Drainage Basin Characteristics- Inputs, Outputs, Stores, Flows Flashcards
Stemflow
water which trickles along twigs and branches and finally falls down the main trunk
Precipitation
Conversion and transfer of moisture in the atmosphere to the land via rainfall, hail, dew and snow.
Interception loss
water that is retained by plant surfaces and is later evaporated away or absorbed by the plant. Interception loss varies with different types of vegetation.
Less from grasses (shoots have smaller surfaces) than from woodland trees such as beeches. For agricultural crops (cereal). In the winter coniferous trees intercept more than deciduous in winter (lose their leaves in autumn and winter and therefore have a lower SA)
Aquifers
rocks which contain significant quantities of water and are permeable providing a reservoir for water. Natural Regulator in hydrological cycle as water moves very slowly and absorbs water which would otherwise reach streams quickly. Also maintain stream flow in dry periods.
Field Capacity
Amount of water held in the soil after excess water drains away-saturation or near saturation.
Channel storage
all water that is stored in rivers, streams and other drainage channels. Some are seasonal and may disapear underground naturally (in areas with carboniferous limestone) or in urban areas where they are culverted
Throughflow
the lateral movement of inflitrated water in soil. The water moves parallel to the surface (horizontally) down the slope to the river channel along percolines (defined lines of seepage).
Soil Moisture Budget
the annual balance between precipitation, evapotranspiration, and runoff i.e. annual balance between the inputs and outputs. It is calculated from the formula:
P = E + R +/- S
(Where P is precipitation, E is evapotranspiration, R is runoff and S represents changes in storage over a period of time, usually one year)
Aeration Zone
zone which is seasonally wetted and seasonally dries out.
Drainage Basin Definition
An area of land drained by a river and its tributaries. Is an open system as it allows for the movement of matter and energy across its boundaries
Groundwater
subsurface water stored in rocks. Accounts for over 96% of all freshwater on earth.
Interception and its 3 main components
when water is caught and stored by vegetation. The 3 main components are Interception loss, Throughfall, and Stemflow.
Water Table
Water table is an underground boundary. It marks the point below which the soil or rocks are permanently saturated with water.
Surface Runoff
water that flows over the lands surface when :
- precipitation exceeds infiltration rate
- the soil is saturated
Saturation
refers to a soil’s water content when practically all pore spaces are filled with water. If precipitation continues on a saturated soil, it will result in surface runoff, water percolation down to the water table & groundwater stores being recharged. If soil is poorly drained and/or compacted so that water is unable to drain away, it can lead to the soil becoming waterlogged.
