Return Flow Water Quality And Reuse In Saline-alkali Paddy Soils

The Songnen Plain in northeast China is an important commoditygrain production base. It plays an important role in food security systemin China. However，the problem of soil salinization is particular becauseof the combined actions of natural and human factors in the Songnei PlainThe Songnen Plain is one of the largest regions affected by salinityandagricultural production is limited due to thereduced soil quality.. Withthe major project of land consolidation and rehabilitation in the west ofJilin province started in2007, the new reclaimed paddy field will reach2.7×105hm2. Such a huge irrigation and drainage system may bringchanges in regional hydrological pattern, water cycle process and waterand salt balance after it puts into operation. The change in water qualityand influence factors of drainage and return water reuse in saline-alkalisoil were studied through column experiment. At the same time, weanalyzed the influence factors of reservoir water quality which receivesthe return flow water, and assessed the feasibility of reservoir water reusewith the field monitoring data. The basis for sustainable development ofirrigation district water resource was provided. The results of this paperwere as follows:(1) The soil salinity and sodicity could be reduced by horizontal flushing. Compared the effect of adding desulfurization gypsum to the conrol(nodesulfurization gypsum application), the soil pH, total alkalinityin surface soil layer (0-20cm) were significantly reduced in severesaline-sodic soil after three horizontal flushings, but the conductivitysignificantly increased.(2) The pH of ponding water and the conductivity of sediment did notdecrease with time extension after steeping field and after four hoursof the second artificial pudding in paddy field of saline-alkali soil.Thus, the ponding water should be kept in field for at least24hoursand pudding two times. And then the ponding water was drained awayfour hours after pudding and supply new irrigation water into thepaddy filed.(3) The ion concentration of horizontal drainage water decreased with theincreasing amount of desulfurization gypsum application. The resultsshowed that the main influence factors on the drainage water qualitywere the degree of soil salinity-sodicityand the amount of thechemical modifier of desulfurization gypsum in saline-alkali paddyfiled.(4) The monitoring data showed that the return flow water quality meetsthe standards of the Water Quality Standard for Farm Irrigation inChina (GB5084-2005) in the saline-alkali paddy soils. We could usethe water as a alternative to irrigate rice, barnyard, tomato and Leymus chinensis.(5) The raising of Eriocheir sinensis in reservoir of the return flowwater from the saline sodic paddy feild showed that the majorparameters of water quality met the requirement of E. sinensisgrowing and the E. sinensis could grow regularly. The water qualitymet the criterion of the Chinese pollution ollution-freeFood–freshwater aquaculture water quality standards (NY5051-2001).The staphylococcus aureus，salmonella and Shigella in the edible partof the E. sinensis were not found.