hydrology Flashcards
are formed when
raindrops are carried
upward by thunderstorm
updrafts into extremely cold
areas of the atmosphere
and freeze.
Hail
is a liquid precipitation
falling from the sky. Rain
occurs when air rises into the
upper atmosphere and cools.
The cool temperatures cause
water vapor to condense into
water droplets, which fall
from the clouds as rain.
Rain
is like a mix of rain and snow, it starts as a snowflake but melts into raindrops as it falls through a layer of warm air
Sleet
is precipitation
that forms when water
vapor freezes. It is ice
crystals that form in the
cold clouds.
Snow
Rapid upward movement of warm
air causes short, intense rainfall,
often with thunderstorms or hail.
Convective Storms
Moist air rises over mountains, leading
to heavy rain on the windward side and
drier conditions on the leeward side
Orographic Storms
Large low-pressure systems bring
widespread, prolonged rainfall
Cyclonic Storms
Intense storms over warm oceans
produce heavy rain, strong winds, and
storm surges
Hurricanes or Tropical Cyclones
Liquid water drops
rain
ice crystals
snow
small ice pelletes
sleet
large ice balls
hail
rain that turns to ice on surface
freezing rain
light, tiny water drops
drizzle
soft ice balls formed on snowflakes
graupel
How much water
has fallen over a
period of time.
depth
Refers to the length
of time rainfall
occurs
duration
Ratio of the total
amount of rain falling
during a period of time
intensity
Graphical representation
between rainfall intensity
and time
hyetography
- Also known as Station Rainfall
it refers to the rainfall data of a station - Daily, weekly, monthly, seasonal, or annual rainfall
point rainfall
Rainfall is expressed in terms of
the _______ to which rainwater
would stand on an area, if all the
rain were collected on it.
depth
what to plant in certain areas, where and when to plant, when
to harvest
agriculture
how and when to irrigate
horticulture/viticulture
design drainage systems and prevent water-related issues in
buildings
engineering
An instrument to measure rainfall rate in a certain
period of time. It catches and represents the
precipitation falling on a respective surrounding
area.
rain gauge
This type of rain gauge is an ordinary rain gauge
non-recording
This type of rain gauge gives automatic rainfall records
without any bottle reading.
recording
WEIGHING BUCKET TYPE
TIPPING BUCKET TYPE
FLOATING TYPE
recording rain gauge
availability of continuous record of previous rainfall
continuity
rainfall data of previous year should be consistent with the
present environmental condition.
consistency
If the normal precipitation at each of the
selected stations is within 10% of that station with
missing data.
arithmetic-mean method
If the normal precipitation/rainfall at any of the
selected stations is more than 10% of that station with
missing records. Consists of weighing the precipitation at
the various stations by the ratios of normal annual
precipitations.
normal ratio method
calculated by taking an
average of the values that are
obtained from several
observation points or stations
within the region.
arithmetical-mean method
method
assigns weightage to stations
based on proximity, superior to
the arithmetic-mean method.
It’s effective for outside
catchment stations and easy to
calculate for fixed networks.
thiessen-mean method
entails
drawing isohyets derived from
precipitation data of different
stations and then taking an
average precipitation by
integrating over the areas
which correspond to these
lines
isohyetal method
A test for consistency of record or for rain gauge
inconsistency.
double-mass analysis
The process by which water in the
ground surface enters the soil
Depending on how saturated the
ground is, the water can continue
downwards to replenish water tables
and aquifers
infiltration
Infiltration is dependent on the condition of the land surface
(cracked, crusted, compacted etc.)
surface entry
Infiltration rates are greatly influenced by
factors like temperature, wind,
freezing/thawing cycles, soil moisture
condition, seasonal fluctuations, and the
intensity and duration of rainfall.
climate and weather condition
The amount and rate of water movement through the soil are
determined by the size and arrangement of soil particles.
soil texture and structure
Sand:
Silt:
Clay:
high infiltration rate
moderate infiltration rate
low infiltration rate
Saturated soils exhibit higher water content, preventing
infiltration and can even increase surface runoff and erosion
soil saturation
Steeper slopes generally experience faster
runoff and reduced infiltration rates, as water
moves downslope quickly. On the other
hand, soft slopes allow greater infiltration
rates because they make it easier for water
to disperse and seep into the soil.
slope of the land
- Roads and concrete pavements produce
an impermeable layer that prevents
infiltration. - Decreasing vegetation due to farming,
tree-cutting, and animal grazing will lower
permeability.
human activities
Increased evapotranspiration rates have the
potential to lower soil moisture content, which can
accelerate infiltration rates because drier soils
initially take up water more easily. Lower
evapotranspiration rates can cause a lower
infiltration rate because of decreased pore space
availability and possible surface sealing.
evapotranspiration
Measure infiltration over a large area
Provides understanding of infiltration
variability of the area
Used in agricultural assessments and
hydrological studies
areal measurement
Measure infiltration of a specific point
in the soil
Easy to perform
Used in site-specific studies
Point Measurement
- the speed at which water enters the soil
infiltration rate
- device used to measure the water infiltration into the soil
infiltrometer
uses a single ring driven in the
ground where water is poured
at a certain depth. The
decrease in water over time
reflects the infiltration rate
single ring infiltrometer
uses two concentric rings into
the ground. The inner ring is
driven into the ground and an
outer ring follows to help the
flow of water
double ring infiltrometer
capacity decreases with
time and ultimately reaches
a constant rate
horton’s equation
an alternative approach to developing a more approximate physical theory that has an exact analytical solution.
green-ampt model
- The soil under consideration is homogenous and stable,
implying that macropores and preferential migration
pathways should not be considered.
2.The supply of ponded water at the surface is not limited.
- A distinct and precisely definable wetting front exists, and
as water continues to infiltrates, the wetting front
advances at the same rate with depth - The capillary suction just below the wetting front is
uniform throughout the profile and constant in time
during the infiltration event. - The soil is uniformly saturated above the wetting front,
and the volumetric water contents remain constant
above and below the advancing wetting front
five principal assumptions of G-A Method
Case 1: i<Kₛ
The rainfall intensity is
less than the maximum
downward hydraulic
conductivity
Case 2: Kₛ< i < f
The rainfall intensity is
greater than the saturated
hydraulic conductivity but
less than the infiltration rate
Case 3: i > f
The rainfall intensity is
greater than the
infiltration rate and
runoff can occur
3 cases of g-a model
is the
amount of time that has passed from the
start of rainfall to the occurrence of ponds in
the observed area. _____ is usually utilized to determine the intensity of rainfall.
ponding time
principles behind the flow in open channels
leonardo da vinci
rainfall is the only source of water for rivers and springs in 15th century
bernard palissy
water came from precipitation
aristotle
who came up with water cycle
leonardo da vinci and bernard palissy
pioneers of modern hydrology
a. pierre perrault
b. marriot
c. hally
water balance equation and catchment area method
pierre perrault
first to measure evaporation in mediterranian
marriot
the study of origin, circulation, and distribution of water
scientific hydrology or simply hydrology
engineering application
applied or engineering hydrology
occurrence and distribution of water in surface
surface water hydrology
occurrence and distribution of water beneath the surface
groundwater hydrology
essential tool for planning of hydraulic structures such as dams
hydrology
