Surface Flow or Deep Soak? Runoff vs Infiltration Quiz

If gravity pulls water down to a porous surface, then it can move into the soil, which is infiltration. If the surface is non-porous or saturated, then the water must stay on top and move laterally, which is runoff.

If the land is steep, then gravity pulls water quickly down the incline. If water is moving quickly across the surface, then it has less time to soak into the pores of the soil. If it cannot soak in, then it remains on the surface as runoff.

If soil is saturated, then all the pore spaces between soil particles are already filled with water. If there is no space left in the soil, then new rain cannot enter the ground. If new rain cannot enter, then it must stay on the surface and become runoff.

If plants are present, then their leaves break the impact of falling rain, slowing it down. If roots grow in the soil, then they create channels and keep the soil loose. If water is slowed and the soil is loose, then infiltration increases.

If water moves from the atmosphere to the surface and then penetrates the ground, it is entering the geosphere. If this specific downward entry through the surface occurs, then the scientific term for the process is infiltration.

If a surface is paved with asphalt or concrete, then it is impermeable (has no holes). If a surface is impermeable, then 0% of the water can soak in. If water cannot soak in, then 100% of it must move across the surface as runoff.

If sand particles are large and irregular, then they do not pack tightly together. If they do not pack tightly, then the spaces (pores) between them are large. If the pores are large, then water can easily and quickly flow into them.

If water successfully infiltrates the surface, then it continues to move downward through the soil (percolation). If it reaches the saturated zone of the geosphere, then it joins the groundwater. If it joins the groundwater, then the aquifer is being refilled.

If rain continues, then the empty spaces in the soil gradually fill up with water. If the soil becomes more filled (approaching saturation), then there is less room for new water to enter. If there is less room, then the rate of infiltration slows down.

If rain falls faster than the soil can absorb it (A), it stays on top. If the surface has no pores (C) or if the pores are blocked by ice (E), water cannot enter. Therefore, A, C, and E all force water to stay on the surface.

If urban areas have many roofs and roads, then infiltration is low and runoff is high. If a large volume of water moves quickly into storm drains and streams all at once, then the water level rises rapidly. If the level rises too fast, then flash flooding occurs.

If gravity pulls water across the land surface, then it eventually collects in low points like gutters or creek beds. If this water is moving over the surface rather than through it, then it is defined as surface runoff.

If soil is compacted, then the particles are squeezed together. If the particles are squeezed, then the pore spaces are crushed or removed. If the pore spaces are gone, then water cannot enter, which means infiltration decreases, not increases.

If a rain garden is designed with loose soil and plants, then it creates a high-capacity area for water to enter. If more water enters the ground (infiltration), then less water flows into streets. If less flows into streets, then local flooding is reduced.

If runoff refers specifically to the liquid water moving across the Earth's surface, then it is a component of the Earth's water systems. If the hydrosphere contains all the liquid water on Earth, then runoff is a process of the hydrosphere.

If soil has many connected pores, then water can travel through it easily. If we are describing the ease of this passage, then the correct scientific term for this soil property is permeability.

If water flows across a surface like a road or a farm, then it picks up loose materials (chemicals, oils). If the water eventually enters a stream as runoff, then those materials are carried with it. Therefore, runoff is a major source of water pollution.

If a sponge has many small holes, then it represents the pores in soil. If you pour water on it and the water disappears into the holes, then it mimics how water moves into the ground. Therefore, a sponge is an accurate model for infiltration.

If soil can only absorb a certain amount of water per minute (infiltration capacity), then any extra must stay on top. If a downpour delivers 2 inches of rain per hour but the soil only takes 1, then the extra inch must become runoff.

If plants (A) or mulch (D) are present, then they physically hold the soil in place and slow down the water. If the water moves slower, then it has less energy to carry away soil particles. Therefore, A and D protect the geosphere.