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目的评价中层取水拦网防止钉螺扩散效果、作用机理和费用-效益。方法采用现场试验、纵向观察和卫生经济学方法评价中层取水拦网防止钉螺扩散效果,进行防螺原理和费用-效益分析。结果重复2次中层取水拦网防螺试验结果均表明其拦(防)螺效果达100%。拦网取水口中心流速达0.88~1.00m/s,而拦网上部非过水断面流速为0.10~0.30m/s。现场应用表明在设置拦螺网后目标保护区的灌区渠系未查出钉螺。费用-效益分析表明中层取水拦螺网净效益费用比为1.43。结论中层取水拦螺网具有显著的防螺效果和优良的效益费用比,完全满足水利要求;其作用机理除中层取水原理外,还与拦网具有的透水性及防螺罩等特殊结构有关。
Objective To evaluate the effect of diffusion prevention, mechanism and cost-benefit of snail prevention in mid-water abstraction block. Methods Field test, longitudinal observation and hygiene economics were used to evaluate the effect of water blocking in the middle layer to prevent the snail from spreading. The anti-spiral principle and the cost-benefit analysis were carried out. Results Repeated two times of middle water block test results showed that the barrier (anti-snail) effect of 100%. Blocking the center of the water inlet flow rate of 0.88 ~ 1.00m / s, while blocking the upper part of the non-cross-section flow rate of 0.10 ~ 0.30m / s. The field application showed that the snail was not found in the irrigation canal of the target protected area after setting the barbed wire. The cost-benefit analysis shows that the net benefit cost ratio of middle water abstraction barrage is 1.43. Conclusion The middle layer of water blocking net has significant anti-spiral effect and excellent cost-effectiveness ratio, fully meet the water requirements; its mechanism of action in addition to the principle of middle water, but also with the block has a water-resistant and anti-nut cover and other special structures.