Hydraulic Gradient Calculator

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Overview

The hydraulic gradient represents the change in total hydraulic head per unit distance in the direction of fluid flow. It functions as the driving force behind groundwater movement through aquifers, effectively quantifying the energy slope that fluid must traverse.

Symbols

Variables

i = Gradient, h_1 = Head 1, h_2 = Head 2, L = Flow Distance

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When To Use

When to use: Apply this equation when calculating the flow direction or velocity of groundwater within a saturated porous medium. It is a fundamental component of Darcy's Law and assumes a linear relationship between head loss and distance.

Why it matters: This metric is vital for predicting the movement of environmental contaminants and designing sustainable well systems. It allows hydrologists to determine how quickly and in which direction groundwater will migrate through the subsurface.

Avoid these traps

Common Mistakes

• Failing to use consistent units for dH and dL.

One free problem

Practice Problem

A monitoring well shows a water level elevation of 120 meters. A second well, located 250 meters away in the direction of flow, shows an elevation of 115 meters. Calculate the hydraulic gradient.

Solve for: $i$

Hint: The gradient is the difference in height divided by the horizontal distance.

The full worked solution stays in the interactive walkthrough.

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Related Formulas

References

Sources

1. Fetter, C.W. Applied Hydrogeology. 4th ed. Pearson Prentice Hall, 2001.
2. Wikipedia: Hydraulic gradient
3. Freeze, R.A. and Cherry, J.A. (1979). Groundwater. Prentice-Hall, Inc.
4. Fetter, C.W. (2001). Applied Hydrogeology (4th ed.). Prentice Hall
5. Fetter, C. W. Applied Hydrogeology. 4th ed. Pearson Prentice Hall, 2001.
6. Freeze, R. A., & Cherry, J. A. Groundwater. Prentice-Hall, 1979.
7. Bird, R. B., Stewart, W. E., & Lightfoot, E. N. Transport Phenomena. 2nd ed. John Wiley & Sons, 2002.
8. A-Level Geology — Hydrogeology