# Outline of hydrology

The following outline is provided as an overview of and topical guide to hydrology:
Hydrology – study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability.

## What type of thing is hydrology?

Hydrology can be described as all of the following:
* a branch of science
** a branch of natural science
*** a branch of physical science
**** a branch of Earth science
** a branch of geography
*** a branch of physical geography

### Essence of hydrology

* Water
* Hydrologic cycle
* Cryosphere
* Origin of water on Earth
* Water distribution on Earth

## Branches of hydrology

* Hydrometry – the measurement of the different components of the hydrologic cycle
* Chemical hydrology – the study of the chemical characteristics of water
* Ecohydrology – the study of interactions between organisms and the hydrologic cycle
* Hydrogeology – the study of the presence and movement of water in aquifers
* Hydroinformatics – the adaptation of information technology to hydrology and water resources applications
* Hydrometeorology – the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere
* Isotope hydrology – the study of the isotopic signatures of water
* Surface hydrology – the study of hydrologic processes that operate at or near the Earth's surface
* Catchment hydrology – study of the governing processes in a given hydrologically defined catchment
* Drainage basin management – covers water-storage, in the form of reservoirs, and flood-protection.
* Water quality – includes the chemistry of water in rivers and lakes, both of pollutants and natural solutes.

## History of hydrology

History of hydrology

## Things studied by hydrology
### Abstract concepts in hydrology

* Field capacity

### Phenomena studied by hydrology
#### Water movement pathways

Water cycle (aka "hydrological cycle")
* Above ground
** Evaporation –
*** Pan evaporation –
** Condensation –
** Precipitation – condensed water, is pulled by gravity back to Earth, in the form of:
*** Drizzle
*** Rain
*** Sleet
*** Snow
*** Graupel
*** Hail
** Interception –
*** Evapotranspiration –
** Stemflow –
** Throughfall –
* On ground
** Surface runoff – flow of surface water
*** First flush
*** Floods
**** Flash floods
** Overland flow –
** Horton overland flow –
* Below ground
** Infiltration –
** Pipeflow –
** Baseflow –
** Subsurface flow – flow of ground water

### Physical things studied by hydrology

* Ground water
* Soil moisture
* Surface water

### Environmental issues

* Desertification/Oasification –
* Hypoxia –
* Erosion –
* Water pollution –

## Measurement tools
### Groundwater

* Aquifer characterization
   * Flow direction
      * Piezometer - groundwater pressure and, by inference, groundwater depth (see: aquifer test)
      * Conductivity, storativity, transmisivity
      * Geophysical methods
* Vadose zone characterization
** Infiltration
*** Infiltrometer - infiltration
** Soil moisture
*** Capacitance probe-soil moisture
*** Time domain reflectometer - soil moisture
*** Tensiometer - soil moisture
*** Solute sampling
*** Geophysical methods

### Surface water

* Water level
   * Mechanical pressure gauge –
   * Electronic pressure gauge –
   * Acoustic pressure gauge –
* Channel shape
   * Dumpy level –
* Discharge
   * Acoustic Doppler velocimeter –
   * Dilution tracing –

### Meteorological

* Precipitation
   * Rain gauge – rainfall depth (unit) and intensity (unit time$^{−1}$)
   * Disdrometer – raindrop size, total precipitation depth and intensity
   * Doppler weather radar – raindrop size, total precipitation depth and intensity, rain cloud reflectivity converted to precipitation intensity through calibration to rain gauges
   * Wind profiler – precipitation vertical and horizontal motion, vertical cross-section of reflectivity and typing
* Frozen precipitation (on ground)
   * Pressure sensors – pressure, depth, and liquid water equivalent
   * Acoustic sensors – pressure, depth, and liquid water equivalent
* Mean windspeed and direction
   * Anemometer –
   * Doppler sonar –
   * Wind profiler – air vertical and horizontal motion
* Mean air temperature
   * Thermometer –
* Humidity
   * Infrared thermometer – a form of remote sensing
   * Hygrometer (Psychrometer) – measures relative humidity
* Air pressure
   * Barometer –
* Heat flux
   * Net radiometer –
   * Pyranometer –
   * Pyrgeometer –
   * Heat flux sensor –
   * Lysimeter –
* Cloudiness/Sunshine
   * Spectroradiometer –
   * Campbell–Stokes recorder –
* Evapotranspiration
   * Water budget method
      * Basin water balance –
      * Evaporation pan –
      * Lysimetry –
      * Soil moisture depletion –
   * Water vapor transfer method
      * Bowen ratio – considers the energy budget
      * Eddy covariance –
   * Component analysis
      * Porometry/Sap flow –
      * Interception loss –
      * Soil evaporation –
   * Large-scale
      * Scintillometer –
      * Remote sensing estimates –
      * LIDAR –

