A hydrological water-balance model used for the Nanni swamps in Surinam is adjusted and applied to a similar swamp in coastal Guyana. A water-balance study was performed in Guyana on two water conservancies; the Boerasirie water conservancy and the East Demerara water conservancy. For the Boerasirie water conservancy thc model is calibrated on a daily basis using thc Boerasirie Conservancy Board records of 1987. The model calculates water levels using rain-fall, evapotranspiration, agricultural use, and spill over different weirs. Calculated and measured water levels are compared, and parameters in thc model are adjusted to minimize the difference. The conclusion is that the adjusted model gives results for the situation in Guyana over a wide range of water levels.