Unit 3

Unit Three – Fundamental Concepts


The Advanced Master Gardener – Water Program Manager and Fundamental Concepts of Water


Water is one of our most important resources.  We emphasize it as Master Gardeners for a number of reasons. Most of the concepts regarding water are well covered in the Master Gardener Handbook. These concepts will be mentioned here again, and some readings are suggested, but most users of this handbook should be at least familiar with these concepts. Including them again will serve to provide materials for Water Program Managers to use in their various programmatically defined projects.

Most importantly, life is water-based. All organisms are composed mainly of water, and water is necessary for the life of every living thing.

Many laws and regulations surround water. There are laws and regulations dealing with protecting water resources as well as protecting users of water resources. There are laws and regulations that enable improvement of water resources or of land uses that help protect or improve water resources. We study water partly because of these legal mandates.  These specific mandates are covered in the unit of this handbook dealing with laws, regulations and legislation. They are not covered again here, but mentioned because these legal requirements underpin much of what MG Water Program Managers do and help fund many of our activities.

Also for the Advanced MG Program Manager it is important to study water issues due to community needs other than those caused by legal mandates. For example, a homeowner may wish to install Best Management Practices, practice conservation (or adapt to living on a conservation easement), proper fertilizer usage etc.

Water Cycle


The water cycle is also known as the hydrologic cycle. A description of it with diagrams is available in the MG Handbook. The concept is also covered several other places in this handbook. The U.S. Geological Survey has a website dedicated to this concept, that points out not only the connectedness among precipitation, infiltration and runoff, but also describes where the earth’s water resides, and summarizes how little fresh water is available for our normal water requirements.

U.S. Department of the Interior, U.S. Geological Survey. 2014. “The Water Cycle.” Accessed December 29. http://water.usgs.gov/edu/watercycle.html.





As water falls from the sky it must infiltrate the earth, evaporate or runoff. Many of the units this handbook require understanding those things that affect runoff as well as how runoff affects water quality. Runoff starts when precipitation exceeds soil absorption (infiltration) capacity. Runoff is affected by existing vegetation, slope or topography of the land, and infiltration rate. The USGS Water Science School covers the basics of runoff and the factors that affect it. A more complete treatment of runoff and the factors that affect it is available from the National Resources Conservation Service (NRCS).

U.S. Department of the Interior, U.S. Geological Survey. 2014. “Runoff.” Accessed December 16. http://water.usgs.gov/edu/runoff.html.

U.S. Department of Agriculture, National Resources Conservation Service. No date. “Hydrology Training Series: Runoff Concepts.” Accessed December 16. http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1082991.pdf.

Runoff is a critical concept both as it relates to the hydrologic cycle and as it relates to water quality. Excessive runoff can carry sediments and nutrients as well as other contaminants into surface waters.  Excessive runoff can cause loss of topsoil, and erosion. The concept of runoff is covered extensively in several units in this handbook.

Existing Vegetation


Master Gardeners are familiar with the ability of vegetation to intercept precipitation and slow the rate that it runs off the land. Trees when in leaf can intercept more water than shrubs; shrubs more than grasses; tall grasses more than turf; and bare earth has almost no ability to intercept and slow runoff.

The season obviously can affect runoff since trees in leaf can intercept much more rain water than winter trees, but vegetation can also affect the hydrologic cycle by seasonal changes in transpiration. In winter, deciduous trees and most plants transpire much less water than they do during the growing season. This means that the seasons and the vegetative cover can have an influence on the amount of runoff as well as the amount of evapotranspiration and ultimately soil moisture content.

Barry, Sheila and Sophie Kolding. 2012. “Vegetation Affects on Water Yield, Learning from the Past.” Agriculture and Natural Resources, University of California. Accessed December 16, 2014. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6844.

Infiltration Rate


Previous precipitation and characteristics of the land such as permeability and soil type affect infiltration rate.  Runoff starts when all the pores in the soil are filled with water or when there are no pores to absorb water (impervious surface). Factors dealing with infiltration are more thoroughly covered later in this handbook in the plant-soil-water relationship unit.

Impervious Surfaces


Impervious surfaces do not allow water to penetrate.  This affects infiltration rate and ground water recharge as described later in this handbook in the unit on residential water systems.




A watershed is the area of land where all of the water that is under it or drains from it goes into the same place. So, for example, all the water that drains into the Chesapeake Bay constitutes the Chesapeake Bay watershed. Most of Virginia lies within the Chesapeake Bay watershed, which reaches from upstate New York, and encompasses parts of six states — Delaware, Maryland, New York, Pennsylvania, Virginia and West Virginia — and the entire District of Columbia. Other major watersheds are the New River, Albemarle Sound, and the Big Sandy and Tennessee Rivers.


