Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Hydrol. Earth Syst. Sci., 21, 4495-4516, 2017
https://doi.org/10.5194/hess-21-4495-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
11 Sep 2017
Necessary storage as a signature of discharge variability: towards global maps
Kuniyoshi Takeuchi1,a and Muhammad Masood2 1International Centre for Water Hazard and Risk Management (ICHARM), Public Works Research Institute (PWRI), Tsukuba, 305-8516, Japan
2Bangladesh Water Development Board (BWDB), Design Circle-1, Dhaka, Bangladesh
acurrently at: Iwakubo-cho 392-2, Kofu, Yamanashi 400-0013, Japan
Abstract. This paper proposes the use of necessary storage to smooth out discharge variability to meet a discharge target as a signature of discharge variability in time. Such a signature has a distinct advantage over other statistical indicators such as standard deviation (SD) or coefficient of variation (CV) as it expresses hydrological variability in human terms, which directly indicates the difficulty and ease of managing discharge variation for water resource management. The signature is presented in the form of geographical distribution, in terms of both necessary storage (km3) and normalized necessary storage (months), and is related to the basin characteristics of hydrological heterogeneity. The signature is analyzed in different basins considering the Hurst equation of range as a reference. The slope of such a relation and the scatter of departures from the average relation are analyzed in terms of their relationship with basin characteristics. As a method of calculating necessary storage, the flood duration curve (FDC) and drought duration curve (DDC) methods are employed in view of their relative advantage over other methods to repeat the analysis over many grid points. The Ganges–Brahmaputra–Meghna (GBM) basin is selected as the case study and the BTOPMC hydrological model with Water and Global Change (WATCH) Forcing Data (WFD) is used for estimating FDC and DDC. It is concluded that the necessary storage serves as a useful signature of discharge variability, and its analysis could be extended to the entire globe and in this way seek new insights into hydrological variability in the storage domain at a larger range of scales.

Citation: Takeuchi, K. and Masood, M.: Necessary storage as a signature of discharge variability: towards global maps, Hydrol. Earth Syst. Sci., 21, 4495-4516, https://doi.org/10.5194/hess-21-4495-2017, 2017.
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Short summary
There are many global maps of hydrology and water resources, but none on necessary storage to smooth out discharge variability. This paper provides a methodology to create such a map, taking the Ganges–Brahmaputra–Meghna basin as an example. Necessary storage is calculated by a new method, intensity–duration–frequency curves of flood and drought (FDC–DDC). Necessary storage serves as a signature of hydrological variability and its geographical distribution provides new insights for hydrology.
There are many global maps of hydrology and water resources, but none on necessary storage to...
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