Questions and Activities for Nepal collaboration with LFUCG water projects
Introduction:
Water quality is the ability of a water body to support all appropriate beneficial uses.
Beneficial uses are the ways in which water is used by humans and wildlife, such
as drinking water and fish habitat. If water supports a beneficial use then water
quality is said to be good. If beneficial use is not supported then the quality is
poor or impaired.
1. Physical Measurements
Physical measurements include water temperature, depth, flow velocity, flow
rate, and turbidity. These are all useful in analyzing how materials and possible
pollutants are transported and mixed in the water environment, and can be
related to habitat requirements for fish and other aquatic wildlife. For instance,
many fish have very specific temperature requirements, and cannot tolerate
water that is either too cold or too hot. Such physical characteristics as number of
trees on the stream banks can influence the temperature of the water.
2. Chemical Measurements
Chemical measurements include a wide range of chemicals and chemical
properties. Most water chemistry tests measure concentration , defined as
milligrams of chemical per liter of water (mg/l).
Even the purest water contains countless chemicals, and it would be impossible
to measure all of them. Water quality studies therefore focus on the chemicals
that are most important for the problem at hand. In agricultural areas, studies
measure chemicals found in manure, fertilizers, and pesticides. In an industrial
area studies focus on measuring chemicals used by the nearby industries.
Some chemical related measurements that are collected in most water quality
studies include the following:
Dissolved Oxygen (DO): Dissolved Oxygen is the concentration of oxygen
dissolved in the water, expressed as milligrams oxygen per liter water (mg/l).
DO is an important measurement of aquatic health, since aquatic organisms must
get all of their oxygen from water. Healthy water bodies usually have DO levels
of 8 mg/l or higher.
Biological Oxygen Demand (BOD) : BOD measures how much oxygen is
consumed by bacteria as they break down pollution and organic matter in the
water. It is measured by observing how much dissolved oxygen levels decrease
in a sealed sample over a 5-day period.
Coliform Bacteria: Coliform bacteria are bacteria that grow in the digestive tracts
of humans and other warm-blooded animals, and indicate the presence of
sewage and other sources of fecal pollution. They are measured by counting the
number of bacteria colonies that grow from a 100 milliliter water sample
(#/100ml). Sources of coliform bacteria include wastewater discharges, septic
tanks, domestic animals, and wildlife. Fecal coliform counts greater than about
200 #/100ml are thought to be unsafe for swimming.
Nitrate (NO3) and Phosphate (PO4): Nitrates and phosphates are nutrients that
come from both natural sources and human activities (fertilizers, detergents,
wastewater). These nutrients determine the productivity of a water body, and are
needed at some level to provide good aquatic habitat. However, pollution from
manure, fertilizer, and wastewater can cause excessive nutrient levels. Too much
nitrate or phosphate causes algae to grow out of control, reducing light and
oxygen for fish.
pH : pH is a measure of the acidity of water, and is important in understanding
the chemical balance of the water. pHs below 7 indicate acid conditions, while
pHs above 7 indicate alkaline conditions. pH is a strong determinant of the
solubility and availability of both nutrients and pollutants. Most natural water
bodies will have pHs close to 7, depending on the local geochemistry. Very low
pHs (less than about 6) can come from acid rain, industrial sources, or mine
drainage.
3. Biologic Indicators
Our understanding of the needs of aquatic wildlife is incomplete, and water
chemistry testing does not tell us everything about the suitability of a water body
as habitat. An alternative approach is to measure the abundance, diversity, and
health of different kinds of aquatic plants and animals. This data is then analyzed
to come up with an indicator of water quality.
The simplest biologic approach is toxicity testing . This involves placing a group
of small animals in a water sample and observing how many die or become sick.
This is most often done with water fleas and small fish. Toxicity testing provides
useful but difficult-to-interpret data. Conditions in a laboratory sample are quite
different from field conditions, and at the end of the test you only know that the
animal died - you don't know what killed it. Still, toxicity testing is a useful check
on chemical test results, especially if there is a toxic pollutant in the water that
you did not include in your water chemistry analysis.
Another biologic approach is to measure the numbers and types of
macroinvertebrates found in a stream. Macroinvertebrates are aquatic insects,
insect larvae, crustaceans, and other smaller animals that spend their lives in
water. We know that different species can tolerate different levels of pollution,
and can use this knowledge to measure water quality. For instance, a stream that
has lots of stone fly and mayfly larvae would have very high water quality, while
a stream that has only water striders and aquatic snails might have poor water
quality. Like toxicity testing, this method doesn't tell you why animals are
present or absent, but it can help you identify what problems to investigate.
In the process of studying the water quality in our urban ecosystem, we will be
collecting some physical data such as the vegetation present in area of the
stream, land cover, slope of surroundings, presence of manmade surfaces and
buildings, etc.
We can collect chemical data on dissolved oxygen and pH. We can collect
biologic data about the macroinvertebrates that are found in the stream. From
this data we can draw some conclusions about the quality of the water as defined
above.
Guiding Questions:
How do stream ecosystems respond physically, biologically and chemically to
urbanization?
How do we measure the quality of the water in nature?
How is water quality affected by urban environments?
How are the stream ecosystems in Kathmandu and Lexington alike and
different?
How do we use water quality information to promote sustainability of urban
environments and urban stream ecosystems?
Activities
Make a map for a certain radius around your home showing different kinds of
urban environments; residential, shopping, parks, office buildings, industrial
areas.
Construct food web diagrams for some ecosystems in your area.
Explore the question of whether your city or community has too many people.
Can your local ecosystem support the population for the foreseeable future?
What are the advantages of having more or less people?
Interview grandparents or others that have lived in your area for a long time.
How have natural, agricultural and urban ecosystems changed? Compare a map
of your community from 50 years ago with a current map.
Two different approaches to the international collaboration could involve:
Students work through activities as a whole class and share information
with the distant partner school. Information sharing could take place through
exchange of flash drives shipped via FedEx packages, or through email or other
internet dependent channels.
Students may work on individual projects with a partner at the distant
school. Students collaborate on an experiment that becomes an entry in the local
or regional science fair. Collaborators may even travel to the distant site to
present projects with their partners at the respective fairs.