The Sistan area is located at the tail end of a large closed inland (endorheic) basin, in one of the driest regions
of the world. It is comprised of three geographical sub-units: (i) the upper plain of the inland delta of
the Helmand (Hirmand) river, which is mostly drained and used for agriculture; (ii) the wetlands (Hamoons)
covering the lower delta plain and (iii) a hypersaline lake (Gowd-e-Zareh) in the lowest part of the basin, which
collects the overspill from the wetlands and – in case of extreme floods – from the Helmand River. There is no
outflow from this terminal lake; water is lost from Gowd-e-Zareh only by evaporation....