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The impact of two cascaded dams and land use change on the hydromorpholgy of the Lhasa River on the Qinghai-Tibet Plateau, China |
Author: isi网站管理员-刘成 Source: Updated: 2022-03-25 |
A recent article entitled ‘Impacts of dams and land-use changes on hydromorphology of braided channels in the Lhasa River of the Qinghai-Tibet Plateau, China’, published in the International Journal of Sediment Research, reported that the two cascaded dams only changed the flow regime of the immediately downstream braided reach. Abstract: Among braided rivers developed on the Qinghai-Tibet Plateau of China at very high elevations (>3,500 m), the middle and lower reaches of the Lhasa River have been affected by comprehensive human activities mainly involving dam construction, urbanization, farming, afforestation, and mining. In the current study, the impacts of these human activities on hydrology and morphology of the four braided reaches downstream of a cascaded of two dams are investigated. The study period was divided into 1985–2006 (P1), 2006–2013 (P2), and 2013–2019 (P3), representing the natural and changed flow regimes by dams. Using available daily discharge data at two stations within the four braided reaches, dam-induced hydrological alteration was analyzed based on the indicators of hydrologic alteration and range of variability approach and key discharge proxies were calculated. Remotely sensed images also were selected in the three periods and morphological metrics extracted from them were compared for the four reaches among these periods. Attenuated hydrological regimes were found for only two reaches. The total channel width (Wc) and braiding intensity (BIt) followed different temporal trends among the four reaches. Annual average shift rates of the main channel in the four reaches were higher in the short (P2–P3) than in the long (P1–P2 and P1–P3) periods. The longitudinal changes of Wc and the number of channels did not have any identifiable trend among the four reaches. By linking the morphological changes to quantified spatial and temporal patterns of various human activities, it was found that (1) the two dams had insignificant impact on channel morphology, suggesting that the studied braided river might have a short relaxation time and (2) the evolutional trajectories of morphological changes in most of the four reaches were similar, suggesting that temporal trends of morphological changes due to complex human activities are not affected by the different physiographic settings of the reaches. Continuous exploitation of the valley area requires comprehensive river management strategies for coordinating various human activities. Highlights l The two cascaded dams only changed the flow regime of the immediately downstream braided reach. l Channel morphology of the near-dam reach likely had a short relaxation time to recover from less intense disturbances. l Urbanization and farming constrain the space available for the braided river to change. l Historical trajectories of channel adjustment in response to human activities are similar among different braided reaches. More information: You, Y., Li, Z., Gao, P., Hu, T. (2022). Impacts of dams and land-use changes on hydromorphology of braided channels in the Lhasa River of the Qinghai-Tibet Plateau, China, International Journal of Sediment Research, Vol. 37, No. 2, pp. 214-228. https://doi.org/10.1016/j.ijsrc.2021.07.003 https://www.sciencedirect.com/science/article/abs/pii/S1001627921000445 |
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