# How Rain Gauges Measure Up Against New Technologies

October 6, 2017 02:30 PM

The following insights and opinions come courtesy of Sam Eathington, chief scientist with The Climate Corporation.

Ask most farmers how they measure precipitation in their fields and they’ll give you a simple answer - a rain gauge. This popular instrument was designed in the 1600s and has changed little since. Don’t get me wrong, rain gauges still have their place in some applications, but like almost every other industry, agriculture has progressed to include new approaches and ways of thinking. For instance, new technologies now make it possible to measure precipitation over large acreage and are helping farmers make better informed decisions. While these technologies are far from a perfect science, transforming the variability of precipitation data into meaningful information that you can use to better understand field conditions is quickly becoming a relied upon management tool.

Let’s take a look at how the conventional wisdom of the rain gauge is stacking up against advances in weather technology.

1. Single point rainfall estimates (rain gauge) are always the most accurate for your field.

False. While a rain gauge records the precipitation for the few square inches of your field that it covers, the intensity of rain can vary enormously from one side of the field to another. Our weather science team recently conducted a study at one of our research farms where they surrounded a 150-acre field with 10 rain gauges. Results of the study indicated a seven percent variance for individual gauges compared to the average – and extreme differences were in excess of 30 percent. What does that mean? Based on this level of variability, if a field received 0.5” of rain in one area, accumulation readings across the same field could range as much as 0.35” to 0.65” of rainfall. So if a crop typically receives 20” of rain during the growing season, areas of the same field could differ as much as 2” to 6” in total precipitation!

2. Whole field precipitation measurements often differ from rain gauge readings in the same field, so they cannot be trusted.

False: Grid rainfall estimates can actually be more trustworthy because they use several input sources as compared to rain gauges which use only one. Grid rainfall estimates are created using sophisticated statistical models that bring together information from dozens of sources to create an overview of a farmer’s operation. For example, a grid model is created that pulls from live weather feeds, including weather stations, rain gauges and weather radar. Raw radar data is gridded on a roughly 250-acre spacing (just over half of a square mile). This data is then combined with all available rain gauge reports using algorithms to create final rainfall estimates, and the grids are then matched up to a farmer’s fields to provide a rainfall estimation. As more data is received, the readings are updated with additional quality-controlled values.

3. Grid rainfall estimates can provide farmers with data to help make informed decisions about their crop and operations.

True. Grid rainfall estimates are designed to highlight the rainfall variability that often exists across a farmer’s full operation of many fields. It is not uncommon for farmers to observe a rain gauge with minimal rainfall only to travel a short distance to find muddy conditions caused by a heavy downpour. The value of grid rainfall estimates is that they allow farmers to understand the precipitation across their entire operation so they can make informed decisions about farming operations, crop development, and yield potential before going out to their fields.

A look to the future

Rain gauges have been a reliable tool for measuring rainfall for centuries, but with today’s new agricultural technologies, we can expand our insights even further, such as determining how much water is in the field, its pattern, and its contribution to germination, crop growth and yield. But this is only the beginning. Further developments in water models and sensors will enable us to see how water moves within fields. These sensors will offer information that farmers can use as they make decisions about seed planting, fertilizing and controlling yield reducing stress in their fields.

So are rain gauges obsolete? Absolutely not. But as grid rainfall estimate technology evolves, it will exceedingly be relied on to provide meaningful, “big picture” precipitation insights for farmers’ fields to help with those short-term, workability decisions made throughout the year.

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