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Iodine, a minor constituent in ground water, is valuable as an indicator of subsurface sources of salinity. A review of iodine geochemistry reveals that exceptions to conservative behavior include sorption onto iron and aluminum oxides and incorporation into marine organic matter with additional enrichment due to sorption. Data from the Milk River aquifer in Alberta, Canada indicate that iodide in the ground water is derived from residual waters in the fine grained, marine sediments within the sandstone formation. This localized enrichment of iodide is superimposed on a more general enrichment of halides downgradient from the recharge area, probably due to ion filtration.

The study described in this report consisted of a year-long field experiment to determine basic features of the circulation of the upper Chesapeake Bay. The experiment consisted of the deployment, between July 1981 and August 1982, of three moorings between Turkey Point and the Bay Bridge. The southern two moorings consisted of an upper and lower Aanderaa current meters equipped with speed, direction, conductivity, and temperature sensors. The northern mooring, near Turkey Point, had one mid-depth meter. The instruments were rotated approximately every six weeks to minimize fouling problems and data loss and the conductivity cells were calibrated in-situ by taking a CTD cast next to the moorings immediately after deployment and before retrieval. The instruments were positioned to sample currents, salinity, and temperature in the upper and lower layers of the most active eastern side of the partially mixed estuarine circulation in the upper Bay.

This report details the completion of the source identification phase and the analytic and conceptual planning for the data acquisition and standardization phase of the construction of a comprehensive historical water temperature and salinity data bank for the Chesapeake Bay and its major tributaries. As such, it represents both a project milestone and deliverable item under the terms of WOLF's proposal and subsequent contract with the State of Maryland, Department of Natural Resources.

A methodology is presented for forecasting the probabilistic response of salinity movement in an estuary to seasonal rainfall and freshwater inflows. The Gambia River basin in West Africa is used as a case study in the research. The rainy season is from approximately July to October. Highest flows occur in late September and early October. Agriculturalists are interested in a forecast of the minimum distance that occurs each year at the conclusion of the wet season between the mouth of the river and the 1 part per thousand (ppt) salinity level. They are also interested in the approximate date that the minimum distance will occur. The forecasting procedure uses two approaches. The first uses a multisite stochastic process to generate long-term synthetic records (100 to 200 years) of 10-day rainfall for two stations in the upper basin. A long-term record of 10-day average flow is then computed from multiple regression models that use the generated rainfall records and real-time initial flow data occurring on the forecast date as inputs. The flow series is then entered into a one-dimensional finite element salt intrusion model to compute the movement of the 1 ppt salinity level for each season. The minimum distances between the mouth of the river and the 1 ppt salinity front that occurred for each season in the long-term record are represented in a cumulative probability distribution curve. The curve is then used to assign probability values of the occurrence of the 1 ppt salinity level to various points along the river. In the second approach, instead of generating a rainfall series and computing flow from regression models, a long-term flow record was generated using a stochastic first-order Markov process. Probability curves were made for three forecast dates: mid- July, mid-August, and mid-September using both approaches. With the first approach, the initial conditions at the time of the forecast had a greater influence on the flow series than the second approach.

Iodine, a minor constituent in ground water, is valuable as an indicator of subsurface sources of salinity. A review of iodine geochemistry reveals that exceptions to conservative behavior include sorption onto iron and aluminum oxides and incorporation into marine organic matter with additional enrichment due to sorption. Data from the Milk River aquifer in Alberta, Canada indicate that iodide in the ground water is derived from residual waters in the fine grained, marine sediments within the sandstone formation. This localized enrichment of iodide is superimposed on a more general enrichment of halides downgradient from the recharge area, probably due to ion filtration.