What is evapotranspiration (ET) and how does it benefit golf courses?


What is evapotranspiration (ET) and how does it benefit golf courses?

Oct 3, 2023
Patrick McKinley

Water management is a paramount concern for golf course superintendents, as it directly impacts the health of turfgrass and the overall playability of the course. One effective method that has gained traction in recent years is Evapotranspiration (ET)-based watering. This approach leverages the natural processes of evaporation and transpiration to optimize irrigation practices. 

Accurate ET measurements offer insights into the water requirements of the golf course, ensuring that watering applications align with the specific needs of the turf. 

By understanding ET, superintendents can optimize watering schedules, conserve water resources, decrease costs and enhance the quality of course conditions.

What is Evapotranspiration (ET) and why is it important?

Evapotranspiration, or ET, is the combined process of evaporation and transpiration. 

Evaporation involves the conversion of liquid water into vapor from various surfaces like soil, water bodies, and vegetation. Transpiration is the release of water vapor from plants through small openings in their leaves, called stomata. ET represents the total loss of water from the Earth’s surface to the atmosphere.

For golf course superintendents, measuring ET can be crucial in providing insights into the water needs of the course’s turfgrass. When properly utilizing ET rates, superintendents can tailor their irrigation schedules to match these specific requirements, thereby optimizing water use and promoting healthier turf.

How is ET measured?

To accurately measure ET, a range of methods and tools can be employed:

Weather-Based ET:

This approach relies on meteorological data such as temperature, humidity, wind speed, and solar radiation to calculate ET rates. It offers a comprehensive view of atmospheric conditions that affect water loss.

Soil Moisture Sensors:
These sensors directly measure soil moisture levels, providing real-time data on the soil’s water content. Superintendents can use this information to make precise irrigation decisions.

ET Models:
Evapotranspiration models use mathematical equations that consider weather data and plant characteristics to estimate ET rates. They offer valuable insights for long-term water management planning.

ET advantages over other watering practices

ET-based watering strategies offer several distinct advantages when compared to traditional, fixed irrigation schedules:

Precision Irrigation:

ET-based strategies enable superintendents to align irrigation practices precisely with the specific water needs of the golf course. This prevents overwatering, which can lead to water wastage, nutrient leaching, and turfgrass diseases, while also avoiding underwatering, which can result in dry, unhealthy turf.

Resource Efficiency:

By synchronizing irrigation with actual ET rates, superintendents can reduce water consumption, leading to lower water bills and contributing to sustainability efforts.

Environmental Responsibility:

Overwatering can lead to runoff and the contamination of nearby water bodies with excess nutrients and chemicals. ET-based practices minimize these environmental risks.

Implications, cost, and environmental benefits

While implementing ET-based watering strategies may require an initial investment in monitoring equipment and technology, the long-term implications are significant:

Cost Savings:

Over time, precise water management can lead to substantial cost savings by reducing water bills and operational expenses. These savings can offset initial investments.

Environmental Benefits:

Responsible water management reduces the ecological footprint of golf courses, conserving water resources and minimizing runoff, which can harm local ecosystems.


Golf courses that adopt ET-based practices demonstrate a commitment to sustainability, which can enhance their reputation and attract environmentally-conscious golfers.

Differences in calculated ET and measured ET with soil sensors

It is essential to recognize that there may be differences between calculated ET and measured ET from soil sensors. These variations can occur due to several factors:

Sensor Accuracy:

While soil moisture sensors are valuable tools, they can have measurement errors. Proper calibration and maintenance are crucial for accuracy.

Plant Health:

The condition of the turfgrass and its ability to transpire can impact measured ET. Stressed or unhealthy turf may transpire less, leading to differences.

Local Variations:

Microclimates within the golf course can result in differences in ET rates that may not be fully captured by calculations.


Evapotranspiration-based watering strategies are a powerful and forward-thinking approach for golf course superintendents seeking to optimize water management practices. Understanding and embracing ET allows for precision irrigation, resource efficiency, cost savings, and environmental responsibility. While there may be some challenges adopting this method in the beginning, the overall benefits make ET-based watering strategies a wise choice for golf courses. By adopting ET, superintendents can contribute to both the sustainability and playability of their courses, ensuring lush, green fairways for years to come.

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