Hydrology
Ancient Egyptians were one of the first to employ hydrology in their engineering and agriculture, inventing a form of water management known as basin irrigation.
The ancient Sinhalese used hydrology to build complex irrigation works in Sri Lanka, also known for the invention of the Valve Pit which allowed construction of large reservoirs, anicuts and canals which still function.
Marcus Vitruvius, in the first century BC, described a philosophical theory of the hydrologic cycle, in which precipitation falling in the mountains infiltrated the Earth's surface and led to streams and springs in the lowlands.
[4] With the adoption of a more scientific approach, Leonardo da Vinci and Bernard Palissy independently reached an accurate representation of the hydrologic cycle.
Pioneers of the modern science of hydrology include Pierre Perrault, Edme Mariotte and Edmund Halley.
The 19th century saw development in groundwater hydrology, including Darcy's law, the Dupuit-Thiem well formula, and Hagen-Poiseuille's capillary flow equation.
Of particular importance were Leroy Sherman's unit hydrograph, the infiltration theory of Robert E. Horton, and C.V. Theis' aquifer test/equation describing well hydraulics.
[9]: 250–275 Soil moisture can be measured in various ways; by capacitance probe, time domain reflectometer or tensiometer.
Methods for measuring flow once the water has reached a river include the stream gauge (see: discharge), and tracer techniques.
In some considerations, hydrology is thought of as starting at the land-atmosphere boundary[11] and so it is important to have adequate knowledge of both precipitation and evaporation.
Detailed studies of evaporation involve boundary layer considerations as well as momentum, heat flux, and energy budgets.
Remote sensing of hydrologic processes can provide information on locations where in situ sensors may be unavailable or sparse.
In hydrology, studies of water quality concern organic and inorganic compounds, and both dissolved and sediment material.
In addition, water quality is affected by the interaction of dissolved oxygen with organic material and various chemical transformations that may take place.
These estimates are important for engineers and economists so that proper risk analysis can be performed to influence investment decisions in future infrastructure and to determine the yield reliability characteristics of water supply systems.
Statistical information is utilized to formulate operating rules for large dams forming part of systems which include agricultural, industrial and residential demands.
The most common pollutant classes analyzed are nutrients, pesticides, total dissolved solids and sediment.
