Aquifer type

Confined

Thickness (m )

40

Conductivity (m/day)

5

Pumping rate (m ³ /day)

5000

River Head - South (m)

10

River Head - North (m)

0

Δx, (m)

10

Δy, (m)

10

Δt, 0-2 yrs (days)

2.5

Δt, 2-5 yrs (days)

5

Δt, 5-10 yrs (days)

10

2 Yr WHPA

5 Yr WHPA

10 Yr WHPA

The site under consideration consists of a sand and gravel aquifer sandwiched between two rivers. The aquifer is about 2000 m long and 1500 m wide. The average land elevation is about 10 m. The head gradient between the two rivers causes a general flow towards the North. A well pumps at a distance of 200 m from the Northern river. The resulting Well Head Protection Area is sub-divided into 2, 5 and 10 year WHPAs. The RED zone denotes an area around the well, in which the water would reach the well within 2 years. Similarly, the YELLOW and BLUE zones denotes 5 and 10 year zones respectively. The classification of these zones is very important. Usually, it is not desirable to have possible sources of contamination, such as gas stations, industries etc within the 2 and 5 Year Zones. The zones are delineated using a process of reverse particle tracking. In this process, several particles are added around the well and then traced backwards in time. Notice that the time displayed has a negative sign. This signifies that particles are being tracked backwards in time.