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Proceedings of the International Association of Hydrological Sciences An open-access publication for refereed proceedings in hydrology
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Volume 371
Proc. IAHS, 371, 167–172, 2015
https://doi.org/10.5194/piahs-371-167-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Proc. IAHS, 371, 167–172, 2015
https://doi.org/10.5194/piahs-371-167-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

  12 Jun 2015

12 Jun 2015

The need of the change of the conceptualisation of hydrologic processes under extreme conditions – taking reference evapotranspiration as an example

S. Liu1, L. Tan1,2, X. Mo1, and S. Zhang1,3 S. Liu et al.
  • 1Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research (IGSNRR), Chinese Academy of Science (CAS), Beijing, 100101, China
  • 2University of Chinese Academy of Sciences, Beijing, 100049, China
  • 3Beijing Forestry University, School of Soil & Water Conservation, Beijing, 100083, China

Abstract. What a hydrological model displays is the relationships between the output and input in daily, monthly, yearly and other temporal scales. In the case of climate change or other environment changes, the input of the hydrological model may show a gradual or abrupt change. There have been numerous documented studies to explore the response of output of the hydrological models to the change of the input with scenario simulation. Most of the studies assumed that the conceptualisation of hydrologic processes will remain, which may be true for the gradual change of the input. However, under extreme conditions the conceptualisation of hydrologic processes may be completely changed. Taking an example of the Allen's formula to calculate crop reference evapotranspiration (ET0) as a simple hydrological model, we analyze the alternation of the extreme in ET0 from 1955 to 2012 at the Chongling Experimental Station located in Hebei Province, China. The relationships between ET0 and the meteorological factors for the average values, minimum (maximum) values at daily, monthly and annual scales are revealed. It is found the extreme of the output can follow the extreme of the input better when their relationship is more linear. For non-liner relationship, the extreme of the input cannot at all be reflected from the extreme of the output. Relatively, extreme event at daily scale is harder to be shown than that at monthly scale. The result implicates that a routine model may not be able to catch the response to extreme events and it is even more so as we extrapolate models to higher temperature/CO2 conditions in the future. Some possible choices for the improvements are suggested for predicting hydrological extremes.

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By taking an example of Allen’s formula as a hydrological model based on long-term data at a Chinese site, the relationships between driving forces and responses for average, minimum and maximum values at daily, monthly and annual scale are revealed. It indicates due to the relationships’ nonlinearity a routine model may not be able to catch hydrological responses extreme from extreme driving events and it is even more so for future. Finding a primary driver is one of the ways for improvements.
By taking an example of Allen’s formula as a hydrological model based on long-term data at a...
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