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| Titel |
Uncertainty analysis of a three-parameter Budyko-type equation at annual and monthly time scales |
| VerfasserIn |
Ameneh Mianabadi, Amin Alizadeh, Hossein Sanaeinejad, Bijan Ghahraman, Kamran Davary, Mehri Shahedi, Fatemeh Talebi |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137619
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| Publikation (Nr.) |
 EGU/EGU2017-394.pdf |
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| Zusammenfassung |
| The Budyko curves can estimate mean annual evaporation in catchment scale as a function of
precipitation and potential evaporation. They are used for the steady-state catchments with
the negligible water storage change. In the non-steady-state catchments, especially the
irrigated ones, and in the small spatial and temporal scales, the water storage change is not
negligible and, therefore, the Budyko curves are limited. In these cases, in addition
to precipitation, another water resources are available for evaporation including
groundwater depletion and initial soil moisture. Therefore, evaporation exceeds
precipitation and the data does not follow the original Budyko framework. In this study,
the two-parameter Budyko equation of Greve et al. (2016) was considered. They
proposed a Budyko-type equation in which they changed the boundary condition of
water-limited line and added a new parameter to the Fu equation. Based on Chen et
al. (2013)’s suggestion, in arid regions where aridity index is more than one, the
Budyko curve can be shifted to the right direction of aridity index axis. Therefore, in
this study, we combined Greve et al. (2016)’s equation and Chen et al. (2013)’s
equation and proposed a new equation with three parameters (y0, k, c) to estimate the
monthly and annual evaporation of five semi-arid watersheds in Kavir-e-Markazi
basin.
E- = F(φ,y ,k,c) = 1 + (φ − c)− (1+ (1− y )k−1(φ − c)k)1k
P 0 0
In this equation E, P and Φ are evaporation, precipitation and aridity index, respectively. To
calibrate the new Budyko curve, we used the evaporation estimated by water balance
equation for 11 water years (2002-2012). Due to the variability of watersheds characteristics
and climate conditions, we used the GLUE (Generalized Likelihood Uncertainty
Estimation) to calibrate the proposed equation to increase the reliability of the model.
Based on the GLUE, the parameter sets with the highest value of likelihood were
estimated as y0=0.02, k=3.70 and c=3.61 at annual scale and y0=0.07, k=2.50 and
c=0.97 at monthly scale. The results showed that the proposed equation can estimate
the annual evaporation reasonably with R2=0.93 and RMSE=18.5 mm year−1.
Also it can estimate evaporation at monthly scale with R2=0.88 and RMSE=7.9
mm month−1. The posterior distribution function of the parameters showed that
parameters uncertainty would decrease by GLUE method, this uncertainty reduction
(and therefore the sensitivity of the equation to the parameters) is different for each
parameter.
Chen, X., Alimohammadi, N., Wang, D. 2013. Modeling interannual variability of
seasonal evaporation and storage change based on the extended Budyko framework. Water
Resources Research, 49(9):6067–6078.
Greve, P., Gudmundsson, L., Orlowsky, B., Seneviratne, S.I. 2016. A two-parameter Budyko
function to represent conditions under which evapotranspiration exceeds precipitation.
Hydrology and Earth System Sciences, 20(6): 2195-2205. DOI:10.5194/hess-20-2195-2016. |
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