Historic Average ET Rates (Evapotranspiration)
Evapotranspiration (ET) is a critical measure for understanding how much water your plants, lawn, or crops need. ET combines the evaporation of water from the soil and the transpiration from plant surfaces to calculate the total water loss. This chart provides the historic average ET rates for cities across Texas, giving you a reliable starting point for managing irrigation effectively.
How to Use This Chart
- Identify Your City’s ET Rates: Locate your city in the chart to see how much water your plants typically lose each month. For instance, in Austin, ET rates peak at 8.12 inches in July, while the lowest rates occur in January at 2.20 inches.
- Match Watering to ET Rates: Use the chart to determine how much water to replace during different months. If your city’s ET rate is 6 inches in a summer month, your irrigation system should provide approximately that amount of water to keep your plants healthy.
- Optimize Irrigation Systems: Combine this data with smart irrigation technologies. Many systems allow you to input ET rates to ensure precise watering based on plant needs and seasonal conditions.
- Plan for Seasonal Variability: Higher ET rates in summer indicate the need for increased watering, while lower rates in winter reduce irrigation requirements. Adjust your schedule accordingly to save water and promote plant health.
FAQs About the Historic ET Rates Chart
1. Why is ET important for irrigation planning?
ET rates help determine the actual water demand of plants by accounting for water lost through evaporation and transpiration. This ensures efficient water usage and prevents overwatering or underwatering.
2. How do I calculate how much water my lawn needs using ET?
Take the monthly ET rate (in inches) for your city and divide it by your irrigation system’s efficiency. For example, if your system is 75% efficient and the ET rate is 6 inches, you’ll need to apply 8 inches of water (6 ÷ 0.75).
3. Can I rely solely on this chart to determine watering needs?
While the chart provides a solid baseline, you should also consider real-time weather, soil moisture, and plant types. Pairing the chart with a weather-based irrigation controller will yield the best results.
4. Why do ET rates vary so much across Texas?
Texas has diverse climates, from humid coastal regions to arid desert areas. For example, Galveston’s ET rates are lower due to higher humidity, while El Paso’s rates are higher because of its dry, arid conditions.
5. Does the chart account for irrigation system efficiency?
No, the chart only shows raw ET data. You’ll need to factor in the efficiency of your irrigation system when calculating water requirements.
Tips for Using ET Data Effectively
- Combine ET Data with Rainfall Information: If you’re also using the historic rainfall chart, subtract the average rainfall from the ET rate to determine how much supplemental irrigation is needed.
- Monitor Seasonal Trends: ET rates peak during the summer when temperatures are highest. Be prepared to increase watering during this time while ensuring it aligns with any watering restrictions in your area.
- Invest in Sensors: Soil moisture sensors and weather-based controllers can use ET data to automatically adjust your irrigation schedule, maximizing efficiency.