River Science Learning Module Answers

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River Science Learning Module Answers
River Science Chapter 1: Nile Basin Geography
1. Question: List the three major rivers that make up the Nile River and two minor
tributaries.
Answer:
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•
While it is generally agreed that the River Nile has several sources, the main river
systems within the Nile basin include the White Nile, with origins in the Equatorial
Lakes Plateau of central Africa, and the Blue Nile and Atbara River, which flow from
the Ethiopian highlands.
Minor Tributaries include: Bahr el Ghazal, Sobat River, Mara River, Nyando River,
Nzoia River, Kagera River, Miriu River, Kuja River, Ruvubu River, Nyawarongo
River, Ruvinzora River and the Little Abbai River.
2. Question: Describe some of the factors responsible for contribution of the flow in
the River Nile.
Answer:
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•
Heavy seasonal rainfall in the Ethiopian highlands swells these rivers and leads to
the annual Nile flood, but during the dry season the flows in these rivers decrease
significantly.
The Equatorial Lakes Plateau contributes a smaller, less variable supply of water to
the River Nile via the White Nile.
Tributaries flowing into the upper White Nile (Bahr el Jebel) in southern Sudan also
contribute water to the White Nile, although approximately half of the water flowing
into the Sudd downstream is lost to evaporation and overflow into the extensive
wetlands of this region.
River Science Chapter 2: Climate
3. Question: Describe the difference between climate and weather, and name the two
most important characteristics of climate.
Answer:
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•
Weather refers to manifestations of atmospheric activity over the scale of a few days,
and includes events such as wind, rain, and storms.
Climate is the long-term average of weather in a particular region, and includes
general patterns of weather conditions, seasons, and weather extremes. The two most
important components of climate are rainfall and temperature.
4. Question: Name and describe the factors that influence temperature.
Answer:
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Temperature depends on latitude, location relative to the ocean, and local
topography.
Cloud cover can reduce the amount of solar energy reaching the earth’s surface. The
hottest regions on earth are not the tropics, which experience frequent cloud cover
•
•
and storms, but the regions between latitudes 25 to 40 , due to low cloud cover and
high sunshine levels throughout the year.
Temperature is significantly affected by proximity to the ocean or other large
waterbodies. The temperature of the ocean can affect temperatures on land; air
masses moving over the ocean can be warmed or cooled by the current before moving
over land. These effects can be seasonal or diurnal.
Temperature can vary significantly and over short distances due to regional
topography. Temperatures decrease by about 0.65º with every 100 m gain in
elevation; mountainous highlands are cooler than low-lying regions.
5. Question: Name and describe three types of rainfall.
Answer:
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•
•
Convective rainfall occurs when land is heated by solar radiation, and warm, moist
air rises into the atmosphere. As the air rises, it cools and forms clouds, which
release rain.
Frontal rainfall occurs due to the interaction of warm and cold air masses. When
these air masses meet, the warm air mass rises over the cold air mass, and is cooled.
This cooling leads to condensation and rainfall.
Orographic rainfall occurs when warm, moist air is forced to rise over topographic
barriers (mountains). The air is cooled as it rises up and over the mountain, leading
to condensation, cloud formation, and rainfall.
6. Question: Describe the origin and effects of the monsoon.
Answer: The term “monsoon” originates from the Arabic word mausim, which means
“season”. The term is used generally to describe seasonal changes in wind direction,
particularly along the shores of the Indian Ocean, as well as the season of heavy rainfall
associated with the winds. Monsoon winds blow from the southwest for six months and
from the northeast for six months of each year.
7. Question: Describe in general terms each of the following: Hadley cell circulation,
Intertropical Convergence Zone, subtropical high-pressure areas.
Answer:
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Hadley Cell circulation: Near the equator, intense solar radiation and the
convergence of the warm, moist trade winds cause air to rise, carrying heat and
moisture into the atmosphere. As the air masses become trapped between the
stratosphere above and the air moving upward from beneath, they are forced to move
either north or south toward the poles. The air masses lose heat as they move
poleward, and begin to descend at about 30 latitude north or south of the equator.
As the air masses spread out over the surface of the earth, air flows back towards the
equator as the trade winds.
