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EART 10 - Geologic Principles		NAME_____________________
Fall 1995		

DARCY'S LAW
due date:  November 9, 1995

Refer to the text (Hamblin and Christiansen):	Discharge and Velocity p. 276
							Factors in Streamflow   p. 244

Coefficient of permeability (K) for some rock types:
	igneous rock, unfractured		1 x 10-10 cm/s
	igneous rock, fractured			1 x 10-3 cm/s
	sandstone				1 x 10-6 cm/s



A person illegally dumps a large quantity of pollutant at point A in the figure
above.  For the following problems, assume that groundwater flows parallel to
the hillside.  Give answers for rates in cm/s and for time in years.  Show all work
on a separate piece of paper that you will turn in with this answer sheet.

PART A	Calculate the rate of flow (Q/A) and how long (t) it will take the
pollutant to travel to point B if the hillside is composed of:
	1.  unfracture igneous rock
	2.  fractured igneous rock
	3.  sandstone

Show your work on a separate paper
 and put your answers in the table below.

		unfractured 		fractured		sandstone
		igneous rock		igneous rock

 		5 X 10-11		5.0 X 10 -7		5.0 X 10 -4
Q/A (cm/s)	__________		__________		_________

		5.65 X 10 8		5.65 X 10 4		5.65 X 10 1
t (years)	__________		__________		__________



What is the effect of rock permeability (K) on the rate of flow?

ÒRate of flow increases with inreasing permeability.Ó
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PART B	Calculate the rate of flow (Q/A) and the time (t) it takes the
pollutant to travel to point B through sandstone given that the slope of the angle
ABC is:
	1.  14.0 degrees
	2.  26.6 degrees
	3.  36.9 degrees

Show your work on a separate paper 
and put your answers in the table below. 

Note:  Length B-C is constant, however length A-C will vary with slope.

			14.0 degrees	26.6 degrees	36.9 degrees

			2.5 X 10-7	5.0 X 10-7	7.5 X 10-7
Q/A (cm/s)		______		_____		_____

			105,000 y	56,000 y	42,000 years
t (years)		______		_____		_____


What is the effect of slope (hydraulic gradient) on the rate of flow?

"Rate of flow increases with increasing gradient."
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