ACTIVE WATER HARVEST CALCULATION

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SUPPLY

Design Narrative: The purpose of this calculator is to estimate a supply water budget based on active rainwater harvesting. The calculator includes many cells of assumptions (step 4 - 8). These cells are showed as text fileds and changing any assumption cell will affect results. The calculator references rainfall data from Environment Canada.
To use this calculator:
1. Enter the areas of your roof in Step 1 below "House", etc. Enter 0 for any areas not used.
2. Select a geographical area in Step 2.
3. Select a type in Step 3 for the efficiency of collection based on the roof types.
4. Modify the values in step 4 - step 8 as you desired or use the default values supplied.
5. Press the "Calculate" button to start computation. Press "Reset" to reset all input values to the default values.
6. The potential average monthly harvests can be read as gallons on the line "TOTALS RWH".
7. The potential average harvests can be read as gallons in the section "Summary for active water harvesting".
8. On the right is a column labelled percent of harvest. This is useful to consider the value of each roof section versus the cost to collect it.

Step 1: Enter square footage for all roof areas in which water will be collected from:

Roof Types House Pool House Shed Deck Roof 5 Roof 6 Roof 7
Areas in Square Feet

Step 2: Select one area:

Abbotsford
Chilliwack
Langley
Mission
N Vancouver Capilano
N VANCOUVER WHARVES
Pitt Meadows
Port Moody
Richmond
Surrey City Hall
Surrey- Newton
Surrey- Kwantlen
Vancouver City Hall
Vancouver Harbour
Vancouver Int Airport
Vancouver UBC
White Rock

Step 3: Select one of roof conditions:

A.Metal roof, gutters, piped conveyance
B.Membrane, nonballasted roof and piped conveyance
C.Ballasted Roof and piped Conveyance
D.Metal or unballasted roof spilling through the air to ground sumps
E.Ballasted Roof spilling through the air to ground sumps

Step 4: Resulting seasonal factors:

Month Jan Feb Mar April May June July Aug Sep Oct Nov Dec
Seasonal Factors:

Step 5: Resulting MONTHLY HISTORICAL ET RATE ( inches / month):

Month Jan Feb Mar April May June July Aug Sep Oct Nov Dec
MHE RATE

Step 6: Enter related irrigation parameters:

Add units irrigation system efficiency (enter as decimal, e.g. 0.68 for 68%)
Total irrigated landscaped area (square feet)

Step 7: Enter tank size:

Tank size (gallons):

Step 8: Enter starting tank beginning of month (gallons) for January:

Starting tank beginning of month (gallons) for Jan:


Summary for Active Water Harvesting

TOTAL HARVESTED AREA Sq Ft
TOTAL HARVEST IN AVERAGE YEAR Gallons Acre Feet
TOTAL HARVEST IN PROJECTED DROUGHT Gallons Acre Feet
TOTAL HARVEST IN 10 YEAR DROUGHT Gallons Acre Feet
TOTAL HARVEST IN 50 YEAR DROUGHT Sq Ft Acre Feet
Total Irrigated landscape area Gallons
Irrigation System Efficiency %
Total Storage Capacity (Tank(s) size) Gallons
Percenatge of tank water used %
Estimated Percentage of Irrigation demand met by Harvested Water. %

RESULTS

Month Jan Feb Mar April May June July Aug Sep Oct Nov Dec Sum Harvest%
Precipitation
Seasonal Factor
House
Pool House
Shed
Deck
Roof 5
Roof 6
Roof 7
Totals RWH

DEMANDS

Jan Feb Mar April May June July Aug Sep Oct Nov Dec Total
monthly historical et rate(inches/month)
conversion to cubic feet
conversion to gallons
conversion to gross based
on irrigated landscaped area
gross-up taking into account
irrigation efficiency

SUPPLY VS DEMAND

Jan Feb Mar April May June July Aug Sep Oct Nov Dec Total
starting tank beginning of month (gallons)
harvested amount
reatined (tanked) amount
demand amount
net increase (decrease) in tank volume
ending tank level
shortfall of supply

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