This study assesses the impact of irrigation on That  Luang Marsh (TLM) in Vientiane, the capital city of  the People’s Democratic Republic (PDR) of Laos. The study finds that the economic benefits provided by  the marsh (particularly in terms of the fish it supplies to  local people) far outweigh the benefits provided by the  extraction of water for irrigation. As extraction of  water for irrigation is threatening the ecology of the  marsh and its ability to maintain a viable stock of fish,  it is clear that the amount of water extracted for  irrigation should be reduced.  The report recommends  that a minimum level for the water in TLM should be  set to ensure the conservation of its precious wetland  ecosystem.  The report finds that, on balance, this  would have a positive impact on the livelihoods of  local people.  This means that the conservation of the  marsh makes good economic sense.    To help the farmers who would be negatively affected  by these measures, the report shows how they could be  trained to use irrigation water more effectively, grow  alternative crops that require less water than rice, catch  fish and collect vegetables.