hydro

• The hydrological cycle and catchments

  
• Hydrological cycle


  The continuous movement of water on, above, and below the Earth's surface

  
• The International System of Units (SI) is the modern standardised metric system of measurement
• Supplementary and Derived Units in the SI system

  • Supplementary units: radian, steradian
  • Derived units: newton, pascal, joule, watt, coulomb, volt, ohm, siemens, weber, tesla, henry, degree Celsius
• Definitions of SI units are based on fundamental physical constants
• Evaporation and evapotranspiration are important hydrological processes
• Evaporation


  The process by which water changes from a liquid to a gas (water vapor)
• Evapotranspiration


  The sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere
• Energy transformations drive the evaporation process
• Evaporation can be measured using evaporation pans, lysimeters, and eddy covariance techniques
• Penman-Monteith equation


  An equation used to calculate reference crop evapotranspiration
• Actual evapotranspiration can be calculated from reference evapotranspiration and other factors
• Precipitation can occur in various forms and is produced by different rain-producing mechanisms
• Precipitation can be measured using rain gauges, radar, and for snowfall
• Errors can occur in rainfall measurement due to various factors
• Double mass curves


  A graphical technique used to detect inconsistencies in rainfall data
• Streamflow can be measured using various techniques
• Streamflow records are important for hydrological analysis
• Design floods are different from actual floods arising from rainfall events
• Annual exceedance probability (AEP)


  The probability that a given rainfall or flood event will be exceeded in any one year
• Average recurrence interval (ARI)

  The average or expected time period between exceedances of a given rainfall or flood event
• Flood frequency analysis involves fitting probability distributions to recorded streamflow data
• Flike software can be used to fit probability distributions and estimate design floods
• Intensity-Frequency-Duration (IFD) relationships are used to estimate design rainfalls

  
• The Rational Method is a simple approach for estimating peak flows
• Regional Flood Frequency Estimation can be used to estimate design floods
• Catchment delineation can be done using topographic maps or digital elevation models (DEMs)
• Catchment averaged rainfall can be estimated using arithmetic mean, Thiessen method, or isohyetal method
• Gridded rainfall products like SILO and Australian Gridded Climate Data are available

  
• Hydrograph analysis and rainfall-runoff modelling are used to estimate streamflow hydrographs

  
• Runoff generation processes include infiltration excess, saturation excess, and groundwater flow
• Hydrograph


  A graph showing the variation of streamflow with time at a particular location

  
• Components of a hydrograph

  • Direct or storm runoff
  • Baseflow
• Factors affecting the shape of a hydrograph

  • Rainfall characteristics
  • Catchment characteristics

  
• Runoff generation processes


  1. Rainfall

  2. Infiltration

  3. Overland flow

  4. Subsurface flow

  5. Groundwater flow

  
• Losses


  Rainfall that does not contribute to direct runoff
• Rainfall excess


  Rainfall that contributes to direct runoff
• Initial loss


  Loss of rainfall before runoff begins
• Continuing loss


  Loss of rainfall during the runoff event
• Rainfall bursts vs complete storms have different effects on losses