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A strategic programme for NERC Lowland catchment research
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Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

adsoption

The process of accumulation of a substance on the surface of a solid, such as river sediments.

advection

Mass transport caused by the bulk movement of flowing groundwater in which the mass is dissolved.

aquifer

Aquifers are water bearing strata, such as Chalk or loose material like sand and gravel, that can transmit water in significant quantity. They are the source of groundwater. Springs and rivers form where the water table meets the surface.

attenuation

The delayed movement of a solute relative to the rate at which the water in which it is dissolved is flowing. Both physical and chemical processes can contribute to attenuation, e.g. diffusion.

B

biofilm

A complex aggregation of microorganisms, typically associated with the excretion of a protective and adhesive matrix.

biota

All of the living organisms (e.g. plants and animals) in a region.

C

catchment

See river catchment. Groundwater catchments also exist, and often have similar (but not necessarily identical) boundaries to the overlying river catchment, in cases where the river and aquifer are hydraulically connected.

chalk streams

Chalk streams are streams which flow over Chalk and receive a significant proportion of their flow from groundwater. Because they are fed by groundwater, their flow volumes are more consistent throughout the year (rather than responding rapidly to rainfall events), and their water is clear with a more constant temperature. However, they typically change in length as groundwater levels rise and fall seasonally. This effect is sometimes called bourne flow. Chalk streams have unique ecological characteristics.

climate change

Long-term change in temperatre, rainfall and other parameters caused by a combination of dynamic changes in the Earth's climate and by other forces such as human activity.

confined aquifer

An aquifer that is confined between two non-aquifers. Confined aquifers usually occur at depth. In a confined aquifer, the water level in a well usually rises above the top of the aquifer.

D

diffusion

Net flux of solutes from a zone of higher concentration to a zone of lower concentration.

double porosity

An aquifer with both intergranular and fracture porosity is said to have double porosity, or dual porosity. Both advection and diffusion can be significant solute transport mechanisms in a double porosity medium.

drift

Geological materials, often sands and gravels, left behind by retreating glaciers. The materials can can be deposited directly from the galciers, from rivers associated with glacial melting or be due to mass movements including landslides. In the UK, the term is commonly used to describe deposits of the Quaternary age.

dry valley

A dry valley is a valley without a surface stream water may move under the surface instead, through the permeable soils or rocks.

E

ecosystem

The biological (and physical) components of an environment considered in relation to each other as a unit or system.

evaporation

The process by which water turns into its gaseous form, water vapour.

F

flow accretion

The increase in flow along a reach of a river.

fracture flow

Flow of groundwater through fractures.

fragmented woodlands

Woody vegetation covering restricted areas, for example hedgerows, shelter belts, small forest patches or riparian woodlands

G

groundwater

Groundwater is underground water in the cracks and pores of the saturated permeable rocks.

H

habitat

Ecological or environmental area inhabited by a particular plant or animal or group of plants and animals.

heterogeneity

A heterogeneous medium has different properties at different points. For example, a sandstone may be more permeable in some layers than in others, and would therefore be described as heterogeneous.

A measure of water pressure or total energy per unit weight above a datum. It consists of two components, the elevation head and the pressure head.

hydrology

Hydrology is the study of the movement, distribution and quality of water.

hydrogeology

Hydrogeology is the part of hydrology that studies groundwater in particular.

hyporheic zone

The hyporheic zone is located at the interface of aquifers and rivers, and comprises the sediments in which there is exchange and mixing of groundwater and river water. It is an important zone for pollutant, energy and carbon cycling, and may be an important component of the riverine habitat. (from Hyporheic Network.)

hypoxic

reduced concentration of dissolved oxygen in a water body.

I

interception loss

The difference between the gross rainfall falling onto a canopy and the sum of the net rainfall and the stemflow reaching the ground.

invertebrates

Collective name for animals withought backbones, for example, insects or worms.

isotope

An isotope is one of several forms of an element all isotopes of an element have the same number of protons, but they have different numbers of electrons.

J


K

karst

Limestone terrains produced by dissolution and attrition by groundwater. Karstic limestone is characterised by the absence of surface drainage and by sinks and rising streams connected underground by flow along major fissures or in cave systems.

L

LOCAR

The Lowland Catchment Research programme.

M

macrophytes

Large plants

matrix flow

Flow of water through the interconnected pores within a rock or soil rather than through fractures (see also fracture flow).

N

nitrate

A compond with the chemical formula NO3. An important component of agricultural fertilizers, but also a major source of diffuse pollution in groundwater and rivers in agricultural areas.

nutrient

A nutrient is a substance, such as nitrogen (N) or phosphorus (P), that is necessary for the growth and survival of a living thing.

O

off-river habitats

Fish habitats outside the main river channel, i.e. side channels and inundated floodplains

P

packer test

A hydraulic test applied to a (usually short, typically up to 5m) interval in a borehole isolated by two inflated packers.

permeability

The term permeability, used in a general sense, refers to the capacity of a rock to transmit water. Such water may move through the rock matrix (intergranular permeability) or through joints, faults, cleavage or other partings (fracture or secondary permeability).

permeable catchment

see river catchment

plant-flow interactions

Processes by which plants influence river flow, and vice versa; for example, aqueous plant growth may reduce flow rates.

propagule

Any part of a plant such as an organ, spore, seed or cutting, used to propagate a new plant

Q


R

rain shadow

The zone on the lee side of a strip of tall vegetation where the amount of rain reaching the ground is reduced despite the absence of a canopy cover

river catchment

A river catchment is the area of land whose water drains into that river. A permeable catchment lies on porous rock, such as chalk or sandstone.

reach

A stretch of a river, often between locations where tributaries join the river.

recharge

The hydrologic process where water moves down from surface water to groundwater. More formally. it is the entry of water from the unsaturated zone above the water table into the water table.

riparian zone

The land adjacent to, and influenced by, a river, e.g. the river banks. A transitional zone between river and upland environments.

S

sediment

Solid matter which has been transported by water. The sediment may be suspended in the water or be deposited, e.g. on a river bed.

sediment budget

A sediment budget compares the volume of sediment brought into the study area to that which is leaving the study area.

solute

A dissolved constituent of water, e.g. sulphate or calcium.

stable isotope

A stable isotope is an isotope which does not undergo spontaneous radioactive decay.

stomatal sensitivity

The degree to which the stomata in the leaves can change their aperture in response to environmental factors such as humidity or irradiance

T

till

A till is an unsorted or poorly sorted glacial deposit (see also drift).

tracer tests

Tracer tests are used to identify pathways of water movement. A chemical or bacterialogical compound (tracer) is added to a body of water (e.g. groundwater), and locations believed to be downstream are monitored for the presence of that tracer.

transpiration

The water evaporated into the atmosphere through the stomata (and, to a lesser extent, the cuticula) of the leaves

U

unsaturated zone

The zone between the land surface and the water table in an unconfined aquifer. The pores may contain some water, but they also contain air (with some exceptions). See also confined aquifer.

V

vadose zone

An alternative name for the unsaturated zone of an aquifer.

W

water table

The water table is the depth below which the soil or rock is saturated with water.

Water Framework Directive

The European Water Framework Directive (2000/60/EC), which came into force in December 2000, is the most significant piece of European legislation relating to water management for at least two decades. The Directive provides a framework to pull together existing legislation relating to water and expands the scope of water protection to all waters. The main aims of the Directive are to prevent further deterioration of, and promote enhancement of, the status (quality and quantity) of water bodies and related ecosystems. This includes the progressive reduction in the pollution of groundwater.

X


Y


Z