Rice is one of the most important agricultural commodities throughout the Mekong River Basin including the Tonle Sap Lake floodplains in Cambodia. Recent increases in hydropower dams along the Mekong River have likely altered the surface water hydrology impacting the arable areas and soil qualities for rice production in the Tonle Sap lowland. Along with the hydrological impacts, the region’s rice farming is facing a rapidly changing climate. It is critical to understand how the hydrological changes associated with dam development impact the region’s rice production in a changing climate. The aims of this study were to assess the impacts of recent increases in hydropower dams on the timing and areas of rice cropping in the Tonle Sap floodplains and to evaluate the effects of changing hydrology, rising temperature, and adaptive farming practices on rice productivity using a process-based rice crop model: ORYZA (v3). The effect of dams on arable areas for rice was identified by a remote-sensing method based on the PhenoRice algorithm for the period of 2001–2019 in two rice-growing provinces: Kampong Thom and Battambang. The PhenoRice method identified an increase in rice growing areas as well as shifts in both timing and location of rice cropping towards the sources of irrigation during the dry season since 2010. The ORYZA model simulated a substantial yield reduction with an increase of 2 °C in air temperature in the region. The model predicted that the rice productivity in the region is sensitive to soil organic carbon content which is expected to change with surface water hydrology. The model also predicted that region’s rice yield can increase by optimizing the timing and amount of N fertilization. The findings from this study highlight how hydrology, climate, and agronomic practices can interact to impact rice production in the Lower Mekong Region and provide insights for effective water management and agronomic practices to attain food security in the region in a changing climate.

大米是整个湄公河流域最重要的农产品之一，包括柬埔寨的洞里萨湖泛滥平原。最近湄公河沿岸水电大坝的增加可能改变了地表水水文，影响了洞里萨湖低地的可耕地面积和水稻生产的土壤质量。随着水文影响，该地区的水稻种植正面临着迅速变化的气候。了解与大坝开发相关的水文变化如何在气候变化中影响该地区的水稻生产至关重要。本研究的目的是评估最近增加的水电大坝对洞里萨河泛滥平原水稻种植时间和面积的影响，并评估水文变化、气温上升、和使用基于过程的水稻作物模型对水稻生产力的适应性耕作实践：ORYZA (v3)。通过基于 PhenoRice 算法的遥感方法，在 2001-2019 年期间在两个水稻种植省：磅同和马德望，确定了水坝对水稻耕地的影响。PhenoRice 方法确定了自 2010 年以来旱季水稻种植面积的增加以及水稻种植时间和地点向灌溉来源的转变。该地区的气温。该模型预测该地区水稻生产力对土壤有机碳含量敏感，预计该含量会随地表水水文变化而变化。该模型还预测，通过优化施氮时机和施氮量，可以提高该地区的水稻产量。这项研究的结果强调了水文、气候和农艺实践如何相互作用以影响湄公河下游地区的水稻生产，并为有效的水资源管理和农艺实践提供见解，以在气候变化中实现该地区的粮食安全。