Abstract. Streamflow regimes are rapidly changing in many regions of the world. Attribution of these changes to specific hydrological processes and their underlying climatic and anthropogenic drivers is essential to formulate an 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 due to limitations in using models to accurately associate changes in observed outcomes with corresponding drivers. Here we present an alternative approach that leverages the method of multiple hypotheses to attribute changes in streamflow in the Upper Jhelum watershed, an important tributary headwater region of the Indus basin, where a dramatic decline in streamflow since 2000 has yet to be adequately attributed to its corresponding drivers. We generate and empirically evaluate a series of alternative and complementary hypotheses concerning distinct components of the water balance. This process allows a holistic understanding of watershed-scale processes to be developed, even though the catchment-scale water balance remains open. Using remote sensing and secondary data, 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. Baseflow analyses suggest different mechanisms affecting streamflow decline in upstream and downstream regions, respectively. These findings offer promising avenues for future research in the Upper Jhelum watershed, and an alternative approach to hydrological attribution in data-scarce regions.
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Top-Down Approach for Time-Variant Anthropogenic Signature Attribution in Socio-Hydrological Systems
In the Anthropocene, humans have altered the properties and processes of hydrological systems across scales. The extent of human intervention in the landscape limits the utility of traditional hydrological modelling schemes. Since purely hydrological conceptual models no longer fit these systems, hydrologists must integrate key human interventions into conceptual models of human-modified catchments. Despite the advances in analyzing the observed changes within the hydrological cycle using bottom-up (or reductionist) modelling approaches, the aptitude of top-down hydrologic schemes for socio-hydrological system analysis is still untested. Here we show the potential of top-down hydrological modelling human modified watersheds using anthropogenic hydrological signatures. Specifically, we assess the ability of the top-down modelling method in human-modified catchments to improve the representation hydrological signatures (e.g. mean monthly runoff, flow duration curve) while ensuring a sufficient, but not excessive, level of complexity in model formulation. First, we develop new conceptual models which include human hydrological modifications commonly identified in the literature. Then, we link these new features in the conceptual models to features in the hydrological signatures. We apply the proposed methodology to the Lake Mendocino Watershed in Northern California, US. We compare a purely hydrological model developed for this catchment based on natural watershed properties using naturalized streamflow to a hydrological model of the human-modified catchment using observed streamflow. We anticipate that the proposed approach contributes to the development of detection and attribution frameworks for key anthropogenic changes of observed hydrological variability and improved model performance in human-modified catchments.
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- Award ID(s):
- 1913920
- PAR ID:
- 10495868
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Format(s):
- Medium: X
- Location:
- American Geophysical Union Fall Meeting, Virtual
- Sponsoring Org:
- National Science Foundation
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