The last couple of months were extremely wet and as a result they have led to widespread flooding in the Murray Darling Basin. Two things are really interesting: 1) why was it so wet? What were the climate drivers and how did they align to produce this exceptionally wet weather? 2) What has been the hydrological response and what will be the ecological response to this extremely wet weather? In this blog I will concentrate on the second question.
One of the interesting things as a hydrologist is how fast the Basin’s major dams have filled. It has been tremendously fast, with all the major dams in the Murray Darling Basin now holding more than 50% water. This is incredible after the dire predictions (including my own) that it would take more than a few more rains to fill the dams that emptied during the drought. Reasons for a possible slower filling were: 1) the land is totally dried out, 2) recently established tree plantations and farm dams remove lots of water before it reaches the river and 3) carbon storage in the soil will increase water holding capacities (my own argument). I personally have been quite amazed by how fast the dams have filled despite this being a very wet (hydrological) year. All this creates of course a fantastic opportunity to better understand the hydrological behaviour of the Australian landscape and now would be the time to set up some fundamental research.
The first question that needs work is whether the rainfall runoff characteristics of the landscape have changed in the last 10 years. Has the drought had a major effect on this, or are the changes in our land management in the last 10 years having any effect. It would be good to compare the rainfall runoff responses from 1998 with the current year and with maybe a smaller flood year in between. There should be good hydrological data for this whole period and it would allow some fundamental understanding of changes in rainfall runoff characteristics. As a result we will understand better how much of the rainfall transforms into runoff and this will help determine future water allocations.
The second question that needs work has to do with the aftermath of the flooding and will. One of the key drivers in the proposed new Murray Darling Basin plan is the deterioration of natural ecosystems due to water extraction. As I have argued it has been very difficult to separate out the impact of the 10 year drought and the impact of the water extraction. There is also limited data on the recovery of ecosystems after flooding. All this is admitted in the new proposed plan, but in my opinion should not slow down any development of the plan (see my earlier blogposts on this topic). One of the problems is that our understanding of these problems has mainly developed over the last 10 years, which have also been a major drought. The current flood, and the fact that now many monitoring programs are well established and have a reasonable data series, offer a great opportunity to study the recovery and resilience of ecosystems. Such fundamental research will allow development of better plans for the Murray Darling Basin and can inform future adjustments of the current proposed plan.
I have always argued that the MDB plan cannot be a rigid plan, but must be an adaptive and flexible plan that can be adjusted if needed. Here is a great opportunity to develop some of this future adjustment.