The specific monitoring design (the choice of location and timing of sample collection) that best meets project objectives will depend on the type and scale of the project and the degree to which other variables can be controlled when monitoring. The monitoring design must be selected before the study begins as it (along with the project objective) dictates many important aspects of a monitoring program including scale, number of sample locations, sample frequency, and station type. It is important to evaluate the data requirements for statistical analysis and potential statistical methods (Section 10) simultaneous with the selection of monitoring design.
Monitoring for BMP effectiveness is often more targeted than other types of monitoring, and, to the extent possible, it should isolate these projects from other influences that may complicate the results. Below, several different approaches to selecting monitoring sites are presented: above and below a management practice; before-and-after control implementation; comparison to a reference site/condition; and using historic data. For each approach, the assumptions inherent in that approach, as well advantages and disadvantages and additional tips on when a particular approach is the best choice are discussed. Not discussed are plot and field-scale designs, which are more common in research studies.