basics of reservoir operations

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Basics of Reservoir Operations Computer Aided Negotiations Fall 2008 Megan Wiley Rivera

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Basics of Reservoir Operations. Computer Aided Negotiations Fall 2008 Megan Wiley Rivera. 0:10. 1:45. Watershed water balance. 2:40. Water Budgets—Conservation of Mass. Mass is not created or destroyed What goes in – what comes out = change in what’s inside. 3:30. $50. ATM $2000 in - PowerPoint PPT Presentation

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Page 1: Basics of Reservoir Operations

Basics of Reservoir

Operations

Computer Aided Negotiations

Fall 2008

Megan Wiley Rivera

Page 2: Basics of Reservoir Operations

0:10

Page 3: Basics of Reservoir Operations

Watershed water balance1:45

Page 4: Basics of Reservoir Operations

Water Budgets—Conservation of Mass

• Mass is not created or destroyed

• What goes in – what comes out = change in what’s inside

2:40

Page 5: Basics of Reservoir Operations

Apply conservation of mass to an atm interaction

• Starting balance: $2000

• Deposit a check for $50

• Take out $30

• Ending balance: $2020

ATM

$2000 in account

$50

$30

What goes in – what comes out = change in what’s inside (final balance – initial balance)

$50 – $30 = $2020 - $2000

3:30

Page 6: Basics of Reservoir Operations

A dollar is easier to track than a unit of water

• Water is “incompressible”

• a unit volume of water is not created or destroyed

• Must define boundaries to apply equation (control volume)

4:05

Page 7: Basics of Reservoir Operations

Time must be considered as well

• Often times, inflows and outflows are measured as flow rates

• The change in storage must therefore also be specified over some length of time

5:15

Page 8: Basics of Reservoir Operations

Try it for a Britta Filter

• How long can you leave your Britta pitcher filling in the sink before it starts overflowing?

6:20

Page 9: Basics of Reservoir Operations

Draw a Control Volume6:50

Page 10: Basics of Reservoir Operations

Some Numbers

• Inflow, Qin = 2.5 gpm

• Outflow, Qout = 1 gpm (note, this is a cheat. The outflow flow rate increases as the chamber fills)

• Chamber dimensions: 8” tall, 24 in2 cross sectional area

• 1 cubic in = 0.00433 gals

7:00

Page 11: Basics of Reservoir Operations

The Equation

• What goes in – what comes out = change in what’s inside

• Qin – Qout = dV/dt

• Work with a partner to figure it out

8:40

Page 12: Basics of Reservoir Operations

Feel free to ask someone else if you get stuck (there are different approaches)

• Inflow, Qin = 2.5 gpm

• Outflow, Qout = 1 gpm (note, this is a cheat. The outflow flow rate increases as the chamber fills)

• Chamber dimensions: 8” tall, 24 in2 cross sectional area

• 1 cubic in = 0.00433 gals

Qin – Qout = dV/dt

Page 13: Basics of Reservoir Operations

The Answer

• Initial volume = 0

• Final volume = 24 in2 * 8” = 192 in3

• Convert to gallons: 192 in3 * (0.00433 gal/1 in3) = 0.83 gal

• Apply equation: 2.5 gpm – 1 gpm = 0.83 gal/x min

• Solve equation: x min = 0.83 gal/(1.5 gpm) = 0.55 min or about 30 second

12:30

Page 14: Basics of Reservoir Operations

Now Let’s Apply It to a Reservoir

lakeriver

dam

town

13:00

Page 15: Basics of Reservoir Operations

Draw Control Volume and Specify Inflows and Outflows

Page 16: Basics of Reservoir Operations

Draw Control Volume and Specify Inflows and Outflows

runoff

evaporationprecipitation

Groundwater exchangeDam release

Water supply diversions (demands)

Effluent (returns)

14:50

Page 17: Basics of Reservoir Operations

An Aside: Identifying Consumptive Uses (water removed from the basin)

runoff

evaporationirrigation

evaporation

infiltration

Groundwater exchange

16:15

Page 18: Basics of Reservoir Operations

An Aside: Identifying Consumptive Uses (water removed from the basin)

runoff

evaporation

Water supply diversions (demands)

Effluent (returns)

Other consumptive uses (e.g. manufacturing)

