751 articles
Global Water Partnership
The Global Water Partnership (GWP) is an international network, founded in 1996 by the World Bank, UNDP, and Sida, that promotes integrated water resources management.
Glomar Explorer
Glomar Explorer, also known as Hughes Glomar Explorer, is a deep-ocean ship built by the CIA in the early 1970s to raise a sunken Soviet submarine.
GR4J
GR4J, French for rural engineering model with 4 daily parameters, is a daily lumped rainfall-runoff model developed at Cemagref in France and widely used across climates.
GRACE Follow-On
GRACE Follow-On, known as GRACE-FO, is a twin-satellite NASA and GFZ mission launched in 2018 that tracks water movement by measuring changes in Earth's gravity field.
Groundwater
Groundwater, also called subsurface water or phreatic water, is water held in cracks and spaces of rock and sediment below the Earth's surface, the largest store of liquid freshwater.
Groundwater age dating
Groundwater age dating is the estimation of the time since water recharged an aquifer, inferred from dissolved tracers like CFCs, tritium, and carbon-14 rather than measured directly.
Groundwater discharge
Groundwater discharge is the outflow of water from the saturated zone back to the land surface or to streams, lakes, wetlands, and, in coastal areas, the ocean floor.
Groundwater model
A groundwater model, also known as a groundwater flow model, is a computational method that predicts hydraulic heads, flows, and solute concentrations in aquifers, most often with the USGS MODFLOW code.
Groundwater pollution
Groundwater pollution, also called contaminated groundwater, is the contamination of underground aquifers by pesticides, fertilizers, sewage, and industrial waste, which threatens the drinking water of half the U.S. population.
Groundwater protection
Groundwater protection: preventing aquifer contamination through vulnerability mapping, protection zones, land-use controls, and SDWA, EU, and managed recharge programs worldwide.
Groundwater recharge
Groundwater recharge, also called deep percolation or aquifer recharge, is the downward flow of water from the surface to the water table; managed recharge deliberately adds water to aquifers for storage and recovery.
Haematococcus pluvialis
Haematococcus pluvialis is a freshwater unicellular green microalga that accumulates astaxanthin in thick-walled resting cells under stress, making it the primary natural source for supplements.
Halocline
A halocline is a layer of water where salinity changes rapidly with depth, separating fresher surface water from saltier water below and limiting vertical mixing.
Hawaii Ocean Time-series
The Hawaii Ocean Time-series (HOT) is a quasi-monthly oceanographic program that has measured hydrography, chemistry, and biology at Station ALOHA, 100 km north of Oahu, since October 1988.
HBV model
The HBV model (Hydrologiska Byråns Vattenbalansavdelning) is a conceptual rainfall-runoff model developed by Sten Bergström at the Swedish Meteorological and Hydrological Institute in 1972, converting precipitation and temperature into river discharge.
Heave compensation
Heave compensation is the set of techniques that remove a vessel's wave-induced vertical motion from a suspended load or sensor, used in lifting and hydrographic surveying.
HEC-HMS
HEC-HMS (Hydrologic Modeling System) is a free hydrology program from the US Army Corps of Engineers' Hydrologic Engineering Center that converts precipitation into streamflow hydrographs, replacing HEC-1.
HEC-RAS
HEC-RAS, the Hydrologic Engineering Center's River Analysis System, is free hydraulic modeling software from the U.S. Army Corps of Engineers, first released in July 1995 and used for floodplain and dam safety studies.
High tide water
High tide water (high water, German Tidehochwasser) is the water level at a tide's highest point. Most coasts see two high tides per 24 h 50 min tidal day; spring and perigean tides raise the highest levels.
High-nutrient, low-chlorophyll region
A high-nutrient, low-chlorophyll (HNLC) region is an open-ocean area where surface waters hold plentiful nitrate and phosphate year-round, yet phytoplankton stays scarce, chiefly because iron is depleted.
HMS Dolphin (1751)
HMS Dolphin was a 24-gun Royal Navy frigate, built in 1751, and the first ship known to sail around the world twice, under Byron and Wallis.
HMS Endeavour
HMS Endeavour, originally the Earl of Pembroke, was a British collier sailed by James Cook from 1768 to 1771 for scientific discovery, later serving as the transport Lord Sandwich.
HMS Erebus (1826)
HMS Erebus was a Royal Navy bomb vessel, launched in 1826, that carried James Clark Ross to Antarctica and was lost with Franklin's 1845 Northwest Passage expedition.
HMS Protector (A173)
HMS Protector is the Royal Navy's only icebreaker and ice patrol ship, a Norwegian vessel commissioned in 2013 that surveys Antarctic waters, supports research stations, and reached farther north than any Royal Navy ship in 2021.
HSPF (hydrology)
HSPF (Hydrological Simulation Program–FORTRAN) is a US EPA watershed model that continuously simulates runoff and water quality, recommended for complex TMDL studies and distributed with BASINS.
Hubbard Glacier
Hubbard Glacier is a tidewater glacier in southeast Alaska flowing into Disenchantment Bay and Russell Fiord near Yakutat, the largest tidewater glacier in North America, which has advanced rather than retreated since 1895.
Humboldt Current
The Humboldt Current, also called the Peru Current, flows northward along the coasts of Chile, Peru, and Ecuador, driving one of Earth's most productive marine ecosystems.
HY-2 (satellite)
HY-2, also known as Haiyang-2 (海洋二号), is a Chinese series of ocean dynamic environment satellites carrying radar altimeters, scatterometers, and radiometers to measure sea surface height, winds, and temperature; the first, HY-2A, launched in 2011.
HYCOM
HYCOM (HYbrid Coordinate Ocean Model) is an ocean general circulation model that switches its vertical coordinate with location, used for global ocean nowcasting and operational hurricane prediction.
Hydraulic conductivity
Hydraulic conductivity, also called hydraulic permeability, measures how easily water moves through a porous or fractured material, and it has the units of a velocity.