Confidence rating for eutrophication assessments

Confidence of monitoring data is dependent on their variability and representativeness of sampling in space and time. Whereas variability can be assessed as statistical confidence limits, representative sampling is related to equidistant sampling, considering gradients or changing rates at sampling gaps. By the proposed method both aspects are combined, resulting in balanced results for examples of total nitrogen concentrations in the German Bight/North Sea. For assessing sampling representativeness surface areas, vertical profiles and time periods are divided into regular sections for which individually the representativeness is calculated. The sums correspond to the overall representativeness of sampling in the defined area/time period. Effects of not sampled sections are estimated along parallel rows by reducing their confidence, considering their distances to next sampled sections and the interrupted gradients/changing rates. Confidence rating of time sections is based on maximum differences of sampling rates at regular time steps and related means of concentrations.