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Superior regulation has a small effect on Michigan-Huron levels

In the earlier stages of plan formulation and evaluation, the IUGLS developed three “fencepost” plans to identify the boundaries of what could be done for specific lakes or interests. The second “fencepost” plan uses Lake Superior as a reservoir, with water retained or released so as to allow Lake Michigan-Huron levels to remain within a range preferred for shipping and coastal interests. This plan showed that Lake Superior regulation could have only a small effect on Lake Michigan-Huron levels even if the regulation were artificially allowed to maximize benefits to interests downstream from Lake Superior. The plan does reduce extremes on Lake Michigan-Huron with historical NBS. But to compress the Lake Michigan - Huron level range by 28 cm (11 in), the plan increased the Lake Superior range by 1.33 m (more than 4 ft), raising the maximum level by half a metre (1.6 ft) and lowering the minimum level by more than a metre (3.3 ft). These results illustrate an important fact about regulating the lakes: it takes a very large change in Lake Superior levels to affect a smaller change in Lake Michigan-Huron levels. This relationship is due primarily to the hydrological differences in basin-to-lake-area ratios and to the local runoff and over-lake precipitation to Lake Michigan-Huron that Lake Superior regulation cannot control effectively.
Related Projects
Shared Vision Modelling
Lake Superior Fencepost Plans
Lake Superior Plan Formulation