Intertropical Convergence Zone: The region encircling the earth between the Hadley
cells of the northern and southern hemisphere. The ITCZ is formed by the
convergence of the trade winds, which flow towards the equator as part of the
Hadley cell circulation pattern, and is characterized by rising air masses and low
pressure.
Subtropical high-pressure areas: Areas of high pressure between 20 and 40
latitude, resulting from the downward movement of air masses. These high-pressure
areas affect the climate of these latitudes, which is dominated by cloud-free and
windless days. The size, intensity, and geographical position of the subtropical
highs vary seasonally due to other seasonal atmospheric effects such as the
movement of the ITCZ.
8. Question: Describe the influence of latitude on temperature.
Answer: Because of the curvature of the earth, solar energy reaching equatorial regions
passes through less atmosphere than solar energy reaching regions at higher latitudes.
The regions near the equator receive more solar energy than higher latitude regions.
Seasonal differences in the sun’s angle, and thus seasonal differences in temperature,
generally increase with latitude. As a result, equatorial regions experience only small
seasonal differences in temperature due to a fairly constant orientation relative to the sun
and high inputs of solar energy throughout the year.
9. Question: Name and describe four types of climates within the Nile basin, and
name a location where each type of climate is found.
Answer:
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Tropical wet and dry climates (savannas) lie between about 5 and 20 degrees latitude;
that is, between equatorial tropical rainforest climates and tropical deserts. These
climates are characterized by seasonal rainfall and warm temperatures and
significant variation in precipitation may occur within a year and between years.
Tropical wet and dry climates are found in portions of the Lake Victoria basin, the
Sudan, and Ethiopia.
Steppe climates are dry, with potential loss of water through evaporation exceeding
yearly rainfall. These climates are found between approximately 20 and 25 degrees
latitude, and have a short, warm rainy season and a longer, hot, dry season. Steppe
climates in the Nile basin are found in the Sudan.
Desert climates in the Nile basin are associated with the subtropical high-pressure
areas resulting from descending Hadley cell air masses. These climates typically
exhibit clear skies, high daytime and low nighttime temperatures, and low rainfall.
The Sahara desert is an example of a desert climate in the Nile basin.
Highland climates are complex and are predominantly affected by the climate of the
surrounding region. Highland climates are predominantly affected by elevation and
exposure (i.e., the direction – north, east, south, or west – an area or slope faces). In
the Nile basin, highland climates are found in the mountains of Rwanda, Burundi,
D.R. Congo, Uganda, and Ethiopia.
10. Question: Describe how rainfall patterns in the Nile basin affect the hydrological
characteristics of the River Nile.
Answer: Rainfall patterns are responsible for the flow regime of the River Nile.
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•
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Rainfall is high at Bahar Dar from June to September due to the influence of the
monsoon moving from the Indian Ocean over the Ethiopian highlands.
In contrast, rainfall at Cairo, Egypt is lowest from June to September, with low
rainfall levels throughout the year.
Heavy seasonal rainfall over the Ethiopian highlands, carried by the Blue Nile, Sobat
River, and Atbara River to the River Nile, accounts for most of the flow in the River
Nile.
The lower, but more continuous, contributions of water from the Equatorial Lakes
Plateau are important during the dry season in the Ethiopian highlands.
11. Question: Describe the significance of drought, flooding, and climate change in
the Nile basin.
Answer:
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•
•
Drought is a significant problem within regions of the Nile basin. Droughts are
especially problematic in the Ethiopian highlands and semi-arid portions of the
basin, although localized droughts occur periodically throughout the basin.
Flooding in the Nile basin occur due to the high variability of climate and river flows
in conjunction with the large number of people inhabiting and dependent on
floodplains. Flooding can also have positive impacts, including increased land
fertility due to sediment deposition, aquifer recharge, and natural watering of
agricultural land (thus reducing the cost of irrigation).
Climate Change Some predict that climate change will lead to changes in the
frequency and intensity of extreme weather events such as floods and droughts. The
impacts of increased variability in climatic patterns within the Nile basin are likely
to be severe.
River Science Chapter 3: River Basin Hydrology
12. Question: Describe the main components of the hydrological cycle.
Answer: The continuous movement of water on and below the earth’s surface, and
between the earth and the atmosphere, is known as the hydrological cycle. The
hydrological cycle includes evaporation and transpiration, condensation of water vapour
in the atmosphere leading to precipitation, and the movement of surface water and
groundwater on the earth.
