The sedimentation of drainage canals is a common process and its intensity depends on several geographical and hydrological factors. Drainage canal sediments are frequently polluted by heavy metals or other pollutants; they need to be periodically dredged and ultimately, have to be safely disposed of. Furthermore, pollution in smaller drainages may go undetected because under the Water Framework Directive (Directive 2000/60/EC), catchment areas < 10 km² do not require monitoring. We investigated the hypothesis that water resources of small sub-catchments exposed to agricultural pollutants accumulate sediment for a longer period (several years) and severely enhance environmental risks. We analyzed the data on sediment mobility in drainage canals for a small lowland catchment in Croatia during 2013–2017. We conducted sediment transport modelling for actual precipitation episodes of a 10-year return period and design precipitation of a 50-year return period. The results indicated that sediments and associated copper pollution persist at the canal bottom for several years, which increases the risk of polluting groundwater and the environment in general. Only copper present at the maximum downstream section of the canal has the possibility of moving to the recipient stream and would only be detected in catchment areas bigger than 10 km². We proved that smaller water bodies evaluated according to monitoring standards prescribed for the closest larger water can enhance environmental risks.

中文翻译：

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克罗地亚低地地区铜污染的排水沟沉积物低迁移率的实地调查

排水渠的沉淀是一个普遍的过程，其强度取决于几个地理和水文因素。排水渠的沉积物经常被重金属或其他污染物污染；他们需要定期疏dr，最终必须安全处置。此外，由于根据《水框架指令》（第2000/60 / EC号指令），集水区<10 km ²不需要监控。我们研究了以下假设：暴露于农业污染物的小流域的水资源会在更长的时期（数年）内积聚沉积物，并严重加剧环境风险。我们分析了2013-2017年克罗地亚低地小流域排水渠中沉积物迁移率的数据。我们对10年回归期的实际降水事件进行了泥沙运移建模，并设计了50年回归期的降水。结果表明，沉积物和相关的铜污染在运河底部持续了数年，这总体上增加了污染地下水和环境的风险。²。我们证明，根据对最接近的大型水所制定的监测标准进行评估的较小水体可以增加环境风险。