| Vegetative buffer strip (VBS) is a typical kind of amphibian habitat crisscross and is the connection and transition zone of the land ecosystem and aquatic ecosystem, playing a role of preventing pollutants and sediments from flowing into the surface runoff and reflecting great ecological benefits. For recent years, the ecological system of VBS has been degenerating and water pollution has been deteriorating. Non-point source pollution is the main source of water pollution. The research of VBS has a very important significance for the pollutants’intercept. The study site in this paper located at Danjiangkou Reservoir. In order to study the pollutant intercepting efficiency of VBS and the best width of VBS in different site conditions of Hubei and Henan provinces and exploring the spatial optimum allocation of VBS in total Danjiangkou Reservoir, we conducted a series of washing tests in fields and water sample tests in lab, using DEM data, remote sensing data and rainfall data and combining the landscape ecology, hydrology, statistics and GIS technology.The main results were as following:(1)The results of the washing test in runoff plot showed that the flow rate and the total phosphorus concentration were negatively related to pollutants removal rate. The total nitrogen concentration had positive correlation to pollutants removal rate. When it was in the large flow, the pollutants removal rate was negatively related to the slope. However, the pollutants removal rate had no significant relationship with the slope. The order of removal rate of different pollutants of VBS was:silt sand> ammonium nitrogen> total phosphorus> total nitrogen. We had set24kinds of scene modes in24different experimental setups under different slope, pollutant concentration and water flow. In the mode, the width of VBS ranged from8.1m to13.6m when silt sand removal rate reached95%. The width of VBS ranged from6.6m to43.5m when total phosphorus removal rate reached80%. The width of VBS ranged from13.7m to58.2m when silt sand removal rate reached50%.(2)The Danjiangkou Reservoir was divided into17catchment areas using DEM data. The total area of the catchment area was2678.9km2. The farmland, woodland and residents’ area respectively accounted for47.7%,51.4%and0.9%. The water area was906.5km2when the highest water level was170m. The Henan area including No.1,2,3,4,5,6,7,11and12catchment area and the Hubei area consisted of No.9,10,14,15,16and17catchment area. No.8and No.13catchment areas were located at the junction of two provinces. Henan area was flat terrain and the most slopes ranged between05degree. The Hubei reservoir area was steep terrain and most slope ranged between5-15degree and a few slopes were more than15degree. The slope of No.2catchment in Henan was minimum and the average slope was1.1degrees, the Hubei No.16catchment slope, average slope is15.5degrees.(3) According to the rainfall data in the Danjiangkou Reservoir, the single precipitation intensity in the region was determined as the heavy rain and the daily rainfall was30mm. We used the SCS-CN model to simulate the rainfall runoff of Danjiangkou Reservoir. When the rainfall was30mm, runoff depth of residential area farmland and woodland respectively were13.8mm,9.2mm and2.9mm. The total runoff of catchment area in different land use types and flow rate were calculated The minimum flow rate was in No.16catchment area of Hubei and the flow rate was of0.06L·S-1·m-1. The maximum flow rate was in No.6catchment area of Henan and the flow rate was of0.77L·S-1·m-1.(4) Different types of land use determined the size of non-point source pollution. The source of nitrogen non-point source pollution in Danjiangkou Reservoir was mainly farmland. The source of phosphorus was mostly woodland. The nitrogen and phosphorus concentrations in EMC value (mean concentrations of rainfall runoff) of resident area were higher than that in farmland and woodland. However, because of its small area, resident area was not the main source of non-point source pollution. When daily rainfall was30mm, beside of No.2catchment area in Henan, the EMC value of total nitrogen in surface runoff of No.12catchment area in Henan was maximum and the value was7.41mg/L and the minimum value appeared in No.16catchment area in Hubei and the value was4.73mg/L. The EMC value of total phosphorus in surface runoff of No.1catchment area in Henan was maximum and the value was0.58mg/L and the minimum value appeared in No.15catchment area in Hubei and the value was0.14mg/L.(5) Henan terrain was flat and land was mostly used to be farmland. The minimum width of VBS was13.7m (No.4catchment area) and the maximum width of VBS was50.6m (No.12catchment area) when total nitrogen removal rate reached50%. The minimum width of VBS was7.6m (No.1catchment area) and the maximum width of VBS was43.5m (No.3and No.12catchment area) when total nitrogen removal rate reached80%. Hubei terrain was steep and land was mostly used to be woodland. The minimum width of VBS was58.2m (No.14, No.16and No.17catchment area) and the maximum width of VBS was26m (No.9, No.10and No.15catchment area)when total nitrogen removal rate reached50%. The minimum width of VBS was6.6m (No.9and No.10catchment area) and the maximum width of VBS was9.7m (No.17catchment area) when total nitrogen removal rate reached80%. In Henan and Hubei border, the width of VBS ranged in43.5-58.2m when total nitrogen removal rate reached50%and the width of VBS ranged in14.2-29.2m when total phosphorus removal rate reached80%. The sediment removal rate in both Henan and Hubei area were high and the width ranged in7.7-13.6m when removal rate reached95%. |
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