### Soil/porous media

* Bulk density & porosity
   * Oven dried sample –
* Matric potential
   * Suction plate – determines relationship between the water volume and matric potential
   * Resistance thermometer – relates to matric potential from previous calibration
* Hydraulic conductivity
   * Disc permeameter – measures soil hydraulic conductivity
   * Rainfall simulator – measures output through the application of constant input ("rain") in a sealed area
   * Slug test – addition or removal of water and monitors the time until return to predisturbance level
* Piezometer –
* Soil moisture content (water volume percentage)
   * Frequency domain sensor –
   * Time domain reflectometer –
   * Neutron probe –

### Water quality

* Conductivity
   * Electrical conductivity – variety of probes used
* pH
   * pH meter –
* Dissolved oxygen (DO)
   * Winkler test –
* Turbidity
   * Nephelometer (Turbidimeter) –
* Water clarity
   * Secchi disk –
* Bed load
* Erosion/deposition

## Modeling

* Behavioral modeling in hydrology

### Equations

Basin
* Hack's law –
Catchment
* Water balance –
Evaporation
* Penman –
* Penman-Monteith –
Infiltration/Soil Movement
* Darcy's Law –
   * Darcy-Weisbach –
* Richards equation –
Streamflow/Open channel
* Fick's law of diffusion –
* Chézy formula –
* Manning formula –
* Strahler number –
* Standard step method – computational technique for modeling steady state open channel surface profiles
Erosion
* Hjulström curve –
Groundwater
* Dupuit–Forchheimer assumption –
* Groundwater flow equation –

### Power/Uncertainty

* Nash–Sutcliffe model efficiency coefficient
* GLUE

#### Models

Hydrological transport model
* Canadian Land Surface Scheme
* CHyM – Cetemps Hydrological Model
* DRAINMOD
* DSSAM
* FEHM
* Flood Modeller Pro
* Groundwater model
* GSSHA
* HBV hydrology model
* HEC-HMS
* HydroGeoSphere
* Hydrologic evaluation of landfill performance
* Hydrological transport model
* Isochrone map
* Litpack
* METRIC
* MIKE 11
* MODFLOW
* Mouse
* RheinBlick2050
* Runoff model (reservoir)
* SahysMod
* SaltMod
* SEDCAD
* SHETRAN
* Stochastic Empirical Loading and Dilution Model
* SWAT model
* Temporal Analyst
* Vflo
* WAFLEX
* WaterGAP
* WEAP
* ZOOMQ3D

## Applications of hydrology

Some examples of applications of hydrology:
* Analyzing the impacts of antecedent moisture on sanitary sewer systems
* Assessing contaminant transport risk and establishing environmental policy guidelines
* Assessing the impacts of natural and anthropogenic environmental change on water resources
* Designing bridges
* Designing dams for water supply or hydroelectric power generation
* Designing irrigation schemes and managing agricultural productivity
* Designing riparian restoration projects
* Designing sewers and urban drainage system
* Determining the agricultural water balance
* Determining the water balance of a region
* Fog collection
* Part of the hazard module in catastrophe modeling
* Predicting and mitigating flood, landslide and drought risk
* Predicting geomorphologic changes, such as erosion or sedimentation
* Providing drinking water
* Real-time flood forecasting and flood warning

