Changes to soil and water environment in reclaimed marshland of Sanjiang Plain

With the conversion of wetlands, there have been changes in the natural soil and water resources of the Sanjiang Plain, located in the northeast corner of Heilongjiang province. The total area of the plain is 10.88 x 10(4) km(2), of which half is marshy wetland. In the past several decades, a large number of modern farms have been built there through large-scale reclamation and construction. So now the Sanjiang Plain has become one of the most important bases for grain commodities in China. The cultivated area has reached 3.5 million ha, mostly reclaimed from marshy wetland. Changes to the soil and water environment in the reclaimed wetlands were intensively studied, to judge whether or not they were compatible with concepts of sustainable agriculture. Key features included changes in landform, conditions of water supply, interception of precipitation by vegetation, accumulation of surface water and changes of soil physical properties. A rainfall-runoff model has been established.