| Uncertainty | Description |
| Speed of land use change / intensity of development. | Rate of development is hard to predict, e.g., economic cycles, Commonwealth government policy on immigration, etc. If change occurs faster than expected, eutrophication risks will increase. |
| Timing and effectiveness of catchment management policies. | For most land uses, the current effectiveness of land management practices is not known in any detail. The likely long-term effectiveness of wetlands in stripping nutrients out of flows is still a matter of debate. |
| Time it will take for rate of release of nutrients from sediment to water column to change. | What is not clear is what buffering role these sediments play. For instance, if we dramatically cut nutrient and sediment inputs now, how long would it take the Lakes system to respond? Understanding the role of exchange of nutrients between the sediments and the water column, which is a natural process, is vital to answering this question. Our understanding of this is poor. |
| Time it will take for the effects of management decisions to become evident. | Long-term changes in catchment management practices should change water quality in the Lakes. Over the short term, rainfall contributes very large variability to water quality data. Consequently, extensive water quality data are needed before an attempt to identify the "signal" from management (i.e., evidence of its presence) is feasible. |
| Reducing sediment loads may trigger phytoplankton blooms. | Either light or nutrients may be limiting the growth of aquatic plants and, in particular, the growth of phytoplankton in the main water bodies, as this is where the creeks deliver their loads. If nutrients are limiting, then erosion controls will reduce phytoplankton growth. However, if nutrients are present in abundance, then increasing the availability of light will allow phytoplankton growth to take off. |
| Potential for sediment under main water bodies to become anoxic. | If this region in the sediments below the main water bodies becomes anoxic or hypoxic, i.e., if the oxygen levels drop to zero or to very low levels, than nutrients could stream out of the sediment into the water column, triggering phytoplankton blooms. |
| Future rainfall sequences. | Long-term strategy might, for example, be seen by the community as a relatively poor strategy because its benefits are not obvious during a prolonged period of high rainfall. |
| Impacts of second entrance on hydrodynamics and ecology. | A second-entrance strategy is a very high-cost strategy (financially and ecologically) compared to the alternatives. The ecological impacts are much more difficult to quantify, with precision, than hydrodynamic impacts, although major shifts in abundance of differing species are likely if the Lakes become much more tightly integrated with the ocean. |