Open channel to Big Lagoon/Little Lake (Coopers Lagoon).

Year proposed

  1875

Status

  Not implemented

Location description

  Southern Lake Ellesmere near Taumutu to Coopers Lagoon (Big Lagoon/Little Lake) 3 miles to the south; Bray (1875) Scheme No. 4 (see designs/drawings figure).

Description of option

  Coopers Lagoon (Big Lagoon/Little Lake) is a small lake with a water level that rises and eventually bursts its banks, between the lagoon and the sea, usually 2-3 times per year. It was therefore proposed that a canal from Taumutu to Coopers Lagoon (Big Lagoon/Little Lake) could be used to pass Lake Ellesmere flows to the sea. It is also likely that this proposal will also require a large sluice gate (100+ feet wide resisting 6-8 feet of water) to prevent rising Big Lagoon water levels from flowing back into Lake Ellesmere.

Opening, closing, and lake level control description

  Big Lagoon has a similar level to Lake Ellesmere so long travel distance means required hydraulic grade difficult to achieve. Problem also when Big Lagoon outlet closes; Big Lagoon water level will rise & water will tend to flow back into Lake Ellesmere.

Maximum discharge

  below 50 cumecs

Maintenance/Management description

  High rates of coastal erosion southwest of Taumutu could compromise any coastal canal structure or increase maintenance costs (e.g. may need dredging due to influx of seawater & gravels).

Cost description

  Likely to need large sluice gate (100+ feet wide resisting 6-8 feet of water) to prevent rising Big Lagoon water levels from flowing back into Lake Ellesmere. 1875 cost: 43,260 pounds for a 3 mile long by 12 ft deep cutting  (excl sluice gate cost).

Fish passage benefit rating

  Low

Potential running impacts or benefits