Assessing the impact of seasonal-rainfall anomalies on catchment-scale water balance components
<p>Although water balance components at the catchment scale are strongly related to annual rainfall, the availability of water resources in Mediterranean catchments also depends on rainfall seasonality. Observed seasonal anomalies in historical records are fairly episodic, but an increase in t...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-06-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/24/3211/2020/hess-24-3211-2020.pdf |
| Summary: | <p>Although water balance components at the catchment scale
are strongly related to annual rainfall, the availability of water resources in
Mediterranean catchments also depends on rainfall seasonality. Observed
seasonal anomalies in historical records are fairly episodic, but an
increase in their frequency might exacerbate water deficit or water excess
if the rainy season shortens or extends its duration, e.g., due to climate
change. This study evaluates the sensitivity of water yield,
evapotranspiration, and groundwater recharge to changes in rainfall
seasonality by using the Soil Water Assessment Tool (SWAT) model applied to
the upper Alento River catchment (UARC) in southern Italy, where a long time
series of daily rainfall is available from 1920 to 2018. We compare two
distinct approaches: (i) a “static” approach, where three seasonal features
(namely rainy, dry, and transition fixed-duration 4-month seasons) are
identified through the standardized precipitation index (SPI) and (ii) a
“dynamic” approach based on a stochastic framework, where the duration of
two seasons (rainy and dry seasons) varies from year to year according to a
probability distribution. Seasonal anomalies occur when the transition
season is replaced by the rainy or dry season in the first approach and when
season duration occurs in the tails of its normal distribution in the second
approach. Results are presented within a probabilistic framework. We also
show that the Budyko curve is sensitive to the rainfall seasonality regime
in UARC by questioning the implicit assumption of a temporal steady state
between annual average dryness and the evaporative index. Although the
duration of the rainy season does not exert a major control on water
balance, we were able to identify season-dependent regression equations
linking water yield to the dryness index in the rainy season.</p> |
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| ISSN: | 1027-5606 1607-7938 |