## Hydrology organizations
### Intergovernmental organizations

* International Hydrological Programme (IHP)

### International research bodies

* International Water Management Institute (IWMI)
* UNESCO-IHE Institute for Water Education

### National research bodies

* Centre for Ecology and Hydrology – UK
* Centre for Water Science, Cranfield University, UK
* eawag – aquatic research, ETH Zürich, Switzerland
* Institute of Hydrology, Albert-Ludwigs-University of Freiburg, Germany
* United States Geological Survey – Water Resources of the United States
* NOAA's National Weather Service – Office of Hydrologic Development, USA
* US Army Corps of Engineers Hydrologic Engineering Center, USA
* Hydrologic Research Center, USA
* NOAA Economics and Social Sciences, USA
* University of Oklahoma Center for Natural Hazards and Disasters Research, USA
* National Hydrology Research Centre, Canada
* National Institute of Hydrology, India

### National and international societies

* Geological Society of America (GSA) – Hydrogeology Division
* American Geophysical Union (AGU) – Hydrology Section
* National Ground Water Association (NGWA)
* American Water Resources Association
* Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI)
* International Association of Hydrological Sciences (IAHS)
* Statistics in Hydrology Working Group (subgroup of IAHS)
* German Hydrological Society (DHG: Deutsche Hydrologische Gesellschaft)
* Italian Hydrological Society (SII-IHS) – http://www.sii-ihs.it
* Nordic Association for Hydrology
* British Hydrological Society
* Russian Geographical Society (Moscow Center) – Hydrology Commission
* International Association for Environmental Hydrology
* International Association of Hydrogeologists

### Basin- and catchment-wide overviews

* Connected Waters Initiative, University of New South Wales – Investigating and raising awareness of groundwater and water resource issues in Australia
* Murray Darling Basin Initiative, Department of Environment and Heritage, Australia

## Hydrology publications
### Hydrology-related journals

* Hydrological Processes, ISSN 1099-1085 (electronic) 0885-6087 (paper), John Wiley & Sons
* Hydrology Research, ISSN 0029-1277, IWA Publishing (formerly Nordic Hydrology)
* Journal of Hydroinformatics, ISSN 1464-7141, IWA Publishing
* Journal of Hydrologic Engineering, ISSN 0733-9496, ASCE Publication
* Journal of Hydrology
* Water Research
* Water Resources Research
* Hydrological Sciences Journal – Journal of the International Association of Hydrological Sciences (IAHS) ISSN 0262-6667 (Print), ISSN 2150-3435 (Online)

## Persons influential in the field of hydrology

* Hein de Baar
* Günter Blöschl
* Chen Xing (hydrologist)
* Ven Te Chow
* Gedeon Dagan
* James Dooge
* Endre Dudich
* G. H. Dury
* Saeid Eslamian
* Philipp Forchheimer
* François-Alphonse Forel
* Pieter Harting
* Majid Hassanizadeh
* Alf Howard
* Jan Vladimír Hráský
* Hydra (skater)
* Shahbaz Khan (hydrologist)
* Vit Klemes
* Michal Kravčík
* Torben Larsen
* John R. Philip
* Giovanni Roncagli
* Arturo Sanchez-Azofeifa
* Alireza Shokoohi
* Bojidar Spiriev
* Valeryan Uryvaev
* Jasper A. Vrugt
* John Williams (water scientist)
* Czesław Zakaszewski

## Allied sciences

* Aquatic chemistry –
* Civil engineering –
   * Hydraulic engineering –
* Climatology –
* Environmental engineering –
* Environmental Engineering Science –
* Geomorphology –
* Hydroacoustics –
* Hydrography –
   * Limnology –
   * Oceanography –
* Physical geography –

## Hydrology lists

* Drainage basins by area – largest hydrologically defined watersheds in the world
* Floods – chronological and geographic list of major floods worldwide
* Waterways – worldwide listing of waterbodies classified as rivers, canals, estuaries, and firths