Akademik Veri Yönetim Sistemi
The European Journal of Research and Development, cilt.4, sa.3, ss.22-37, 2024 (Hakemli Dergi)
Evaporation (Epan)
measured from Class-A pan evaporimeter is widely used in many studies within
the scope of hydrology. Due to various reasons, it may be necessary
to complete the unmeasured evaporation data using empirical estimation methods. The reliability of these methods varies
depending on climatic and environmental conditions. Therefore, they need to be
tested under the local conditions and calibrated if necessary. This study aims
to test the usability of Christiansen evaporation estimation method under the conditions
of Van, and to calibrate it in compatible with local conditions. Firstly, the
original equation of this method was tested using nine years of daily climate
data measured between 2012 and 2020. Then, the original equation was calibrated
using the same data and its modified equation was created. The validity of evaporation
values estimated using both the original and modified equations was tested with
climate data from the period of 2021–2022. The performance of Christiansen
method, calibrated using the linear regression approach, in estimating daily evaporation
was evaluated using the determination coefficient (R2), mean
absolute percentage error (MAPE), and Nash–Sutcliffe Efficiency (NSE)
statistical metrics. While the original Christiansen equation estimated evaporation
values with 74.90% accuracy (R2= 0.79, MAPE= 25.10%, NSE= 0.48), the
accuracy improved to 86.58% (R2= 0.79, MAPE= 13.42%, NSE= 0.77)
using the modified equation. The differences between the means
of the data groups consisting of the measured evaporation values and those
estimated using the modified Christiansen equation were not statistically
significant (p > 0.05). It has been concluded that, the daily evaporation
values estimated by the modified Christiansen equation can be used instead of
the measured values.
Keywords: Calibration, Class-A pan,
Estimation method, Evaporation, Reliability analysis