三江平原有大面积涝洼地,有人认为,只要挖好排水沟,达到沟渠、桥涵配套,就可根治涝灾了。其实,挖排水沟只能排除地表水而不能排除壤中水,只能减轻涝灾而不能根治涝灾。如洪河农场,虽然沟,渠成网,但在方整的地块内部,仍要遭受不同程度的涝灾。为什么排水沟不能排掉壤中水呢?这是因为三江平原的易涝土壤土质粘重而紧实,如白浆层几乎达到夯实的程度。孔隙度比例严重失调,大孔隙极少,小孔隙极多,微小的毛管孔隙占土壤总孔隙的90%,透水、通气性极差,促使毛管储水量接近饱和储水量。据41个剖面测定,20厘米土层,毛管储水量占饱和储水量的91%;在一米土层内,毛管储水量占饱和储水量的94.6—95.7%。由此可见,90%以上的水分,都保持在极细 Sanjiang Plain has a large area of ​​waterlogging depression, some people think that as long as digging a good drainage ditch to reach ditches, bridges and culverts supporting, we can cure floods. In fact, digging drains can only rule out surface water and can not rule out soil water, can only reduce waterlogging and can not cure floods. For example, the Honghe Farm, although ditches and channels have become nets, will still suffer different degrees of waterlogging within the fragmented plots. Why can draining ditch soil water drainage it? This is because the waterlogged soil in the Sanjiang Plain sticky and solid, such as white pulp layer almost reached the level of compaction. The proportion of porosity is seriously imbalanced, the number of macropores is very small and the number of small pores is very small. The tiny capillary pores account for 90% of the total soil pores, and the water permeability and air permeability are extremely poor, which causes the capillary water storage capacity to approach the saturated water storage capacity. According to the determination of 41 sections, the capillary storage accounts for 91% of the saturated water storage in 20 cm of soil layer. The capillary storage accounts for 94.6-95.7% of the saturated water storage in one meter of soil layer. This shows that more than 90% of the water, are kept very thin