Modeling the climate change impact on hydroclimate fluxes over the Beas basin using a high-resolution glacier-atmosphere-hydrology coupled setup

Rapidly rising temperature is posing a high vulnerability towards stored water resources in the Himalayan region. However, different regions may have different response to global warming and, per se, different consequences. In this study, we coupled Weather Research & Forecasting Model (WRF) and WRF-Hydro to estimate present and future hydroclimate fluxes over the Beas basin to understand ongoing and projected impacts of climate change. WRF simulations are carried out at convection-permitting scale to produce high resolution atmospheric forcing that are fed to a calibrated WRF-Hydro to produce the future projection of hydrological fluxes.

In our results, no large difference in the amount of precipitation but contrasting pattern is noted. Higher reaches of the baisn are expected to experience lesser precipitation in future under both RCP4.5 and RCP8.5 scenarios (RCP: Representative Concentration Pathway). Contrastingly, downstream reaches and valley side region is expected to be wetter under these scenarios. Notably, the contrasting pattern is a composite effect of differential response of precipitation during different seasons (JJAS and DJF) under the changing climate. More so this region is expected to be warmer by 1–3 °C under RCP4.5 and 3–4 °C under RCP8.5 for JJAS at the end-21^st-century. For DJF, 2.5–3.5 °C warming under RCP4.5 and 4.5–5 °C warming under RCP8.5 at end-21^st-century is expected.

Surface runoff is expected to decrease almost throughout the basin except over some regions of higher elevation during early-21^st-century under RCP4.5 and during mid-21^st-century under RCP8.5. The largest decline is found at end-21^st-century under both RCP4.5 and RCP8.5 over high altitude regions. Subsurface flow (UGDRNOFF) decreased consistently under both RCP4.5 and RCP8.5, with a stronger declining signal under RCP8.5. UGDRNOFF is expected to decrease by ∼60 % under RCP4.5 and ∼70 % under RCP8.5 at the end of 21^st century. Under RCP4.5, snow water equivalent (SNEQV) decreased for the regions having altitude <5 km, however, is found to be increased for the higher elevated regions. A similar response is expected under RCP8.5 until mid-21^st–century. But, towards the end-21^st-century, SNEQV is expected to decline throughout the year across the region. The highest decline in SNEQV is found to be occurred during the end-21^st-century for both RCP4.5 and RCP8.5 scenarios.