Global Water Issues
Earth is known as the “blue planet” because, when viewed from the distance of outer space, surface water in oceans, seas, lakes, rivers, and wetlands dominate the blue light spectrum. By far (96.5 percent) of this water is contained in the oceans. Icecaps and glaciers contain the next largest component of earth’s water (about 2 percent). The third largest component of earth’s water is groundwater (about 0.6 percent). The amount of groundwater far surpasses all the water in lakes, rivers, and wetlands. Because groundwater is “out of sight,” its importance is often overlooked. However, the large amount of groundwater does not mean that all of it is available for use by humans. Springs, where groundwater discharges at the land surface, have been utilized as sources of water for millennia, and wells have been drilled to tap groundwater for centuries; however, the earliest quantitative studies of groundwater began with a French hydraulic engineer named Henry Darcy in 1856. Most early groundwater studies focused on public, private, and industrial water supplies, and on water for irrigation. In the last several decades, however, a larger scientific effort has been devoted to understanding the role of groundwater as part of the overall water cycle and its role in maintaining ecosystems. The interaction between surface water and groundwater, especially in areas with sandy soils, is critical for understanding global groundwater issues. In many uncontrolled streams, much of the water that flows during periods of little or no precipitation is derived from the seepage of groundwater into the stream. As climate-change issues unfold, groundwater withdrawal will increase in places with lowered precipitation. Increased withdrawals from aquifers can lead to groundwater-level declines which, in turn, can cause streamflow depletion, saltwater intrusion, and even land subsidence in some hydrogeologic settings. Groundwater can be contaminated by chemicals, nutrients, pesticides, and herbicides, as well as septage from leaking sewers and septic tanks. Such contamination can alter the availability of groundwater for human and ecosystem uses.
Groundwater and Groundwater Modeling Survey - Generic Groundwater and Groundwater Modeling Survey (for pre- and post-module analysis). (Global Water Issues- 9)  
Groundwater Contamination Videos Exercise Watch videos and respond. Background: Modern civilizations have a profound impact on groundwater quality. From industrialization and urbanization associated with 21st-century `mega cities' and population increase, to intensive farming and deforesting, there is a significant use of resources and generation of waste that make groundwater unsuitable for use. Examples of groundwater contaminants include dissolved inorganic substances (e.g., chloride, sulfate, etc.) or organic liquids, dissolved organic/inorganic constituents, or pathogens from anthropogenic sources. (Global Water Issues- 9)  
Groundwater Contamination - Introduction Virtually any activity whereby chemicals or wastes may be released to the environment, either intentionally or accidentally, has the potential to pollute ground water. When ground water becomes contaminated, it is difficult and expensive to clean up. What the related video and answer the short questions that follow. (Global Water Issues- 9)  
Groundwater Contamination - Variability & Natural Sources Given its importance as a supply of freshwater needed to support society, the quality of groundwater is of paramount importance. Groundwater may not be suitable for use because it contains dissolved inorganic substances coming from natural sources (e.g., chloride, sulfate, etc.) or organic liquids, dissolved organic/inorganic constituents, or pathogens from anthropogenic sources. The purpose of this exercise is to explore variabilities in groundwater contamination that make management a challenge. (Global Water Issues- 9)  
Groundwater Contamination - Agricultural & Nitrate Nitrate has emerged as one of the most alarming and widespread contaminant of groundwater and surface water resources reported around the globe. Nitrate formation is an integral part of nitrogen cycle and is added either by the natural processes (atmospheric fixation, lightning storms) or through anthropogenic activities (fertilizer applications, septic tanks). Nitrate enters the hydrosphere easily, and its ingestion causes various health risks such as methemoglobinemia, cancer, diabetes, etc. on humans and to some extent on livestock populations as well. Agricultural practices and subsequent fertilizer application along with other anthropogenic activities are assumed to be the primary reason behind elevated levels of nitrate in groundwater. (Global Water Issues- 9)  
Groundwater Contamination - Emerging Contaminants & PFAS PFAS, also known as highly fluorinated chemicals, are a group of man-made substances used in products ranging from firefighting foam to microwavable popcorn packaging. When released into the environment, PFAS can travel far from their source, which heightens the chance of human exposure through drinking water or food. An analysis by the Environmental Working Group has shown that nearly 100 million Americans may have PFAS in their water. (Global Water Issues- 9)  
Land Subsidence and Sinking Cities Subsidence is a global problem and, in the United States, more than 17,000 square miles in 45 States, an area roughly the size of New Hampshire and Vermont combined, have been directly affected by subsidence. Land subsidence is most often caused by human activities, mainly from the removal of subsurface water. Other things that can cause land subsidence: aquifer-system compaction, drainage of organic soils, underground mining, hydrocompaction, natural compaction, sinkholes, and thawing permafrost. (Global Water Issues- 9)  
Groundwater Depletion In the drier areas of the world where surface water is scarce, groundwater is abstracted in large volumes in order to irrigate crops, and to a lesser extent for drinking water supply and industry. If groundwater abstraction exceeds groundwater recharge for extensive areas and long time, overexploitation or persistent groundwater depletion can occur. The resulting lowering of groundwater levels can have devastating effects on natural streamflow, groundwater fed wetlands and related ecosystems. (Global Water Issues- 9)