13. Question: Describe the relative distribution of earth’s water resources among the
oceans, glaciers and ice caps, groundwater, surface water, and the atmosphere.
Answer: 97.476% of the world's total water supply is salt water; 2.522% of the world's total
water supply is fresh water that is frozen or underground; and only 0.010 % of the world's
total water supply is fresh water is not frozen or underground. Of the world's supply of
fresh water, 69.56% is frozen, 30.06% is groundwater, and 0.389% is in lakes, soil moisture,
water vapour, wetlands, rivers, etc.
14. Question: Define the term “watershed”, and discuss how the concept of stream
order relates to the definition and boundaries of a watershed.
Answer: A watershed or river basin (also known as a catchment) can be defined as an
“area of land that drains water, sediment, and dissolved materials to a common outlet at
some point along a stream channel”.
15. Question: Describe the characteristics of headwaters/upper river, middle river,
and lower river.
Answer:
•
Upper River: The upper river basin is usually characterized by steep gradients and
erosional processes that contribute to downstream sediment transport. Streams in
this upper region are usually steep and torrential, and often include rapids and
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•
waterfalls. These streams generally have little floodplain, although part of the bank
and surrounding land may be wetted during periods of high flow.
Middle Section: The middle section of a river system is often characterized by gentler
slopes, a larger river channel, wider floodplain, and greater degree of river
meandering than in the upper river basin.
Lower river: The lowest section of a river system (extending to the mouth or delta)
usually exhibits a very low slope, perhaps changing by only a few centimetres in
elevation over many kilometres of river channel length. The landscape is usually
very flat and the floodplain may cover large areas.
16. Question: Define sinuosity, and describe how braided and anastomosed channels
form.
Answer:
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•
Sinuosity refers to the amount of curving in a river channel, and can be calculated by
dividing the length of the channel between two points by the length of the valley
between those points.
Anastomosed river channels exist where the river is divided into multiple channels
separated by islands, also known as braided channels.
17. Question: Define pools and riffles, and describe the importance of each to aquatic
organisms.
Answer:
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•
Riffles are shallow areas with a slightly steeper slope and faster flow than other areas
of the river channel, and are composed of coarse sediments (boulders, pebbles and
cobbles). Many species of invertebrates and fish are adapted to life in the turbulent
waters of riffles, adhering to the stones of the stream substrate or by seeking refuge
in the numerous spaces between stones. Riffles are also one of the main areas for
spawning by fish migrating from downstream because of the clean, well-oxygenated
water found there, and the shelter that can be given to eggs laid or buried amongst
the stones.
Pools are deeper areas with shallower slope and slower flow. Some deposition of
sediments occurs in pools because of the lower flows, and bottom sediments are finer
than in riffles. Different habitats found in pool areas include the deep portions or
plunge pools, shallow bars with quiet areas often filled with floating vegetation, and
riparian areas with emergent vegetation.
18. Question: Explain the relationship between stream discharge and the transport of
suspended sediment and bedload.
Answer: This relationship is based on the capacity of water to pick up and transport
particles is related to the amount and size of available sediment particles, channel
characteristics, and flow conditions – particularly the speed of the current. The faster the
water flows, the larger the particles it can carry. Sediment transported by water can be
classified as suspended sediment or bedload sediment.
19. Question: Define hydrological regime.
Answer: Hydrological Regime is the long-term flow pattern of a river, which can vary
throughout the year due to seasonality of the rains or other water inflows to the river
system (e.g., snowmelt).
20. Describe how flooding is important to aquatic organisms.
Answer: The characteristics of a flood event (shape and timing of the hydrograph flood)
are very important for the ecology and behaviour of most aquatic organisms, in particular
the floodplain vegetation that depends entirely on the flood for growth. Minor flood
events in the main channel are also important, especially in smaller rivers, as they can
clean sediment from the gravels that provide important habitat for many invertebrate and
fish species. Minor flood events also play an important role in stimulating the breeding
and migratory behavior of some species.
21. Question: Describe how human activities related to forests can impact the river
system and hydrological regime.
Answer: Removal of forest cover can impact the river system in the following ways:
Forests directly affect the water balance through uptake, use, and release
(transpiration) of water by trees and other vegetation, reducing the amount of water
that would otherwise move to and through a river system.
