Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK, 74078, USA.
Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK, 74078, USA.
J Environ Manage. 2024 Apr;357:120780. doi: 10.1016/j.jenvman.2024.120780. Epub 2024 Apr 3.
Water availability in the subhumid region is highly vulnerable to frequent droughts. Water scarcity in this region has become a limiting factor for ecosystem health, human livelihood, and regional economic development. A notable pattern of land cover change in the subhumid region of the United States is the increasing forest area due to afforestation/reforestation and woody plant encroachment (WPE). Given the distinct hydrological processes and runoff generation between forests and grasslands, it is important to evaluate the impacts of forest expansion on water resources, especially under future climate conditions. In this study, we focused on a typical subhumid watershed in the United States - the Little River Watershed (LRW). Utilizing SWAT + simulations, we projected streamflow dynamics at the end of the 21st century in two climate scenarios (RCP45 and RCP85) and eleven forest expansion scenarios. In comparison to the period of 2000-2019, future climate change during 2080-2099 will increase streamflow in the Little River by 5.1% in the RCP45 but reduce streamflow significantly by 30.1% in the RCP85. Additionally, our simulations revealed a linear decline in streamflow with increasing forest coverage. If all grasslands in LRW were converted into forests, it would lead to an additional 41% reduction in streamflow. Of significant concern is Lake Thunderbird, the primary reservoir supplying drinking water to the Oklahoma City metropolitan area. Our simulation showed that if all grasslands were replaced by forests, Lake Thunderbird during 2080-2099 would experience an average of 8.6 years in the RCP45 and 9.4 years in the RCP85 with water inflow amount lower than that during the extreme drought event in 2011/2012. These findings hold crucial implications for the formulation of policies related to afforestation/reforestation and WPE management in subhumid regions, which is essential to ensuring the sustainability of water resources.
亚湿润地区的水资源极易受到频繁干旱的影响。该地区的水资源短缺已成为生态系统健康、人类生计和区域经济发展的限制因素。美国亚湿润地区一个显著的土地覆盖变化模式是由于造林/再造林和木本植物入侵（WPE）导致森林面积增加。鉴于森林和草原之间明显不同的水文过程和径流产出，评估森林扩张对水资源的影响非常重要，特别是在未来气候条件下。在这项研究中，我们关注的是美国一个典型的亚湿润流域——小河流域（LRW）。利用 SWAT + 模拟，我们预测了在两个气候情景（RCP45 和 RCP85）和 11 个森林扩张情景下，21 世纪末的溪流动态。与 2000-2019 年相比，2080-2099 年未来气候变化将使 RCP45 下小河的径流量增加 5.1%，而 RCP85 下的径流量将显著减少 30.1%。此外，我们的模拟显示，随着森林覆盖率的增加，径流量呈线性下降。如果 LRW 中的所有草原都转化为森林，将导致径流量额外减少 41%。值得关注的是，Thunderbird 湖是向俄克拉荷马城大都市区供应饮用水的主要水库。我们的模拟表明，如果所有的草原都被森林取代，那么在 RCP45 下，2080-2099 年期间，Thunderbird 湖的平均入流水量将比 2011/2012 年极端干旱事件期间低 8.6 年，而在 RCP85 下将低 9.4 年。这些发现对制定与亚湿润地区造林/再造林和 WPE 管理相关的政策具有重要意义，这对于确保水资源的可持续性至关重要。
