**GROUND WATER HYDROLOGY -NUMERICALS **

**Numerical 1:**

In an area of 22km², the water table dropped by 3m. If the porosity is 30% and the specific retention is 14% , Determine (i) the specific yield of the aquifer and (ii) change in ground water storage.

**Numerical 2:**

A field test for permeability consists in observing the time required for a tracer to travel between two observation wells. A tracer was found to take 10 h to travel between two wells 50 m apart when the difference in the water-surface elevation in them was 0.5 m. The mean particle size of the aquifer was 1mm and the porosity of the medium 0.3. If v=0.01 cm²/s estimate (a) the coefficient of permeability and intrinsic permeability of the aquifer, and (b) the Reynolds number of the flow.

**Numerical 3:**

An artesian aquifer 20 m thick has a porosity of 20% and bulk modulus of compression 10^8 N/m² and Bulk modulus of Elasticity of water is 2.1 * 10^9 N/m². Estimate the storage coefficient of the aquifer.

**Numerical 4:**

A 30 cm well completely penetrates an unconfined aquifer of saturated depth 25 m. After a long period of pumping at a steady rate of 2100 lpm, the drawdown in two observation wells 30m and 90m from the pumping well were found to be 5m and 4m respectively. Determine the transmissibility of the aquifer. What is the drawdown at the pumping well?

**Numerical 5:**

A tube well penetrates fully in an unconfined aquifer. Calculate the discharge from the tube well under the following conditions:

Diameter of the well = 30 cm

Drawdown = 3 m

Effective length of the strainer = 15m

Coefficient of permeability of aquifer = 0.05 cm/sec

Radius of zero drawdown = 300 m

**Numerical 6:**

Design a tube well for the following data:

Yield required = 0.20 cumecs

Radius of circle of influence = 300m

Drawdown = 6 m

Thickness of confined aquifer = 40m

Permeability coefficient = 80 m/day

**Numerical 7:**

A well penetrates fully a 10 m thick water bearing stratum of medium sand having coefficient of permeability of 0.004 m/sec. The well radius is 100 mm and is to be worked under a drawdown of 4 m at the well face. Calculate the discharge from the well. What will be the percentage increase in the discharge if the radius of the well is doubled? Take R = 300 m in each case.

**Numerical 8:**

In a recuperation test of a 3.0 m diameter open well the water level changed from 114.60 m to 115.70 m elevation in 120 minutes. If the water table elevation is 117.00 m. Determine (i) the specific capacity per unit well area of the aquifer, and (ii) discharge in the well under a safe drawdown of 2.75m.