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55 Cards in this Set
- Front
- Back
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Hydrological Cycle
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Water cycle
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Closed System
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Because, with just a few minor exception, no water enters or leaves the system
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Drainage Basin
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The area drained by a river and its tributaries
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Drainage Divided (or watershed)
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The line defining the boundary of a river or stream drainage basin and separating it from adjacent basin
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Water Balance
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The relationship between the inputs and outputs of a drainage basin
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Maximum Sustainable yield
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The maximum level of extraction of water that can be maintained for a given area, indefinitely
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Wetlands
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Areas that are regularly saturated by surface water or ground water, including freshwater marshes, swamps and dogs
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Vegetation effects the movement of water in six ways
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+ By storing intercepted precipitation
+ By providing points for re-formation of raindrops + By providing protecting of the ground surface from the impact of raindrops + By providing leaf litter for debris dams + By removing water from the soil (that is later evaporated back into the atmosphere as a gas) + By disturbing the surface soil and construction of root channels |
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Precipitation
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The transfer of moisture (as dew, hail, rain, sleet or snow) to the earth's surface from the atmosphere
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Interception
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The capture of raindrops by plant cover, which prevents direct contract with the soil
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Runoff
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Precipitation that does not soak into the ground but flow over it into surface waters
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Groundwater
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Water held underground in soil or porous rock, often feeding springs and wells
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Evapotranspiration (EVT)
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The loss of water from vegetation and water surfaces to the atmosphere
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Evaporation is the process by which a liquid becomes a gas. It is a function of
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+ Vapour pressure
+ Air temperature + Wind + Rock surface (e.g. bare soil and rock have higher rates of evaporation than surfaces with a protective tilth, where rates are low) |
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Potential Evapotranspiration (pEVT)
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The rate of water loss from an area if there were no shortage of water
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Condensation
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Is the process by which gas (water vapour) becomes liquid
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Eustatic Change
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Refers to a global change in sea level
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Isostatic Adjustment, or Isostacy
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The change in the level of the land relative to the level of the sea
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Throughfall
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Water that reaches the ground either directly or after being intercepted by vegetation
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Permeability
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The ease with which water moves downwards through soil and rock material
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Aquifers
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Stores of groundwater/ Rock that hold water
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Drainage Basin Hydrological Cycle: Infiltration
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Is the process by which water sinks into the ground
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Drainage Basin Hydrological Cycle: Infiltration Capacity
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Refers to the amount of moisture that a soil can hold
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Drainage Basin Hydrological Cycle: Infiltration Rate
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Refers to the speed with which water can enter the soil
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Drainage Basin Hydrological Cycle: Percolation
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Refers to water moving deep into the groudwater zone
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Drainage Basin Hydrological Cycle: Overland Runoff
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Occurs when precipitation intensity exceeds the infiltration rate, or when the infiltration capacity is reached and the soil saturated
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Drainage Basin Hydrological Cycle: Groundwater Zone
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IS normally divided into a zone of saturation, in which the underground water fills all the spaces in the rock, and a zone of aeration above it, in which the water does not fully saturated the pores
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Drainage Basin Hydrological Cycle: Water Table
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Divides one zone from the other
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Drainage Basin Hydrological Cycle: Zone of Aeration
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Is a transitional zone in which water is passed upwards or downwards through the soil
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Drainage Basin Hydrological Cycle: Overland flow occurs in two main ways
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+ When precipitation exceeds the infiltration rate
+ When the soil is saturates (all the pore spaces are filled with water) |
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Drainage Basin Hydrological Cycle: Through Flow
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Refers to water flowing through the soil in natural pipes and percolines (lines of concentrated water flow between soil horizons)
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Drainage Basin Hydrological Cycle: Baseflow and Interflow
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Refer to the movement of water within the zone of aeration (interflow) and within the zone of saturation (baseflow)
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Soil Moisture Recharge
