SOIL Studies

SOIL Studies

2019, Vol 8, Num, 3     (Pages: 001-008)

Estimation of Potential Evapotranspiration in the Karaman Province

Soner Çağatay BAĞÇACI 1 ,Nermin ŞARLAK 1

1 Karamanoğlu Mehmetbey Üniversitesi, İnşaat Mühendisliği Bölümü, Karaman

DOI: 10.21657/topraksu.654742
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Irrigation scheduling is performed with the water budget calculations considering the plant water consumption by transpiration and evaporation, at the farmlands around the world. Sum of these transpiration and evaporation events which takes place at the plant covered areas, composes evapotranspiration which is the hardest components of the hydrological cycle to measure. The potential values of evapotranspiration, under assumptions as certain reference plant cover, watering and growing conditions, can be estimated with empirical methods developed by many researches. At the top of them, FAO56 Penman-Monteith (FAO56 PM) is widely used reference potential evapotranspiration estimation (PET) method worldwide through its strong theoretical background and reliability of estimation.Despite of its reliable estimation, complicated calculation steps and requirement of various observed meteorological data impel us to use more practical PET estimation methods which require more easily findable meteorological data. In this study, the potential amounts of evapotranspiration, occuring in the Karaman province located in the Konya Closed Basin where advanced agricultural activities are carried out, were calculated by FAO56 PM method with daily time steps and by Turc (TC), Makkink (MK), Priestley Taylor (PT), Jensen Haise (JH), Hargreaves Samani (HS), Blaney Criddle (BC), Thornthwaite (TH) methods with monthly time steps. The monthly PET values were obtained by summing of daily estimations of FAO56 PM and then compared with the monthly PET values estimated by other empirical methods. As a conclusion, among seven PET estimation methods, Turc yielded most compatible results in comparison with FAO56 PM by 0.97 correlation coefficient value (R2) and 16.97 mm (monthly) root mean square error (RMSE) value. Turc was recommended with convenient calibration and remained methods were discussed.

Keywords : FAO56 Penman Monteith, hydrological cycle, Karaman, potential evapotranspiration