A contaminated plume is found having capture zone type curve Q/BU = 1600 m. U is

Question

A contaminated plume is found having capture zone type curve Q/BU = 1600 m. U is the regional groundwater velocity; Q is pumping rate and B is the aquifer thickness. The aquifer also has a hydraulic conductivity of 2 × 10-5 cm/sec, a hydraulic gradient of 0.007 and a storavity of 0.006. The aquifer is 20 m thick. The diameter of the well is 10 inch and the equation for non-equillibrium condition is
?0?? = (3.4??/4????)??????(1.8????/??2??)
Where T is transmissivity, r is the radius of the well, t is the pumping duration and ho – h is the drawdown.
a) What is the groundwater velocity?
b) What is the Pumping rate?
c) What is the Transmissivity?
d) What is the drawdown this aquifer can support with the pumping rate of (a) after two years of pumping?

Explanation / Answer

a) Groundwater velocity= K x hydraulic gradient = 2 x 10-5 x 10-2 x 0.007 = 14 x 10-10 m/ sec

b) Pumping rate from an aquifer = Q = KA(h/L) = 2x10-5 x 0.007 = 14 x 10-8 cm3/sec

c) Transmissivity is a property of an aquifer is defined as the ability of the aquifer to transmit an unit cm3 of water in an unit hydraulic gradient per unit thickness of the aquifer.

Therefore, Transmissivity T = KB = 2x10-5 x 10-2 x 20 = 40 x 10-5 m2/sec

d) We know that,

Storativity = Volume of water released from the storage / cross sectional area x drawdown

therefore , drawdown = volume of water released from the storage / storativity x cross sectional area

= 14 x 10-10 / 0.006 x 3.14 x 10 x 2.54 x 10-2 = 1.755 x 10-5 m

Now since drawdown is greater than the storativity, therefore it cannot support the the pumping for 2 years.

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