Answer:

The constant of proportionality between seepage velocity and hydraulic gradient is called the coefficient of percolation.

Explanation:

Seepage velocity is the velocity at which water flows through a porous medium, such as soil or rock. It is influenced by the hydraulic gradient, which is the change in hydraulic head per unit distance. The hydraulic head is the potential energy per unit weight of water at a specific point in a flow system.

The coefficient of percolation, also known as the coefficient of seepage or coefficient of permeability, is a measure of the ease with which water can flow through a porous medium. It represents the rate at which water can percolate through the medium under a unit hydraulic gradient.

Key Points:

- The coefficient of percolation is denoted by the symbol "k" and has units of length per unit time, such as meters per second or centimeters per day.
- It is a fundamental property of the porous medium and is influenced by factors such as the size and shape of the pores, the connectivity of the pore network, and the viscosity of the fluid.
- The coefficient of percolation can vary widely depending on the characteristics of the porous medium. For example, highly permeable materials, such as gravel or sand, may have high coefficients of percolation, while less permeable materials, such as clay or silt, may have lower coefficients.
- The coefficient of percolation is an important parameter in groundwater flow calculations and is used in various engineering applications, such as the design of drainage systems, the analysis of seepage through dams or embankments, and the evaluation of the potential for contaminant transport through the subsurface.
- The coefficient of percolation can be determined experimentally through laboratory tests, such as constant-head or falling-head permeability tests, or it can be estimated using empirical correlations or derived from field measurements.

In conclusion, the coefficient of percolation is the constant of proportionality between seepage velocity and hydraulic gradient and represents the ease with which water can flow through a porous medium. It is an important parameter in groundwater flow calculations and is influenced by the characteristics of the porous medium.