Chesapeake Bay Foundation. 2014. “Chesapeake Bay Watershed Geography and Facts.” Accessed December 16. http://www.cbf.org/about-the-bay/more-than-just-the-bay/chesapeake-bay-watershed-geography-and-facts.

Watersheds consist of the land around the surface water and the surface water. While most of Virginia lies within the Chesapeake or New River watersheds, it is important to understand that watersheds can be smaller in their description and often it is useful to talk about smaller-sized units of watersheds. Resources exist for identifying these smaller watersheds relevant to Advanced Master Gardener programs.

U.S. Environmental Protection Agency. 2014. “Surf Your Watershed.” Accessed December 17. http://cfpub.epa.gov/surf/locate/index.cfm.

A watershed can be described as small as any named body of water, but often regulatory discussions of watersheds choose to discuss a Hydrologic Unit Code (HUC). The HUC described by 8-digits or HUC-8 is the watershed unit of size most often utilized in regulatory discussions of watersheds. For example, wetlands removed by a project generally must be replaced within the same HUC-8, or in Virginia within one HUC-8 adjacent to where the project removed the wetlands. One can use HUC-10 or HUC-12 watershed designations to drill down even further into watersheds, and it is often very instructive to do so for projects and programs within the MG realm. The Virginia Department of Conservation and Recreation (DCR) maintains an on-line tool to help learn more about the HUCs in Virginia.

Department of Conservation and Recreation. No date. “Virginia Hydrologic Unit Explorer.” Accessed December 16, 2014. http://dswcapps.dcr.virginia.gov/htdocs/maps/huexplorer.htm.

Surface Water


Surface water is a term used to describe water that is on the surface of the earth such as streams, ponds, lakes, estuaries and oceans. Wetlands are often classified as surface waters though seemingly no water shows. The USGS maintains a website with an extensive discussion of surface water information and concepts.

U.S. Department of the Interior, U.S. Geological Survey. 2014. “Surface Water Information.” Accessed December 16. http://water.usgs.gov/edu/mearthsw.html.



Groundwater is that water within the earth’s surface in the soil pore spaces, in fractured rock formations and in other voids. It can be close to the surface or very deep. Well users tap into groundwater to obtain their water, but groundwater also influences surface water amount and quality. Basic concepts of groundwater including saturated zone, water table, recharge and flow are well covered by USGS.


Alley, W.M., T.E. Reilly and O.L. Franke. 2013. “General Facts and Concepts about Ground Water.” In Sustainability of Ground-Water Resources. U.S. Department of the Interior, U.S. Geological Survey. Accessed December 16, 2014. http://pubs.usgs.gov/circ/circ1186/html/gen_facts.html.




There are many things that, when they are present in either the wrong place, or at the wrong concentrations, are termed pollution. It is important to try to understand the sources of the contaminants, the way the contaminants reach the water (point vs. non-point) and the difficulties they cause (eutrophication – proliferating algae growth, toxicity, etc.).

Point and Non-point Pollution


Point source pollution can be shown to come from a single source (e.g., a pipe) where non-point pollution is used to describe contamination that enters water from more diffuse sources. The concept is well discussed in the MG Handbook.

Types of Pollution




Sediments enter the watershed predominantly from runoff arising from erosion or from dust and soil on streets. Prevention by erosion control strategies or street sweeping are known to be effective best management practices for reducing sediment contamination of water. Sediments are important in and of themselves as contaminants and water quality issues, because they bury habitat, fill harbors and channels (requiring dredging), and suffocate animals and plants that live on the bottom of water bodies. They are also important in that sediment particles are the main pathway for many other types of contaminants such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), heavy metals, etc., and particularly phosphorus (P) to enter the surface waters.


Mid-America Regional Council. No date. “What is Sediment Pollution?” Accessed December 16, 2014. http://cfpub.epa.gov/npstbx/files/ksmo_sediment.pdf.


Ongley, Edwin D. 1996. “Pollution by sediments.” In Control of water pollution from agriculture. Food and Agriculture Organization of the United Nations, Rome. Accessed December 16, 2014. http://www.fao.org/docrep/w2598e/w2598e05.htm.




The nutrients nitrogen (N), phosphorus (P), and potassium (K) can potentially contaminate water from a number of sources. Air is a significant source of N contamination, but fertilization practices can be significant sources of N, P and sometimes K to water. The contribution of nutrients to water contamination is of critical interest covered in the MG Handbook and considered in an entire Unit in this Handbook.


Animal Waste


Animal wastes consist of both large scale contributors such as livestock operations and small scale contributors such as wildlife and pets. Since pet parks and curbing the dog are questions that are posed to MGs on a more or less regular basis, it is important to understand the basics of pet waste management.


