Water used in Zurich being used for recreation and transportation.
Water is a strange substance, we use it every day to for cleaning to prevent disease and death and yet it causes death to millions all over the world when they use it.
By the end of this chapter, students will be able to:
Compare regional and national responses to water issues.
Explain water-related problems (for example water scarcity, water-borne diseases, water pollution, flooding) from different regions of the world.
Describe solutions to water-related problems
Demonstrate knowledge of some of the major regulations related to water in the USA.
As described in Chapter 7, water is a very important commodity for human life and survival. We need to consume it to stay alive and use it to clean our food, utensils, clothes, bodies, and surrounding to prevent disease. Unfortunately, this same water is responsible for about 80% of all diseases in developing countries and over three million deaths a year globally. It is therefore very important that we understand why this important commodity can be vital and at the same time cause so much harm. This chapter is devoted to the availability and quality of water. Water quality will be defined as the physical, chemical and biological properties of water that impact its intended use. This definition recognizes that quality designations of any given water can vary depending on water purpose it is serving. A single water body may have different quality designations depending on the intended uses. For instance, water considered good quality for fishing is not necessarily good for swimming or drinking. It is for this reason that different regulations and standards have been created for the different water uses. These standards are created to ensure that there is no water shortage due to mismanagement, overuse, and contamination.
8.2 Water Scarcity and Shortage
Water has been identified as one of the major environmental crisis facing the world today. More than one billion people in the world lack access to clean drinking water. The demand for water has grown at a very fast pace in response to the rate of global population growth. Figures 8.1 illustrates this change in water use over time in the United States of America (US). It is predicted that over the next two decades, the average supply of water per person will drop by a third. When looking at the trends in the figures below you will notice some encouraging leveling off or slight drop of use in recent years.
Can you think of reasons for these observations?
Both groundwater and surface water withdrawals had increased over time until 1980 when the withdrawals peaked and stabilized. Water withdrawals in the US show a major divide between the western and eastern parts of the country. The western part withdraws most of the water for agriculture, as these are the farm areas while eastern half withdraws most of its water for Thermoelectric cooling and industry (Figure 8.2). California and Texas account for over 20% of all water withdrawn. In fact, California consumes more water than is available within the state and is therefore forced to get water from the other states. Despite this deficiency almost everyone in California has access to clean and safe drinking water. Contrast this to Lusaka, the capital city of Zambia, which has more water available than is withdrawn but more than a third of its population has no access to safe drinking water.
Figure 8.1: Trends in fresh and saline water withdrawals in response to population growth (A) surface water withdrawals (B) Groundwater withdrawal trends
Figure 8.2: US water withdrawals by category for the calendar year 2015 (Image credit: USGS)
8.3 Water Scarcity and Availability
There is enough fresh water on Earth to supply every human being with enough drinking water. The main problem we face with regards to water is that it is unevenly distributed, polluted, mismanaged and wasted. Tony Allan, the author of “Virtual Water”, asserts that water follows money. This refers to the fact that rich countries and societies with more money and affluence have more access to safe drinking water even when they live in regions without much water. It also means that areas with large supplies of water can still have water scarcity if they lack the financial resources and infrastructure to supply people with clean and safe drinking water. Water scarcity is caused by the demand for water or a certain quality being greater than the supply. Scarcity can be defined as either physical scarcity or economic scarcity.
Physical water scarcity is a situation where there is an actual shortage of water, regardless of quality or infrastructure. It is estimated that about 1.2 million people around the world are experiencing physical water scarcity. Economic scarcity is a condition where countries lack the financial resources and/or infrastructure to supply their citizens with reliable safe drinking water. About 1.6 billion people are experiencing economic water shortage; most of them live in less industrialized countries. For a lot of places in the world, scarcity is a transient condition that can be reduced or eliminated by installing the right infrastructure. The major problem in less industrialized countries is the lack of political, financial, and physical structures to provide water to everyone. A few rich people in these countries get the clean water while the majority of the people who cannot afford to pay for it are left out. Examples of such communities include many villages in Africa, Asia, and South America. Figure 8.3 shows communities in south east Kenya that are experiencing severe water shortages primarily due to lack of infrastructure coupled with physical scarcity. Women and children in these communities must walk long distances to get untreated and contaminated water for drinking and other household needs (Mutiti et al. 2010).
