Hydrology and Fluvial Geomorphology: The drainage basin system Flashcards
What is precipitation?
Water falling from sky as rain, hail, sleet or snow
What is interception?
The capture and storage of precipitation by level, branches, etc of trees and vegetation such that it does not directly fall to the ground. The water may then be evaporated or absorbed by the plant or reach the ground as throughfall or stemflow
What is surface storage?
Water that has not infiltrated the surface and is stored on the surface in the form of puddles lakes etc. Some is temporary but others are permanent
What is soil moisture storage
Subsurface water in the soil and subsurface layers above the water table
What is groundwater storage?
Percolated water that is held within the aquifers below the water table (phreatic water). Groundwater accounts for 97% of all freshwater on earth. Recycling timeframe 20,000 yrs
What is channel storage?
All water stored in rivers, streams and other drainage channels
What is stemflow?
The progression of intercepted precipitation down the stems and trunks of vegetation
What is through fall?
Water that falls to the Earth’s surface from branches/leaves through gaps in the vegetation or that drops from leaves & twigs
What is overland flow?
Movement of water across the surface of the ground or downslope as it can’t be absorbed into the ground; leads to the low of water on the surface direct to the channel
What is hortonian overland flow?
Movement along the surface which occurs when rainfall exceeds the infiltration capacity of the soil. This can be due to intensity of rainfall/snow melt/antecedent moisture/impermeability of the surface/slopes
What is saturated overland flow?
Water is not infiltrated on a slope due to the saturated nature of the soil, and flows across the surface. This most frequently occurs on the lower parts of slopes that have been saturated by water from above.
What is infiltration?
The movement of water downwards into the soil from the surface
What is percolation?
The downward movement of infiltrated water under gravity through the pores, joints etc. of the soil and underlying permeable rock
What is throughflow?
the lateral downslope movement of water below the surface within soils after it has been infiltrated into the soil. Soil flows under gravity towards a stream channel or lake through percolines and pipes
What is groundwater flow/base flow?
Water flows under gravity and hydrostatic pressure towards the river channel. Discharge into a stream from the groundwater store, especially sustaining flow between rainfall events. Relatively constant, but increase slightly following rain
What is groundwater recharge
Water that has soaked into the ground and moved through pores and fractures in the soil and rock to the water table to fill up previously depleted groundwater stores. Recharge maintains the supply of water that flows through the ground water system to wells, streams and springs. Occurs when precipitation exceeds evapotranspiration and water percolates downwards to the aquifer
What is a spring?
Flows of water where the water table intersects with the surface
What is channel flow/stream flow
Movement of water in channels such as streams or rivers
What is evapotranspiration?
Combination of moisture loss due to evaporation and transpiration from the stomata of vegetation
What is evaporation?
Process by which a liquid is changed into a gas
What is sublimation?
Process by which solid is changed into a gas
What is transpiration?
The movement of water within plants and its loss as vapour through the stomata of the leaves to the atmosphere.
What is river discharge?
Movement of water in channels such as streams and rivers.
What is the water table?
Upper layer of phreatic zone. This varies seasonally depending on precipitation levels.
What is the phreatic zone?
Permanently saturated zone within solid rocks and sediments
What is the aeration zone
Zone that is seasonally wetted and seasonally dries out above the water table.
What is an aquifer?
Rocks that contain significant quantities of water
What is porosity?
The proportion of pore space to solid material and therefore the ability to hold water
What is permeability?
Permeability is the rate and ease with which water may be transmitted within a rock or the rate with which it is able to pass through it via joints and fissures
What is antecedent moisture?
Moisture in the soil that is retained after a period of rainfall
What is the hydrological cycle?
Cycle of water between atmosphere, lithosphere & biosphere
What is infiltration capacity?
Maximum rate at which rain can be absorbed by a soil in a given condition
