Natural Environment Monitoring 2009, No 10, pp. 73-78
COMPARISON OF EVAPORATION ESTIMATION RESULTS FOR LĘKUK LAKE OBTAINED BY CALCULATED AND MEASUREMENT METHODS
The lake water balance estimation largely depends on the water-surface evaporation estimation, which is defining by basing on mathematical formulas with empirical coefficients or basing on direct evaporation measurement.
In this article evaporation estimations obtained by two methods: calculated and measurement is presented. The first method is using (from 2003) in the Institute Environmental Protection in Warsaw and is based on Peneman formula. The second method was entered in 2008 and is based on Wild type’s evaporator installed at the meteorological garden of Puszcza Borecka Station. Using apparatus is a electronic weight (type EWA-992), surrounded by meteorological cage. The main advantage of this method is an automation of evaporation estimations. In the measurement method it was needed apply corrective coefficient. This coefficient was determined by comparison the evaporator EWA-992 and the standard evaporator GGI 3000, which was placed on a raft anchored on Sławskie Lake near the Station of Institute of Meteorology and Water Management in Radzyń.
The comparison evaporation estimation methods shows that calculated method based on Peneman formula lowers months sums of evaporation indifferently about 20 per cent beside measurement method. This faults, which sometimes may be higher, have an importing contamination on the estimation of lake water balance. As the estimation analysis presented, monthly proportional differences of the lake retention defined by mathematical formula and directly evaporation mensurations are from -20% to +120% .
Analysis of presented data shows that application Wild’s type evaporator needs a apparatus calibration with a cover in the area conditions where there are realizing surveys, also during different seasons.
Using uncalibrated apparatus give rise to the faults of evaporation estimation as like the faults appearing during using the Penman formula.