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EPA On-line Tools for Site Assessment Calculation

Hydraulic Gradient -- Magnitude and Direction
Gradient Calculation from fitting a plane to as many as thirty points

a x1 + b y1 + c = h1
a x2 + b y2 + c = h2
a x3 + b y3 + c = h3
. . .
a x30 + b y30 + c = h30

where (xi,yi) are the coordinates of the well and
hi is the head

i = 1,2,3, ... , 30
The coefficients a, b, and c are calculated by a least-squares fitting of the the data to a plane

The gradient is calculated from the square root of (a2 + b2) and the angle from the arctangent of a/b or b/a depending on the quadrant
Illustration of model results showing relationship between coordinate directions and model outputs: angle and direction of flow
Inputs
Site Name
Date
Calculation basis
Coordinates  
I.D. x-coordinate y-coordinate head
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Results
Number of Points Used in Calculation
Max. Difference Between Head Values
Gradient Magnitude (i)
Flow direction as degrees from North (positive y axis)
Coefficient of Determination (R2)

Contact Jim Weaver to ask a technical question on this material.

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