103
Research into the impact of irrigation on urban microclimate demonstrates that it can significantly alter thermal conditions in arid regions.Scientists have found that the presence of irrigated fields near urban areas can significantly affect the microclimate. According to a study published in Nature Geoscience, irrigation can reduce the maximum temperature in a city by 0,79 °C, and the minimum relative humidity increases by 2,72%. This effect is especially noticeable during the daytime in arid regions, where small urban clusters experience the cooling effect the most.
Urbanization creates “urban heat islands” due to the large number of impervious surfaces that accumulate and radiate heat. Irrigation, which accompanies agricultural activities around cities, changes the balance of temperature and humidity, sometimes reducing heat stress. At the same time, as the authors note, the impact of irrigation is ambiguous, since increased air humidity can increase the subjective feeling of heat.
The team, led by Tirthankar Chakraborty, used the highly accurate Weather Research and Forecasting (WRF) model to assess the impact of irrigation on heat stress in 1660 urban clusters in North America. The analysis was conducted using four main indices: Heat Index, Humidex, wet bulb temperature (Tw) and wet bulb temperature (WBGTThe results showed that irrigation not only cools cities, but also increases humidity levels, reducing most heat stress indices.
However, as the researchers emphasize, it is important to choose the right index to assess the impact of irrigation. WBGT, unlike Tw, takes into account not only temperature and humidity, but also solar radiation and wind speed, which provides a more accurate understanding of the heat load on the human body.
Irrigation has been shown to reduce heat stress in most urban areas of the United States, but in other regions, such as northern India, the effects can be unexpected. For example, winter irrigation, introduced to increase crop yields, has caused a 71% increase in fog over the past 40 years, creating problems for transportation and aviation. This highlights the need to consider local climates when planning irrigation projects.
