2: Evaporation & Ponding Time

Evaporation

is the process by which water is converted from its liquid state to its vapor form and thus transferred from land and water masses to the atmosphere.

Radiation

Evaporation is directly proportional to?

Strength of intermolecular forces

The ease of evaporation of a liquid is related to the strength of the attractive forces between the molecules in the liquid. In polar liquids cohesive forces are strong while in non-polar liquids the forces are very weak and the molecules escape easily.

Humidity of Air

If ____ (quantity of water vapor in the atmosphere) is high, the water holding capacity of air is less therefore less evaporation.

Surface Area

Rate of evaporation of a liquid can be increased by increasing the surface area of the liquid

Soluble salts

When salts are present, vapour pressure is decreased and hence the rate of evaporation is also decreased.

Pan

is a container of some standard material installed adjacent to the body of water

Pan evaporation

An amount of evaporation/time unit (the difference between the two measured water depths) is calculated

Ponding

term used in hydrology and refers to the instance when a land surface becomes saturated (from rain) and ___ of water occurs

48 hours

The excessive accumulation of water at low-lying areas that remain after ____ after the end of rainfall

no ponding

If the infiltration rate is greater than the rainfall rate

ponding occurs

If the rainfall rate is equal to or greater than the infiltration rate

infiltration rate

Dry soils tend to have pores and cracks that allow water to enter faster. As soil becomes wet, the ____ slows to a steady rate based on how fast water can move through the saturated soil

Rainfall intensity

Intensity measured over time of concentration of the watershed.

Suction head

The capillary attraction on the soil voids.

Hydraulic conductivity

Physical property which measures the ability of materials to transmit fluid through the pore spaces and fractures in the presence of applied hydraulic gradient

Hydraulic Gradient

slope of the water table, the change in water level per unit of distance along the direction of maximum head decrease

latent heat of vaporization

is the amount of heat absorbed by a unit mass of a substance.

Solar radiation

is the main source of heat energy.

Evaporation rate

is a function of several meteorological and environmental factors

Net radiation

The energy term for all transfer processes that organize and maintain the ecosystem

Latent heat of vaporization

is the amount of heat absorbed by a unit mass of a substance

Relative humidity

is the ratio of the actual water vapor pressure to the saturation water vapour pressure at the prevailing temperature.

Convection

mixes parcels of warm and cold air together and so changes the temperature of the two parcels.

latent heat

Energy may be transferred indirectly, without changing the temperature of the air parcel, through a change in phase of water in the atmosphere, otherwise known as?

Heat conduction

is governed by the thermal soil properties, volumic heat capacity, and heat conductivity. Many processes occurring in soils are strongly influenced by temperature.

Chlorophyll

is the molecule that absorbs sunlight and uses its energy to synthesise carbohydrates from CO2 and water. This process is known as photosynthesis and is the basis for sustaining the life processes of all plants.