Figure 8.3: Communities in southeast Kenya without easy access to safe drinking water. (top left)
Groundwater in the area is too salty for consumption. (top right) Maasai women in Amboseli National Park collecting water from a wetland. (bottom left) Women in Magwede village in SE Kenya walking long distances to get water from a Kiosk. (bottom right) Children collecting water in Bungule Village from a water kiosk that is only open for about an hour every day. Photo credit: Jonathan Levy, Sam Mutiti and Christine Mutiti
8.4 Water pollution
Water pollution is a major problem facing many of our surface and ground water sources.
Contamination can both be natural due to geologic or meteorological events and anthropogenic (human causes). Human sources of contamination can be categorized as either point source or nonpoint source. Point-source pollution is water pollution coming from a single point, such as
a sewage-outflow pipe. Non-point source (NPS) pollution is pollution discharged over a wide land area such as agricultural runoff and urban stormwater runoff, not from one specific location. Non-point source pollution contamination occurs when rainwater, snowmelt, or irrigation washes off plowed fields, city streets, or suburban backyards and carry pollutants into the water sources. As this runoff moves across the land surface, it picks up soil particles and pollutants, such as nutrients, metals and pesticides.
8.4.1 Types of Water Pollution
Contamination of water resources comes in the form of chemical, biological, and physical pollution. Chemical pollution includes things such as toxic metals, organic compounds, acidic waters from mining activities and industry, pharmaceuticals and many other chemical compounds from industries and wastewater treatment plants. Another form of chemical pollution is radioactive waste which has a significant potential to cause harm to living things. Most of the radioactive pollution comes from agricultural practices such as tobacco farming, where radioactive phosphate fertilizer is used. Physical pollution includes sediment pollution, trash thrown in the water bodies, thermal (temperature) and other suspended load. High temperatures typically affect the metabolism of aquatic fauna in a negative way and can encourage eutrophication. Biological pollution usually refers to pathogenic bacteria, viruses, and parasitic protozoa. Common pathogenic microbes introduced into natural water bodies are pathogens from untreated sewage or surface runoff from intensive livestock grazing. Biological pollution is a common cause of illness and death in less industrialized countries where population density, water scarcity and inadequate sewage treatment combine to cause widespread parasitic and bacterial diseases.
8.4.2 Sources of surface water pollution
Surface water pollution can come from a variety of sources and includes an extensive list of chemical compounds, mixtures and elements. Below is a short description of some of these sources and impacts of a few pollutants.
22.214.171.124 Chemical Pollution
Most of the common inorganic chemical water pollutants are produced by non-point sources, mainly intensive agriculture, and activities from urban areas. Specific inorganic chemicals and their major sources are: ammonium nitrate and a host of related phosphate and nitrogen compounds used in agricultural fertilizers; heavy metals (present in urban runoff and mine tailings area runoff). However, some inorganic contaminants such as chlorine and related derivatives are produced from point sources, ironically employed in water treatment facilities.
Moreover, some of the large dischargers of heavy metals to aquatic environments are fixed point industrial plants.
High concentrations of nitrogen (N) and phosphorus (P) in water can cause eutrophication. You see this whenever you notice the greenish tint to the water in your local streams and rivers during low-flow times, or if you have ever seen a green farm pond. These nutrients are primarily coming from treated wastewater (laden with P and N) being dumped into mainly rivers from sewage plants. Another source of high nutrients are, agricultural areas where farmers allow livestock direct access to streams and ponds. Urban and suburban areas where there is intense fertilizer application for esthetics. Public and private landscapes (homes, gardens, golf courses) with fertilizer runoff.
Increased supply of nutrients into an aquatic system leads to alterations of the primary production from low to high. Algal blooms are natural events and all algae can bloom. Cyanobacteria (Blue green algae) are not always harmful but can produce toxins when conditions allow. The frequency at which conditions for toxic algal blooms’ occurrence have become common lately in coastal areas of the US. Harmful algal blooms are possible under prolonged sunlight in summer, high surface water temperatures, and when water stays static in the presence of fertilizer runoff from the surrounding areas. When a bloom occurs, it can be difficult to identify whether or not it is toxic (if you see dead fish it is probably toxic, Figure 8.4).
Figure 8.4: Eutrophication process representation leading to algal blooms (Feem re-elaboration from Arpa Umbria, 2009)
The N and P act as fertilizers in the water and promote algae blooms. As the algae die, they are decomposed by aerobic bacteria in the water. These bacteria use up the oxygen in the water and the low dissolved oxygen (DO) levels can results in “fish kills” where large numbers of fish, and other aquatic life, die because of suffocation (Figure 8.5 and 8.6).
