Dayboro Smart Watering Calculator
Calculate how much and when to water your Dayboro garden using real rainfall data, soil moisture, and evapotranspiration from our local weather station
Southeast Queensland's subtropical climate means watering needs change dramatically with the seasons. A 35°C January day with an ET rate of 7 mm can suck moisture out of your soil faster than you'd believe, while a mild 22°C winter day barely needs a drink. Throw in Dayboro's afternoon thunderstorms (that dump 30 mm in 20 minutes then vanish) and working out how much to water gets complicated fast. This calculator does the maths for you.
Smart Watering for Dayboro Gardens
Dayboro's position in the D'Aguilar Range foothills creates a microclimate that makes generic watering advice almost useless. We're hotter than coastal Brisbane in summer (less sea breeze), cooler in winter (valley cold-air drainage), and our rainfall is genuinely unpredictable — you can get 50 mm in an afternoon thunderstorm then nothing for three weeks. The Bureau's "Brisbane" rainfall figures are about as useful as a chocolate teapot when you're trying to work out whether your tomatoes need a drink.
This calculator uses evapotranspiration (ET) data from the Dayboro weather station. ET measures how much water the atmosphere is actually pulling out of your soil and plants through evaporation and transpiration. On a hot, dry, windy day the ET rate can hit 7–8 mm, meaning your garden loses that much moisture per square metre per day. On a cool, humid, overcast day it might be 1–2 mm. The difference between those two days is enormous for your watering schedule.
How Much Water Does Your Garden Actually Need?
The answer depends on three things: what you're growing, what the weather is doing, and what your soil is like. Here's a breakdown of typical water requirements for common Dayboro garden crops:
| Crop | Water Need | Litres/Week/Plant | Mulch Saving |
|---|---|---|---|
| Tomato | High | 10 | 30% |
| Cucumber | High | 12 | 30% |
| Zucchini | High | 10 | 30% |
| Pumpkin | High | 10 | 30% |
| Broccoli | High | 8 | 30% |
| Capsicum | Moderate | 8 | 25% |
| Beans | Moderate | 6 | 25% |
| Potato | Moderate | 6 | 30% |
| Lettuce | Moderate | 5 | 30% |
| Strawberry | Moderate | 5 | 30% |
| Carrot | Moderate | 4 | 25% |
| Spinach | Moderate | 4 | 30% |
| Basil | Moderate | 3 | 25% |
| Onion | Low | 3 | 25% |
| Garlic | Low | 2 | 20% |
| Sweet Potato | Low | 5 | 30% |
The Best Time to Water in Southeast Queensland
There's an ongoing debate about morning vs evening watering. The short answer for Dayboro: early morning (before 8 AM) is usually best. Here's why:
- Less evaporation: Morning temperatures are lower, humidity is higher, and wind is typically calm. More of your water reaches the roots instead of evaporating off the soil surface.
- Disease prevention: Watering in the evening leaves foliage wet overnight, which promotes fungal diseases like powdery mildew and downy mildew — both common in Dayboro's humid conditions. Morning watering gives foliage time to dry during the day.
- Plant physiology: Plants open their stomata (leaf pores) during the day to photosynthesise. Having water available at the start of the day means they can function efficiently from sunrise.
The exception: on extremely hot days (above 35°C), an additional late-afternoon watering (around 4–5 PM) can help stressed plants recover before the evening cool-down. Just water the soil, not the foliage.
Methodology: ET-Based Watering Calculations
The calculator uses the Penman-Monteith reference evapotranspiration (ET0) from the Dayboro weather station as the baseline for all calculations. This is the standard method used by irrigation scientists worldwide.
Calculation Steps
- Base need: Each crop has a weekly litres-per-plant requirement at baseline conditions (average summer ET of 5 mm/day).
- ET adjustment: Actual daily needs are scaled by the ratio of today's
ET to the baseline:
adjusted = base × (ET_actual / 5.0) - Temperature adjustment: Hot days (above 30°C) add 30% to account for plant stress; cool days (below 18°C) reduce by 20%.
- Rainfall credit: Actual rainfall is subtracted from the calculated need. Only effective rainfall counts — heavy downpours where most water runs off are discounted by 50%.
- Mulch reduction: If mulching is enabled, the crop-specific mulch reduction percentage is applied (typically 20–30%).
Formula
daily_need = (base_weekly / 7) × (ET / 5.0) × temp_factor − rain_credit
if mulched: daily_need = daily_need × (1 − mulch_reduction)