|LO, MIN-HUI - National Taiwan University|
|WEY, HAO-WEI - National Taiwan University|
|IM, EUN-SOON - Hong Kong University Of Science|
|TANG, LOIS - National Taiwan University|
|Anderson, Raymond - Ray|
|WU, RENJIE - National Taiwan University|
|CHIEN, RONG-YOU - National Taiwan University|
|WEI, JIANGFENG - Nanjing University Of Information Science And Technology (NUIST)|
|AGHAKOUCHAK, AMIR - University Of California|
|WADA, YOSHI - International Institute For Applied Systems Analysis|
Submitted to: Environmental Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2021
Publication Date: 5/28/2021
Citation: Lo, M., Wey, H., Im, E., Tang, L.I., Anderson, R.G., Wu, R., Chien, R., Wei, J., Aghakouchak, A., Wada, Y. 2021. Intense agricultural irrigation induced contrasting precipitation changes in Saudi Arabia. Environmental Research Letters. 16(6). Article 064049. https://doi.org/10.1088/1748-9326/ac002e.
Interpretive Summary: Irrigation can have a major impact on regional air temperatures and precipitation. However, the link between irrigation and temperature and precipitation changes depending upon the amount and location of irrigated agricultural lands. The impact of changing irrigation amounts and area on climate is also poorly understood. To evaluate the impact of irrigation on climate, we used multiple land surface models to simulate the impact of irrigation in a region that experienced large and recent changes in irrigated agriculture (Saudi Arabia). We also used weather station data to see if modeled changes matched the precipitation record from three stations in central Saudi Arabia. The results showed that irrigation increased rain upwind of the agricultural regions while decreasing rain within the agricultural region. Increased rain generally came from more intense storms rather than more frequent storms. The results are important for managers and policymakers who need to understand how temperature and precipitation may change as irrigated acres increase and decrease with changing water availability.
Technical Abstract: Groundwater extraction has grown tremendously in Saudi Arabia to meet the irrigation water demand since the 1980s, and irrigation is one of the major anthropogenic factors modulating regional hydroclimate. However, the link between irrigation and hydroclimate is not well understood in a dry region such as Saudi Arabia. In this study, we utilize three different regional climate models to explore the physical mechanisms behind the irrigation impacts in this region. The results are robust across models and show that when irrigation is applied, wetter soil results in higher evapotranspiration and cools the lower atmosphere, leading to an anomalous pressure field and alters vapor transportation. Precipitation decreases locally because of the local cooling effect, whereas additional water vapor convergence enhances precipitation west to the irrigated region. This west–east contrast of precipitation change indicates a possible link between irrigation expansion in the 1980s and subsequent decadal precipitation variations in central Saudi Arabia. We further find from observations a decadal west–east contrast of precipitation changes in Saudi Arabia to support the similar finding in the models. This study implies the importance of including anthropogenic water management in climate models and provides a better understanding of how irrigation impacts local-to-regional climate.