Figure 8.5: Lake Sinclair, Georgia. Left image: recreational area with expected accumulation of algae; Right image: water clarity loss measured with a Secchi Disk due to an algal bloom. Photos credit Kalina Manoylov.
Figure 8.6: Visible algal blooms leading to Fish Kills in some cases. A: Minnewashta Lake, IA, photo credit: Kalina Manoylov GCSU; B: photo credit Jennifer L. Graham at USGS.
The dead zone in the Gulf of Mexico is a huge area of low DO (less than 2 mg/L or ppm) that has a large negative impact on the fishing industry along the Gulf Coast near the mouth of the Mississippi River (Figure 8.7). The dead zone occurs annually when fertilizers, from farm fields in the Midwest, wash down the Mississippi river.
Figure 8.7: The dead zone in the Gulf of Mexico 2017, Top photo: Showing the watershed of the
Mississippi river. Bottom image: oxygen levels in the Gulf of Mexico. (Image Source: NOAA. ORG)
Improper storage and use of automotive fluids produce common organic chemicals causing water pollution. These chemicals include methanol and ethanol (present in wiper fluid); gasoline and oil compounds such as octane, nonane (overfilling of gasoline tanks); most of these are considered non-point sources since their pathway to watercourses is mainly overland flow. However, leaking underground and above ground storage tanks can be considered point sources for some of these chemicals, and even more toxic organic compounds such as perchloroethylene. Grease and fats (such as lubrication and restaurant effluent) can be either point or non-point sources depending upon whether the restaurant releases grease into the wastewater collection system (point source) or disposes of such organics on the exterior ground surface or transports to large landfills. Table 8.1 shows a summary of some common chemical pollutants and their sources.
Table 8.1: Chemical compounds and their common sources
|Mines, industries, rocks, power plants|
|Sewage, wastewater treatment plants, agriculture, fertilizer use)|
|Industrial activities, hormones and hospitals|
|Agriculture, golf courses, lawns|
|Industry, powerplants, transformers, gas stations|
|Nuclear powerplants, Hospitals|
|Animal farms, sewage, runoff|
126.96.36.199 Physical surface water pollution
The most significant physical pollutant is excess sediment in runoff from agricultural plots, clear-cut forests, improperly graded slopes, urban streets, and other poorly managed lands (especially when steep slopes or lands near streams are involved). Other physical pollutants include a variety of plastic refuse products such as packaging materials; the most pernicious of these items are ring shaped objects that can trap or strangle fish and other aquatic fauna in our rivers, lakes and oceans. Oceans house many forms of living things that are uniquely adapted to survive in these salty habitats. Unfortunately, humans have degraded oceans through pollution, overfishing, carbon dioxide acidification and resource exploitation. Other common physical objects are timber slash debris, waste paper and cardboard. Figure 8.8 shows a couple of examples of human impacts on the ocean environment.
Figure 8.8: Trash washed up on the beach (left photo) and seal tangles up and being struggled by plastic trash in the ocean (right photo). Photo Credit: NOAA Libraries
Finally, power plants and other industrial facilities that use natural water bodies for cooling can cause thermal pollution (Figure 8.9) in surface water. Thermal pollution can change the ecology of the water bodies and harm living things. The warm water discharged is usually only used for cooling in the plant and does not contain other contaminants.
Figure 8.9: Schematic of the plant causing thermal pollution (Credit: USEPA)
188.8.131.52 Biological Pollution
Common biological pollutants include pathogenic microbes such bacteria, viruses, protozoa and helminths. The most frequently encountered bacteria are E.coli, Shigella, Vibrio cholerae, Campylobacter, and species of the genus Salmonella (which variously cause typhoid fever and food-borne illnesses). Common viral pollutants include the Norwalk virus, Enteroviruses, Adenovirus and Hepatitis A/E, while protozoans are dominated by G. lamblia, and species in the genus Cryptosporidium. All these are fecal-oral route parasites often transmitted as water pollutants and are associated with inadequate sanitation. They originate from various sources that include sewage treatment facilities, animal fecal waste, leaky septic tanks, and recreational areas such as swimming pools. In addition, we also have parasitic worms (helminth) and amoeba (protist E. histolytica) that live inside faunal digestive systems for part of their life cycle that are partially spread as water pollutants, with an estimated three billion people currently affected globally. These parasites are transmitted into the water by direct contact of human fecal matter in swimming pools or from untreated sewage.
