The effect of ground water level variations on some gravitational field characteristics in Poltava

It is established that seasonal ground water level variations (of about 2 m) lead to a free-fall acceleration variation with an amplitude of 30 x 10 to the -8th m/sq sec. This leads to variations of the components of deflections of the vertical of about 0.001 arcsec as well as a quasi-geoid height variation of up to 2 mm. Therefore, allowance should be made for ground water level variations during precise gravimetric, astrometric, and geodetic work.