A monthly and annual water budget has been created for the entire Shark River Slough (SRS) within the Everglades National Park (ENP) over 2002-2008. Inputs considered are surface water inflows (S12s and S333 canal structures) and rainfall, while outputs consist of discharge to the Gulf of Mexico (Lostman, Shark, Broad, Harney and North rivers) and evapotranspiration (ET). Using a mass balance approach, monthly change in volume of SRS (from water level changes) is equated to the sum of inputs, outputs and a residual term that includes error in each of the inputs and outputs as well as net groundwater exchange. Data for inflows, rainfall and discharges are obtained from LTER researchers, USGS, ENP and South Florida Water Management District. ET has been modeled using a simple net radiation based model that was found to closely track ET values obtained by the FAO-Penman Montieth equation using meteorological data from the 4 eddy covariance towers located in ENP managed by FIU researchers and ENP. Net radiation was found to be similar at the 4 sites (SRS1, SRS2, TSPh1 and TSPH7b), hence permitting the use of the model all across the SRS. Preliminary results for 2002-2008 indicate that rain was the largest input to the SRS, while ET was the largest output. This indicates the importance of increasing surface water inflows to pre-canalization era levels to maintain the ridge and slough landscape, maintain hydroperiods/depths required by various plant and animal communities and increase freshwater discharge into the Gulf of Mexico. Increased discharge would maintain salinity levels conducive to estuarine breeding communities as well as buffer against increased saltwater intrusion into coastal terrestrial habitat.