§671.APPENDIX C. Todd Uniform Flow Equation

If hydrogeologic information (e.g., transmissivity, porosity, hydraulic gradient, hydraulic conductivity, and saturated thickness of the aquifer) is available the lateral area of influence can be calculated for unconfined/confined unconsolidated or non-fractured bedrock aquifers as follows:

 

X	=	1.19 Q		Y	=	7.48 Q
		Ti				Ti

 

where

 

Q	=	daily flow from the well under normal operational conditions (cubic feet per day)
i	=	hydraulic gradient of the water table or potentiometric surface
T	=	aquifer transmissivity (gallons per day per foot)
X	=	Lateral area of influence or down gradient divide (feet)
Y	=	Maximum width of the lateral area of influence or the maximum width of the influx zone (feet)

 

The distance to the upgradient divide is established as the distance to the upgradient regional groundwater divide.