Water Security Calculator

Daily Water Collection Table (Litres)

Floor Space (sqm/sqft)	50 mm 2 in	100 mm 4 in	150 mm 6 in	200 mm 8 in	250 mm 10 in	300 mm 12 in	350 mm 14 in	400 mm 16 in	450 mm 18 in
50 sqm 550 sqft	82 lts 22 gal	164 lts 43 gal	247 lts 65 gal	329 lts 87 gal	411 lts 109 gal	493 lts 130 gal	576 lts 152 gal	658 lts 174 gal	740 lts 195 gal
100 sqm 1,100 sqft	164 lts 43 gal	329 lts 87 gal	493 lts 130 gal	658 lts 174 gal	822 lts 217 gal	987 lts 261 gal	1151 lts 304 gal	1316 lts 348 gal	1480 lts 391 gal
150 sqm 1,600 sqft	247 lts 65 gal	493 lts 130 gal	740 lts 195 gal	987 lts 261 gal	1234 lts 326 gal	1480 lts 391 gal	1727 lts 456 gal	1974 lts 521 gal	2220 lts 586 gal
200 sqm 2,150 sqft	329 lts 87 gal	658 lts 174 gal	987 lts 261 gal	1316 lts 348 gal	1645 lts 434 gal	1974 lts 521 gal	2303 lts 608 gal	2632 lts 695 gal	2961 lts 782 gal
250 sqm 2,700 sqft	411 lts 109 gal	822 lts 217 gal	1234 lts 326 gal	1645 lts 434 gal	2056 lts 543 gal	2467 lts 652 gal	2878 lts 760 gal	3290 lts 869 gal	3701 lts 977 gal
300 sqm 3,250 sqft	493 lts 130 gal	987 lts 261 gal	1480 lts 391 gal	1974 lts 521 gal	2467 lts 652 gal	2961 lts 782 gal	3454 lts 912 gal	3947 lts 1043 gal	4441 lts 1173 gal

Average Monthly Rainfall (mm)

City	January	February	March	April	May	June	July	August	September	October	November	December
Sydney	103 mm 4.1 in	117 mm 4.6 in	130 mm 5.1 in	115 mm 4.5 in	108 mm 4.3 in	133 mm 5.2 in	95 mm 3.7 in	86 mm 3.4 in	70 mm 2.8 in	77 mm 3.0 in	84 mm 3.3 in	78 mm 3.1 in
Melbourne	48 mm 1.9 in	49 mm 1.9 in	54 mm 2.1 in	57 mm 2.2 in	59 mm 2.3 in	50 mm 2.0 in	48 mm 1.9 in	50 mm 2.0 in	57 mm 2.2 in	66 mm 2.6 in	59 mm 2.3 in	59 mm 2.3 in
Auckland	70 mm 2.8 in	77 mm 3.0 in	91 mm 3.6 in	96 mm 3.8 in	108 mm 4.3 in	130 mm 5.1 in	135 mm 5.3 in	122 mm 4.8 in	109 mm 4.3 in	93 mm 3.7 in	83 mm 3.3 in	78 mm 3.1 in
Wellington	65 mm 2.6 in	61 mm 2.4 in	68 mm 2.7 in	76 mm 3.0 in	78 mm 3.1 in	81 mm 3.2 in	87 mm 3.4 in	80 mm 3.1 in	70 mm 2.8 in	68 mm 2.7 in	67 mm 2.6 in	68 mm 2.7 in
Suva	371 mm 14.6 in	265 mm 10.4 in	374 mm 14.7 in	366 mm 14.4 in	270 mm 10.6 in	163 mm 6.4 in	136 mm 5.4 in	158 mm 6.2 in	177 mm 7.0 in	221 mm 8.7 in	245 mm 9.6 in	277 mm 10.9 in
Nadi	343 mm 13.5 in	292 mm 11.5 in	341 mm 13.4 in	160 mm 6.3 in	89 mm 3.5 in	65 mm 2.6 in	45 mm 1.8 in	65 mm 2.6 in	70 mm 2.8 in	102 mm 4.0 in	132 mm 5.2 in	178 mm 7.0 in
Port Moresby	282 mm 11.1 in	299 mm 11.8 in	318 mm 12.5 in	308 mm 12.1 in	250 mm 9.8 in	195 mm 7.7 in	120 mm 4.7 in	105 mm 4.1 in	115 mm 4.5 in	115 mm 4.5 in	140 mm 5.5 in	200 mm 7.9 in
Lae	427 mm 16.8 in	389 mm 15.3 in	404 mm 15.9 in	389 mm 15.3 in	370 mm 14.6 in	327 mm 12.9 in	270 mm 10.6 in	253 mm 10.0 in	230 mm 9.1 in	245 mm 9.6 in	330 mm 13.0 in	357 mm 14.1 in

How to Use the Water Security Calculator

This water security calculator helps you estimate your daily and total water usage, as well as the potential water collection from your roof based on average monthly rainfall. To use this calculator, follow these steps:

Number of People: Enter the number of people in your household. This helps calculate the total daily water usage.
Number of Days of Resiliency: Enter the number of days you want to have water stored for in case of a water supply disruption.
Roof Area (sqm): Enter the area of your roof in square metres. This will be used to estimate the amount of water you can collect from rainfall.
Average Monthly Rainfall (mm): Select the average monthly rainfall for your area from the dropdown menu. This data can be found in the "Average Monthly Rainfall" table below for various cities.

How the Calculator Works:

The calculator uses the input data to estimate your daily water usage based on standard consumption rates for drinking, cooking, hygiene, and cleaning.
It calculates the daily water collection potential from your roof based on the selected average monthly rainfall and your roof area.
The calculator then computes the total water usage and collection for the specified number of days and determines the additional water storage required to meet your resiliency needs.

Understanding the Tables:

The "Daily Water Collection Table (Litres)" provides an estimate of how much water can be collected daily based on different roof areas and various monthly rainfall amounts.
The "Average Monthly Rainfall (mm)" table shows the average rainfall for each month in different cities. Use this data to select the appropriate rainfall value for your area in the calculator.

By using this calculator and the tables, you can plan your water storage needs and ensure you have adequate water security for your household.