Diffuse groundwater contamination by intense fertilizer use is a widespread problem in most of the agricultural regions in West-Europe and in many other countries worldwide. As a result elevated nitrate concentrations in groundwater are found, and as groundwater is the source of baseflow into rivers and streams, also surface waters show increased nitrate levels. Flanders in the north of Belgium is no exception and despite restrictions on the fertilizer use and remediation practices initiated in the mid-1990s, and still ongoing, in many stream monitoring points, peak concentrations are measured above the 50 mg/l criterium. In many monitoring stations there is apparently a long delay between the start of the restrictions and effect on water quality. Often this delay is related to high concentrations in the groundwater inflow and long residence and travel times of groundwater feeding the streams. To better understand this behavior and estimate response times a tool was developed that incorporates the main water flows in a typical catchment and considers the effects of varying groundwater ages. This tool is conceived as a parsimonious lumped parameter model, simple and easy enough to be used by many people but still capturing the main mechanisms end processes. In this paper the tool is explained and it is applied on two testcases in Flanders to show its performance.

扩散地下水污染大量使用化肥是西欧大部分农业地区和世界许多其他国家普遍存在的问题。结果发现地下水中硝酸盐浓度升高，并且由于地下水是流入河流和溪流的基流来源，地表水的硝酸盐含量也增加。比利时北部的佛兰德斯也不例外，尽管在 1990 年代中期开始限制肥料使用和补救措施，但仍在进行中，在许多河流监测点，峰值浓度测量值高于 50 毫克/升的标准。在许多监测站，从限制开始到对水质的影响之间显然有很长的延迟。通常，这种延迟与地下水流入的高浓度以及注入溪流的地下水的滞留和流动时间长有关。为了更好地理解这种行为并估计响应时间，开发了一种工具，该工具包含典型集水区的主要水流并考虑不同地下水年龄的影响。这个工具被认为是一个简约的集总参数模型，简单易行，可以被很多人使用，但仍能捕捉到主要机制结束进程。本文解释了该工具，并将其应用于法兰德斯的两个测试用例以展示其性能。这个工具被认为是一个简约的集总参数模型，简单易行，可以被很多人使用，但仍能捕捉到主要机制结束进程。本文解释了该工具，并将其应用于法兰德斯的两个测试用例以展示其性能。这个工具被认为是一个简约的集总参数模型，简单易行，可以被很多人使用，但仍能捕捉到主要机制结束进程。本文解释了该工具，并将其应用于法兰德斯的两个测试用例以展示其性能。