Selection and Testing of Stream Reference Sites in Developed Areas of Delaware USA and Auckland NZL Using Macroinvertebrates

The selection and testing of reference sites for wadeable streams is an important element of a monitoring program because it sets the standard against which all sites will be assessed. The setting of criteria for reference sties (e.g., 100% native forest, no roads, no dwellings) is the easy part. The hard part is finding sites that meet the criteria in already developed areas. The process often results in compromise to a set of sites defined as "minimally disturbed". A key step is then to test the reference site data to (1) ensure that the sites accurately define undisturbed conditions, and (2) to define the variability in the data in space and time. Experiences developing and testing reference sites in the USA (Delaware) and NZL (Auckland) using macroinvertebrates will be presented. Testing in Delaware involved a multi-state study, and concluded that differences between reference sites followed Ecoregion boundaries and latitude. Testing in Auckland found similarities between sites with differing geologies, vegetation maturity, and feral animal grazing (e.g., goats). Differences detected using multi-dimensional scaling did not affect assessment using 4 common metrics. Reference sites distinguished a wide range of urban and rural land use disturbances.