Forests can also indirectly affect water balance through physical processes such as soil
formation.
Forest soils generally allow higher infiltration of water and adsorb more water than
soils exposed directly to the sun, which may become hard and relatively impermeable.
Forest ecosystems therefore retain water from rainfall in the soil, and release it over a
greater period of time than do landscapes with no forest cover. This directly
influences water regimes by reducing the flashy nature of the hydrograph that would
otherwise respond more quickly to rainfall. Deforested hill slopes, sometimes used
for agriculture, are especially susceptible to flashy hydrographs and increased soil loss
and serious erosion.
Forest cover also changes the way in which rainfall reaches the earth. Rainfall falling
over forested areas is intercepted and dispersed by the canopy of leaves and does not
have the energy of water drops falling directly on the soil.
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River Science Chapter 4: Physical and Chemical Characteristics
22. Question: List the main physical and chemical components of the river system.
Answer:
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Physical
ο Water temperature;
ο Light and shade;
ο Substrate and sediment; and
ο River flow.
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Chemical
ο Dissolved oxygen;
ο pH, Alkalinity, Acidity;
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ο
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Nutrients;
Total Dissolved Solids and Conductivity;
Metals;
Biological Contaminants; and
Industrial Chemicals.
23. Question: Name and describe two types of pollution, and provide an example of
each.
Answer:
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Point source pollution refers to pollution that can be related to a single outlet. Point
source pollution can often be collected, treated, or controlled. Point source pollution
originates from a single place, and includes, for example: municipal sewage outfall
or industrial discharge pipe.
Non-point source pollution (or diffuse pollution) cannot be related to a single source
or human activity, although it may result from many individual point sources (e.g.,
many automobile exhaust systems). Non-point source pollution originates from a
widespread area, and includes, for example: Agricultural runoff, urban runoff and
waste disposal sites.
24. Question: Describe how dams influence or change the abiotic and biotic
components of a natural river system.
Answer: Construction of dams and the formation of reservoirs can significantly alter the
physical and chemical characteristics of aquatic ecosystems over a large area. Reservoirs
(or impoundments) are formed where dams block the natural flow of a river and water
accumulates upstream of the dam. Dams may be constructed for a variety of purposes,
including water supply for domestic or industrial use, irrigation, river regulation and
flood control, fisheries, recreation, navigation, canalization, and hydroelectric power
production.
25. Question: List five ecological functions of soils.
Answer:
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Physical support and resource supply (e.g., nutrients, water) for plant growth;
Regulation of water movement through the landscape;
Habitat for numerous organisms, including small animals, insects, bacteria, fungi,
and plants;
Medium for recycling of dead and decaying organic matter; and
Building material for human structures.
26. Question: List the major threats to water quality within the Nile basin.
Answer: The main threats to basin-wide water quality include:
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Insufficiently treated domestic, urban, and industrial wastes;
Non-point source pollution from agricultural chemicals;
Sedimentation due to poor agricultural practice;
Saltwater intrusion; and loss of wetlands;
Localized impacts on water quality from toxic wastes and mining activities occur in
some areas; and
Waterborne diseases.
27. Question: Describe the purpose of water quality guidelines.
Answer: Water quality guidelines can be used as a “benchmark” to assess the suitability of
water for different uses. Guidelines for drinking water quality are usually based on
considerations of human health, and may be set to ensure that the level of contaminants
within water provide a minimal risk to human health.
River Science Chapter 5: Aquatic Ecology
28. Question: Define the terms ‘ecology’ and ‘ecosystem’.
Answer:
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Ecology is the scientific study of how organisms interact with each other and with
their environment. It includes the study of relationships between members of the
same species, between members of different species, and between organisms and
their physical environment.
Aquatic ecology includes the study of these
relationships in all aquatic environments, including oceans, estuaries, lakes, ponds,
wetlands, rivers, and streams.
An ecosystem includes a community of living organisms plus the physical and
chemical environment in which they live, linked by flows of energy and nutrients.
Ecosystems function as a discrete ecological unit, and can be defined at a variety of
scales.
29. Question: Name the main resources required by living organisms, and the ways in
which different types of organisms obtain these resources.
Answer:
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Water: A fundamental requirement for life. Living things cannot function without it,
although the resting stages for some organisms can survive with very little. Aquatic
organisms depend on water not only for internal biochemical processes but also for
habitat.
