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 inflow represents an important part of groundwater assessment methodology within the hydrological cycle. This article reviews chief methodology for estimating the...
FreshwaterLast Updated on 2014-09-06 18:32:23
The definition of freshwater is water containing less than 1000 milligrams per liter of dissolved solids, most often salt. The global distribution of freshwater resources varies greatly from region to region (see Figure 1). An 'inventory' of Earth's waters shows that approximately 97% of the global water supply is found in the oceans, which are saline. A very small amount of salty water is also located in saline lakes (e.g., the Caspian Sea). The remaining water inventory (3%) is 'freshwater'. Permanent ice (e.g., continental and mountain glaciers) is the largest freshwater storage on Earth, accounting for about 2% of the total global supply - or nearly 69% of the total freshwater supply. Freshwater is also found beneath the Earth's surface as groundwater (approximately 30% of the total freshwater supply) and in surface water storages such as lakes, streams,... More »
WheatLast Updated on 2014-05-21 15:51:12Wheat is any of a number of species of the genus Triticum within the grass family of Poaceae.
Wheat is an important grain food crop supplying the second highest caloric intake for humans, closely behind rice. Wheat is used to produce flour for bread, pasta, couscous and other foods.
However, wheat generally consumes large amounts of nitrate and other fertilizers, so that the outcome of widespread wheat farming is often associated with extensive water pollution impacts, expecially related to nitrate laden runoff.
Wheat is one of the earliest cultivated crops, and has a clear association with the emergence of sedentary agriculture around twelve millennia ago.
Products Made From Wheat: 1. Crossaint; 2. Wheat Flour; 3. Noodles;
4. Wheat Dalia; 5. Sewai; 6. Refined Wheat Flour; 7. Common Brown Bread;
8. ... More »
Aquifer depletionLast Updated on 2013-11-21 23:14:56Scores 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 »
Limpopo RiverLast 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 scienceLast 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.[2
The adjacent image 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 »
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