Yu Liang, Rozemeijer Joachim C, van der Velde Ype, van Breukelen Boris M, Ouboter Maarten, Broers Hans Peter
Faculty of Science, Vrije University Amsterdam, Amsterdam 1181HV, the Netherlands; Waternet Water Authority, Amsterdam 1096 AC, the Netherlands; TNO Geological Survey of the Netherlands, Utrecht 3584 CB, the Netherlands.
Deltares, Utrecht 3508 TC, the Netherlands.
Sci Total Environ. 2019 Aug 15;678:288-300. doi: 10.1016/j.scitotenv.2019.04.428. Epub 2019 Apr 29.
Urban areas in coastal lowlands host a significant part of the world's population. In these areas, cities have often expanded to unfavorable locations that have to be drained or where excess rain water and groundwater need to be pumped away in order to maintain dry feet for its citizens. As a result, groundwater seepage influences surface water quality in many of such urban lowland catchments. This study aims at identifying the flow routes and mixing processes that control surface water quality in the groundwater-influenced urban catchment Polder Geuzenveld, which is part of the city of Amsterdam. Geuzenveld is a highly paved urban area with a subsurface rain water collection system, a groundwater drainage system, and a main surface water system that receive runoff from pavement and roofs, shallow groundwater and direct groundwater seepage, respectively. We conducted a field survey and systematic monitoring to identify the spatial and temporal variations in water quality in runoff, ditch water, drain water, and shallow and deep groundwater. We found that Geuzenveld receives a substantial inflow of deep, O-depleted groundwater, which is enriched in ammonium and phosphorus due to the subsurface mineralization of organic matter under sulfate-reducing conditions. This groundwater is mixed in the ditches during wet periods with O-rich runoff, and iron- and phosphate-rich drain water. Unlike natural catchments, the newly created, separated urban flow routes lead to mixing of water in the main surface water itself, shortcutting much of the soil and shallow subsurface. This leads to low O and high ammonia concentrations in dry periods, which might be mitigated by water level management or artificially increasing O levels by water inlet or artificially aeration of the main water canals. Further research is necessary how to optimize artificial urban systems to deliver a better ecological and chemical status of the surface water.
沿海低地的城市地区承载着世界上相当一部分人口。在这些地区，城市常常扩张到了一些不利的位置，这些地方需要进行排水，或者需要抽排多余的雨水和地下水，以便让市民有干燥的生活环境。因此，在许多这样的城市低地集水区，地下水渗漏会影响地表水水质。本研究旨在确定控制受地下水影响的城市集水区豪达泽费尔德圩田（阿姆斯特丹市的一部分）地表水水质的水流路径和混合过程。豪达泽费尔德是一个高度城市化且铺设了大量路面的地区，拥有地下雨水收集系统、地下水排水系统以及一个主要地表水系统，分别接收来自路面和屋顶的径流、浅层地下水和直接的地下水渗漏。我们进行了实地调查和系统监测，以确定径流、沟渠水、排水以及浅层和深层地下水水质的时空变化。我们发现，豪达泽费尔德接收了大量深层的、贫氧的地下水，由于在硫酸盐还原条件下有机物的地下矿化作用，这种地下水富含铵和磷。在潮湿时期，这种地下水在沟渠中与富氧径流以及富含铁和磷酸盐的排水混合。与自然集水区不同，新形成的、分离的城市水流路径导致主要地表水本身的水体混合，绕过了大部分土壤和浅层地下区域。这导致在干旱时期水体含氧量低且氨浓度高，这可以通过水位管理或通过进水口人工增加含氧量或对主要水渠进行人工曝气来缓解。有必要进一步研究如何优化人工城市系统，以使地表水具有更好的生态和化学状态。
