Flows in unregulated rivers can only be protected through controls on extraction. In most unregulated rivers, it is during drier periods when flows are naturally low that there is generally greatest concern for the health of the river. This is when pools contract, water quality deteriorates rapidly, algal blooms occur, oxygen levels decline and fauna compete for the reducing food supplies. The water sharing plans for the unregulated rivers therefore require licence holders to stop pumping when the river flow falls below a certain level, referred to as cease to pump (CtP) rules. In addition many of the plans set limits on how much water can be taken from different flow ranges or classes. Additional measures including daily extraction limits are being considered for unregulated systems such as the Barwon-Darling.