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Freshwater resources of coastal communities in the United States and world over are threatened by the rate of sea level rise. According to recent estimates by various governmental agencies and climate researchers, the global sea level rise is likely to be between 0.6 and 2.1 m by the year 2100. South Florida is a coastal community and much of its coastline is subject to sea level rise and potential impacts to wetlands and the water resources of the area. To understand what the impact of sea level rise would cause to the groundwater level and salinity intrusion, an integrated groundwater and surface water model was developed for North Miami-Dade and Broward Counties of South Florida. The model was calibrated against daily groundwater heads, base flows in canals, and chloride concentrations for a period of one year and six months. Three separate sensitivity analyses were conducted by increasing the sea level by 0.6, 0.9, and 1.22 m. Results of the simulations shows increase of groundwater heads in some areas from 4 to 15%; whereas the average relative chloride concentrations increased significantly by 100-600% in some wells. The increase in groundwater elevations and chloride concentrations varies from location of the wells and its proximity to the coast. The model results indicate that even a 0.6 m increase in sea level (which is the conservative estimate) is likely to impair the vital freshwater resources in many parts of South Florida.(KEY TERMS: density dependent model; sea level rise; salt water intrusion; well field impacts; Biscayne aquifer; coastal aquifers.) Guha, Hillol and Sorab Panday,

Development of any numerical ground‐water model is dependent on hydrogeologic data describing the subsurface. These data are obtained from geologic core analyses, stratigraphic analyses, aquifer performance tests, and geophysical studies. But typically in remote areas, these types of data are very sparse and site‐specific in terms of the aerial extent of the resource to be modeled. Uncertainties exist as to how well the available data from a few locations defines a heterogeneous surficial aquifer such as the Biscayne Aquifer in Miami‐Dade County, Florida. This is particularly the case when an exceptionally conductive horizontal flow zone is detected at one site due to specialized testing that was not historically conducted at the other at sites that provided data for the model. Not adequately accounting for the potential effect of the high flow zone in the aquifer within a ground‐water numerical model, even though the zone may be of very limited thickness, might underpredict the well field protection capture boundaries. Applied Stochastic ground‐water modeling in determining well field protection zones is steadily becoming important in addressing the uncertainty of the hydrogeologic subsurface parameters, specifically in karstic heterogeneous aquifers. This is particularly important in addressing the uncertainty of a 60‐day travel time capture zone in the Northwest Well Field, Miami‐Dade County, where a predominantly high flow zone controls much of the flow in the production wells. A stochastic ground‐water modeling application along with combination of pilot points and regularization technique is presented to further consolidate the uncertainty of the subsurface.

A simple and inexpensive method for reacting carbonate samples with phosphoric acid for the measurement of stable carbon and oxygen isotope ratios in carbonates is described. The technique is applied to samples taken in a sealed septum tube inside which a small tube is attached using ordinary household glue. The acid is loaded into this small tube. The whole assembly is evacuated and the vessel is tilted so that the acid makes contact with the carbonate. Isotope determinations were made using calcite at 25 °C and calcite and dolomite at 50 °C. With dolomite, the reaction was complete in 12 h. Measurements of yield and isotope ratios confirm that this method is as good as the traditional method, which uses potentially breakable Pyrex reaction vessels and costly grease or greaseless stopcocks.

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