Useful water data
Conversion tables
1 megalitre + 0.82 acre feet or 220,000 gallons
10 mm = 1 cm = 0.01 m = 0.4 inch
1 inch = 25.4 mm = 2.54 cm
1 m = 3.3 ft. 1 ft = 0.3 m
1 litre = 1000 ml = 0.22 gallon = 1.8 pints
1 kilolitre = 1000 litres = 220 gallons
1 gallon = 4.55 litres
1 kg = 1000 g = 2.2 lb
1 oz = 28.3 g, 10 g = 1/3 oz
1 p.p.m. = 1 mg/litre = 0.00016 oz/gal
Water requirements of plants
| Berries, pome fruit, stone fruit | 3 megalitre per Ha |
| Summer veg | 1 megalitre per Ha |
| Winter veg | 0.6 megalitre per Ha |
| Perennial flowers | 0.6 megalitre per Ha |
| Annual flowers | 1 megalitre per Ha |
| Nut trees | 0.6 megalitre per Ha |
| Grapes | 1.5 megalitre per Ha |
Minimum infiltration rates for different soils
| Soil type | minimum infiltration rate (mm per hour) |
| Deep sands, aggregated silts | more than 20 |
| Deep sandy loams | 10 to 20 |
| Clay loams, shallow sandy loams, soils | |
| low in organic matter | 5 to 10 |
| Sodic clay soils | less than 1 |
Example of a deep, dry loam soil
- A steady rain delivers 20 mm water per hour
- Rain falling during the first 10 minutes soaks in quickly (infiltration rate 40 mm per hour)
- The infiltration rate then begins to fall
- After 10 minutes it is 17 mm per hour
- After 20 minutes it is 15 mm per hour
- It continues to fall until it reaches the minimum
ie. only three quarters of rain arriving at 20 mm per hour can soak in.
Water held in soils of different textures
| Soil texture | Water held in different soil (mm per cm of depth) | ||
| Field capacity | Wilting point | Available water | |
| Sand | 0.9 | 0.2 | 0.7 |
| Loamy sand | 1.4 | 0.4 | 1.0 |
| Sandy loam | 2.3 | 0.9 | 1.4 |
| Sandy loam plus OM | 2.9 | 1.0 | 1.9 |
| Loam | 3.4 | 1.2 | 2.2 |
| Clay loam | 3.0 | 1.2 | 2.2 |
| Clay | 3.8 | 2.4 | 1.4 |
| Well structured clay | 5.0 | 3.0 | 2.0 |
Evaporation rate - Adelaide
| Month | mm per day |
| Jan | 8.5 |
| Feb | 7.9 |
| Mar | 5.8 |
| Apr | 4.1 |
| May | 2.6 |
| Jun | 1.9 |
| Jul | 2.0 |
| Aug | 2.6 |
| Sep | 3.8 |
| Oct | 5.4 |
| Nov | 6.7 |
| Dec | 8.1 |
| Total Annual Evaporation | 1806 mm |
Minimum maintenance application for lawns and ornamentals (rain plus irrigation)
| mm per week | Kilolitres of water per week for 500 square metres |
Jan | 15 | 7.5 |
Feb | 14 | 7.0 |
Mar | 10 | 5.0 |
Apr | 7 | 3.5 |
May | 5 | 2.5 |
Jun | 3 | 1.5 |
Jul | 4 | 2.0 |
Aug | 5 | 2.5 |
Sep | 7 | 3.5 |
Oct | 9 | 4.5 |
Nov | 12 | 6.0 |
Dec | 14 | 7.0 |
Multiplication factors for vegetables and fruit trees
Ground covered by plants | Factor | |
| unmulched | mulched |
Full | 0.7 | 0.6 |
60% | 0.6 | 0.5 |
20% | 0.4 | 0.3 |
Stock and water salinity tolerance
Stock tolerance for salinity of drinking water varies depending on the type of feed. Stock on green pick can handle higher rates that stock on dry feed. Pregnant and lactating animals require a lower salinity. Changes from high to low, or low to high salinity are best made slowly. Storage tanks and troughs may also need to be flushed to prevent excessive build-up of salt from evaporation. The composition of salts is also important as ions of sulphate, chloride, sodium and magnesium cause most problems.
| Animal | Maximum salinity for healthy growth | To maintain condition | Maximum tolerance |
| Sheep | 6,000 | 13,000 | 10,000 “ 14,000 depending on feed type |
| Beef cattle | 4,000 | 5,000 | 10,000 |
| Dairy cattle | 3,000 | 4,000 | 6,000 |
| Horses | 4,000 | 6,000 | 7,000 |
| Pigs | 2,000 | 3,000 | 4,000 |
| Poultry | 2,000 | 3,000 | 3,500 |
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