Calculating Recharge and Contaminant Transport in a Confined Groundwater Aquifer

[Lois Chang]

Homework Statement

The following questions apply to a confined groundwater aquifer consists of a homogeneous sandy soil with hydraulic conductivity, K, of 3 x10-2cm/sec. In the area of interest, the hydraulic head is 500 m, the aquifer length is 10 km, and the cross-sectional area of the aquifer is 100 m x 100 m.

2.
Question A:
If the watershed (the surface area over which rainfall is collected by the aquifer) for this aquifer is 10 km long x 1 km wide, how much rainfall per year must fall in order to recharge the aquifer discharge? Hint: Figure out the volume the aquifer delivers in a year and match that to the volume of rainfall in the catchment area.

Question B:
Since the fraction of time an organic contaminant spends in the moving aquifer determines how fast it moves through the environment. Consider a spill of an organic contaminant into this aquifer 500 m the delivery surface of the aquifer. The contaminant has a partitioning ratio of 9:1 between soil and water respectively. How much time will pass between the spill of this contaminate at the upstream end and the contamination of a well found at the end of the aquifer so described? Hint: Material only moves when in the water phase. Figure out how long it takes for the aquifer to move the final 500 m then use the retardation (90%) determine how long it takes the contaminant to move the same distance.

 

[Chestermiller]

I haven't seen any equations from you yet. How is the superficial velocity related to the head gradient and the hydraulic conductivity?