Bio 346 - Freshwater Eco. (Chpt 29) --> Reservoirs Flashcards
What are 3 things reservoirs are primarily used for?
- Irrigation
- Water supply
- Fish farming
How are reservoirs typically constructed?
Constructed by damming rivers in regions where evaporation approaches or exceeds precipitation with the water typically derived from local rivers during rainy periods
What are large volumed reservoirs primarily used for?
Hydroelectric power generation
- Constructed where precipitation can be low or high to have river discharge
What has major ramifications on reservoirs for river discharge and its timing for sediment and nutrient retention behind dams?
Water retention
What are 3 things that happens to reservoirs at lower latitudes?
- Longer growing season
- Longer stratification period
- Higher water temp
- Lack of ice cover
- Receives a much greater put of inorganic matter from their well-vegetated catchments than dimicdic lakes
Epilimnion
The upper layer of water in a stratified lake
Thermocline
A steep temp gradient in a body of water such as a lake, marked by a layer above and below which the water is at different temps
Hypolimnion
The lower layer of water in a stratified lake
- Typically cooler than the water above
Lacustrine (define)
In the deepest region downstream from the transition zone and where strictly limnteic processes dominate
Riverine Zone (define)
An island or coastal area comprising both land and water, characterized by limited land lines of communication with extensive water surface and/or inland waterways that provide natural routes for surface transportation and communications
Transition zone (define)
Area between 2 states (land and water)
What does increase in erosion lead to? (5 things)
- Degradation of the original river channel
- Effects sediment characteristics
- Lowers the groundwater table
- Impacts the feeding and spawning habitats of fishes
- Impacts the biota of the rivers in general
Whats happens when you trap sediment and their absorbed nutrients behind dams?
It removes the rivers role as a fertilizing agent to previously undisturbed and seasonally flooded wetlands, crop-growing areas downstream and the receiving estuaries
- Dams act as barriers
What kind of sediment is in high flowing waters?
Course sediment
What kind of sediment is in low flowing waters?
Fine sediment
What do flood control dams do?
Reduce seasonal variations in discharge
What are 6 factors both artificial and natural lakes lie along?
- Gradients of climate
- Geology
- Morphometry
- Flushing
- Chemistry
- Biology
What are the 3 types of reservoirs?
- Mainstream reservoirs
- Tributary storage reservoirs
- Mainstream storage reservoirs
Mainstream reservoirs (4 things)
- Most river like (WRT = days–>weeks)
- Constructed to generate electricity
- Experience no temp stratification
- Experience no seasonal lowering of the water
Tributary storage reservoirs (4 things)
- Longest WRT (month–> years)
- Greatest possibility of temp stratification
- Built on small rivers
- Usually built for flood control and irrigation
Mainstream storage reservoirs (2 things)
- Intermediate WRT (usually a few months)
- Its more lotic during high runoff periods and switches to more lentic at other times
When does washout of phytoplankton commence?
At lower WRT in turbid, deeply mixed or cold reservoirs where conditions for photosynthesis are much less favourable than in shallow systems of low turbidity at summer temps
Larger organisms have what kind of growing rate and doubling time?
- Slower
- Longer
Riverine Zone (7 things)
- Narrow
- High flow and rapid water flushing
- High turbidity - High suspended spoils
- Low light
- limits planktonic pp, but high benthic pp - Relatively high nutrients
- Growth rate is less than flushing rate
- Coarse sediment
Transition zone (7 things)
- Broader
- Reduced flow and flushing
- Low turbidity - Reduced suspended solids
- Increased light availability
- High planktonic pp, low benthic pp - Low nutrient supply
- Fine sediment
- Dissolved O2 is high when unstratified and low when stratified
Lacustrine zone (7 things)
- Broad and deep
- Little flow and slowest water flushing
- Relatively clear = good lighting (better higher up)
- Nutrient supply by internal recycling
- Growth rate is higher than flushing rate
- Fine sediment
- Dissolved O2 is variable
What is very important about resident time?
It creates a stable community
What does shortening of the resident time do?
Cant double up which results in low transparency (due to low grazers)
Storage reservoirs experience what annually?
Drawdown
- which is a primary response to seasonably changing needs for hydroelectric power or irrigation water
What is aging linked to?
- Oxidation of the terrestrial vegetation
- Flooded soil organic matter
- Shifts in the composition and abundance of biota during its transition from a primary riverine (lotic) to a lake (lentc) assemblage
Trophic upsurge
During the early years after it is filled, nutrient [ ] and productivity at all trophic levels are usually elevated
What percent of global water is fresh?
3%
- drinking, irrigation and industrial use
How much fresh of the 3% of freshwater is hard to use? And why?
- 99.7%
- Held in glaciers and deep aquifers
What does water balance depend on?
Ratio between inflow, precipitation and evaporation
What can the balance of water be effected by?
- Dams or diversion
- Climate change
- Resulting open systems into closed systems with no outflow
How are salts and chemicals transported?
By wind
Health consequences (5 things)
- Higher child mortality
- Lower life expectancy (64 –> 51 years)
- Increase in cancer
- DNA damage
- Birth abnormalities
How do you stabilize lake levels?
Increase water input into basin
What are 5 problems due to dams?
- Human displacement
- Blockage of fish passage and transportation
- Holdback of sediment, erosion downstream
- Changes downstream quality
- Reduced productivity
3 Gorges dam in China
- Flood control, hydro power, transportation, water supply
- Loss of agricultural land, historical sites
- Local climate, public health, soil stability
Dam diversion (Past and future problems)
- Largely political
- Careful consideration of economics
- Education of public as to value of water and increase cost
- International co-operation efforts
- Conservation
- Re-use
What are some impacts due to dams?
- Increase in accumulation of Hg in fish and neurodegenerative symptoms in humans
What happens to the loading of oceans and salinity if the creation of dams increase to meet the increasing rate of consumption?
- Loading to oceans will decrease
- Salinity would increase as a result