Energy: Almost all energy used by organisms is derived, directly or indirectly, from
the sun. Plants use energy from sunlight to manufacture a range of sugars by the
chemical process of photosynthesis.
Carbon: The basis of the sugars and complex proteins that are the major building
blocks of all organisms, and is also the basis of structural materials and energy
stores. The breakdown of carbon-containing molecules provides the major source of
energy for heterotrophs, organisms that cannot manufacture their own food using the
sun's energy and must consume other organisms to obtain carbon and energy.
Nutrients: Nitrogen and phosphorus are the most important nutrients for the growth
of algae and plants, as they are often in short supply relative to the needs of these
organisms. Other nutrients (e.g., potassium, iron, sulphur, selenium) are also
required, though these are usually abundant relative to the amount that algae and
plants require.
Oxygen: An essential requirement for life for most organisms. In aquatic
environments, the availability of oxygen is an important factor in determining both
the types of life that can occur and the interactions among different organisms
30. Question: Define ‘autotroph’ and ‘heterotroph’ and explain the relationship
between the two groups.
Answer:
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Autotrophs, or producers, are organisms that can manufacture their own organic
material from inorganic sources.
Heterotrophs, or consumers, are organisms that must obtain energy by consuming
other organisms (autotrophs or other heterotrophs).
31. Question: Name and describe the four classifications of heterotrophs.
Answer: From the perspective of energy flow in ecological systems, there are four general
types of heterotrophs:
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Herbivores are called primary consumers because they eat only plants (autotrophs).
They may consume autotrophs entirely, such as animals that filter microscopic
autotrophs from the water, or feed only on parts of an autotroph, such as an insect
feeding on a large aquatic plant.
Carnivores are called secondary consumers because they feed on other animals.
Omnivores are heterotrophs that feed on autotrophs and on other heterotrophs; that
is, they eat both plants and animals.
Detritivores - Organisms that consume dead organic matter (called detritus) are
called detritivores. Some organisms that are classified as detritivores may have a
mixed diet, also consuming some autotrophs and heterotrophs.
32. Question: Describe what is meant by a food web, and give a simple example.
Answer:
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A food chain consists of a simple linkage of producer to consumers through feeding
relationships. For example, when a fish eats an aquatic insect, and a larger fish eats
the first fish, the two fish and the insect are linked in a food chain.
Food webs are more complex, and consist of a network of linked food chains. Each
one of these food chains connects an autotroph, at the lowest feeding level, to the
herbivores that comprise the primary consumers, and then to the various carnivores
that comprise the secondary consumers.
33. Question: Define biomass and production
Answer:
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Biomass is the organic matter produced by autotrophs and heterotrophs in excess of
what they need to sustain; the biomass in an ecosystem includes the mass of all
living and dead organic matter.
Production refers to the quantity of biomass produced by an organism over a period
of time.
34. Question: Define primary production and explain its importance.
Answer: Primary production refers to organic matter (e.g., body tissue) produced by
autotrophs – mainly photosynthetic plants – and is expressed as a rate of biomass
production (e.g., the amount of wood produced each year).
35. Question: List and briefly describe the various types of aquatic habitats in the
Nile River basin.
Answer:
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Lakes can be defined as permanent waterbodies that are greater than 0.25 ha in
surface area and have a water depth of more then 2m.
Wetlands are areas of the landscape where the water table is at or near the surface, or
where the land is covered by shallow water for a significant portion of the year.
According to the Ramsar Convention on Wetlands, there are three general categories
of wetlands: (1) marine/coastal wetlands; (2) inland wetlands; and (3) artificial
wetlands.
Streams and rivers differ from other types of aquatic habitats in their physical
characteristics (i.e., shape, substrate) and hydrology, which is dominated by flowing
water and is often seasonally dependent.
36. Question: Name the major types of life in aquatic systems and give examples of
each.
Answer:
Microorganisms
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Bacteria
Fungi
Protozoa
Algae
Phytoplankton
Periphyton
Plants
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Macrophytes
Riparian Vegetation
Animals
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Invertebrates
ο Worms
ο Molluscs
ο Insects
ο Zooplankton
Vertebrates
ο Fish
ο Amphibians
ο Reptiles
ο Birds
ο Mammals
37. Question: Describe some of the major impacts on aquatic systems, and give
specific examples from the Nile basin.