8.5 Groundwater Pollution
Surface water is not the only water source that can get contaminated by the pollutants discussed under surface water. Groundwater can also become contaminated from both natural and anthropogenic sources of pollution. Naturally occurring contaminants are present in the rocks and sediments. As groundwater flows through sediments, metals such as iron and manganese are dissolved and may later be found in high concentrations in the water. Industrial discharges, urban activities, agriculture, groundwater withdrawal, and disposal of waste all can affect groundwater quality. Contaminants from leaking fuel tanks or fuel or toxic chemical spills may enter the groundwater and contaminate the aquifer. Pesticides and fertilizers applied to lawns and crops can accumulate and migrate to the water table.
Leakage from septic tanks and/or waste-disposal sites also can contaminate ground water as well (Figure 8.10). A septic tank can introduce bacteria to the water, while pesticides and fertilizers that seep into farmed soil can eventually end up in water drawn from a well. Or, a well might have been placed in land that was once used as a garbage or chemical dump site.
Figure 8.10: Contaminated groundwater from a septic tank (Image Credit: USGS)
8.6 Water Management
Pollution control begins with testing and monitoring of water quality. Water quality is usually monitored using easy to measure indicators such as pH, specific conductance (commonly referred to as conductivity), temperature, fecal and total coliform bacteria, dissolved oxygen, macroinvertebrates, and algae. Polluted sites typically have reduced DO levels, lower pH (more acidic), higher nutrient levels, more bacteria, and higher temperatures compared to less impacted or pristine sites.
Non-point source control relates mostly to land management practices in the fields of agriculture, mining and urban design and sanitation. Agricultural practices leading to the greatest improvement of sediment control include: contour grading, avoidance of bare soils in rainy and windy conditions, polyculture farming resulting in greater vegetative cover, and increasing fallow periods. Minimization of fertilizer, pesticide and herbicide runoff is best accomplished by reducing the quantities of these materials, as well as applying fertilizers during periods of low precipitation. Other techniques include avoiding of highly water soluble pesticides and herbicides, and use of materials that have the most rapid decay times to benign substances.
The main water pollutants associated with mines and quarries are aqueous slurries of minute rock particles, which result from rainfall scouring exposed soils and also from rock washing and grading activities. Runoff from metal mines and ore recovery plants is typically contaminated by the minerals present in the native rock formations. Control of this runoff is chiefly achieved by preventing rapid runoff and designing mining operations that avoid tailings either on steep slopes or near streams. Without proper runoff controls in place, water from active and abandoned mines can become acidic and produce what’s called acid mine drainage (AMD). This is runoff with low pH and high concentrations of iron and other heavy metals that are harmful to aquatic life.
In the case of urban stormwater control, good urban planning and design can minimize stormwater runoff. By reducing impermeable surfaces (pavement that doesn’t allow water through), then cities can reduce the amount of surface water runoff the carries pollutants into surface water and causes flooding. Additionally, the use of native plant and xeriscape techniques reduces water use and water runoff, and minimizes the need for pesticides and nutrients. Regarding street maintenance, a periodic use of street sweeping can reduce the sediment, chemical and rubbish load into the storm sewer system
The two common approaches to water management fall under either voluntary programs or the regulatory programs. The regulatory approach has been very successful in controlling and reducing point source pollution, which was the focus of regulations when they were first introduced. Voluntary programs, together with new amendments to regulations, have had great success in increasing conservation and reducing diffuse nonpoint source pollution. One of the most widely used voluntary programs is Watershed Management while the regulatory approach in the US is centered on the Clean Water Act (CWA).
8.6.1 Watershed Management
The watershed management approach recognizes that water contamination problems are complex and not localized to a section of a river. Water pollution problems are caused by multiple activities within the watershed and, therefore, require holistic approaches in the entire watershed. A watershed (drainage basin or catchment) is an area of land that drains to a single outlet and is separated from other watersheds by a drainage divide. Rainfall that falls in a watershed will generate runoff (if not trapped or infiltrated into groundwater) to that watershed’s outlet. Topography (elevation) is used to define a watershed boundary. A focal point of water management plans is the Best Management Practices (BMPs) section. BMPs are designed to consider all of the various uses of water, maximize conservation and minimize pollution.