Page 19: Basics of Reservoir Operations

Back to Conservation of Mass

runoff

evaporationprecipitation

Groundwater exchangeDam release

Water supply diversions (demands)

Effluent (returns)

Net demands, D

Unimpaired inflow, I

Net Evapotransporation, ET

Qout

24:45

Page 20: Basics of Reservoir Operations

What Is Unimpaired Inflow?25:35

Page 21: Basics of Reservoir Operations

Why Might We Want to Calculate It

• If you want to model different operational scenarios, you need to know how much water is reaching the river via runoff (as opposed to upstream operations)

• Also gives information about flow in the river without the presence of reservoirs (possible point of comparison)

26:25

Page 22: Basics of Reservoir Operations

Use the equation to calculate unimpaired inflows (daily average)

runoff

evaporationprecipitation

Groundwater exchangeDam release

Water supply diversions (demands)

Effluent (returns)

Net demands, D

Unimpaired inflow, I

Net Evapotransporation, ET

Qout

32:20

Page 23: Basics of Reservoir Operations

Use the equation to calculate unimpaired inflows (daily average)

Net demands, D

Unimpaired inflow, I

Net Evapotransporation, ET

Qout

measured

measured

measuredBeginning and end of day stages

Measured/modeled/estimated from meteorological info

Page 24: Basics of Reservoir Operations

Storage-Area-Elevation Table

Storage = volume of water

Surface area

elevation

Mean sea level

Storage (af)

Area (acres)

Elevation (ft)

0 5.8 32

1181 378 43

9930 1780 53

11957 2272 54

34055 4978 60

32:30

Page 25: Basics of Reservoir Operations

Use the equation to calculate unimpaired inflows (daily average)

• What goes in – what comes out = change in what’s inside• Qin – Qout = dV/dt, or over the day: • Qin,daily ave – Qout, daily ave = Storageend of day – Storagebeginning of day

• I – ET – Qout – D = Storageend of day – Storagebeginning of day

• I = ET + Qout + D + Storageend of day – Storagebeginning of day

Net demands, D

Unimpaired inflow, I

Net Evapotransporation, ET

Qout Beginning and end of day stages

Work with your partner again

32:40

Page 26: Basics of Reservoir Operations

Use the equation to calculate unimpaired inflows (daily average)

• What goes in – what comes out = change in what’s inside• Qin – Qout = dV/dt, or over the day: • Qin,daily ave – Qout, daily ave = Storageend of day – Storagebeginning of day

• I – ET – Qout – D = Storageend of day – Storagebeginning of day

• I = ET + Qout + D + Storageend of day – Storagebeginning of day

Net demands, D

Unimpaired inflow, I

Net Evapotransporation, ET

Qout Beginning and end of day stages

35:20

Page 27: Basics of Reservoir Operations

Fun with units

• I = ET + Qout + D + Storageend of day – Storagebeginning of day

Net demands, D

Unimpaired inflow, I

Net Evapotransporation, ET

Qout Beginning and end of day stages

Stage = 54’ Stage = 53’

50 mgd

100 cfs

0.3”

Do calculations first in af/day and then mgd

Page 28: Basics of Reservoir Operations

Net demands, D

Unimpaired inflow, I

Net Evapotransporation, ET

Qout Beginning and end of day stages

Stage = 54’ Stage = 53’

50 mgd

100 cfs

0.3”

Do calculations first in af/day and then mgd

Storage (af) Area (acres) Elevation (ft)

0 5.8 32

1181 378 43

9930 1780 53

11957 2272 54

34055 4978 60

• I = ET + Qout + D + Storageend of day – Storagebeginning of day

39:30

Page 29: Basics of Reservoir Operations

Stage = 54’ Stage = 53’

50 mgd

100 cfs

0.3”

• I = ET + Qout + D + Storageend of day – Storagebeginning of day

ET: Multiply by average surface area for the day (see SAE) = 2026 acres 0.3” * 2026 acres = 0.025’ * 2026 acres = 50.7 af in one day

Outflow: 100 cfs * 1.98 af/day / 1cfs = 198 af/day

Demands: 50 mgd * 1 af/day / 3.069 mgd = 16 af/day

I = 50.7 af/day + 198 af/day + 16 af/day + (11957 af – 9930 af)/day = 2292 af/day

This is 747 mgd