Answer:
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Pollution has had a major impact on the lakes, rivers, and wetlands in the Nile River
basin. ‘Pollution’ is a very broad term, and can include pesticide runoff, industrial
effluents, poisons used in fishing, nutrient inputs, and sediments. Pollutants can
degrade drinking water quality, affect public health, and disrupt ecosystem health.
Nutrient inputs to aquatic systems, particularly those of nitrogen and phosphorus,
often result in eutrophication. Eutrophication is the enrichment of aquatic systems
with excessive nutrients, which can then lead to excessive biomass of unwanted
algae, such as cyanobacteria. The decomposition of this biomass can lead to the
depletion of oxygen, threatening fish and other animals, and can result in unhealthy
drinking water.
Poisons are sometimes used in fishing, and can have serious negative consequences
for the biological structure of an aquatic ecosystem. Agricultural herbicides and
insecticides are often added directly to waterThese poisons are a serious threat to
aquatic ecosystems, killing fish, including juveniles, indiscriminately. Poisons are
also detrimental to human health, contaminating both the fish and drinking water.
Biomagnification is the concentration of contaminants up through a food web. Some
contaminants that enter aquatic systems are preferentially stored (usually in fat
tissue) in organisms rather than released. This results in an accumulation of the
contaminant in them. An organism at the base of a food web may contain low levels
of a contaminant. Its consumer, however, will concentrate the contaminant, as it
consumes many individuals of its food source over its lifetime.
River Science Chapter 6: Biodiversity and Conservation
38. Question: Define biodiversity and describe three levels at which it can be
considered.
Answer: Biodiversity refers to the variety of life on earth. The most widely accepted
definition of biodiversity is found in Article 2 of the Convention on Biological Diversity:
‘Biological diversity’ means the variability among living organisms from all sources
including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological
complexes of which they are part; this includes diversity within species, between species
and of ecosystems.
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Species or organism diversity refers to the variety of species that exists within a
region. Species diversity can refer to either the actual number of species or to other
indices of diversity that account for the relationships between species.
Genetic diversity refers to variety in genes or gene pools that exists within a species.
It is genetic diversity that leads to differences in genetic characteristics between
individuals or groups of individuals within a species.
Ecosystem diversity refers to the variety of identifiable ecosystems in which
organisms live, and can include habitats, plant or animal communities, and food
webs.
39. Question: Explain ecotones and their importance.
Answer:
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•
Ecotones are transitional areas between two habitat types. The greatest species
richness usually occurs in zones of transition between habitat types, where the range
of species inhabiting each habitat overlap. Unique environmental conditions
incorporating characteristics of each of the habitat types may provide habitat for
species found nowhere else.
Ecotones can include areas such as wetlands (transitional between terrestrial and
aquatic habitats), estuaries (transitional between freshwater and marine
environments), and grassland/forest boundaries.
40. Question: Describe the spatial pattern in biodiversity according to latitude,
elevation/depth, and river channel zonation.
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Latitude - The species richness of most plant and animal taxa increases with
decreasing latitude. This means that tropical latitudes and the habitats found there,
including terrestrial, marine, and freshwater ecosystems, generally contain more
species than temperate regions; tropical habitats also frequently contain more genera
and families.
Elevation/Depth - Species richness declines with increasing altitude (in terrestrial
environments) and depth (in aquatic environments).
River channel zonation - Changes in biodiversity occur along the length of rivers
and, for fishes, species richness decreases with increasing altitude. Ecological
biodiversity of fishes tends to be greatest in lower river reaches, where a wide variety
of lifestyles and niches are available. The unique habitat and resources available on
the seasonally inundated floodplain contribute to the rich environment of lower
river areas. In contrast, biodiversity is lower in the stony upper courses of rivers,
where the diversity of habitat types and resources may be limited.
41. Question: Describe what is meant by the term resilience.
Answer: Resilience describes the ability of a community to return to its former state after
some disturbance. Resilience results from a wide range of species performing different
functions, a wide range of species performing the same function, and a wide range of
species that respond to disturbances on different spatial and temporal scales.
42. Question: Describe three threats to biodiversity.
Answer:
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Direct habitat loss results from changes in land use such as wetland drainage,
urbanization, conversion of land to agricultural use, and forestry.