8.6.2 The regulatory approach
Water management through policy and laws seeks to clean up polluted water, prevent further pollution and apply punitive measures for polluters. In the US water-related regulations go as far back as 1899 with the Rivers and Harbors Act, also known as the Refuse Act that prohibited the dumping of solid waste and obstruction of waterways. This regulation, however, did not include waste flowing from streets and sewers. In 1948 another regulation, the Federal Water Pollution Act (which is the basis of the Clean Water Act) was enacted. This regulation covered contamination from sewage outfalls. It was created to reduce contamination of both interstate groundwater and surface waters. Through this regulation funding was made available to states and local governments for water quality management.
One of the major water-related regulations in the US is the Clean Water Act (CWA) of 1972.
The regulation was very comprehensive with lots of programs that empowered the Environmental Protection Agency (EPA) to create goals, and objective laws for its implementation. The legislation has programs for both point and nonpoint source pollution. One other major piece of regulation governing water was the 1974 Safe Drinking Water Act (SDWA).
In 1974, amended in 1986, the SDWA was enacted to establish standards for many chemical constituents for public water supplied by water agencies. In the regulation, maximum contaminant level goals (MCLG), which are non-enforceable and maximum contaminant levels (MCLs) that are enforceable where created. MCLG are what would be ideal and desirable while MCL are what should be attained in any drinking water supplied by a public municipal agency. For any carcinogen, the MCLG is 0 even though many contaminants have MCLs and detection limits in the parts per billion (ppb) range. Some of them (e.g. dioxin) have MCLs in the parts per trillion (ppt). To give you a sense of how small this ppt is, it is the same as 0.4 mm divided by 348 470 Km (238,900 miles) which the distance from Earth to the moon.
8.7 A Closer Look at the Clean Water Act
The 1972 Clean Water Acts was an overhaul of the 1948 Federal Pollution Control Act. The current regulation includes numerous programs for water quality improvement and protection. The EPA works with its federal, state and tribal regulatory partners to monitor and ensure compliance with clean water laws and regulations in order to protect human health and the environment. The Clean Water Act is the primary federal law governing water pollution. One of the objectives of the CWA was to restore and maintain the integrity of the nation’s physical, chemical, and biological waters quality. The ultimate goals of the act are to establish zero pollutant discharge, as well as fishable & swimmable waters in the country. One main component of the CWA is regulations on industrial and municipal discharges into navigable US waters. The act is designed to be a partnership between states and the federal government. The federal government sets the agenda and standards while the state carries out the implementation of the law. States also have the power to set standards that are more stringent than the federal standards if needed. Under the CWA, discharge into US waters is only legal if authorized by a permit. Perpetrators of the law can be punished using administrative, civil, or criminal charges. The second component of the act is providing funding for constructing municipal waste water treatment plants and other projects to improve water quality (Title II and Title VI).
The act covers both point sources (discharge from sources such as pipes) and nonpoint sources (pollution from diffuse sources such as stormwater runoff). Point sources are explicitly covered under section 402, National Pollutant Discharge Elimination System (NPDES). This section requires industries and municipalities to get permits from the EPA before discharging into US waters. The permits require the use of control technology to reduce and prevent pollution.
8.8 Water Quality Assessment
To effectively utilize the tools described above for water management, a series of water quality parameters are measured or monitored (Table 8.2). These are physical, chemical or biological parameters that typically have a set maximum (or minimum) standard that is used as a bench mark for determining whether the quality of the water is good or poor. These standards are a set of measurable or observable characteristics that are established by a recognizable body (agency or authority) such as the World Health Organization, any national, state, local or tribal environmental protection agency, or the government. These authorities use the scientific method to decide what the safe limits are for different contaminants. They also constantly keep testing/monitoring and continually adjusting these standard as more data (evidence) becomes available.
Table 8.2: Water Quality Assessment
|Ion electrode (Handheld probe)|
|Colorimeter, chromatography, stoichiometry|
|Colorimeter, chromatography, stoichiometry|
|Colorimeter, chromatography, stoichiometry|
|stoichiometry, ion electrode (handheld probe)|
|Ion electrode (Handheld probe)|
|Microscope, Ion electrode (Handheld probe)|
|Agar and plate count|
|Handheld probe, colorimeter|
|Ion electrode (Handheld probe)|
|Ion electrode (Handheld probe)|
Colorimetry: measuring wavelengths when light is passed through a liquid to measure color changes that correspond to specific values. These can use either a colorimeter such as Hach Colorimeter or
Stoichiometry: reacting chemicals together and using titrations to determine the neutral point of either the acid or the base
Ion specific electrodes: measuring the potential between two electrodes to determine concentrations of specific ions. The electrodes can be single ion handheld probe or multi-parameter hand instruments such as, Extech meters and YSI multi-parameter systems.
