Groundwater - All subsurface water found in the pore space of soils and rocks.

Capillary Water - Moisture held in the soil by surface tension and hydrogen bonding with soil materials.

Gravity Water - Water in excess of capillary water that is able to flow down through a permeable earth layer.

Porosity - The amount of space between rock and soil particles (affects water storage)

Permeability - The ability of soil or rock to allow water to pass through (affects ground water movement)

Zone of Aeration - Upper soil/rock level in which pore space is a combination of capillary water and air

Zone of Saturation - Lower soil/rock level in which pore space is full of water.

Water Table - The top of the zone of saturation where it meets the zone of aeration.

Aquifer - A layer of porous earth materials that stores and transmits water.

Aquiclude - A layer of impermeable earth material that prevents the movement of water through it.

Artesian Well - The flow to the surface of pressurized water trapped in an aquifer between aquicludes

Cone of Depression - The lowered level of the water table around  an active well (The cumulative affect of pumping over a larger area it is known as draw down)

Subsidence – The sinking of land due to the removal of water from the ground below.

Recharge zone - Area in which rain and surface water percolate down into an aquifer

Karst Topography - Pitted surface and cave topography created by chemical weathering of limestone regions

Sinkhole - A dip (depression) in the surface of a Karst landscape

Pothole - A vertical opening which links a sinkhole to a cavern

Disappearing Stream (Lost River) - A stream that leaves the earth surface by way of a Karst pothole

Doline - Large sinkholes often created by the collapse of a cavern

Karst Valley (Valley Sinks) - The joining together of sinkholes and dolines so that they create a valley.

Cavern - A large, room-like cave

Speleology - The scientific study of caves

Haystacks (Karst Towers) - The remaining limestone hills in a highly eroded Karst landscape.

Runoff - The flow of water on the land surface in unchannelled sheet flow and channelled stream flow

Fluvial - Stream related processes and land features

Tributaries - Smaller streams that join a larger stream

Base Level - The hypothetical elevation below which a river or stream cannot erode any further.

Drainage Divides - The higher land between two watersheds that divides the the flow of water between those watersheds (Interfluves divide flow between streams)

Watershed - Land area drained by a group of streams upstream from a point on the stream network [or from the mouth of a river] (aka Catchment Area or Drainage Basin)

Stream Networks:
 Dendritic - Finger or Leaf like
 Trellis - Parallel channels with right angle connecting streams
 Radial - Diverging streams moving away from a center, high point
 Rectangular - Guided by right angle joints and faults in bedrock
 Centripetal - Converging streams moving inwards toward a basin
 Parallel - Streams flowing side by side for a while before joining
 Deranged - Flow in various directions (seems like a random pattern)

Intermittent - Streams that flow only part of the year

Perennial - Streams that flow all year long

Graded - A stream whose gradient (slope) has been reduced to a level where erosion and sedimentation are balanced.

Hydraulic Action - The suction and pressure applied by moving water on the bottom of a stream which causes particles to be lifted up and moved.

Abrasion - Wearing down of stream bed materials by the grinding action of moving particles in the stream.

Bed Load - Materials moved along the stream bottom (traction)

Suspended Load - Materials moved above the stream bottom (suspension)

Oxbow Lake - A curved lake found where a former meander in a river was cut off, isolating it from the river

Floodplain - The flat land next to a river which is occassionally flooded and covered with alluvium.

Braided Stream - A stream that is divided into many interconnected channels due to heavy sedimentation

Delta - The depositional feature, often triangular shaped, where a stream or river meets a water body.

Estuary - A body of water at the mouth of a river where freshwater and saltwater mix.

Arroyo/Wash/Barranca/Wadi - An intermittent streambed in a dry climate, usually with steep walls

Drought - A period of time in which there is little or no rain, or when the amount received is below what usually falls.  Common in arid and semi-arid climates.

Pluvial - Refers to a region's past climate in which there was more rainfall.

Interior Drainage Basin - An inland area which receives inflow of runoff but has no outlet to drain the water away.

Exotic Streams - A stream that originates in a wet area (often up in the mountains) and has enough water volume to flow through a desert area without drying up.

Badlands - A region of rain carved hills and gullies with little or no vegetation.  It is a rugged landscape created by the easy erosion of soft materials.

Mesa - A flat-topped, steep-sided remaining portion of a plateau or tableland.

Butte - A mesa that has eroded on all sides to create a flat topped hill.

Bolson - The basin and hillside area between two adjacent ridges in a desert.

Alluvial Fan - The fan shaped depositional feature created when a stream with a heavy sediment load slows down as it enters a valley.

Bajada - A sloped area at the base of desert mountain slopes in which a number of alluvial fans have merged.

Alluvial Plain - The extensive alluvial deposits (stream deposited materials) on a desert valley floor.

Pediment - The slightly sloped bedrock surface covered by alluvial materials at the base of desert mountains.

Playa - Dry lake bed found in desert basins which often is covered with evaporites (salt crystals).

Inselbergs - Remaining tips of mountains sticking up through the alluvial materials of an extensive alluvial plain.

Eolian - Wind related erosional processes and landforms.

Deflation - The removal of surface material by wind action.

Saltation - The bouncing movement (in water or air) of particles large enough to be lifted off the surface, but too large to become suspended.

Abrasion - The grinding up of surface materials as they are moved against each other by wind (or water).

Dust Storm - The movement of large quantities of lighter materials in the air column.  Can darken the sky.

Sandstorm - Like a dust storm, but with heavier sand particles that move closer to the ground.

Desert Pavement - The remaining rocky desert surface after deflation and sheet flow have removed the lighter particles.

Dunes - A desert or beach feature created by the movement and piling up of sand and other course materials by the winds.

Erg - A desert region covered by dunes ("sand sea").

Slipface - The steep, downwind ("back side") of a dune.

Loess - Large deposits of wind blown silts and clays from arid areas (that may have been covered earlier by glaciers.)