The upstream slope of an earth dam under steady seepage condition is

Explanation:

Equipotential line

• A line in the seepage flow field where the hydraulic head is constant.

• No water flow occurs along this line (flow is always perpendicular to it).

• Helps in plotting flow nets but is not the upstream slope itself.

Additional InformationFlow line

• A line that shows the path of water particles as they move through soil.

• Water flows along flow lines, and these are perpendicular to equipotential lines.

• Represents direction of seepage flow but not the surface slope of the dam.

Phreatic line

• The true free water surface within the dam where pore water pressure is atmospheric (zero gauge pressure).

• Separates saturated zone below from unsaturated above inside the dam.

• The upstream slope of an earth dam under steady seepage coincides with the phreatic line.

• It is a curved line starting from the reservoir water level and ending at the downstream toe, indicating the seepage surface.