Water Management Regime. The amount and time of occurrence of fluctuations in water levels and flows, which occur as a result of the needs of hydrogenerating facilities and flood control, are important to various wildlife and fish species. Waterfowl benefit from stable water levels for nesting and brood rearing. Furbearers can be flooded out if water levels are raised after they go into winter quarters, or stranded if areas are dewatered after they become established for the winter. Drawdowns in early spring could prevent smelt from reaching spawning areas in lake tributaries. Lake trout (togue) eggs could be exposed and frozen by winter drawdowns. Bass spawn along shallow shorelines in late spring and early summer. Drawdowns during this period can destroy nests. Anadromous (alewife, Atlantic salmon, shad, smelt) and catadromous (eels) fish need good stream flows to migrate to spawning areas. Trout and salmon resident in streams often must move to particular areas to spawn successfully. Adequate year-round minimum stream flows are critical to the survival of stream-dwelling fish species (especially salmon, brook trout), as well as to the production of all aquatic life required to support these fish.
Where significant waterfowl, loon, or other shorebird nesting habitat may be affected by project-induced impoundment fluctuations, IF&W generally recommends no greater than one foot surface elevation change during the period from ice-out to July 15. Greater fluctuations as a result of natural, unregulated causes are acknowledged to occur at some projects. Impoundments containing significant bass populations dependent upon natural spawning will also be subject to recommendations for restricting the degree of fluctuations to one foot during the period May through July 1, or for the same period as for waterfowl if both are of concern.
Impoundment drawdown regulation is also recommended for the protection and success of fall spawning lake trout populations. Water elevations adequate to cover identified spawning areas are to be established and specified. Drawdown to this level should occur prior to October 1 in northern portions of the State and October 15 in southern areas. During the overwinter period (November 15 to May 1) the impoundment level may be allowed to rise and fall provided it does not drop below the elevation occurring during the October/November spawning period.
Aquatic furbearer populations can be protected by regulating impoundment fluctuations to no greater than one foot surface elevation change during the period October 15 through ice-out in the spring.
Impoundments used primarily for annual storage and release present special problems for maintenance of fish and wildlife resources due to the degree and timing of fluctuations. Specific recommendations require a detailed description of the hydraulic cycle, species present, and habitat affected.28 In all cases, management of water levels for protection of fish and wildlife must be balanced against the need to protect lives and property against the threat of flooding, particularly during the period March 15th to May 15th.