Current measurements for environmental studies

Environmental impact studies differ from scientific or engineering studies in the uses to which the data are put, and because they may become the object of legal proceedings. This imposes unique requirements on the type and accuracy of current sensors. An environmental study must be done by any company wishing to build a major facility. Data and impact analyses are turned over to regulatory agencies, who in turn review or enlarge the analyses and issue their own Environmental Impact Statement. Typical analyses for coastal facilities are concerned with dispersion of thermal or effluent plumes; probability of advection of effluent to inhabited or otherwise critical areas; determination of mean velocities, tidal velocities, and other "climatological" parameters; and establishment of predictive modeling capability, for use in hindcast studies and for extrapolation to extreme conditions. Issuance of construction permits follows public hearings, at which opponents may attack the conclusions indirectly, by attacking the accuracy or adequacy of the data itself. Major current meter considerations thus are: (1) There is a need to accurately measure low velocities, which are important in dispersion studies; (2) There is a need for commercially available sensors, for direct measurement of probability of advective impact; and (3) There is a need for traceability in current meter calibrations, to avoid needless exposure of data to unwarranted criticism. On a higher plane, there is also a need for a methodology for current measurements in environmental studies, to establish achievable goals and assure credible results.