ABSTRACT Artificial drainage of agricultural fields represents a major flow path way of both water and nutrients which may contribute to eutrophication issues in the recipient waters. Several studies have shown that riparian lowlands (alluvial plains, wetlands, meadows), if present, may act as buffer zones with high nutrient retention capacities. To assess the fate of water and nutrient flow in riparian lowlands in tile drained catchments, it is essential to know the locations of tile drainage outlets as sources of nutrient input. Using a thermal infrared (TIR) remote-sensing survey, we identified potential tile drainage outlets in a riparian lowland. We also applied a normalized differentiated vegetation index (NDVI) approach to illustrate how tile drainage outlets can be identified with free broadband RGB-NIR data. The positions of identified outlets were validated in the field by visual observation. Our study finds that TIR remote sensing is a strong tool when assessing the sources of water input. NDVI is also applicable, however the background values are very variable making the outlets difficult to locate. The results can be applied in studies of water movement and solute transport via tile drainage as well as model studies where knowledge of input areas through tile drainage is of great importance.

中文翻译：

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使用热红外和 RGB-NIR 遥感定位河岸低地的瓦片排水口和地表流量

摘要 农田的人工排水是水和养分的主要流动途径，这可能导致受援水域的富营养化问题。几项研究表明，河岸低地（冲积平原、湿地、草地），如果存在的话，可以作为具有高养分保留能力的缓冲区。为了评估瓦片排水集水区河岸低地的水和养分流的归宿，必须了解作为养分输入源的瓦片排水口的位置。使用热红外 (TIR) 遥感勘测，我们在河岸低地确定了潜在的瓷砖排水口。我们还应用了归一化差异植被指数 (NDVI) 方法来说明如何使用免费宽带 RGB-NIR 数据识别瓷砖排水口。通过目视观察在现场验证已识别出口的位置。我们的研究发现，TIR 遥感是评估水输入来源的有力工具。NDVI 也适用，但背景值变化很大，因此难以定位出口。结果可应用于通过瓷砖排水的水运动和溶质传输研究以及模型研究，其中通过瓷砖排水的输入区域知识非常重要。