How water markets work
Most farmers who irrigate crops own a certain amount of water, known as their "entitlements" or "shares", which is their ongoing right to water. Depending on water availability, each water season they receive a percentage of this water - known as their allocation - depending on the type of entitlement they have.
For example, a farmer in South Australia's Riverland who owns 100 megalitres (one megalitre equals one million litres) of "high security" water, will in high rainfall and good years receive their full allocation.
However, in times of drought, they might only receive 30% of their allocation by the end of the water year. Other farmers in the Murray-Darling Basin who own "low security" entitlements, might receive nothing.
What happens if farmers don't have enough water from what they own, or if they have water they are not using? This is where water markets come in.
Such markets allow those who have surplus water (and there are many who do) to sell water, either in the permanent entitlement or temporary allocation market.