Quantifying seasonal ground deformation in Taiyuan basin, China, by Sentinel-1 InSAR time series analysis
Published in May 20, 2023
The presence of seasonal surface deformation in areas that are subsiding/uplifting due to groundwater pumping/recovery can indicate aquifer recharge. Understanding seasonal surface deformation and the existing relationship between triggering factors and the deformation supports effective groundwater management and subsidence mitigation. Here, we investigated seasonal ground displacement in response to the aquifer compaction and expansion due to groundwater extraction and recharge within the Taiyuan basin, Northern China. We obtained Sentinel-1 InSAR displacement time series data from 2017 to 2020 and quantitatively analyzed relationships between triggering factors (e.g., groundwater level and precipitation) and the associated displacements using wavelet-based methods. The results show that the seasonal deformation is concentrated in the irrigated areas within the central basin, with a 1-year periodicity. The annual peak-to-peak amplitude was up to 2 cm, peaking in March with troughs in August. This seasonality present in the displacement time series is found to be ‘in-phase’ with respect to groundwater levels and ‘anti-phase’ in relation to natural precipitation. These results are consistent with the irrigation pumping practices in the basin, with increased groundwater withdrawals to meet irrigation water demand prior to the monsoon precipitation season, resulting in water level decline and land subsidence from mid-March to mid-August. During the non-irrigated season, groundwater extraction decreases, and the aquifer systems are replenished by precipitation, causing water levels to recover and the ground to uplift from late August to mid-March. A geological analysis indicates that the seasonal deformation is controlled by the thickness of Quaternary strata and fault systems, which play a critical role in forming the earth fissures in the basin. The elastic and inelastic deformation was separated; the estimated elastic/inelastic ratio was about 0.6–0.7, indicating that the inelastic component dominates the main aquifer compaction in the central basin. Our analysis is of hydrologic importance which could be used to guide groundwater management and subsidence mitigation, given the inter-basin water diversion projects in this arid basin.
季节性地表变形在由于地下水抽取/回补而发生沉降/抬升的地区的存在，可以指示含水层的回补。理解季节性地表变形及其与触发因素之间的关系有助于有效的地下水管理和沉降减缓。在本研究中，我们调查了在太原盆地（中国北方）地下水抽取和回补导致的含水层压实和膨胀响应下的季节性地面位移。我们获取了2017年至2020年间的Sentinel-1 InSAR位移时间序列数据，并使用基于小波的分析方法定量分析了触发因素（如地下水位和降水量）与相关位移之间的关系。结果表明，季节性变形主要集中在盆地中央的灌溉区，表现出1年的周期性。年峰值至谷值的振幅最大达到2 cm，峰值出现在3月，谷值出现在8月。位移时间序列中的这种季节性变化发现与地下水位呈“同相”关系，与自然降水呈“反相”关系。这些结果与盆地的灌溉抽水实践一致，即在季风降水季节之前，为满足灌溉水需求而增加地下水抽取，导致水位下降和地面沉降，时间范围为3月中旬至8月中旬。在非灌溉季节，地下水抽取减少，含水层系统通过降水得到补充，水位回升，地面从8月下旬至次年3月中旬抬升。地质分析表明，季节性变形受第四纪地层厚度和断层系统的控制，断层系统在形成盆地内的地裂缝中发挥了重要作用。弹性与非弹性变形被分离，估算的弹性/非弹性比率约为0.6–0.7，表明非弹性部分在盆地中央的主要含水层压实中占主导地位。我们的分析具有水文意义，可为地下水管理和沉降减缓提供指导，特别是在该干旱盆地的跨流域调水项目背景下。