Animal waste is a potential pollutant due to BOTH nutrient and diseases or pathogens. Animal waste is rich in nutrients and quite soluble, but can also promote growth of unhealthy microbes in water columns, and contribute pathogens in the waste.


U.S. Environmental Protection Agency. 2014. “Pet Waste Management.” Accessed December 16. http://water.epa.gov/polwaste/npdes/swbmp/Pet-Waste-Management.cfm.


U.S. Environmental Protection Agency. 2014. “Animal Waste: What’s the Problem?” Accessed December 16. http://www.epa.gov/region9/animalwaste/problem.html.




Natural waters are naturally teaming with microbial life. Drinking water is generally not. When surface waters contain too many pathogens, they can cause disease, swimming bans, shell fishing bans and potential illness to those who come into contact with the water. When drinking water becomes contaminated it is a major public health issue. The drinking water issues are covered extensively in this handbook in the unit dealing with drinking water and septic systems. Issues dealing with pathogenic contamination of surface and drinking water are covered in http://www.usawaterquality.org/volunteer/ecoli/june2008manual/chpt2_ecoli.pdf.


Pandey, Pramod K., et al. “Contamination of Water Resources by Pathogenic Bacteria.” AMB Express 4 (2014): 51. PMC. Accessed September 9, 2016. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4077002.


U.S. Environmental Protection Agency. 2013. “Basic Information about Pathogens and Indicators in Drinking Water.” Accessed December 16, 2014. http://water.epa.gov/drink/contaminants/basicinformation/pathogens.cfm.


U.S. Department of Agriculture, Cooperative State Research, Education, and Extension Service. 2006. “Bacteria and Water Quality.” In Citizens Monitoring Bacteria: A training manual for monitoring E. coli, 7-10. Accessed December 16, 2014. http://www.usawaterquality.org/volunteer/ecoli/june2008manual/chpt2_ecoli.pdf.




MGs are familiar with pesticide issues and concepts. A review of the pesticide chapter of the MG Handbook may be helpful. MGs have a unique opportunity to influence homeowners in their pesticide usage and in safety precautions to prevent introduction of pesticides into surface waters. A number of fact sheets are available to help MGs communicate pesticide issues to the public from The National Pesticide Information Center and others.


National Pesticide Telecommunications Network. 2000. “Pesticides in Drinking Water.” Oregon State University and the U.S. Environmental Protection Agency. Accessed December 16, 2014. http://npic.orst.edu/factsheets/drinkingwater.pdf.


National Pesticide Information Center. 2014. “Pesticides and Water Resources.” Oregon State University and the U.S. Environmental Protection Agency. Accessed December 16. http://npic.orst.edu/envir/waterenv.html.


Bay Area Stormwater Management Agencies Association. 2008. “Our Water – Our World Fact Sheet: Pesticides and Water Pollution.” Accessed December 16, 2014. http://www.ourwaterourworld.org/QuickLinks/PesticidesandWaterQuality.aspx.




A toxicant is any toxic substance, but toxicants are toxic substances produced by an organism. For example bee venom, snake venom and urushiol, the component of poison ivy that causes some to itch, are toxins. PCBs, PAHs, heavy metals, pesticides, etc. are toxicants, but not toxins. The U.S. Environmental Protection Agency (U.S. EPA) regulates the release of toxicants and the monitoring of them in the environment. A list known as the Priority Pollutants are the main ones the U.S. EPA is interested in, but are by no means the only ones they are concerned about. Toxicants cause toxicity in an organism at different concentrations depending on the organism, the other stresses the organism may be undergoing, the age and/or life stage of the organism and the amount of toxicant available to the organism. The presence of a toxicant is not necessarily a cause for alarm. Rather, it is the dose of the toxicant that determines the risk from an exposure.


U.S. Environmental Protection Agency. 2014. “Toxic and Priority Pollutants.” Accessed December 16. http://water.epa.gov/scitech/methods/cwa/pollutants-background.cfm#content.




Thermal pollution is defined as sudden increase or decrease in temperature of a natural body of water. Heat transfer to water can result in significant changes in habitat, aquatic health, and can exacerbate the growth of microbes. Heat can come from industrial sources such as power plants, although generally those sources are fairly tightly regulated and no longer represent a significant source of thermal pollution. Thermal pollution can be the result of precipitation over impervious surfaces. When an asphalt parking lot or flat roof absorbs sunlight and then precipitation washes over it significant heat transfer to receiving waters can occur.


Watershed Basin Center. “Thermal Pollution of Water.” University of Georgia, Eugene P. Odum School of Ecology. Accessed December 29, 2014. http://www.rivercenter.uga.edu/education/watershed/thermal.htm.