Hydrology and Watersheds Quiz

Engineering Hydrology (CEI 541)

• Course covers hydrological cycle components and processes
• Lecture 1: Introduction to the hydrological cycle
• Lecture topics cover a range of subjects, from hydrometeorology, to the effect of climate change on water cycles, to water loss, runoff computations, rainfall-runoff simulation, flood routing, and reservoir routing
• Topics include flood hazards, methods for controlling flash floods, and mitigating flood damage
• The course further includes sediment transport, sediment volume estimation, control, and sediment loss in wadis (using USLE)
• Hydrology is the science of water dealing with water occurrence, circulation, and distribution in the Earth's atmosphere.
• A good understanding of hydrological processes assists in the assessment of water resources, management, and conservation.
• Engineering hydrology specifically deals with water resources estimation, the processes of precipitation, evaporation, evapotranspiration, runoff, and their interplay.
• Flood and drought studies involve strategies for managing and combating these phenomena.

Introduction to Hydrometeorology

• Hydrometeorology studies the transfer of energy and water between the land surface and lower atmosphere.
• Temperature, humidity, wind, and solar radiation influence water distribution and movement within the hydrological cycle.
• Hydrometeorology is critical in understanding precipitation patterns, evaporation, and extreme weather events.
• This knowledge aids in water management and helps predict water availability in reservoirs and rivers.

Expressions

• Evaporation: Liquid water transforms into vapor.
• Transpiration: Liquid water from plants changes to vapor.
• Sublimation: Solid water directly transitions to vapor.
• Condensation: Transported water vapor transforms into tiny droplets in clouds.
• Transport: Atmosphere movement of water from oceans to land.
• Precipitation: The primary method of water transfer from the atmosphere to the Earth's surface.
• Groundwater: Water infiltrated into the soil, flowing downward to impermeable rock, then laterally.
• Runoff: Water flowing downhill on land.

Water Budget/Water Balance

• The water volume globally remains constant but shifts between phases.
• Water budget states the change in storage within a domain equals the sum of inflow, outflow, groundwater, evaporation, and precipitation.
• Inputs - Outputs + Accumulation = 0 (simplified water budget equation)

Watershed

• Watersheds are areas of land where rainfall, snowmelt, and runoff channel into a common body of water
• Watershed boundaries and characteristics such as size, slope, and shape are crucial for understanding the interactions within a basin.
• Quantitative characteristics include stream frequency, drainage density, and time of concentration

Time of Concentration

• The time needed for water from the most distant point in a basin to reach the outlet.
• Various variables influence time of concentration: hydraulic characteristics of the basin, flow paths, length, slope, etc.

Equations to estimate Tc

• Several equations exist for estimating the time of concentration, including Kirpich, Horton, and Kerby's.
• Input variables for calculating time of concentration include maximum flow length, watershed slope, and average flow velocity.

Precipitation

• Precipitation is any form of water (liquid or solid) falling from the atmosphere onto the Earth's surface.
• Different forms include rain, snow, hail, and sleet.
• Precipitation is a crucial part of the water cycle, directly affecting various hydrological processes.

Measuring Precipitation

• Several methods measure precipitation, including standard rain gauges, automated rain gauges, tipping bucket gauges, weather radar, and weather satellites.
• Standard and automated rain gauges directly collect precipitation, while weather radar and satellites analyze atmospheric conditions to provide insights.

Estimating Missing Data

• The Normal Ratio method assists in estimating missing precipitation data in regions.
• It uses nearby weather/rainfall stations with consistent data patterns to predict missing data or adjust rainfall values. The method calculates a weighted average.

Adequacy of Rain Gauge Stations

• Determines the ideal number of rain gauges required to estimate the average rainfall within a specific area.
• Using precipitation data from existing stations allows calculation of an ideal number of rain gauges needed, given a specified level of accurate representation.

Rainfall Maps in GIS

• Geographical Information Systems (GIS) assist in handling and representing rainfall data in maps for better visualization.
• Several techniques are used to plot spatial distributions of areas, such as Inverse Distance Weighted and spline methods.

Hydrograph Components

• Hydrograph components: • Approach segment: The part of the hydrograph beginning and ending with the peak rainfall. • Peak rainfall (W): The time of highest rainfall intensity. • Peak discharge: The peak flow rate at the outlet of a basin. • Lag time: The delay between peak rainfall and peak discharge. • Rising limb: The segment showing the rising flow rate of the basin outlet. • Falling limb: The part of the hydrograph showing gradual decrease in the rate of outflow flow at basin outlet. • Crest segment: The portion of a hydrograph representing peak flow at the outflow of the basin.

Base Flow Separation

• Base flow separation: Techniques to divide a hydrograph into base flow and quick flow components.
• Methods included direct approach methods, such as the straight-line method, constant slope method, and a fixed base method. Each method utilizes a different conceptual approach to delineate the base flow from the total hydrograph, resulting in a surface flow hydrograph.

Factors Affecting a Hydrograph

• Factors that influence a hydrograph's shape and characteristics include weather, climate, drainage basin characteristics (area, slope), soil and rock type, and human activity.

Case Studies

• Examples of hydrological phenomena in specific locations, helping to illustrate theoretical principles or practical application of techniques, models, or models.

Streamflow Measurements

• Streamflow measurement: The quantitative assessment of water flowing through a river over time
• Common methods used to measure stream flow include direct methods (velocity-area, float, weirs, flumes), and indirect methods (stage-discharge relationships, hydraulic modeling, and remote sensing).
• Instruments used in stream flow measurement: Electromagnetic, acoustic, mechanical flow meters, pressure transducers, ultrasonic sensors for water level measurement, satellite imagery (remote sensing).