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.

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

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

• 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

• Field capacity

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

• Ground water
• Soil moisture
• Surface water

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

• 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

• Water level

• Mechanical pressure gauge –
• Electronic pressure gauge –
• Acoustic pressure gauge –

• Channel shape

• Dumpy level –

• Discharge

• Acoustic Doppler velocimeter –
• Dilution tracing –

• Precipitation^[1]

• 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 ^[2]

• 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 –

• 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 –

• 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

• Behavioral modeling in hydrology

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 –

• Nash–Sutcliffe model efficiency coefficient
• GLUE

Hydrological transport model

• Canadian Land Surface Scheme
• CHyM – Cetemps Hydrological Model
• DRAINMOD[1]
• 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

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

• International Hydrological Programme (IHP)^[3]

• International Water Management Institute (IWMI)^[4]
• UNESCO-IHE Institute for Water Education^[5]

• Centre for Ecology and Hydrology – UK^[6]
• Centre for Water Science, Cranfield University, UK^[7]
• eawag – aquatic research, ETH Zürich, Switzerland^[8]
• Institute of Hydrology, Albert-Ludwigs-University of Freiburg, Germany^[9]
• United States Geological Survey – Water Resources of the United States^[10]
• NOAA's National Weather Service – Office of Hydrologic Development, USA^[11]
• US Army Corps of Engineers Hydrologic Engineering Center, USA^[12]
• Hydrologic Research Center, USA^[13]
• NOAA Economics and Social Sciences, USA^[14]
• University of Oklahoma Center for Natural Hazards and Disasters Research, USA^[15]
• National Hydrology Research Centre, Canada^[16]
• National Institute of Hydrology, India^[17]

• Geological Society of America (GSA) – Hydrogeology Division^[18]
• American Geophysical Union (AGU) – Hydrology Section^[19]
• National Ground Water Association (NGWA)^[20]
• American Water Resources Association^[21]
• Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI)^[22]
• International Association of Hydrological Sciences (IAHS)^[23][24]
• Statistics in Hydrology Working Group (subgroup of IAHS)^[25]
• German Hydrological Society (DHG: Deutsche Hydrologische Gesellschaft)^[26]
• Italian Hydrological Society (SII-IHS) – http://www.sii-ihs.it
• Nordic Association for Hydrology^[27]
• British Hydrological Society^[28]
• Russian Geographical Society (Moscow Center) – Hydrology Commission^[29]
• International Association for Environmental Hydrology^[30]
• International Association of Hydrogeologists^[31]

• Connected Waters Initiative, University of New South Wales^[32] – Investigating and raising awareness of groundwater and water resource issues in Australia
• Murray Darling Basin Initiative, Department of Environment and Heritage, Australia^[33]

• 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)

• 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

• Aquatic chemistry –
• Civil engineering –

• Hydraulic engineering –

• Climatology –
• Environmental engineering –
• Environmental Engineering Science –
• Geomorphology –
• Hydroacoustics –
• Hydrography –

• Limnology –
• Oceanography –

• Physical geography –

• 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

• Outline of meteorology

Other water-related fields

• Oceanography – more general study of water in the oceans and estuaries.
• Meteorology – more general study of the atmosphere and of weather, including precipitation as snow and rainfall.
• Limnology – study of inland waters (running and standing waters, both fresh and saline, natural or man-made), including their biological, chemical, physical, geological, and other attributes.^[34] This includes the study of lakes and ponds, rivers, springs, streams and wetlands.
• Water resources – sources of water that are useful or potentially useful. Hydrology studies the availability of those resources, but usually not their uses.

• Hydrology.nl – Portal to international hydrology and water resources
• Decision tree to choose an uncertainty method for hydrological and hydraulic modelling
• Experimental Hydrology Wiki