Western New York GSFLOW Model

Globally, the number of people experiencing water stress is expected to increase by millions by the end of the century. The Great Lakes region, representing 20% of the world’s surface freshwater, is not immune to stresses on water supply due to uncertainties on the impacts of climate and land use change. It is imperative for researchers and policy makers to assess the changing state of water resources, even if the region is water rich. This research developed the integrated surface water-groundwater GSFLOW model and investigated the effects of climate change and anthropogenic activities on water resources in the lower Great Lakes region of Western New York. To capture a range of scenarios, two climate emission pathways and three land development projections were used, specifically RCP 4.5, RCP 8.5, increased urbanization by 50%, decreased urbanization by 50%, and current land cover, respectively. Model outputs of surface water and groundwater discharge into the Great Lakes and groundwater storage for mid- and late century were compared to historical to determine the direction and amplitude of changes. Both surface water and groundwater systems show no statistically significant changes under RCP 4.5 but substantial and worrisome losses with RCP 8.5 by mid-century and end of century. Under RCP 8.5, streamflow decreased by 22% for mid-century and 42% for late century. Adjusting impervious surfaces revealed complex land use effects, resulting in spatially varying groundwater head fluctuations. For instance, increasing impervious surfaces lowered groundwater levels from 0.5 m to 3.8 m under Buffalo, the largest city in the model domain, due to reduced recharge in surrounding suburban areas. Ultimately, results of this study highlight the necessity of integrated modeling in assessing temporal changes to water resources. This research has implications for other water-rich areas, which may not be immune to effects of climate change and human activities.全球范围内，至本世纪末，面临水资源压力的人口规模预计将新增数百万。占全球地表淡水总量20%的五大湖（Great Lakes）区域，同样无法摆脱气候与土地利用变化影响的不确定性所带来的供水压力。即便该区域水资源丰沛，研究人员与政策制定者仍亟需对水资源的动态变化态势开展评估。本研究构建了地表水-地下水耦合模型（GSFLOW），针对纽约州西部的大湖下游区域，探究了气候变化与人类活动对当地水资源的影响机制。为覆盖多类情景组合，本次研究采用了两种气候排放路径与三种土地开发情景方案，具体分别为典型浓度路径（Representative Concentration Pathway）4.5、RCP 8.5、城市化率提升50%、城市化率降低50%以及现状土地覆盖情景。将世纪中期与世纪末期的地表水径流量、入湖地下水径流量以及地下水储量的模型输出结果与历史基准值进行对比，以明确水资源变化的方向与幅度。在RCP 4.5情景下，地表水与地下水系统均未出现统计学意义上的显著变化；但在RCP 8.5情景下，至世纪中期与世纪末期，二者均出现了可观且令人担忧的水量损失。在RCP 8.5情景下，世纪中期的径流量较基准下降22%，世纪末期则下降42%。调整不透水地表面积的情景显示出土地利用影响的复杂性，导致地下水水头出现空间异质性波动。例如，模型覆盖范围内最大城市布法罗周边郊区的地下水补给量因不透水地表面积增加而减少，致使当地地下水位下降0.5米至3.8米。综上，本研究结果凸显了耦合建模在评估水资源时序变化过程中的必要性。本研究结论对其他水资源丰沛区域同样具有参考价值——这些区域同样可能受到气候变化与人类活动的影响。