The marshes were reduced to a small fraction of their pre-1990s extent by deliberate drainage, and reflooding has been underway since 2003, but published figures for the currently restored area diverge significantly by source and by year, and many describe the recovery only in relative terms (a share of the historic maximum) rather than a settled square-kilometer figure. Water flow from the Tigris and Euphrates, itself affected by upstream damming in Turkey, Syria and Iran and by regional drought, keeps changing the extent year to year rather than letting it settle.
What would resolve this A current, dated satellite-derived wetland-extent survey, ideally repeated over consecutive years by the same methodology, published by a body such as UN Environment, the Iraqi government's own marshland restoration program, or a peer-reviewed remote-sensing study, would give a figure that can be cited with real confidence rather than the mixed and dated estimates currently circulating.
OpenWetland ecology and remote sensingUNESCO World Heritage Centre