Preprints
https://doi.org/10.5194/hess-2021-274
https://doi.org/10.5194/hess-2021-274

  01 Jun 2021

01 Jun 2021

Review status: this preprint is currently under review for the journal HESS.

Empirical attribution of a drying Himalayan river through remote sensing and secondary data

Gopal Penny1,2, Zubair A. Dar3, and Marc F. Müller1,2 Gopal Penny et al.
  • 1Environmental Change Initiative, University of Notre Dame, Indiana, USA
  • 2Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Indiana, USA
  • 3Energy and Resources Group, University of California, Berkeley, California, USA

Abstract. Streamflow regimes are rapidly changing in many regions of the world. The ability to attribute these changes to specific hydrological processes and their underlying climatic and anthropogenic drivers is essential to formulate effective water policy. Traditional approaches to hydrologic attribution rely on the ability to infer hydrological processes through the development of catchment-scale hydrological models. However, such approaches are challenging to implement in practice. In particular, models have difficulty capturing hydrological regime shifts, where changes in the dominant hydrological processes alters the relationship among hydrological fluxes. Additionally, observational uncertainties might preclude closure of the catchment-scale water balance, which is a pre-requisite for most catchment-scale hydrological models. Here we present an alternative approach to hydrological attribution that leverages the method of multiple hypotheses. We generate and empirically evaluate a series of alternative and complementary hypotheses that pertain to hydrological change. These hypotheses concern distinct components of the water balance and are evaluated independently. This process allows a holistic understanding of watershed-scale processes to be developed, even if the catchment-scale water balance remains open. We apply the approach to understand changes in the Upper Jhelum river, an important tributary headwaters of the Indus basin, where streamflow has declined dramatically since 2000 and has yet to be adequately attributed to its corresponding drivers. Using remote sensing and secondary data collected from the watershed, we explore changes in climate, surface water, and groundwater. The evidence reveals that climate, rather than land use, had a considerably stronger influence on reductions in streamflow, both through reduced precipitation and increased evapotranspiration.

Gopal Penny et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-274', Anonymous Referee #1, 06 Jul 2021
  • RC2: 'Comment on hess-2021-274', Anonymous Referee #2, 21 Jul 2021

Gopal Penny et al.

Gopal Penny et al.

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Short summary
Hydrological attribution is essential for linking changes in water resources with corresponding drivers. We develop an empirical approach to attribute declining streamflow in the Upper Jhelum watershed, a key sub-watershed of the Indus basin. We find that a loss of streamflow since the year 2000 resulted primarily due to interactions among vegetation and groundwater in response to climate, rather than local changes in land use, revealing the climate sensitivity of this Himalayan watershed.