A WATER-BUDGET AND HYDROLOGY MODEL OF A BASIN MANGROVE FOREST IN ROOKERY BAY, FLORIDA

Water budgets of two basin mangrove forests in Rookery Bay were determ ined by measuring during a 2-year period the inputs of precipitation a nd tides, together with losses through seepage, runoff and evapotransp iration. Precipitation inputs to the forest floor were 75.1% from thro ughfall and 19% from stemflow for a total of 1097 mm year(-1), or 91% of annual rainfall. Runoff was estimated at 896 mm year(-1), or nearly 77% of the combined input of throughfall and stemflow. Loss from evap otranspiration was linear with saturation deficit of the atmosphere an d was 967 mm year(-1) (0.7-4.5 mm day(-1)). Loss from horizontal flow of groundwater in shallow mangrove soils was similar to 285 mm year(-1 ). Frequency of tidal inundation was seasonal, ranging from <5 tides m onth(-1) in February to 30 tides month(-1) in September. Tides recharg ed soil saturation deficits, the cumulative tidal input being 12 276 m m year(-1) and efflux being Il 767 mm year(-1). The relative significa nce of tides and rainfall deficits (rainfall - evapotranspiration) on the seasonal patterns of soil saturation (water levels) and soil salin ity were simulated with a finite-difference hydrology model (HYMAN). M odel simulations demonstrate that soil salinity at higher elevations i n the intertidal zone, where tidal inundation frequency is reduced, is more sensitive to changes in rainfall deficit.