塘坝整治上游水土拦截植被过滤带适宜宽度的理论计算研究

Theoretical calculation study on appropriate width of upstream soil and water conservation intercepting vegetative filter strips in dam regulation

植被过滤带是防治水土和养分流失、减少氮磷污染物流入水体的重要途径,确定过滤带的最佳宽度是研究过滤带合理建设的关键问题之一。为确定合适的过滤带宽度,通过Overcash方法计算得出,在总长度为50 m的坡面上,当分别要求输出VFS的污染物降至入流浓度或负荷量的85%时,要求过滤带宽度分别达到1.20 m或1.41 m;当要求将流入浓度为11.0 mg·L^(-1)的NH_4-N降至流出浓度为7.85 mg·L^(-1)或将污染物输移量减少至0.28 kg·hm^(-2)时,要求过滤带宽度分别达到2.60 m或2.95 m。采用Phillips水文模型计算则要求宽度达到2.79 m。在理论计算基础上确定过滤带宽度为3.0 m。采用VFS宽度为3 m的过滤带进行野外试验,实测值与计算值一致性较好,平均减少污染物至入流浓度的34.6%,减少污染物输入负荷量的30.6%,控制流入浓度为11.0 mg·L^(-1)的NH_4-N至流出为7.42 mg·L^(-1),减少污染物输移量0.274 kg·hm^(-2)。

The vegetative filter strips is an important way to prevent the loss of soil and nutrients, to reduce nitrogen and phosphorus flow into water. To determine the optimum width of the filter strip is one of the key problems for the reasonable construction. In order to determine the appropriate width of filter strip, the Overcash method was used to calculate. On the total length of 50 meter slope, when the pollutant of VFS was required to be reduced to 85% of the inflow concentration or load respectively, the filter strip width should be 1.20 meter or 1.41 meter. When the concentration of NH_4-N was required to be reduced from an inflow concentration of 11.0 mg·L^(-1) to an outflow concentration of 7.85 mg·L^(-1), or the pollutant transport amount reduced to 0.28 kg·hm^(-2), the width of filter strip should be 2.60 meter or 2.95 meter respectively. And using Phillips hydrological model to calculate, the width was required to be 2.79 meter. In a word, the width of filter strip was determined as 3.0 meter based on theoretical calculation. Carrying out the field test with the VFS width of 3.0 meter, the measured value was consistent with the calculation value. On average, the pollutant concentration was reduced to 34.6% of the inflow concentration, the input load of pollutants was reduced by 30.6%, the concentration of NH_4-N was controlled from an inflow concentration of 11.0 mg·L^(-1) to an outflow concentration of 7.42 mg·L^(-1), and the pollutant transport amount reduced by 0.274 kg·hm^(-2).