Estimating Seepage Discharge

To estimate the seepage discharge from river A to river B per unit length of the rivers, we can use the concept of equivalent coefficient of permeability. The equivalent coefficient of permeability is a measure of the overall permeability of the medium through which the seepage occurs.

Step 1: Understand the Problem
We have two parallel rivers, A and B, separated by a land mass. The seepage occurs from river A to river B through the land mass. We need to estimate the seepage discharge per unit length of the rivers.

Step 2: Gather Data
To compute the seepage discharge, we need the following data:
- Length of the rivers (L): This is the distance over which the seepage occurs.
- Coefficient of permeability (k): This is the measure of the ability of the soil to transmit water.
- Hydraulic gradient (i): This is the rate of change of hydraulic head over a certain distance.

Step 3: Compute Seepage Discharge
The seepage discharge (Q) can be calculated using Darcy's law, which states that the seepage velocity is directly proportional to the hydraulic gradient and the coefficient of permeability. Mathematically, it can be expressed as:

Q = k * i * A

where:
- Q is the seepage discharge per unit length (m³/day)
- k is the coefficient of permeability (m/day)
- i is the hydraulic gradient (m/m)
- A is the cross-sectional area perpendicular to the flow (m²)

Step 4: Compute Transmissibility
The transmissibility (T) is a measure of the ability of an aquifer to transmit water. It is the product of the coefficient of permeability and the thickness of the aquifer. Mathematically, it can be expressed as:

T = k * h

where:
- T is the transmissibility (m²/day)
- k is the coefficient of permeability (m/day)
- h is the thickness of the aquifer (m)

Step 5: Round off the Results
Once the seepage discharge and transmissibility are calculated, round off the results to two decimal places.

Explanation
The equivalent coefficient of permeability provides an overall measure of the permeability of the medium through which the seepage occurs. It takes into account the properties of the soil and the thickness of the aquifer. By using Darcy's law, we can estimate the seepage discharge per unit length of the rivers. The transmissibility, on the other hand, gives us an idea of the overall ability of the aquifer to transmit water.

By following these steps, we can estimate the seepage discharge and transmissibility, which are important parameters for analyzing seepage and designing appropriate drainage systems in civil engineering projects.