Upstream Hydrology And The Importance Of Snowmelt In Buffering Droughts In The Karnali Basin In Nepal
--
https://doi.org/10.3389/frwa.2025.1720178 <-- shared paper
--
https://nepalitimes.com/banner/a-karnali-portrait <-- shared media article
--
^^^^ shared video, Megh Ale, Nepal River Conservation Trust on the Karnali R.
--
H/T Pranisha Pokhrel | Hydrologist | PhD Candidate
“In this study, [they] use the distributed SPHY model at 500 m resolution to better understand how different components contribute to river discharge in this Himalayan basin. The Karnali is a predominantly rain-fed basin with 40% originating from rain-runoff.
Key insights from [their] analysis:
• Discharge variability has increased over the historical period.
• Meteorological droughts frequently translate into hydrological droughts, often with a short lag.
• Snow storage at different elevations strongly influences drought onset and recovery.
• Snow acts as a critical natural buffer, sustaining flows and moderating drought impacts for up to six months.
As climate change shifts precipitation patterns from snow to rain, this buffering effect may weaken with important implications for downstream water security which is to be considered for future study and planning…”
--
“Understanding the hydrology in the upstream mountainous part of the Karnali basin in Nepal is vital, considering the importance of streamflow for downstream nature conservation and water supply. [They] use[d] a fully distributed hydrological model to understand the current hydrology, the associated vulnerability of the basin, and the importance of the different hydrological components in regulating flow. Downscaled ERA5 meteorological data is used to force the model for the period 1991–2022 at a high spatial resolution (500 meters). [They] calibrate[d their] model using observed discharges, and the model performance is considered good with a reported Kling-Gupta efficiency of 0.84 and a bias of −3.33%. [Their] results show that 40% of the overall discharge generated in the Karnali basin originates from rain runoff, 35% from baseflow, 24% from snowmelt, and a negligible 0.8% from glaciers. The water balance components vary spatially in magnitude, but the overall monthly patterns are comparable. On average, the basin receives 1,485 mm/year of precipitation, peaking in July, and is a pronounced southwest region. The annual average evapotranspiration in the basin is 574 mm/year, and discharge is 914 mm/year. Analysis of anomalies reveals that the discharge has become increasingly more variable over the last decades and, therefore, less predictable. [Their] results also reveal that the basin is frequently experiencing meteorological droughts, often translating into a hydrological drought with a lag time of a month. The average duration of a hydrological drought period in the basin was about 6 months. Snow storage plays an important role in modulating these droughts, and variability in initial snow storage impacts basin streamflow for up to 6 months. A climate change-induced shift from snow to rain may therefore impact the climate resilience of the Karnali considerably…”
#water #hydrology #hydrography #surfacewater #catchment #waterresources #Nepal #Karnali #snowmelt #drought #SPHY #model #modeling #ERA5 #Himalya #river #basin #fluvial #pluvial #precipitation #rainfall #discharge #history #record #weather #climate #snow #climatechange #watersecurity #watersupply #conservation #planning #risk #hazard #rain #runoff #baseflow #waterbalance #evapotranspiration #ET #variability #spatiotemporal #change #time #streamflow #resilience