WATER 1 SUMMARY
microtopography: topographic wetness
index at small scale
C1: Catchments presence and type of vegetation impacts water
1.1 catchment characteristics porosity: fraction of open pore space
between soil particles -> determines how
Catchment (basin): area from which excess
much water can be stored in ground
water flows toward river’s outlet/
conductivity: permeability: how easy water
debouchment (at sea/when river joins larger
flows between soil particles -> determines
river) (channels + hillslopes)
how quickly water is transported
Behavior catchment determined by:
porosity and conductivity is determined by
(1) surface and subsurface
size/shape/origin of soil particles:
(2) climate (P/ET/T)
gravel: large: high conductivity
Flood risk determined by:
sand: average: average conductivity
(1) local slope (large ->water flows quickly)
clay: small: low conductivity
(2) draining area (large->large amount of
peat: high porosity, low conductivity (plant
water passes)
material fixates water)
(λ) = risk of flood = A/slope = topographic wetness index
aquifer: layer of permeable soil, can store
topographic index: probability of saturation
and transport water well
➔ high in hillslope, low on hilltop
bedrock: solid rocks (under layer of soils)
topographic wetness index:
sub-catchments: parts of large catchment
high -> ponds form low -> dry area
DEM: digital elevation model: elevation for
Catchment delineation: determining
each pixel on a map (measure: radars/satellites)
catchment boundary
GIS: geographical information systems:
- Surface water divide: determined with
mapping of P+ET and land use and soil type
river channels till their sources
- Topographical water divide: determined
by highest points 1.2 channels
- Groundwater divide: determined by surface of catchment: land and water
groundwater topology: channel networks
polders: low-lying land protected by dikes geomorphology: origin of landscape+channels
(catchment boundary) dendritic↴ channel network is determined by preferred
the catchment area increases downstream: route and landscape formation
ZONE 1: upper course: production zone classify channel networks:
(surface water and sediments are formed) (1)drainage density (2) pattern analysis
ZONE 2: middle course: transport zone (1)drainage density (Dd): [km-1] channel
(main meandering channel, few branches) density, dependent on length channels and
ZONE 3: lower course: deposition zone catchment area; how much km of channel is
(delta (multiple branches) because of (1) flat necessary to drain a catchment of 1 km
landscape and (2) large amounts of sediment high drainage density in semi-arid climates
and water) (temporary large water discharge)
topography: variation in elevation high drainage density=low conductivity
draining area: the surface area uphill from a (2)drainage patterns:
point till water divide hillslopes:
1)Dendric pattern: many channels, most
efficient for transport (with homogeneous
landscapes: soil/rock)
2)Radial pattern: one central point into all
direction (volcanoes and mountains)
3)Trellis pattern: many channels in same
direction each side river (folds in earth crust)
,4)Parallel pattern: fast flow (steep slopes) Precipitation measurements techniques:
tributaries: branches rain gauge: collect water in reservoir –
Channels in headwater (upstream part of measure volume divided by surface area
catchments) often run dry and overflow. gauge = rainfall sum in mm. (can also be
Source: location upstream where channel heated for measuring snow); influenced by
starts wind (rain droplets blown over gauge =
links: channel segments underestimation rainfall)
junctions: locations where channels merge weather radar: sense location + severity
Strahler order numbering: all outer rivers precipitation on large distance: radio waves
get 1, same number link-> number up sent to atmosphere and reflected by water
otherwise highest remains (highest number is droplets/ice particles: reflected % of radio
found at outlet) waves = P intensity; overestimated rainfall->
exterior link: link between source first junction measure P high above surface (=less than
interior link: link between two junctions ground): corrected with gauge measurements.
1.3 climate
In channels water is added by precipitation
(rain, snow, hail, fog, dew) and removed by
evapotranspiration: effective precipitation:
P-ET, the water which is discharged
Discharge is determined by climate+weather
flux: movement through surface in a certain t
two types of precipitation:
1)Stratiform precipitation (frontal precipitation)
- winters in temperate climates
- long period
- low precipitation intensity
- thin grey clouds
- low special variability Evaporation: transition of water from liquid to
2)Convective precipitation water vapor (requires heat of vaporization:
- tropical/summer in temperate climates 2,45*106 J)
- short period Sun provides short-waves radiation
- high precipitation intensity albedo: shortwave radiation reflected by land
- small white clouds with vertical structure surface; depends on land cover
(caused by upward movement water droplets) deciduous forests: normale bomen
- high spatial variability coniferous forests: kerstbomen
spatial variability in P is determined by size Earth emits long-wave radiation, partly
and shape of clouds reflected back by clouds.
