An Outdoor Replicated Artificial Stream System: Design, Operating Conditions, and Initial Invertebrate Colonization

The design and operating conditions of an outdoor replicated stream system are described. The facility is composed of a long inlet stream, a header weir which diverts inflowing water to six artificial stream channels (each 45 m long and 40 cm wide), a settlement pond at the end of the channels, and an outlet stream which diverts the water back to an irrigation channel. Flow regulation is achieved by "V-notched" gates at the head of each stream and depth by a second set of gates at the end of each stream. Physicochemical conditions were monitored over a 260-day period and even though significant temporal variation was detected, little between-stream variation was observed for most parameters. Small, but significant, between-stream differences in dissolved oxygen and pH were detected but were attributed to sampling procedure rather than real between-stream differences. A relatively rich invertebrate fauna colonized the streams. Invertebrate densities increased rapidly after initiation of flow and stabilized after 38 days. Chironomoid midge larvae were numerically the most important taxa, although the proportion of total density contributed by this group changed significantly with time. Taxon richness, chironomid taxon richness, diversity, and eveness also increased with time until a stable point was reached after 90 days of flow. No significant between-stream difference in any of these parameters was detected suggesting that colonization dynamics were similar in each stream.