The exchange of water thorough the lakes' entrance is minimal most of the time. Less than 1 per cent of the water interchanges between the lakes and the ocean each day. This ratio varies based on the distance from the entrance. Scientists have calculated the average retention time for each lake, which is the amount of time water stays in each lake, as 220 days for Tuggerah Lake, 460 days for Budgewoi Lake and 520 days for Lake Munmorah. Tides are limited to the immediate entrance area, and water levels do not fluctuate because of them as they do in other types of estuaries, e.g. drowned river valleys.
The water flow from the catchment is substantial. Around 193,000 million litres of water come into the estuary each year, which significantly outweighs the amount of water flowing in from the ocean. With this information alone, a focus on keeping the catchment runoff as clean and free of pollution as possible is likely to have the greatest impact on water quality in the lake itself.
The water that enters Tuggerah Lakes is mixed by the wind, not by tides. With long expanses of open water, wind waves can become quite large, and be treacherous for watercraft at times. Taking advantage of natural wind circulation and mixing is a proven strategy to improve water quality throughout the estuary.