High precipitation: downwind areas water Net radiation [W/m2] = difference incoming –
evaporates (oceans/lakes/rainforest/wetlands) outgoing radiation (short and long radiation):
+ windward side mountains because 1)sensible heat flux: heating land surface/air
condensation and sublimation + near cities 2)latent heat flux: evaporation
(rising hot air to colder air) 3)soil heat flux: heating ground below
rain shadow: small amount precipitation energy balance = all heat fluxes
downwind side mountain (leeward side) Total evapotranspiration = transpiration +
P Netherlands: 750 mm/y interception evaporation + soil evaporation +
ET Netherlands: 500 mm/y open water evaporation
runoff Netherlands: P-ET=250 mm/y 1)transpiration: water through stomata during
Precipitation events P with dry spells in photosynthesis when gas exchange takes place
between (long in semi-arid clim) 2)interception evaporation: E of P which
monsoon: rainy season falls on leaves, don’t reach soil (faster than 1)
Climate change effects 1.average annual P 3)soil evaporation: evaporation from moist
sum and 2.type of P; higher T = less snow soil (no precipitation -> decreases each day)
precipitation -> more rain -> discharge peaks
, 4)open water evaporation: evaporation from surface closing the pores and hindering
lakes and rivers infiltration
amount of ET is determined by: Water transportation capacity of sublayer
1)meteorological factors: net radiation, high increases when soil wetness increases (more
air T (because more moisture), low air water = more transport)
humidity, high wind speeds (moist air is Hydrophobic soil: water resistant – small
refreshed with dry) infiltration capacity (very dry soil)
2)land use: vegetated land, coniferous = high
ET, agricultural crops = low ET (only few months) soil consists of:
3)low amount of water in ground: ET=low (1)soil matrix: soil particles
measuring ET: (2)pore space: space between soil particles
Evaporation pan: water container which level is filled water/air. Macropores: cracks in clay
measured, the decrease in water level = open soil/rock. pore fraction↴
water evaporation. Porosity: ratio pore space to total volume
Lysimeter: container filled with soil and
vegetation. loss of mass (weighed) or outflow
at bottom is measured
Reference evapotranspiration (ETref) ET that
theoretically might occur for meteorological
conditions on watered grassland
Potential evapotranspiration (ETpot) ET that
theoretically might occur for meteorological
conditions on local vegetation
crop factor (f)
Actual evapotranspiration (ETact): ET in reality
Wet areas ETact=ET pot -> soil dries ETact < ETpot
1.4 rainfall-runoff processes
rainfall-runoff processes: processes which
determine the routes of surface runoff
(determined by catchment features and climate)
interception: storage of P water on leaves
throughfall: part of rainwater fall on -Saturated zone: area below groundwater
vegetation which is not stored there level, where all pores are filled water.
stemflow: movement of water down stems of -Unsaturated zone: area above groundwater
vegetation. level, where pores are filled water and air.
interception capacity: the maximum volume Capillary fringe: thin zone just above
of water that vegetation can intercept/store groundwater, saturated.
(depends on type vegetation, growing pattern, Percolation: gravity causes downward
P intensity/duration/frequency/type) movement of water through unsaturated zone
infiltration: downward movement of water towards saturated zone.
from soil surface through soil. Determines Capillary rise: shallow groundwater table –
distribution between (sub)surface storage and water sucked upwards by negative pressure
(sub)surface runoff. caused by ET in topsoil.
infiltration speed: speed at which water
moves into soil [mm/h] water is stored on land surface because of:
infiltration capacity: maximum possible - almost impermeable layer
infiltration speed at a certain moment (depend - infiltration excess:
on land cover, soil type and wetness). P intensity > infiltration capacity
P intensity < infiltration capacity (all P will infiltrate) - saturation excess: soil is already
P intensity > infiltration capacity (P stays on land) saturated
Infiltration capacity decreases during rainfall - seepage: groundwater flowing up to surface
events -> topsoil wet -> less space water
soil compaction: small soil particles are (1)depression storage: ponding in low-lying
transported to and deposited on the soil parts of landscape.
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