Hydrology and Water Supply - Concept Map
Hydrology and Water Supply Engineering
Related concepts
The Hydrologic Cycle
Sub concepts
- Precipitation
- Interception
- Infiltration
- Surface Runoff
- Streamflow
- Evaporation
- Transpiration
- Evapotranspiration
Relationship to central
Foundation for understanding water movement in the environment and how precipitation becomes runoff
Runoff and Peak Discharge
Sub concepts
- Rational Method (Q = CiA/360)
- Runoff Coefficient (C)
- Rainfall Intensity (i)
- Catchment Area (A)
- Time of Concentration (tc)
- Peak Discharge Calculation
- Design Storm Duration
Relationship to central
Core quantification method for designing drainage and conveyance systems
Rainfall Intensity-Duration-Frequency (IDF)
Sub concepts
- IDF Curves
- Return Period (T)
- Design Duration
- Intensity Variation
- Frequency Analysis
- Local Rainfall Data
Relationship to central
Provides design rainfall data tied to return periods and local climate
Runoff Volume
Sub concepts
- Volume Calculation (V = CPA)
- Precipitation Depth (P)
- Runoff Coefficient (C)
- Catchment Area (A)
- Unit Conversions
- Cumulative Yield
Relationship to central
Quantifies total water yield from a storm for storage and conservation planning
Water Supply Fundamentals
Sub concepts
- Population and Per-Capita Consumption
- Average Daily Demand
- Maximum Day Demand
- Peak Hour Demand
- Demand Factors
- Storage Requirements
Relationship to central
Demand estimation and source selection for safe and reliable supply
Water Supply Sources
Sub concepts
- Surface Water Sources
- Reservoirs
- Rivers and Streams
- Groundwater Sources
- Wells
- Spring Sources
- Rainwater Harvesting
Relationship to central
Selection and sizing of intake and storage facilities
Well Hydraulics
Sub concepts
- Well Yield
- Drawdown
- Aquifer Properties
- Specific Capacity
- Pump Selection
- Well Spacing
Relationship to central
Design and operation of groundwater extraction systems
Reservoir Analysis and Sizing
Sub concepts
- Mass Balance
- Inflow vs Demand
- Seasonal Variation
- Draft and Yield
- Capacity Curves
- Reliability Analysis
Relationship to central
Determination of storage volume to meet annual demand and variability
Unit Conversions and Practical Calculations
Sub concepts
- mm/hr to m³/s conversion
- Hectares to m² conversion
- mm depth to m³ volume
- L/day to m³/s conversion
- Per-capita demand scaling
Relationship to central
Critical for correct application of SI-based rational method in field practice
Common Board-Exam Errors and Pitfalls
Sub concepts
- The 360 conversion factor
- Duration-intensity relationship
- Unit inconsistencies
- Peak vs average demand confusion
- Runoff coefficient misapplication
Relationship to central
Awareness of frequent mistakes ensures accurate licensure-exam performance
Concept connections
- The Hydrologic CycleRunoff and Peak DischargeThe hydrologic cycle defines how precipitation becomes runoff; the rational method quantifies peak discharge from that runoff
- Runoff and Peak DischargeRainfall Intensity-Duration-Frequency (IDF)The rational method requires design rainfall intensity from IDF curves, selected at the time of concentration
- Runoff and Peak DischargeRunoff VolumeBoth use the runoff coefficient C and catchment area A; peak discharge is instantaneous rate, volume is cumulative over storm duration
- Water Supply FundamentalsWater Supply SourcesEstimated demand determines the capacity and type of source infrastructure needed
- Water Supply SourcesWell HydraulicsFor groundwater sources, well equations predict yield and drawdown under pumping
- Water Supply SourcesReservoir Analysis and SizingFor surface sources, mass-balance analysis determines required storage volume to meet variable demand
- Rainfall Intensity-Duration-Frequency (IDF)Runoff VolumeIDF data provides the precipitation depth P used in the runoff-volume formula V = CPA
- Runoff CoefficientRunoff and Peak DischargeC is a critical parameter in Q = CiA/360, varying from 0.1 (lawns) to 0.95 (pavement)
