中层取水防钉螺拦网的研究

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。

Study on blocking network for Oncomelania snails via collecting water from middle layer

Objective To evaluate the effect,mechanism and cost-benefit of blocking spread of Oncomelania snails with the blocking network via collecting water from middle layer.Methods The field tests and the longitudinal observation had been conducted to observe the effect,and the mechanism of the blocking network was investigated.The cost-benefit of the blocking network was analyzed by using health economic.Results The filed test was repeated twice.Both results showed that the blocking rate was 100%.The velocity of water flow was 0.88-1.0m/s at the center of the water inlet on the blocking network.However,the flow velocity was lower（0.1-0.3m/s）above the blocking network.Furthermore,no snail had been detected in irrigation ditches since the blocking network were set up.The cost-benefit analysis shows that the net benefit-cost ratio was 1.43.Conclusion The blocking network has a significant effect on blocking spread of Oncomelania snails.Also,the blocking network has a good benefit-cost ratio.Moreover,the blocking network has fully met the requirements of water conservancy.In addition to collecting water from middle level,the mechanism of blocking network also involves the water permeability of the blocking network and special structures as snail-proof cover.