Chromatography: physically separating solutes and suspended substances in a liquid based on their adsorption and absorption characteristics
8.9 Water in Crisis (case studies)
Your instructor will assign you a specific case study for the course if needed.
Test Your Understanding
Carefully examine figures 8.1 and 8.2 and explain the trends shown in the figure 8.1
(focus on periods of increase, stabilization and decline, and why they happened)
Fully explain the differences in water scarcity issues between highly industrialized countries and less industrialized countries. Why do these differences exist?
Explain and justify the best water management for less industrialized countries.
What is major type of ocean pollution and how can we prevent it?
What are some of the reasons why not everyone in Lusaka (with abundant natural water resources) has access to clean and safe drinking water while California (with limited natural water supplies) has safe clean water accessible to all its residents?
What are practical ways to prevent toxic algal blooms?
Discuss some of the parameters and pollutants that would you look for in water to distinguish between mining and sewage treatment sources of pollution
Based on your understanding of the water management strategies provided in this text and other sources of your choice, discuss a situation where a regulatory approach would be more effective than the watershed management approach.
Find out which of the equipment listed in Table 8.2 your school owns (make a list)
Using USGS and EPA sources make discuss why it is important to measure and monitor each of the following water quality parameters:
Biology and Concepts in Biology texts (OpenStax)
Clausen C John. 2018. Introduction to water resources. Long Grove, Illinois. Waveland Press, Inc. Print.
EPA. (2013). Clean Water: Lakes. http://water.epa.gov/type/lakes/. Last updated on Tuesday, July 30, 2013
Fetter C.W. Jr. Applied Hydrogeology, 4th Edition. Upper Saddle River, New Jersey: Prentice Hall. 2000. Print
Hogan, C. 2014. Water pollution. Retrieved from http://www.eoearth.org/view/article/51cbef2a7896bb431f69cd56
Howard Perlman, the USGS Water Science School. 2015. The Worlds Water.
Howard Perlman. The USGS Water Science School: Aquifers.
http://water.usgs.gov/edu/earthgwaquifer.html. Last modified Thursday, 30-Jul-2015 14:17:07
NASA: Mississippi Watershed https://svs.gsfc.nasa.gov/vis/a000000/a004400/a004493/Mississippi_large.png
James L., Sipes. Sustainable Solutions for Water Resources. Hoboken, New Jersey: John Wiley and Sons Inc, 2010. Print.
John C. Manning. Principles of applied hydrology 3rd, Edition. Upper Saddle River, New Jersey: Prentice Hall, 1996. Print.
Kenneth, M. Brooks, Peter, F. Fflolliott and Joseph, A. Magner. Hydrology &
Management of Watersheds, 4th Edition. Hoboken, New Jersey: Wiley-Blackwell, 2012. Print
Leiter, M., Levy, J., Mutiti, S. et al. Environ Earth Sci (2013) 68: 1. https://doi.org/10.1007/s12665-012-1698-8
Martin R. Hendriks. Introduction to Physical Hydrology. Oxford: Oxford University Press, 2010. Print
Mutiti, S., Levy, J., Mutiti, C., & Gaturu, N. U. S. (2010). Assessing ground water development potential using Landsat imagery. Groundwater, 48(2), 295-305.
Steam Electric Power Generating Effluent Guidelines – 2015: Final Rule
The World Oceans. 2015. 5 Oceans of the World. http://theworldsoceans.com/
Retrieved July 30th 2015.
Thomas V. Cech Principles of Water Resources: History, Development, Management, and Policy, 3rd Edition. Wiley and Sons Inc. 2009. Print
U.S. Department of the Interior, U.S. Geological Survey
This page is: http://sofia.usgs.gov/publications/reports/rali/eqpollution.html Last updated: 04 September 2013 @ 02:04 PM(TJE)
Page Last Modified: Wednesday, 11-Mar-2015
Visualizations by Horace Mitchell Released on September 12, 2016
Withgott, j. & Laposata, m. Essential Environment; the science behind the stories. 4th Edition. New York City, New York. Pearson 2012. Print