Quick Answer
LOCAL WEATHER PATTERNS SIGNIFICANTLY INFLUENCE CISTERN WATER NEEDS BY DETERMINING RAINFALL AMOUNTS, EVAPORATION RATES, AND WATER STORAGE REQUIREMENTS.
Understanding Local Weather Patterns
Local weather patterns play a crucial role in determining water storage needs for cisterns. A key factor is the average annual rainfall, which can vary significantly depending on the location. For example, regions with intense but infrequent rainfall may require larger cisterns to capture and store water, while areas with more consistent but lighter rainfall may require smaller cisterns.
Rainfall Intensity and Cistern Sizing
Cistern sizing should take into account the rainfall intensity, measured in inches per hour. A common rule of thumb is to size the cistern based on the 2-year, 24-hour rainfall event, which represents the worst-case scenario. For example, in regions with an average annual rainfall of 20 inches, a cistern designed for a 2-year, 24-hour rainfall event of 4 inches might be a suitable size.
Evaporation and Water Loss
Evaporation rates also need to be considered when sizing a cistern. A general rule of thumb is to assume an evaporation rate of 0.2-0.5 inches per month, depending on the climate and location. This can significantly impact the amount of water available for use. For example, in a region with high evaporation rates, the cistern may need to be larger to account for the water lost through evaporation.
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