Irrigation enhances local warming with greater nocturnal warming effects than daytime cooling effects

Abstract

To meet the growing demand for food, land is being managed to be more productive using agricultural intensification practices, such as the use of irrigation. Understanding the specific environmental impacts of irrigation is a critical part of using it as a sustainable way to provide food security. However, our knowledge of irrigation effects on climate is still limited to daytime effects. This is a critical issue to define the effects of irrigation on warming related to greenhouse gases (GHGs). This study shows that irrigation led to an increasing temperature (0.002• C year −1 ) by enhancing nighttime warming (0.009• C year −1 ) more than daytime cooling (−0.007 • C year −1 ) during the dry season from 1961-2004 over the North China Plain (NCP), which is one of largest irrigated areas in the world. By implementing irrigation processes in regional climate model simulations, the consistent warming effect of irrigation on nighttime temperatures over the NCP was shown to match observations. The intensive nocturnal warming is attributed to energy storage in the wetter soil during the daytime, which contributed to the nighttime surface warming. Our results suggest that irrigation could locally amplify the warming related to GHGs, and this effect should be taken into account in future climate change projections.

Improvement of the Irrigation Scheme in the ORCHIDEE Land Surface Model and Impacts of Irrigation on Regional Water Budgets Over China

“…Sacks et al () demonstrated that irrigation can cool the surface by 0.5 K in Southeast Asia over year, whereas Thiery et al () found that the cooling effect is 0.10 K. Our study find that irrigation can decrease by 0.05 and 0.13 K in YZRB and YLRB, respectively. The maximum decrease is found in the North China Plain with 0.8 K. In fact, this is conjunct results of decreasing max and increasing min , which are consistent with Chen and Jeong () but with different magnitudes. Nevertheless, both studies confirmed that irrigation can reduce temperature amplitude between day and night.…”

“…Surface cooling by irrigation was investigated by numerous studies (Chen & Jeong, ; Kang & Eltahir, ; Sacks et al, ; Shah et al, ; Thiery et al, ). Sacks et al () demonstrated that irrigation can cool the surface by 0.5 K in Southeast Asia over year, whereas Thiery et al () found that the cooling effect is 0.10 K. Our study find that irrigation can decrease by 0.05 and 0.13 K in YZRB and YLRB, respectively.…”

Warming of hot extremes alleviated by expanding irrigation

“…Comparison of simulated and satellite-based land surface ARTICLE temperatures indeed confirms that CESM appears to underestimate irrigation effects on present-day land surface temperatures across South Asia (see Supplementary Note 2). Implementing paddy irrigation in CESM would thus be beneficial, especially since observational studies [39][40][41] demonstrate that paddy field expansion in China may locally lead to land surface temperature reductions on the order of 1-2 K on average during the growing season.…”

Impact of Irrigation on Regional Climate Over Eastern China

“…The North China Plain (NCP, 34°N to 41°N; 113°E to 121°E; Figure a) is the largest irrigated area in China, and the irrigated area has been dramatically increased from 1.9 to 14 million ha over the second half of the twentieth century (Figure b). Partly because irrigation has added the necessary supplemental water for crop maintenance and improved yield, the crop (i.e., wheat) yield of the NCP has increased rapidly and is now almost twice that of the global average (Chen & Jeong, ). Although irrigation contributed to improvement in crop‐yield, it has also led to perceptible environmental problems such as the significant reduction of groundwater storage and potential accumulation of salt in the topsoil layer in the NCP (Chen, ; Taylor et al, ).…”