Define precipitation, interception, and infiltration. What causes surface runoff?

Precipitation is the process by which moisture is released from the atmosphere to the Earth's surface. It occurs in various forms such as rain, snow, sleet, or hail. The amount of precipitation depends on factors like temperature, humidity, wind, and atmospheric pressure.

Interception refers to the process where precipitation is intercepted by vegetation, buildings, and other surface features before it reaches the ground. The intercepted water is either evaporated or absorbed by the vegetation, reducing the amount of water that reaches the ground as direct precipitation.

Infiltration is the process by which water seeps into the soil or porous rock from the ground surface. The rate of infiltration depends on various factors such as soil type, vegetation cover, and land use. When precipitation falls on the ground, some water infiltrates into the soil, while the rest flows as surface runoff or is stored in depressions.

Surface runoff occurs when the rate of precipitation exceeds the rate of infiltration. This can be due to several reasons: - Saturated soil: When the soil is already saturated with water, it cannot absorb more, and the excess precipitation becomes surface runoff. - Impervious surfaces: Urban areas with large amounts of concrete and asphalt prevent infiltration, increasing surface runoff. - Steep slopes: Sloped areas can cause water to flow faster, reducing the infiltration rate and increasing surface runoff. - Compacted soil: Soil compaction reduces the pore spaces in the soil, which decreases infiltration and leads to more surface runoff. - Vegetation: The presence or absence of vegetation affects the infiltration rate. Dense vegetation can promote infiltration by slowing down water flow, while barren land can increase surface runoff.