Water-Quality Assessment Under Rice Wetlands in North-East China. Annex IV

The Sanjiang Plain in northeast of China is the largest food supply base in China. In the 1940s, more than 5 million ha of marshes and wet meadows existed in the plain. However, in order to meet the food demand for the increasing population, part of the plain was reclaimed for agriculture. Since 1950s about 35% of wetlands in the plain have been converted for rice production. About 6.65 mega litres of ground–water ha–1 has been extracted annually to meet the water demand for rice production in the region (corresponding to 665 mm) with an annual fertiliser application of 170 kg N ha–1. Sustainable management of these rice wetlands is important to protect water resources. In this case study, isotopic signatures δ¹⁸O and δ²H, water chemistry and depth of ground–water and surface water were monitored on three farms, namely, Honghe, Qianfeng and Qianshao