Engineering Hydrology - The Hydrologic Cycle and Rainfall Runoff Processes

This set of vocabulary flashcards covers the fundamental concepts of engineering hydrology, components of the hydrologic cycle, and methods for calculating average rainfall.

Hydrology

The science of water that studies the occurrence, character, and movement of water within and between the physical and biological components of the environment.

Hydrologic Cycle

A continuous, orderly scheme used to systematically examine and analyze the movement of water through the landscape, which has no beginning or end.

Evaporation

The process by which water is transferred from the surface to the atmosphere as vapor, changing from a liquid into a gas.

Surface Runoff

Runoff that travels over the soil surface to the nearest stream channel.

Infiltration

The passage of water through the surface of the soil.

Percolation

The passage of water under hydrostatic pressure through the interstices of soil and rock.

Precipitation

The primary mechanism for transporting water from the atmosphere back to the surface of the earth; common forms include rain, hail, snow, and sleet.

Hail

A frozen form of precipitation associated with thunderstorms.

Sleet

Wintry precipitation consisting of snow that has partially melted on its way to the ground.

Tropical Cyclone

A storm system characterized by a large low-pressure centre and numerous thunderstorms that produce strong winds and heavy rain.

Transpiration

The evaporation of water into the atmosphere from the leaves and stems of plants, accounting for approximately 10% of all evaporating water.

Zone of Aeration

The soil layer nearest the surface where gaps between soil particles are filled with both air and water.

Zone of Saturation

The soil layer below the zone of aeration where gaps between soil particles are completely filled with water.

Water Table

The boundary between the zone of aeration and the zone of saturation; it rises or falls as the amount of groundwater changes.

Runoff

The movement of landwater to the oceans, chiefly via rivers, lakes, and streams, consisting of precipitation that does not evaporate, transpire, or penetrate the surface.

Basic Equation of Hydrologic Cycle

The unsteady flow equation represented as $I - Q = dS/dt$, where $I$ is input, $Q$ is output, and $dS/dt$ is the time rate of change of storage.

Infiltration Capacity

The maximum rate at which soil can absorb water, which depends on soil texture, structure, and moisture content.

Depression Storage

The filling of surface puddles, ditches, and other depressions that occurs after the rainfall intensity exceeds the infiltration capacity but before runoff is generated.

Arithmetic Mean Method

The simplest method for calculating average rainfall depth by averaging the values from a number of uniformly distributed gauges.

Thiessen Method

A method for calculating average precipitation by determining the area of influence for each station to form a series of irregular polygons.

Isohyetal Method

The most accurate but laborious method for representing spatial distribution of rainfall by drawing lines of equal rainfall (isohyets).

Isohyets

Lines drawn on a map that connect locations receiving equal amounts of rainfall.