Search

• More negative glacier-wide mass balance corresponds to higher catchment-wide runoff and vice versa. • Hydrology is dominated by precipitation in Monsoon catchment regime and by glacier mass balance in Alpine catchment regime. • Glacier buffer system is more critical in Alpine catchment regime than Monsoon catchment regime. Glacier mass balance (MB) and runoff relationship is poorly explored in the Himalaya due to limited in-situ data. A simplified glacio-hydrological model is used to reconstruct the long-term MB and runoff on Dokriani Bamak Glacier (DBG) in the Monsoon regime and Chhota Shigri Glacier (CSG) catchments in the Alpine regime of the Himalaya. Since 1950, DBG and CSG show limited mass wastage with mean annual glacier-wide MB of – 0.09 ± 0.35 m w.e. a−1 and – 0.12 ± 0.28 m w.e. a−1, respectively. The mean annual catchment-wide runoff are also almost similar 0.13 ± 0.01 106 m3 a−1 and 0.14 ± 0.01 106 m3 a−1 from DBG and CSG catchments, respectively over 1950–2020. Available in-situ short-term MB and runoff data from eight glacierized catchments do not show any significant MB-runoff relationship, except for CSG. The long-term modelled MB and runoff data on both DBG and CSG catchments suggest that the higher catchment-wide runoff corresponds to more negative MB, and vice versa. This is in contrast to the previously suggested MB-runoff relationship on DBG catchment. Present detailed analysis also indicates that the hydrology of the DBG catchment is mainly dominated by the summer precipitation, while in CSG catchment, it is mainly controlled by the glacier-wide annual MB. In dry years, the corresponding negative annual MB on both the glaciers provides additional glacier-degraded runoff to the catchment streams that can be as high as 13% and 38% of total runoff on DBG and CSG catchments, respectively. [ABSTRACT FROM AUTHOR]

• We developed a glacier mass balance-runoff model for a monsoon-dominated catchment in the central Himalaya. • Decadal mass balances suggest that Dokriani Glacier was close to steady-state conditions preceding 2000. • Heterogeneous debris-cover distribution over lower ablation area protects the glacier from higher melting. • Snow- and ice-melt runoff contribute 56% of the total catchment-wide runoff. • Mass balance and runoff are most sensitive to a unit change in air temperature. Glacier-wide mass balance and catchment-wide runoff were reconstructed over 1979–2018 for Dokriani Glacier catchment in Garhwal Himalaya (India). A glacier mass balance-runoff model, including temperature-index, accumulation, and rain modules was used for the reconstruction using daily air-temperature and precipitation fields from ERA5 reanalysis products. The model was calibrated using 6 years of observed annual glacier-wide mass balances (1993–1995 and 1998–2000) and observed summer mean monthly runoff (1994, 1998–2000) data. Model validation was done using satellite-derived snow line altitudes and field-observed runoff (1997–1998). Modelled mass balance on Dokriani Glacier is moderate with annual loss of −0.25 ± 0.37 m w.e. a–1 over 1979–2018. The mean winter glacier-wide mass balance is 0.72 ± 0.05 m w.e. a–1 while mean summer glacier-wide mass balance is −0.97 ± 0.32 m w.e. a–1 over 1979–2018. The mean annual catchment-wide runoff is 1.56 ± 0.10 m3 s−1 over 1979–2018. Maximum runoff occurs during summer-monsoon months with a peak in August (6.04 ± 0.34 m3 s−1). Rainfall contributes the most to the total mean annual runoff with 44 ± 2% share, while snow melt and ice melt contribute 34 ± 1% and 22 ± 2%, respectively. The heterogeneous debris-cover distribution over lower ablation area (<5000 m a.s.l.) retards melting and protects the glacier. Modelled decadal mass balances suggest that Dokriani Glacier was close to steady-state conditions over 1989–1997 because of negative temperature anomalies and positive precipitation anomalies over this period. Mass balance and runoff are most sensitive to the threshold temperature for melt with sensitivities of 0.77 m w.e. a–1 °C−1 and −0.20 m3 s−1 oC–1, respectively. [ABSTRACT FROM AUTHOR]