumping Impact Analysis
Problem:Same well with pumping water level dropping to 12m below ground surface.
Solution:Drawdown = 12 - 5 = 7 m\nRemaining head after pumping = 20 - 12 = 8 m\nDrawdown ratio = 7/15 = 47% of water column\nThis is within the recommended two-thirds limit.
Result:Drawdown: 7.0 m | Remaining head: 8.0 m | Sustainable pumping
Frequently Asked Questions
What is the water table and why does its depth matter?
The water table is the upper surface of the saturated zone where pore water pressure equals atmospheric pressure. Its depth below ground surface determines how deep wells must be drilled, affects foundation design, controls whether basements will have seepage problems, and influences vegetation patterns. Shallow water tables (less than 2 meters) can cause issues with septic systems and building foundations, while deep water tables (greater than 30 meters) increase well drilling costs significantly.
How is water table depth measured in the field?
The most common method is lowering an electronic water level meter (e-tape) down a well or borehole until it contacts the water surface, then reading the depth from the cable markings. Piezometers can also be installed for continuous monitoring. For preliminary site investigations, hand-augered boreholes can be used to observe where water seeps in. Geophysical methods like electrical resistivity surveys can estimate water table depth without drilling, though they are less precise than direct measurements.
What causes the water table to rise or fall?
The water table fluctuates seasonally and in response to human activities. It rises during periods of heavy rainfall or snowmelt as recharge exceeds discharge, and falls during dry seasons or drought. Pumping from wells causes localized drawdown that can lower the water table in a cone of depression around the well. Land use changes such as deforestation or urbanization alter recharge patterns. Climate change, irrigation, and nearby river or lake levels also influence water table elevation over time.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy