Volume (\( V_t = \frac{W (C_1 D_0 + E_1)}{X_1} \)):

Where:

• \( V_t \) is the volume of water on the surface of the soil at time \( t \).
• \( W \) is the width of the border check, in meters (m).
• \( D_0 \) is the depth of water at the upper end, in meters (m).
• \( C_1 \) is the shape factor.
• \( E_1 \) is the distance leading to the edge in time \( t_1 \), in meters (m).
• \( X_1 \) is the depth correction factor.