12. reserviors, Dams and hydropower

Question 1

what is a reservoir

Answer 1

man made lakes used for storing water

Question 2

two types of reservoirs

Answer 2

impounded lakes

dammed rivers

Question 3

exampoe of single purpose reservoir

Answer 3

industry relater-town water supply,

Question 4

example of multipurpose

Answer 4

water supply
irrigation
silt retention
transportation
electricity
recreation
flood mitigation

Question 5

different types of dams

Answer 5

arc dam
butteress (seires of vertical supports)
gravity (resist by own weight)
Timber
Embankment (rock or earth)

Question 6

what is an earth dam

Answer 6

trapezoidal embankment

Question 7

what does an earth dam design ensure

Answer 7

impermeable enough
settlement must not be excessive so as to reduce freeboard
upstream must withstand waves
downstream must withstand rain
bond to foundation to prevent seepage paths

Question 8

what is piping

Answer 8

internal erosion of foundation or embankment due to seepage, starts at reservoir toe and works pack through most permeable route

Question 9

avoid seepage by

Answer 9

increasing flow paths

Question 10

how to increase flow paths

Answer 10

cut off walls (under dam)
impermeable core
blankets upstream and downstream
chimeny drains

Question 11

what is that top flow path called again

Answer 11

the phreatic surface

Question 12

and where should the phreatic surface be

Answer 12

below the downstream toe

Question 13

types of earth filled dams

Answer 13

homogeneous
hydraulic fill (shell gets placed by sedimentaiton)
thic core, thin core, inclined core, rolled rockfill core
concrete deck
asphalt concrete deck

Question 14

notes on soil placement for earth dam

Answer 14

course-larger than 200 sieve
fine-smaller than 200 sieve
layers should be less than 15cm thick after compaction

Question 15

pore pressure issue

Answer 15

in rockfill damns, during compaction , pore pressure become greater than uplift from a filled reservoir, meaing construction is less stable

Question 16

environmental impacts of dams

Answer 16

land inundation
moves people
threat to wildlife
beauty
river regiem
effects of storage on water quality
water bourne diseases
induced earthquakes
air noise pollution etc

Question 17

additional structures required

Answer 17

coffer dams-built upstream for construction
fish ladders
gates
power plants
locks
spillway
tunnels
valves, vaulve vaults

Question 18

what is an engineers responsibiity to saftey

Answer 18

-act with integrity-to ultimate effects of human and nature
responsibke fore the cost of the structure
liable to community first, then client

Question 19

what is live storage made up off

Answer 19

inactive and active storage

Question 20

types of turbines

Answer 20

Kaplan
Pelton
Francis
cross flow

Question 21

what is kaplan

Answer 21

reaction, high flow low head

Question 22

what is pelton

Answer 22

impulse, low flow high head

Question 23

what is francis

Answer 23

in between

Question 24

parts of a hydro system

Answer 24

intake
forebay -must be able t cope with largest flow)
penstock - keep short
powerhouse-should be close to settlement
trailrace-empty into natural water course

Question 25

parts of the powerhouse

Answer 25

control
generator
coupling
trubine

Question 26

who made a sedimentery trap model

Answer 26

Brune

Question 27

three depositional zones in reservoir

Answer 27

topset bed
foreset bed
bottomset bed

Question 28

what is topset bed

Answer 28

coarse (delta deposits )

Question 29

foreset bed

Answer 29

face of the delta deposits (steeped slope, decrease in grain size)

Question 30

bottomset bed

Answer 30

fine, by turbididty , floods can bring larger

Question 31

consequence of reservoir sedimentation

Answer 31

loss of storage
upstream:loss of navigable depths 
downstream:degredation fo channel:loss of land
hydropower: abrasion of trubines 
loss of coast lines

Question 32

5 elements of sediment management

Answer 32

1 reduce sediment inflow
2 route sediment
3 sediment removal
4 proved large storage volume
5 sediment placement, deposit it where it can be removed or doesnt matter

Question 33

routeing sediment techniques

Answer 33

drawdown during flods
off stream reservoirs
sediment bypass
venting