PART 2 Flashcards
Area which contributes runoff or drains water into the reservoir (PAES 609:2016).
Watershed
A thermometer that has a constriction above the bulb that permits the mercury to rise in the
capillary tube but does not allow it to descend the capillary tube unless the thermometer is
reset (PAGASA, 2022).
Maximum thermometer
The science that encompasses the occurrence, distribution, movement and properties of the
waters of the earth and their relationship with the environment (USGS, 2022).
Hydrology
The study of the biological, chemical, and physical features of lakes and other bodies of fresh
water (Oxford Languages, 2022)
Limnology
A branch of meteorology and hydrology that studies the transfer of water and energy between
the land surface and the lower atmosphere (Wikipedia, 2022).
Hydrometeorology
Heavy rainfall or rain that accumulates at a rate of 3 tenths of an inch (0.3 inch or about 7.5
mm), or more, per hour (US National Weather Service, 2022)
Torrential rain
Dominant form of precipitation in the Philippines.
RAINFALL
Kind of thermometer with pin inside its tube which does not go with the expanding liquid when
temperature increases.
Minimum thermometer
Method of areal rainfall determination done by computing the weighted average.
Arithmetic method
An instrument to measure depth of rainfall.
Rain gage
Part of rainfall which runs off the soil as surface or subsurface flow.
Runoff
Ratio of runoff over rainfall.
Runoff coefficient
The part of rainfall that is stored in the root zone and can be used by the plants (FAO, 2022).
This excludes rainfall that does not reach the soil and percolation below the root zone. For
grassed soil surface, it is estimated that this rainfall is greater than 0.5 mm/day.
Effective rainfall
The inverse of the probability of exceedance of a certain hydrologic event.
Return period
Airmass lifting process which is mountain-facilitated.
Orographic
Airmass lifting process facilitated by sunlight or heating.
Convective
Indicates to what depth liquid precipitation would cover a horizontal surface in an
observation period if nothing could drain, evaporate or percolate from this surface
(Graf-Water, 2022).
Precipitation depth
The precipitation depth that corresponds to a liquid quantity of 1 liter falling into a 1 square
meter of ground area.
1 mm
Probability of occurrence in any year of hydrologic event recurring once in 4 years.
P=(1/Return Period)x100
25%
What is the probability of occurrence in any year of a hydrologic event recurring every year?
100%`
Rainfall depths recorded were as follows: 8mm and 2mm for 8:00 A.M. and 2:00 P.M.,
respectively on 7-7-2022 and 5 mm and 9 mm for 8:00 A.M. and 2:00 P.M., respectively on
7-8-2022. What is the total rainfall depth on 7-7-2022?
2 mm
Rainfall on 7-7-2022 = Rainfall at 2:00 P.M. on 7-7-2022 + Rainfall at 8:00 A.M. on 7-8-2022
= 2 mm + 5 mm
= 7 mm
The agrometeorological station uses electronic rain gage. The rainfall depths were recorded on
June 1, 2022 as follows: 2 mm from 6:00 to 8:00 A.M., 7 mm from 8:00 to 10:00 A.M., 9 mm
from 12:00 noon to 2:00 P.M. and zero rainfall for all other times of the day and the previous
day. What is the rainfall intensity recorded on June 1, 2022?
4 mm/hr
Intensity = Depth/Time, time is from 8:00 AM of current day to 8:00 AM of the next day
= (7mm from 8:00 to 10:00 A.M. + 9mm from 12:00 noon to 2:00 P.M.)/(2hr +2 hr)
= 4 mm/hr
Estimate the time of concentration of a certain watershed having a time lag
1.43 hours
TC = TL / 0.70
= 1 hr / 0.70
= 1.43 hrs
The maximum permissible water velocity for clay loam canal surface based on PAES
603:2016.
0.80 m/s