CIV250 - Hydraulics and Hydrology | Weeks 1-3

Hydrology

Study of water in its different forms

Hydraulics

Study of liquid movement

Hydrologic systen

A set of interacting parts that take in water and other inputs, processes them internally, and then produces outputs.

Water Cycle

Evaporation, Evapotranspiration, Sublimation, Condensation, Precipitation, Infiltration, Runoff

Watershed

Area of land that drains to the same lowest hydrographic feature, separated from other watersheds by a watershed divide or surface divide

Open Watershed

Flow exits through an outlet

Closed Watershed

Flow within boundaries of a watershed

Watershed Characteristics

Area, slope, shape, soil type, land use

Lumped

Averaged as a single spatial unit where flow is a function of time.

Distributed

Various points in space where flow is a function of space and time.

Unsteady

Changes with time

Steady

No change with time

Event Based

Single event

Continuous

Multiple events

Deterministic

Same input always results in a consistent output

Stochastic

Model includes some random component

Frontal Air Mass

Warm air is lifted over cooler air by frontal passage

Orographic Air Mass

Air mass rises to pass over a mountain range

Convective

Air is drawn upwards by surface heating

Conditions for Precipitation

i) satruated atmosphere
ii) small particles for condensation/sublimation
iii) water coalesce enough to fall

Drizzle

Diameter < 0.5 mm, intensity < 1 mm/hr

Rain

Diameter > 0.5 mm

Sleet

Small frozen raindrops

Snow

Ice crystals formed by sublimation

Hail

Ice particles, from thunderstorms with strong upward wind

Atmospheric Circulation

Process where the atmosphere functions as a vast heat engine, transferring energy from the equator toward the poles

Circulation Cells

Hadley Cell, Ferrel Cell, Polar Cell

Areal Measurement

The process of quantifying the area of a specific region, often used in hydrology to assess watershed characteristics

Microwave Sensors

Detect microwave radiation reflected by precipitation particles

Infrared Sensors

Detect the temperature of cloud tops

Visible and Near-Infrared Sensors

Observe cloud cover, identify cloud types, and estimate cloud motion

Precipitation Intensity

depth/time

Precipitation Hyetograph

depth/intensity over time

Precipitation Mass Curve

Cumulative precipitation hyetograph

Arithmetic Mean

Method that takes the average of the precipitation gages

Thiessen Polygons

Method that takes the average of the precipitation gages weighted by area

Isohyetal Method

Method that takes the average of the precipitation gages weighted by contour lines

Inverse Distance Weighted (IDW) Interpolation

Interpolate values at locations with no precipitation gages

Evapotranspiration

i) evaporation from the soil
ii) evaporation of the intercepted water
iii) evaporation from the depression storage
iv) transpiration of water by plants and trees

Transpiration

evaporation of water absorbed by plants

Factors Affecting Transpiration

humidity, temperature, wind speed, solar radiation

Potential Evapotranspiration (PET)

Max amount of water to evapotranspire

Actual Evapotranspiration (AET)

Actual amount of water to evapotranspire

Reference Crop Evapotranspiration (ETo)

PET of an idealized crop of a uniform height, completely covering the ground, growing actively

Crop Evapotranspiration (ETc)

is determined from ETo by applying a crop coefficient (Kc) that simulates the condition of the specific crop