Overexploitation occurs when populations are harvested at a rate that exceeds their
ability to replace themselves – that is, the harvest rate is unsustainable.
Introduction of foreign species can threaten biodiversity if the new species competes
with indigenous species for resources and alters the food web, habitat, or other
aspects of the original community.
43. Question: Name the three classifications of threatened species.
Answer:
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•
Critically Endangered;
Endangered; and
Vulnerable.
44. Question: Describe in general terms the objectives of the Convention on
Biological Diversity.
Answer:
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•
Conservation of biological diversity;
Sustainable use of the components of biological diversity; and
Fair and equitable sharing of the benefits arising from the use of genetic resources.
45. Question: Describe the biodiversity of the Eastern Afromontane hotspot.
Answer: This hotspot is termed the Eastern Afromontane hotspot, and includes the
mountains of Ethiopia, the Albertine Rift (including portions of Uganda, D.R. Congo,
Burundi, Rwanda, and Tanzania), as well as areas of Kenya, Tanzania, and Sudan. It is
rich in species of plants, mammals, birds, reptiles, amphibians, and fish, and numerous
species are endemic to the region.
46. Question: Describe Egypt’s coastal wetlands.
Answer: The coastal wetlands of Egypt fall within Conservation International’s
biodiversity hotspot, the Mediterranean Basin hotspot. In northern Egypt, a series of
coastal lagoons, separated from the Mediterranean Sea by a narrow sandbar, provide rich
habitat for numerous species. Lake Burullus, in the northwestern part of the Nile delta, is
a Ramsar site and is considered the most productive wetland in the Egyptian Nile delta, as
well as one of the most important wetlands in the Mediterranean region. Other lakes in
the delta include Lakes Idku, Maryut, and Manzala.
47. Describe the biodiversity significance of the Sudd .
Answer: The seasonally flooded grasslands of the Sudd are important habitat for
numerous species of resident and migratory birds and mammals.
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The Sudd is home to the world’s largest population of Shoebills, or Whale-headed
storks (Balaeniceps rex), and is also the wintering ground of the endangered White
pelican (Pelecanus onocrotalus). Many other species of birds use the Sudd on their
long migrations. In all, over 400 species of birds have been identified in the region.
The Sudd is also an important area for migrating mammals, such as the Mongalla
gazelle (Gazella thomsonii albontata), that follow the seasonal growth of vegetation.
The white-eared kob (Kobus kob) is one of the most abundant species in the area, and
over a million individuals migrate a distance of 1,500 km through the area.
The resources of the Sudd support numerous species of resident mammals, including
the Nile lechwe (Kobus megaceros) and the hippopotamus (Hippopotamus
amphibius).
48. Question: Describe the biodiversity in the Sahara Desert.
Answer: Vegetation in the area includes approximately 500 species, primarily ephemeral
plants and species adapted to desert environments; as many as 162 species are endemic.
70 species of mammals, including 20 species of large mammals, 90 species of resident
birds, and about 100 species of reptiles are also found in the central desert ecosystem.
Arthropods, particularly ants, are also numerous.
River Science Chapter 7: Wetlands
49. Question: Describe what a wetland is, and list five major types of wetlands.
Answer: Wetlands are defined as areas of marsh, fen, peatland or water, whether natural or
artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or
salt, including areas of marine water the depth of which at low tide does not exceed six
metres. Wetlands are areas where water is the most important factor affecting the
environment and the associated plant and animal life. Although they are neither truly
terrestrial nor aquatic environments, wetlands are often the link between land and water,
and the zones of transition between these different environments. Wetlands occur where
the water table is at or near the land surface, or where shallow water covers the land.
The five major types of wetlands are:
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Coastal wetlands;
Estuaries;
Lakes;
Riverine; and
Palustrine.
50. Question: Explain why wetlands are ecologically and economically valuable.
Answer:
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The ecological value of wetlands results from the sum and interaction of biological,
physical, and chemical components that maintain wetland characteristics and
functions. The interaction of these components and the high productivity of wetland
ecosystems typically lead to rich and varied habitats and food resources for
numerous types of organisms.
Wetlands provide direct and indirect benefits that can be defined as goods and
services. Many of these goods and services can be economically valued according to
how much they would cost to replicate or replace or by the cost of losing it.
