1. What is a Water Harvestable Right Calculator?

Definition: This calculator estimates the volume of water that can be harvested based on catchment area, rainfall, and runoff coefficient.

Purpose: It helps property owners determine how much rainwater they can legally harvest according to NSW regulations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( V \) — Harvestable volume (liters)
• \( A \) — Catchment area (square meters)
• \( R \) — Rainfall (meters)
• \( k \) — Runoff coefficient (dimensionless, between 0 and 1)

Explanation: The catchment area multiplied by rainfall gives total water volume, then adjusted by the runoff coefficient to account for collection efficiency.

3. Importance of Water Harvest Calculation

Details: Proper calculation ensures compliance with water rights regulations and helps design appropriate storage systems.

4. Using the Calculator

Tips: Enter the catchment area in m², rainfall in meters, and runoff coefficient (default 0.8). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a runoff coefficient?
A: It's the fraction of rainfall that becomes available runoff (0.8 for roofs, 0.6 for paved areas, 0.2 for lawns).

Q2: How do I measure catchment area?
A: For roofs, calculate the footprint area. For land, use GIS tools or property plans.

Q3: Where do I get rainfall data?
A: Use historical averages from the Bureau of Meteorology for your location.

Q4: Are there legal limits in NSW?
A: Yes, NSW allows harvest of 10% of average annual rainfall from roofs or 100% from first-flush systems.

Q5: Why convert to liters?
A: Water storage is typically measured in liters, and 1 m³ = 1000 liters.