Understanding the response of Himalayan-Karakoram (HK) rivers to climate change is crucial for ~1 billion people who partly depend on these water resources. Policymakers tasked with the sustainable water resources management for agriculture, hydropower, drinking, sanitation, and hazards require an assessment of rivers’ current status and potential future changes. This review demonstrates that glacier and snow melt are important components of HK rivers, with greater hydrological importance for the Indus than Ganges and Brahmaputra basins. Total river runoff, glacier melt, and seasonality of flow are projected to increase until the 2050s, with some exceptions and large uncertainties. Critical knowledge gaps severely affect modeled contributions of different runoff components, future runoff volumes and seasonality. Therefore, comprehensive field- and remote sensing-based methods and models are needed.

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Baseflows have declined for decades in the Lesser Himalaya but the causes are still debated. This paper compares variations in streamflow response over three years for two similar headwater catchments in northwest India with largely undisturbed (Arnigad) and highly degraded (Bansigad) oak forest. Hydrograph analysis suggested no catchment leakage, thereby allowing meaningful comparisons. The mean annual runoff coefficient for Arnigad was 54% (range 44-61%) against 62% (53-69%) at Bansigad. Despite greater total runoff Q t (by 250 mm year -1 ), baseflow at Bansigad ceased by March, but was perennial at Arnigad (making up 90% of Q t vs. 51% at Bansigad). Arnigad storm flows, Q s , were modest (8-11% of Q t ) and occurred mostly during monsoons (78-98%), while Q s at Bansigad was 49% of Q t and occurred also during post-monsoon seasons. Our results underscore the importance of maintaining soil water retention capacity after forest removal to maintain baseflow levels.

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