The Karnali River is one of the major transboundary rivers of the Nepalese central Himalaya and a major tributary of the Ganges River. Though there is a huge potential for dendrohydrological research in the Karnali River Basin (KRB) region in Nepal, no multi-centuries streamflow reconstruction is available yet. 

In a study published in Journal of Hydrology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) present the first multi-centennial spring- to early-summer season (March–July) streamflow reconstruction for the Karnali River in the central Himalaya by using moisture-sensitive tree ring-width chronologies of multiple tree species. 

The researchers compiled eleven tree ring-width chronologies based on 354 exactly dated tree cores from five coniferous species (A. spectabilis, C. deodara, P. smithiana, P. roxburghii, and P. wallichiana) for the Karnali River catchment.  

The tree-ring site chronologies from the Karnali River Basin showed high dendroclimatological potential. The composite chronologies from the KRB were generally positively correlated with spring and early summer season precipitation and drought index and negatively correlated with spring season temperature. The growth of trees is mainly limited by the moisture availability during spring and early summer seasons. 

Their reconstruction revealed annual to multi-decadal fluctuations in the streamflow of the Karnali River. Several moderate and extreme flow years were also observed in their reconstruction. An increasing frequency of extreme events occurred during the recent decades.  

Moreover, Karnali river flow has short-term (inter-annual) to decadal periodicities, similar to frequencies of broad-scale climate modes/phases like El Ni？o-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO).  

“Since periodic (decadal or even longer period) below average streamflow was found during the past four centuries, streamflow-based water and energy sectors could be affected periodically. Therefore, dynamic water resource management and use approach is required to adapt the climate change and water-induced disasters,” said FAN Zexin of XTBG. 

Contact 

FAN Zexin Ph.D Principal Investigator         

Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China