Geo lecture #16

Hydrologic Cycle

The continuous movement of water on, above, and below the surface of the Earth.

Residence Time

The average length of time that water spends in a reservoir, calculated as reservoir size divided by yearly flux.

Average residence time of oceans

4,000 years.

Average residence time of glaciers

20 to 1,000 years.

Average residence time of seasonal snow cover

2 to 6 months.

Average residence time of soil moisture

1 to 12 months.

Average residence time of groundwater

100 to 10,000 years.

Average residence time of lakes

50 to 100 years.

Average residence time of rivers

2 to 6 months.

Average residence time of atmosphere

10 days.

Low pressure

Occurs at the surface where air rises, causing moisture to condense and rainfall to occur.

High pressure

Occurs where air sinks, resulting in dry conditions and the formation of deserts.

Monsoon

A seasonal wind pattern that brings significant precipitation.

El Nino/La Nina

Interannual changes in ocean and atmospheric circulation across the tropical Pacific that impact rainfall patterns.

Drought

A prolonged deficiency of precipitation, typically lasting at least one season.

Groundwater

Water present in the subsurface, including soil moisture and water below the water table.

Water Table

The upper surface in the Earth's subsurface where all pore spaces in sediments and rocks are filled with water.

Aquifers

Rock and sediment units below the surface that can hold and transport water.

Overdraft

Occurs when the supply of water to a water-table aquifer is less than its discharge, causing the water table to lower.

Glaciers

Large accumulations of ice that exist year-round on the land surface.

Climate change impact on glaciers

Higher temperatures lead to greater summer melt, shrinking ice areas, and shifting peak discharge to late spring/early summer.

Sea level rise causes

Thermal expansion of seawater and melting of glaciers.

Seawater invasion of aquifers

Rising sea levels causing seawater to intrude into coastal freshwater aquifers.