- Time of ConcentrationRainfall Intensity-Duration-Frequency (IDF)Design duration in IDF lookup equals time of concentration; correct pairing ensures proper intensity selection
- Unit Conversions and Practical CalculationsRunoff and Peak DischargeThe 360 conversion factor is essential when using Q = CiA/360 with intensity in mm/hr and area in hectares
- Unit Conversions and Practical CalculationsRunoff VolumeCorrect unit consistency is critical: mm depth + ha area gives m³; m depth + m² area also gives m³
- Water Supply FundamentalsUnit Conversions and Practical CalculationsPer-capita demand (L/person/day) must be scaled to population and converted to m³/day for system sizing
- Common Board-Exam Errors and PitfallsRunoff and Peak DischargeAwareness of the 360 factor, intensity-duration pairing, and peak vs. average demand prevents frequent calculation errors
- Common Board-Exam Errors and PitfallsWater Supply FundamentalsUnderstanding the distinction between average, max-day, and peak-hour demand is critical for correct system design and exam success
- Catchment AreaRunoff and Peak DischargeArea A is a direct input to Q = CiA/360; errors in area unit conversion lead to incorrect discharge
- Demand FactorsWater Supply FundamentalsMultipliers (1.5× for max-day, 2–3× for peak-hour) transform average demand into design-point demand
- Well YieldWell HydraulicsYield is the sustainable pumping rate; determined by aquifer properties, well design, and drawdown limits
- Mass BalanceReservoir Analysis and SizingInflow (from hydrologic analysis) versus demand (from consumption) determines required storage capacity
- Precipitation DepthRunoff VolumeRainfall depth P from IDF or observed storms is multiplied by C and A to compute total runoff volume
- Per-Capita ConsumptionWater Supply FundamentalsPopulation × per-capita consumption (L/person/day) is the foundation for all demand estimates
Diagrams
Hydrology and Water Supply — Full Concept Hierarchy
Comprehensive hierarchical mind map showing all major topics in Hydrology and Water Supply, from the hydrologic cycle through water demand and source selection. This diagram organizes the subject into logical branches representing conceptual groups.
The Hydrologic Cycle — Process Flow
Step-by-step illustration of the complete hydrologic cycle, showing how precipitation enters the system and follows different pathways (interception, infiltration, and runoff) before returning to the atmosphere through evaporation and transpiration.
Rational Method Calculation Procedure
Complete workflow for applying the rational method, from area identification through runoff-coefficient selection (with typical ranges for different land uses) to final peak-discharge calculation. Shows decision points and intermediate checks.
Water Demand Estimation and Peak Factor Application
Complete procedure for estimating water demand from population data, applying peak factors (1.5× for maximum day, 2–3× for peak hour), and selecting appropriate source capacity. Critical for right-sizing water systems.
Runoff Volume Calculation from Storm Events
Complete procedure for calculating runoff volume from a storm event, including unit conversions and handling of mixed-use catchments. Emphasizes the importance of consistency and verification.
Runoff Coefficient Distribution — Mixed Urban Catchment Example
Example showing how a mixed urban catchment (40% impervious, 60% pervious) is composed of different land uses, each with its own runoff coefficient. Illustrates the need for area-weighted averaging when computing C for heterogeneous catchments.
Water Supply Source Selection and Yield Assessment
Decision tree for evaluating different water sources (surface reservoirs, rivers, wells, rainwater) and assessing whether each source can reliably meet the estimated demand. Includes mass-balance and yield-assessment approaches.
States of Water in the Hydrologic Cycle
State diagram showing water transitions throughout the hydrologic cycle, with key processes (evaporation, transpiration, infiltration, runoff) linking different states. Includes residence-time perspective and dependency factors.