51. Question: Explain the value of wetlands to human society by listing at least three
tangible resources and three non-material resources obtained from wetlands.
Answer:
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Three tangible resources obtained from wetlands:
ο Food;
ο Construction materials; and
ο Medicinal plants.
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Three non-material resources of wetlands:
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Flood control;
Erosion prevention; and
Water supply and water quality improvement.
52. Question: List examples of major threats to wetlands.
Answer: Wetlands are threatened by drainage, filling, dredging and stream
channelization, hydrological alteration, groundwater abstraction, siltation, and discharges
of pesticides, herbicides, and sewage.
53. Question: Describe an important wetland in Uganda and the role that wetlands
play in Uganda.
Answer: Lakes and associated wetlands in Uganda are one of the most important areas in
Africa for biodiversity and food production. Examples of Uganda wetlands, and their
benefits:
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Ugandan wetlands provide important water storage and purification capacities for
the White Nile.
Lake Victoria is the largest lake in the Nile basin, and provides purification and
oxygenation for the Victoria Nile.
The Lake Nabugabo wetland system is a designated Ramsar site, and includes
satellite lakes of Lake Victoria.
The swampy margins of Lake Kyoga, downstream of Lake Victoria, improve water
quality and provide water storage capacity for the Victoria Nile.
The basins of Lakes George, Edward, and Albert contain numerous floodplains,
smaller satellite lakes, and wetland ecosystems, and exhibit high biodiversity of
plants and animals.
The northern shores of Lake George have been designated as a Ramsar site, and
support rich flora and fauna, including the elephant, hippopotamus, and antelope, as
well as wintering Palaearctic water birds and more than 50 species of fish.
54. Question: Discuss the importance of Yala Swamp for biodiversity, ecosystem
services and livelihoods.
Answer:
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Important bird area, with two globally threatened species, the Great White Egret
(Egretta alba) and Baillon’s Crake (Porzana pusilla obscura), supported by the swamp
habitat. The ecosystem is also important habitat for birds endemic to East Africa’s
papyrus wetlands and the threatened Sitatunga antelope (Tragelaphus spekeii).
Three freshwater lakes – Kanyaboli, Sare, mand Namboyo – are termed “living
museums” because they support species of fish that have disappeared from Lake
Victoria.
Contain extensive areas of dense papyrus, reeds, and grasses.
Supports livelihoods through fisheries, agriculture, livestock grazing, materials,
water, and transportation.
Performs ecosystem services such as flood regulation, water purification, and control
of eutrophication and siltation.
55. Question: Discuss the role of the Sudd for habitat and biodiversity.
Answer: The Sudd provides important habitat and resources for numerous species of
birds, fish, and other wildlife. Examples include:
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Important habitat for migrating birds, and also supports numerous species of
resident birds, including the world’s largest population of Whale-headed storks
(Balaeniceps rex).
Up to 1 million livestock (cattle, sheep, and goats) are kept by the inhabitants of the
Sudd, who also depend on fishing within the extensive system of waterways.
A total of sixty-two species of fish have been identified in the region, with the
highest variety found in the lakes, streams, and side arms of the river channels.
Numerous large wild herbivores within the region migrate seasonally depending on
the period of high river discharge and rainfall and the dry season.
56. Question: Discuss the importance of the Nile delta wetlands for biodiversity:
Answer:
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The Nile delta remains one of the world’s most important bird habitats. Wetlands
within the delta are important stopover sites for the millions of birds that migrate
every year between European and African habitats, while numerous waterbirds
winter in the delta itself.
These overwintering species include, in Lake Manzala, the world’s largest
concentrations of little gull (Larus minutus) and whiskered tern (Chlidonias
hybrida).
Wetland habitats in the delta support one endemic frog (Bufo kassasii) and aquatic
reptiles, including two endangered species of marine turtles (loggerhead and green
turtle) that may breed at Lake Burullus.
The delta supports marine fish as well as economically important species found in
the lakes and lagoons, such as tilapia and catfish.
57. Question: Explain the purpose of the Ramsar Convention (Ramsar, Iran, 1971).
Answer: The objectives of the Convention on Wetlands (Ramsar, Iran, 1971) – otherwise
known as the Ramsar convention – are to ensure the conservation and wise use of
wetlands.
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