Pan coefficients using penman approach with different vapor pressure deficits

الملخص EN

Daily lake evaporation at Malham and Al-Amalih reservoirs (Central Saudi Arabia) was determined using Penman’s equation with dif- ferent methods of calculating vapor pressure deficit.

The variability of an- nual, monthly and seasonal pan coefficients at the two sites was investi- gated.

Available data for a three-year period was utilized in the study.

Re- sults showed that the proposed model gave reasonable predictions of an- nual lake evaporation and pan coefficients.

The predictions were best with the first method of computing vapor pressure deficit.

The model gave simi- lar trends when applied to other stations in the region.

However, the results were not as good as at Malham and Al-Amalih reservoirs sites.

Monthly pan coefficients showed lower values during summer months than for the rest of the year which is consistent with physical reality.

Estimates of both monthly and seasonal pan coefficients were reasonable for Malham and Al-Amalih sites.