This study examines stream modification efforts to increase the productive capacity of an isolated system of three small lakes in the Barrenlands region of Arctic Canada by enhancing system connectivity. The lakes’ outlet streams were modified to create conditions favourable for fish passage and thereby promote migration among the lakes and the large lake into which they drain. Gabion step pools (in two streams) and a nature-like choke-and-pool structure (in one stream) were installed. Two years of post-construction hydraulics data were compared to data collected for two years prior to construction to determine the efficacy of the various stream modifications. Initial evaluations indicated unsuccessful performance of gabion step pools, so after the first year, they were retrofitted with boulders to increase flow depth, restrict discharge, improve flow duration, and create unimpeded connections rather than sudden drops. Variation of lake levels and duration, variability, and depth of stream flow indicated that outlet geometry and lake catchment area should be important considerations when enhancing connectivity for fish migration in ephemeral systems. A narrow, rectangular cross-section was deemed effective for increasing flow depth while decreasing discharge, resulting in increased duration of flows. Catchment area was an effective indicator of a headwater lake’s potential response to connectivity enhancements. Smaller catchments may provide inadequate runoff to sustain minimum storage requirements for enhanced connectivity. Our findings should advance the knowledge of headwater system hydraulics in the Barrenlands and assist in designing future fish habitat compensation projects on similar systems.
Silicon in ultrafresh groundwater: a case study of the Imandra Lake catchment, The Kola Peninsula
