Fiener P, Auerswald K
Geographisches Institut, Universität zu Köln, Albertus Magnus Platz, D-50923 Cologne, Germany.
J Environ Qual. 2009 Feb 6;38(2):548-59. doi: 10.2134/jeq2007.0525. Print 2009 Mar-Apr.
A modified type of grassed waterway (GWW) with large hydrodynamic roughness has proven ability to reduce sediment load and surface runoff under conditions where best management practices on the delivering fields reduce sediment inputs that could otherwise damage the grass cover. It is unknown how such a GWW affects the loading of surface runoff with dissolved reactive phosphorus (DRP). The effect on DRP was tested in a landscape-scale study where DRP concentrations and loads in surface runoff were measured in two watersheds in which GWWs were newly installed and increased in effectiveness over time. Both watersheds were compared with paired watersheds without GWW installation; all watersheds were continuously monitored over 5 yr (1993-1997). Additionally, DRP concentrations were measured in open field and throughfall precipitation under growing grass and crops in field experiments, and DRP concentrations in surface runoff from straw covered surfaces were determined with laboratory rainfall simulation experiments. Dissolved reactive P in throughfall for the different cover types was highly variable, and the highest concentrations (up to 2.8 mg L(-1)) occurred especially during flowering of the respective crop and after frost events. Dissolved reactive P concentrations in runoff from straw-covered surfaces were slightly higher compared with those from bare soil. On average, there was a small difference in DRP concentrations between throughfall under growing crops and grass and in runoff from bare or straw covered soil surfaces. Hence, the introduction of a relatively small grassed area has little effect on the DRP concentration in surface runoff from the total watershed. This finding was supported by the watershed data, where watersheds with and without GWW showed similar DRP concentrations. No change in DRP concentrations occurred over the 5-yr period. Such GWWs will thus reduce the DRP load analogously to the reduction in total surface runoff.
一种具有较大水力粗糙度的改良型草地水道（GWW）已被证明在输送田块采用最佳管理措施减少沉积物输入（否则可能破坏草地覆盖）的条件下，有能力减少沉积物负荷和地表径流。目前尚不清楚这种GWW如何影响地表径流中溶解态活性磷（DRP）的负荷。在一项景观尺度研究中测试了其对DRP的影响，该研究测量了两个新安装了GWW且随着时间推移有效性增加的流域地表径流中的DRP浓度和负荷。将这两个流域与未安装GWW的配对流域进行比较；所有流域在1993 - 1997年的5年期间持续监测。此外，在田间试验中测量了生长着草和作物的开阔田地及穿透雨中的DRP浓度，并通过实验室降雨模拟试验测定了秸秆覆盖表面的地表径流中的DRP浓度。不同覆盖类型的穿透雨中的溶解态活性磷变化很大，最高浓度（高达2.8 mg L⁻¹）尤其在相应作物开花期间和霜冻事件后出现。与裸土相比，秸秆覆盖表面径流中的溶解态活性磷浓度略高。平均而言，生长作物和草下的穿透雨与裸土或秸秆覆盖土壤表面径流中的DRP浓度存在微小差异。因此，引入相对较小的草地面积对整个流域地表径流中的DRP浓度影响不大。这一发现得到了流域数据的支持，有GWW和没有GWW的流域显示出相似的DRP浓度。在5年期间DRP浓度没有变化。因此，这种GWW将类似于减少总地表径流那样减少DRP负荷。
