Geographic information system A geographic information system (GIS) is a type of database containing geographic data (that is, descriptions of phenomena for which location is relevant), combined with software tools for managing, analyzing, and visualizing those data. In a ...

s (GISs) have become a useful and important tool in the field of

hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...

to study and manage Earth's

water resources Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. 97% of the water on the Earth is salt water and only three percent is fresh water; slight ...

. Climate change and greater demands on water resources require a more knowledgeable disposition of arguably one of our most vital resources. Because water in its occurrence varies spatially and temporally throughout the

hydrologic cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly const ...

, its study using GIS is especially practical. Whereas previous GIS systems were mostly static in their geospatial representation of hydrologic features, GIS platforms are becoming increasingly dynamic, narrowing the gap between historical data and current hydrologic reality. The elementary

water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly const ...

has inputs equal to outputs plus or minus change in storage. Hydrologists make use of this hydrologic budget when they study a

watershed Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to: Hydrology * Drainage divide, the line that separates neighbouring drainage basins * Drainage basin, called a "watershe ...

. The inputs in a hydrologic budget include

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, Rain and snow mixed, sleet, snow, ice pellets, ...

, surface flow, and groundwater flow. Outputs consist of

evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpira ...

, infiltration, surface runoff, and surface/groundwater flows. All of these quantities can be measured or estimated based on environmental data and their characteristics can be graphically displayed and studies using GIS.

GIS in surface water

In the field of hydrological modeling, analysis generally begins with the sampling and measurement of existing hydrologic areas. In this stage of research, the scale and accuracy of measurements are key issues. Data may either be collected in the field or through online research. The

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific government agency, agency of the Federal government of the United States, United States government. The scientists of the USGS study th ...

((USGS)) is a publicly available source of remotely sensed hydrological data. Historical and real-time streamflow data are also available via the internet from sources such as the

National Weather Service The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...

(NWS) and the

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...

(EPA). A benefit of using GIS softwares for hydrological modeling is that digital visualizations of data can be linked to real-time data. GIS revolutionized curation, manipulation, and input for complex computational hydrologic models For surface water modeling,

digital elevation model A digital elevation model (DEM) or digital surface model (DSM) is a 3D computer graphics representation of elevation data to represent terrain or overlaying objects, commonly of a planet, moon, or asteroid. A "global DEM" refers to a discrete gl ...

are often layered with hydrographic data in order to determine the boundaries of a watershed. Understanding these boundaries is integral to understanding where precipitation runoff will flow. For example, in the event of

snowmelt In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many par ...

, the amount of snowfall can be input into GIS to predict the amount of water that will travel downstream. This information has applications in local government asset management,

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

and

environmental science Environmental science is an interdisciplinary academic field that integrates physics, biology, and geography (including ecology, chemistry, plant science, zoology, mineralogy, oceanography, limnology, soil science, geology and physical geograp ...

. Another useful application for GIS regards

flood risk assessment A flood risk assessment (FRA) is an assessment of the risk of flooding from all flooding mechanisms, the identification of flood mitigation measures and should provide advice on actions to be taken before and during a flood. The sources of water ...

. Using digital elevation models combined with peak discharge data can predict which areas of a floodplain will be submerged depending on the amount of rainfall. In a study of the Illinois River watershed, Rabie (2014) found that a decently accurate flood risk map could be generated using only DEMs and

stream gauge A stream gauge, streamgage or stream gauging station is a location used by hydrologists or environmental scientists to monitor and test terrestrial bodies of water. Hydrometric measurements of water level surface elevation ("stage") and/or vol ...

data. Analysis based on these two parameters alone does not account for manmade developments including levees or drainage systems, and therefore should not be considered a comprehensive result.

GIS in groundwater

The use of GIS to analyze groundwater falls into the field of hydrogeology. Since 98% of available freshwater on Earth is groundwater, the need to effectively model and manage these resources is apparent. As the demand for groundwater continues to increase with the world’s growing population, it is vital that these resources be properly managed. Indeed, when groundwater usage is not monitored sufficiently, it may result in damage to aquifers or

groundwater-related subsidence Groundwater-related subsidence is the subsidence (or the sinking) of land resulting from groundwater extraction. It is a growing problem in the developing world as cities increase in population and water use, without adequate pumping regulation a ...

, as occurred in the Ogallala aquifer in the United States. In some cases, GIS can be used to analyze drainage and groundwater data in order to select suitable sites for

groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs i ...

References

{{reflist *Girish Kumar, M., Bali, R. and Agarwal, A.K (2009). GIS Integration of remote sensing and electrical data for hydrological exploration- A case study of Bhakar watershed, India. Hydrological Sciences Journal 54 (5) pp 949–960. * Dingman, S. Lawrence, Physical Hydrology, Prentice-Hall, 2nd Edition, 2002 * Fetter, C.W. Applied Hydrogeology, Prentice-Hall, 4th Edition, 2001 * Maidment, David R., ed. Arc Hydro: GIS for Water Resources, ESRI Press, 2002

External links

Spatial Hydrology

GIS Lounge

US Army Geospatial Center
— For information on OCONUS surface water and groundwater. Applications of geographic information systems Hydrology

GIS in surface water

GIS in groundwater

See also

References

External links