THE NSW Government has to ensure pumping embargoes on river systems in the Murray-Darling Basin are timely in the event monsoon rain provides flows in the coming months, say river activists.

The Bureau of Meteorology on Thursday released its 2019 climate statement, in which head of climate monitoring Dr Karl Braganza said monsoon activity was likely to return to northern Australia in mid-January which "raises the chance that we could see some periods of higher rainfall move south in the coming months".