What type of water movement occurs with moving water?

• A. Capillary action
• B. Osmosis
• C. Mass flow
• D. Diffusion

Answer: (C)

Mass flow is the transport of water and dissolved substances as a bulk fluid through soil pores. When water is moving, the solutes are carried along with that flow, so the movement of water drives the movement of dissolved materials. Capillary action describes water movement in very small pores due to cohesive and adhesive forces, which can happen without bulk water flow. Osmosis involves water crossing a semi-permeable membrane from low to high solute concentration, not general soil water movement. Diffusion is the spread of dissolved substances down a concentration gradient in place, which can occur without bulk water movement. So, when water moves as a bulk fluid through soil, the accompanying transport of solutes is best described as mass flow.