Department of Geography, University of Gour Banga, Malda, India.
Environ Sci Pollut Res Int. 2023 Jan;30(5):11634-11660. doi: 10.1007/s11356-022-22761-y. Epub 2022 Sep 13.
Flow modification pursuing dams is widely found. Some works also focused on its impact on floodplain wetland hydrology. However, how this change can pose an impact on habitat conditions, ecological conditions, and trophic state is also a matter of investigation. The very least attention has been paid to this so far. Therefore, the present study focused on these, taking the dam-induced Lower Tangon river basin of India and Bangladesh as a case. The degree of flow alteration in the river was presented in a heat map. Multi-parametric machine learning (ML) approaches were applied to model hydrological instability and habitat condition. The ecological consequences like evaluating eco-deficit using flow duration curve (FDC) approach, trophic state using trophic state index (TSI), fish habitat zone using image-based hydrological parameters, etc. were measured. The study exhibited that after damming, the degree of river flow modification was about 41%. Consequently, the wetland hydrological instability and habitat conditions were degraded. In the post-dam period, > 50% of wetland area was lost, and hydrological instability was enhanced considerably over wider parts of the wetland. Habitat conditions of the existing wetland also witnessed fragility (poor and very poor areas increased by about 22.23 and 9.34%). As a result of this, adverse ecological responses were found. For instance, the eco-deficit area was increased by 36.19%, a good proportion (100%) of wetlands was witnessed the transformation of TSI from oligotrophic to mesotrophic state, and optimum fish habitat area was declined. The ecological strength map integrating all the cause-effect model parameters showed that good ecological strength was reduced from 49 to 2% in the post-dam. The result of the study would be very useful for wetland restoration for ecological and human well-being.
河流筑坝导致的水流形态改变广泛存在，一些研究也集中于其对河漫滩湿地水文学的影响。然而，这种变化如何影响栖息地条件、生态条件和营养状态也是一个研究课题，迄今为止这方面的关注最少。因此，本研究以印度和孟加拉国的唐根河下游受水坝影响的流域为例，重点关注这些问题。采用热图呈现河流的水流改变程度，应用多参数机器学习（ML）方法对水文不稳定性和栖息地条件进行建模。采用流量持续曲线（FDC）方法评估生态赤字、营养状态指数（TSI）评估营养状态、基于图像的水文参数评估鱼类栖息地带等，来衡量生态后果。研究表明，筑坝后，河流水流改变程度约为 41%。因此，湿地水文不稳定性和栖息地条件恶化。在大坝建成后的时期，超过 50%的湿地面积消失，湿地更广泛的区域水文不稳定性显著增强。现有湿地的栖息地条件也变得脆弱（较差和很差的区域增加了约 22.23%和 9.34%）。因此，出现了不利的生态响应。例如，生态赤字面积增加了 36.19%，很大比例（100%）的湿地见证了 TSI 从贫营养状态到中营养状态的转变，最佳鱼类栖息地面积减少。综合所有因果模型参数的生态强度图显示，大坝建成后的良好生态强度从 49%下降到 2%。本研究的结果将对湿地恢复以实现生态和人类福祉非常有用。
