Separating surface runoff from tile drainage flow in agricultural lowland catchments based on diatoms to improve modeled runoff components and phosphorous transport

在发达国家或发展中国家制订可持续战略时，以生态和经济上适当的方式进行水资源综合管理正日益受到重视。SWAT模型等生态水文模型是广泛应用于流域尺度水资源可持续管理的工具。然而，流域管理如何驱动水文平衡和集水区水质的变化，目前仍不清楚。这在低水力梯度低、地势平坦、水潴留潜力大、大量瓷砖排水以及地表水和地下水密切相互作用的低地集水区尤其明显。因此，该项目的目的是测试生物示踪剂（即硅藻）在德国北部基尔斯托集水区（50平方公里）地表径流和排水流量检测中的适用性。基于每日混合降雨事件的河流和瓦片排水样本的硅藻和水质分析，我们的目标是：1)量化地表径流对低地河流总排放量的贡献；2)根据不同的硅藻浓度将地表径流从瓦片排水流量中分离出来，并确定磷进入河流的途径。3)将检测到的产流和输磷过程引入到新引入的生态水文SWAT模型的坡面排水例程中，以改善例程结构和模型性能。

Integrated water resources management in an ecologically and economically adequate way is receiving more and more attention when it comes to the development of sustainable strategies in either developed or developing countries. Ecohydrological models like the SWAT model are widely applied tools for sustainable management of water resources at river basin scale. Nevertheless it is still not clearly understood, how river basin management drives changes in the hydrological balance and the water quality of catchments. This is especially apparent in lowland catchments characterized by low hydraulic gradients, flat topography, high potential for water retention, a large amount of tile drainages and a close interaction of surface- and groundwater.The objective of this project is thus to test the applicability of a biological tracer (i.e. diatoms) for the detection of surface runoff and drainage flow in the example case of the Kielstau catchment (50 km2) in northern Germany. Based on the diatom and water quality analyses of daily mixed, rain event based river and tile drainage samplings, we aim to1) quantify the contribution of surface runoff to total river discharge in lowlands,2) separate surface runoff from tile drainage flow based on different diatom concentration of each flow component and determine the entry pathways of phosphorus into the river, and 3) implement the detected runoff generation and phosphorous transport processes into the newly introduced tile-drainage routine of the ecohydrological SWAT model to improve the routine structure and the model performance.