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Occurs when precipitation exceed potential EVT - there is some refilling of water in the dried up pore or the soil
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The Drainage Basin: Humid Terrains
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Areas where running water id the main influence on the formation of landforms
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The Drainage Basin: Water from high area to low area
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It usually taking the path where the least amount of energy is needed. The higher the altituded of water in a stream, the greater the amount of potential energy it possesses to erode the land scape
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The Drainage Basin: Eroding
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(or wearing away) the land surface. A stream cannot erode below a base level
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The Drainage Basin: Inputs and Outputs
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Each stretch of river receives inputs of water and sediment from upstream. These inputs combine with the water and sediment in the section of river, and a quantity of water and sediment will leave the stretch of river as outputs
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The Drainage Basin: Deposition
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More sediment enters the stream than leaves it
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The Drainage Basin: Dynamic Equilibrium
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This means that while individual particles of water and sediment are constantly moving (and therefore dynamic), the overall pattern is not changing (and therefore in equilibrium)
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The Drainage Basin: Drainage Density
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Is the ratio of the total length of the streams in a basin, measure in km, to the total area of the basin, measured in km2
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Discharge
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The volume of water that passes through a stream's cross section in a given a period of time
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Hydraulic Action
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Is simply the erosive force of water beating on rocks erosion by the impact of water
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River Regimes
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Is the seasonal variation in the flow of river. Variations in a river flow depend on many factors:
+ The amount and nature of precipitation + Seasonal Variations in temperature and evaporation + Changes in vegetation cover + Variations in rock types, soil types and the shape and size of the drainage basin of these, seasonal changes in climate generally have the greatest impact on changes in river flow |
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Load
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Materials carried by the river
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The main types of erosion
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+ Abrasion (or corrasion): the wearing away of the bed and bank by the load carried by a river
+ Attrition: the wearing away of the load carried by the river. It creates smaller, rounder particles + Hydraulic Action: the force of air and water in the sides of ricers and in cracks + Solution (or corrosion): the removal of chemical ions, especially calcium, which causes rocks to dissolve |
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There are three important features on Hjulstrom curve
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+ The smallest and largest particles require high velocities to lift them
+ Higher velocities are require for entrainment than for transport + When velocity falls below a certain level (settling or fall velocity), particles are deposited |
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The main types of transportation
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+ Suspension: small particles help up by turbulent flow in the river
+ Saltation: heavier particles bounced or bumped along the bed of the river + Solution: the chemical load carried dissolved in the water + Traction: the heaviest material dragged or rolled along the bed of the river + Flotation: leaves and twig carried on the surface of the river |
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Urban hydrology and the storm hydrograph
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urban hydrograph have:
+ A shorter lag time + A steeper rising limb + A higher peak flow (discharge) + A steeper recessional limb |
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Levee
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When the velocity of the river is reduced, the river has to deposit some of its load. It drops the coarser, heavier material first to form raised bank, or levees, at the edge of the river. This means that over centuries the levees are built up of coarse material such as sand and gravel, while the flood plain consist of fine silt and clay
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Meader
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Meandering is the normal behavior of fluid and gases in motion. Meander development occurs in conditions where channel slope, discharge and load combine to create a situation where meandering is the only way that the stream can use up the energy it possesses equally throughout the channel reach
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River Terrances
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A river terrace is an eroded floodplain, generally separated from the new floodplain by a steep slope. it is formed by changes in gradient, sediment load, climate change or human activity or any combination of these. It is the result of both deposition and erosion
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Human Modification of floodplains
Urban hydrology |
+ Encroachment on the river channel occurs as a result of embankments, reclamation and riverside roads
+ Replacement of vegetated soils with impermeable surfaces reduces infiltration, percolation and storage and so increases runoff and the velocity of overflow + building activity clear vegetation, which exposes soil and increases overland flow, and disturb and sumps the soils, increasing erodability + dams help reduce flood peak, by storing eater in reservoir |
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Alternative Stream Management Strategies
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+ Bearing the loss
+ Emergency action + Flood-proofing + Flood control + Land-use zoning + Flood insurance |
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Loss and degradation of wetlands is caused by several factors, including:
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+ Increased demand for agricultural land
+ Population growth + Infrastructure development + River flow regulation + Invasion of non-native species and pollution |
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Case Studies
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· Flooding e.g. Argentina, 2013
· Benefits & problems of dams e.g. Aswan, Egypt · Ground Water Management, Coca Cola, India |
