Area 2 - Hydrology, Irrigation & Drainage, SWCE Flashcards
PART 3: Objective type under bloodied knife- disguised as soil and water, irrigation
Hydraulics: Basic equation
- Continuity Equation
- Energy Equation
- Momentum Equation
Flow classification under hydraulics
- time as the criterion
- space as the criterion
- based on flow regimes
Types of channel
- original-based
- geometry-based
The physical removal of topsoil by various agents. The process of detachment and transport of soil particles.
soil erosion
Formula for design peak runoff
q=CiA or q=0.0028CiA
Formula for runoff volume estimation
Q=0.5qT
Maximum wind speed of 30-34 kph
tropical depression
maximum wind speed of 65-117 kph
tropical storm
maximum wind speed of >117 kph
typhoon
SW monsoon
habagat
Characteristics of raindtorm
- intensity
- duration
- area extent
- frequency
NE monsoon
amihan
Probability that a T-year storm may occur in any series of N-years
P exceedance= 1-(1- 1/T) ^N
Flow measuring devices/structures
weirs, parshal flume, orifice, trajectory
Probability that a T-year storm may not occur in any series of N-years
P non-exceedance = (1- 1/T)^ N
Probabilistic analysis of hydrologic processes
hydrologic frequency analysis
Undergoes continuous change in T
Hydrologic process
Definite law of certainty exists
deterministic process
Chance phenomena, cannot be readily identified, time independent
probabilistic process
Chance, time dependent
stochastic process
Gumbel distribution
XT=M+S (0.78 lnT-0.45)
Flow over a surface
runoff
Drainage after it reaches a defined channel
streamflow
travels over the ground surface
surface runoff
- Infiltration excess overland flow
- Saturation excess overland flow
types of surface runoff
Part of precipitation, which infiltrates into the soil surface and moves laterally through the upper soil horizons towards thee streams
interflow
ground discharge into a stream due to deep percolation of the infiltrated water into groundwater aquifer
groundwater runoff
surface runoff that flows over the surface towards stream channel
overland flow
surface runoff
direct runoff
interflow
subsurface runoff, through flow
groundwater runoff
base flow
factors affecting runoff
- climatic factors
- physiological factors
record of the highest stage at a stream
crest stage gage
record the pressure required to maintain a small flow of gas
bubbler gage
motion of a float is recorded on a graph
float-type water stage recorder
discharge measurement
float method, current meter
caused by a raindrop
splash/ raindrop erosion
thin film of soil layer detached and transported by water flowing
sheet erosion
combination of splash and sheet erosion
interrill erosion
finger-like rills appear on the soil surface
rill erosion
advanced rills, rills that developed in size
gully erosion
erosion of stream bank by flowing water
stream bank erosion
caused by waves
coastal erosion
land slides and slips due to saturation of steep hills and slopes
slip erosion
universal soil loss equation
A = R x K x LS x C x P
erosion control: vegetative measures
- reforestation,
- agroforestation,
- strip ropping,
- mulching,
- contour cultivation,
- cropping system
erosion control: engineering measures
- terracing,
- grassed waterways,
- check dams/ weirs,
- farm ponds/ water impounding dams,
- diversion canal,
- gabion,
- riprap,
- stone walls
suited for 2:1 slope or less
riprap
contours that cuts into the hill slope in a step-like formation
bench
bench slope
25-30%
for maximum soil and water conservation
zingg/ conservation bench terrace
zingg/ conservation bench terrace slope
9-24%
2 types of broad-based terrace
- graded/ channel type
- level/ridge type
open channels protected with suitable grasses along the slope and act as outlet for terraces
grassed waterways
conservation structures
- drop structure
- chute spillways
- vengineering
discharge is constant with respect to time
steady flow
discharge in not constant with respect to time
unsteady flow
depth of flow is the same at every section of the prismatic channel
uniform flow
depth changes along the length of channel
varied flow
if the depth changes abruptly over a comparatively short distance (such as hydraulic jump)
rapidly varied flow
if the depth changes smoothly over a distance
gradually varied flow
Fr =1
critical flow
Fr > 1
supercritical flow
Fr < 1
subcritical flow
fluid moves in parallel with no cross-currents, Re < 2000
laminar flow
pulsatory cross-current velocity, Re > 4000
turbulent flow
special case of flow discharge with distance along the channel
spatially variable flow
to measure the flow in a large river, the river is usually divided into sections
direct method
use of orifice, weir, flume, and other control structures
indirect method
formula for free discharge orifice
Q = cA sqrt of 2gh
formula for rectangular weirs
Q = 1.84 LH ^(3/2) or
Q = 1.84 (L-0.20H) H^(3/2)
formula for triangular weirs
Q = 1.42H^(5/2)
Trapezoidal weir (cipolletti)
Q = 1.86LH^(3/2)
magnitude of floods, design of structure (drainage canals, flood spillways, and culverts)
peak flow (qp)
flood warning time, watershed response, water quality
time to peak (tp)
total water yield from a storm for a given watershed
runoff volume (v)
time for surface flow and interflow to reced, duration of flooding
recession time (tr)
tp + tr
base time (tb)
low flow, dependable flow, groundwater recharge
base flow (bf)
passage of water into soil surface
infiltration
process by which precipitation reaching the earth’s surface is returned to the atmosphere
evapotranspiration
movement of water through the phreatic zone
groundwater flow
geologic formation containing water in its voids/ pores that maybe extracted economically and used as water supply
aquifer
confined under pressure grater than atmospheric by overlaying impermeable strata, aka artesian/ pressure aquifer
confined aquifer
water table serves as the upper surface of the zone of saturation, aka free phreatic/non-artesian aquifer
unconfined aquifer
exist when the piezometric surface lies above the ground
flowing artesian well
completely obstructs the flow of groundwater
aquiclude
impervious and semi confined nature which transmits water at a very slow rate
aquitard
the ability of the soil to transmit water
hydraulic conductivity
velocity through the void spaces obtained by dividing the average velocity by the porosity
seepage velocity
to make a liquid or gas pass through a porous substance, vertical subsurface movement of water
percolation
runoff paths
- through flow
- overland flow
- groundwater flow
a gradual process in liquid which something is changed from liquid
evaporation
a process by which vapor lose heat and changes into a liquid
condensation
rain, snow, or hail, all of which are formed by condensation of moisture in the atmosphere and fall to the ground
precipitation
a chemical process in which a solid substance is converted into a gas directly, without passing through an intermediate liquid phase
sublimation
the horizontal transfer of a property such as heat, caused by air movement
advection
forms of precipitation
drizzle/ mist,
rain,
glazed,
rime,
snow,
snow pellets,
hail,
ice pellets
average precipitation
arithmetic mean, thiessen method, isohyetal method
consists of the vaporization of liquid water contained in the plant tissues and the vapor removal to the atmosphere
transpiration
