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Groundwater

Groundwater is water that permeates the ground whether by precipitation or from surface waters such as lakes and rivers. Water that seeps into the ground is first used by various biotic factors such as root systems of plants. Yet, ample water will continue to move downward through porous layers, filling empty spaces until it reaches an impervious layer. This area of porous and permeable rock and soil surrounded by an impermeable layer is called an aquifer. Aquifers are classified as either confined or unconfined. Groundwater stored in aquifers can be found at various depths anywhere between a few feet to several hundred feet below the Earth’s surface. The rate of recharge of an aquifer depends on numerous factors including, size, depth, permeability, whether it is confined or unconfined, water demand and amount of water available. Groundwater is commonly extracted using wells, yet also discharges naturally forming springs or into lakes and rivers. It is estimated that roughly 50% of people in the US rely on groundwater for multiple every-day uses. Groundwater quality is threatened by agricultural and urban runoff, industrial waste effluent as well as salt water intrusion from over extraction.

  • Groundwater assessment methodology Featured Article Groundwater assessment methodology Groundwater assessment methodology

    Groundwater assessment methodology is vital for understanding the relationship of aquifer dynamics to precipitation and to the characteristics of the land surface of the Earth.... More »

  • Groundwater inflow Featured Article Groundwater inflow Groundwater inflow

    Groundwater inflow represents an important part of groundwater assessment methodology within the hydrological cycle. This article reviews chief methodology for estimating the... More »

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Aquifer depletion Last Updated on 2013-11-21 23:14:56 Scores of countries are overpumping aquifers as they struggle to satisfy their growing water needs, including each of the big three grain producers—China, India, and the United States. These three, along with a number of other countries where water tables are falling, are home to more than half the world’s people. (See Table at end of article.) There are two types of aquifers: replenishable and nonreplenishable (or fossil) aquifers. Most of the aquifers in India and the shallow aquifer under the North China Plain are replenishable. When these are depleted, the maximum rate of pumping is automatically reduced to the rate of recharge. For fossil aquifers—such as the vast U.S. Ogallala aquifer, the deep aquifer under the North China Plain, or the Saudi aquifer—depletion brings pumping to an end. Farmers who lose their irrigation water have the option of returning... More »
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Limpopo River Last Updated on 2012-04-27 00:00:00 The Limpopo River is one of the great rivers of southern Africa, with a [catchment] basin of approximately 410,000 square kilometers. The human population in the Limpopo Basin is approximately fifteen million, with a greater concentration in the lowlands of the downriver portion of the basin; the majority of the basin population is considered to be living in poverty, with the catchment generally overpopulated with respect to land that can be supplied by water for farming. Topography of the Limpopo River basin. Source: Food and Agricultural Organization (FAO), 2005 The Waterberg Massif and Soutpansberg Mountains are the highest topographic features in the basin, although the larger portion of the catchment is a low lying eastern coastal plain comprising approximately two thirds of the land area of the basin. The majority of the Limpopo Basin incurs less than 40... More »
Atmospheric science Last Updated on 2012-03-27 00:00:00 Atmospheric science is the umbrella term for the study of the atmosphere — the blanket of air covering the Earth. It is a relatively new discipline that is concerned with the composition, structure and evolution of the atmosphere as well as its processes and how those processes interrelate with other systems.[1][2 The adjacent image[4] depicts the various processes occurring in the atmosphere and how they relate to other Earth systems such as agriculture, land, sea and air transportation, other ecosystems, air pollutant emissions, the water cycle (evaporation and rainfall), forests and forest fires, deserts and desert dust, industry, etc. To the extent that atmospheric science focuses primarily on the Earth's atmosphere, it can be regarded as a subfield of the "Earth sciences" discipline, each of which is a particular synthesis of the fundamentals of... More »
Basic Groundwater Hydrology Last Updated on 2011-03-05 00:00:00 Ground-water hydrology is the subdivision of the science of hydrology that deals with the occurrence, movement, and quality of water beneath the Earth's surface. It is interdisciplinary in scope in that it involves the application of the physical, biological, and mathematical sciences. It is also a science whose successful application is of critical importance to the welfare of mankind. Because ground-water hydrology deals with the occurrence and movement of water in an almost infinitely complex subsurface environment, it is, in its most advanced state, one of the most complex of the sciences. On the other hand, many of its basic principles and methods can be understood readily by nonhydrologists and used by them in the solution of ground-water problems. The purpose of this report is to present these basic aspects of ground-water hydrology in a form that will encourage more... More »