Given the recent debate around this issue, Shoalhaven City Council is reminding residents and visitors that Lake Conjola is an ICOLL - an Intermittently Closed and Open Lake or Lagoon, and there are a range of important considerations given this designation.
Under the NSW Coastal Management Act 2016, the preference for this type of lake is to maintain natural processes and not modify ICOLL entrances.
ICOLLs are complex systems adapted to varying conditions, including water level and degree of salinity. They are very sensitive to human disturbance.
The NSW Marine Estate Threat and Risk Assessment identified the modification of coastal estuary entrances as the third highest risk (behind agricultural runoff and stormwater) to the health of the marine estate.
Natural processes are considered to be the best processes for an ICOLL and also a closed lake is not necessarily an unhealthy lake.
Since Lake Conjola closed in April this year, Council has been monitoring water quality in the lake every week at three locations. This is in addition to the regular quarterly testing at 10 other sites within the lake.
Test results, from May until now, have consistently shown that the water quality is suitable for swimming.
The rating categories are derived from the microbial assessment categories used in the National Health & Medical Research Council (2008) Guidelines. The guidelines rate water quality as Good, Fair, Poor and Bad. Both Good and Fair results indicate that it’s suitable for swimming.
Since the lake closed in April, the water quality in Lake Conjola has consistently rated as ‘Good’. (see diagram below explanation of ratings)
In response to current community concerns, Council has also commenced water quality monitoring at an additional four popular swimming locations. This brings the total of monitoring locations to seven, all of which are on the southern shore of the lake.
If test results fall to a ‘Poor’ level, the community will be notified immediately that it is unsuitable for swimming.
Any artificial lake opening is undertaken according to the Lake Conjola Interim Entrance Management Policy (August 2013) which was adopted by Council and the NSW Government following extensive community consultation.
The Policy outlines that the lake is only to be opened when the lake water level is at, or exceeding, 1.0 metre AHD.
If the lake is opened at a lower level than the trigger, it’s likely to close again very quickly (unless it’s followed by heavy rain). This is due to the fact that the volume of onshore sand transported into the lake entrance from the ocean, is greater than the volume of water moving out of the lake catchment. Opening the lake before there are sufficient volumes of water in the lake can cause significant and long-lasting environmental impacts on the ecosystems in and around the lake.
Any actions to artificially open Lake Conjola outside the adopted conditions outlined in the Entrance Management Plan would require additional approvals from NSW State Government Agencies.
Given that this would be acting outside of the agreed entrance management plan and the potential environmental impacts of artificially opening the lake, it is highly unlikely that Council would be successful in gaining such approval.