Constructed wetlands (CWs) are one of the main countermeasures to reduce diffuse phosphorus (P) losses, but there is still a lack of systematic guidance accounting for spatially variable effects of hydraulic and P load on P retention. We present a three-step modelling approach for determining suitable placement of CWs in four different size groups (0.1–1.0 ha), based on incoming hydraulic and P load. The modelled hypothetical CW area was only 17% of that previously estimated and area of efficient CWs is even lower. The mean area-specific P retention increased with CW size. However, the spatial variation in retention was large for all size groups and largest (6–155 kg ha⁻¹ year⁻¹) for the smallest CWs due to highly variable incoming P loads, showing the possible benefits of targeted placement of CWs. The presented modelling approach has also flexibility to include and account for possible future changes in land cover and management.

人工湿地（CWs）是减少弥散性磷（P）损失的主要对策之一，但是仍然缺乏系统的指导来考虑水力和磷负荷对磷保持力的空间变化影响。我们基于输入的水力和P载荷，提出了一种三步建模方法来确定CW在四个不同尺寸组（0.1–1.0公顷）中的合适位置。建模的假设CW面积仅为先前估计的面积的17％，有效CW的面积甚至更低。随CW大小的增加，平均面积特异性P保留量增加。但是，所有尺寸组的保留空间差异都很大，最大（6-155 kg公顷- ¹年^-1），因为传入的P负载变化很大，因此最小。提出的建模方法还具有灵活性，可以包括并考虑土地覆盖和管理方面的未来可能变化。