Hadley cell circulationThe generalized circuit of air mass movement occurring between the equator and 30° latitude (north and south of the equator). The Hadley cell circulation is characterized by rising air masses at the equator and descending air masses at approximately 30º north and south latitude.
Hard waterWater in which relatively high amounts of minerals, mainly of calcium and magnesium salts, are dissolved.
HardnessWater in which relatively high amounts of minerals, mainly of calcium and magnesium salts, are dissolved.
HDIThe Human Development Index (HDI) measures human development by combining three dimensions of development: longevity (life expectancy at birth), knowledge (adult literacy and mean years of schooling), and income (UNDP HDR 2008).
Heavy MetalsIncludes cadmium, copper, nickel, zinc, chromium, arsenic, mercury, lead; are persistent in the environment and can bio-accumulated in aquatic organisms.
HepatitisInflammation of the liver caused by a viral infection.
HerbivoreAn animal that consumes living plants or their parts.
HereroOne of the major tribal groups of the Orange-Senqu River basin.
HeterotrophAn organism that requires organic molecules as a source of energy and nutrients because it is unable to manufacture their own food using the sun’s energy.
HibernateA period of biological rest that some animal species use to conserve energy during winter months.
HimbaOne of the major tribal groups of the Orange-Senqu River basin.
HIVHuman Immuno-deficiency Virus (HIV) is the retrovirus that attacks the human immune system resulting in AIDS. It is transmitted through direct contact of a mucous membrane with a bodily fluid containing HIV. This transmission can come in the form sexual contact; blood transfusion; contaminated needles; exchange between mother and infant during pregnancy, childbirth, or breastfeeding; or other exposure to one of the above bodily fluids.
Homo SapiensThe modern species of humans, the species to which all living humans belong. The Latin meaning, ‘wise man’ reflects the greater endowment of the brain power compared to his predecessors. The species is defined in terms of anatomy, and the first member of the species is recognized from about 150 000 years ago.
HorizonA layer of soil with physical and chemical properties distinct from layers above and below.
HotspotAn area of extraordinarily high biodiversity.
Human DevelopmentA complex concept of development, based on the priority of human well-being, and aimed at ensuring and enlarging human choices which lead to equality of opportunities for all people in society and empowerment of people so that they participate in - and benefit from - the development process.
Human Development IndexA composite index developed to measure progress in Human Development (above) through three basic components of human development: longevity, knowledge and standard of living.
HumidityA general term used to describe the amount of water vapor found in the atmosphere.
HusbandryThe agricultural practice of breeding or raising livestock.
Hydroelectric Power GenerationThe conversion of the flow of water into electricity.
HydrographGraph showing the variation in time of some hydrological data such as stage, discharge, velocity, sediment load, etc. (hydrograph is mostly used for stage or discharge) .
Hydrologic cycleRefers to the cycling of water from the ocean to the land and back again, including all the pathways and processes connected with the storage and movement of water in solid, liquid, and gaseous states.
Hydrological droughtOccurs when the surface and ground water resources are in a below average depleted state for a prolonged period, usually in response to below average rainfall.
Hydrological regimeThe long - term history of flow levels in a river.
Hydrology(1) Science that deals with the waters above and below the land surfaces of the Earth, their occurrence, circulation and distribution, both in time and space, their biological, chemical and physical properties, their reaction with their environment, including their relation to living beings. (2) Science that deals with the processes governing the depletion and replenishment of the water resources of the land areas of the Earth, and treats the various phases of the hydrological cycle.
HypertrophicAn acute concentration of nutrients.
HyphaeLong, thread-like branching filament found on fungus.
HyphomycetesA class of fungi.