地下水的年龄可以随大跨度。那一刻一滴雨进入地面变得地下水和当它到达地下水位,水开始(流)[1]对较低的水平面,通常向海,河流或湖泊。如果你有一个好,你将泵水降低油井附近的水平面,所以当地地下水的流动将向相反的海洋。流的速度取决于许多参数[2]。自然,距离补给区、静水压力、流量的高差,最后但不是最不重要的,土壤和岩石的渗透率它流过。如果地面包含如多孔砂、砾石沉积飞机或非常破碎岩石的水会流快速向较低的水平,但如果不透水地面,如。页岩或火成岩裂缝,会慢得多。[!(Creative Commons Attribution-Share都3.0 Unported USGS][3]][3]如果你有沙质地面,浅层地下水位,杀虫剂的地下水位将达到短时间(也许天?),如果(含水层)[4]是由粘土、可能需要几千年。这也取决于上述mosture非饱和区和地下水位。 So, unfortunately, it's impossible to answer your question(s) without more information. Shallow groundwater is typically from zero to a couple of hundred hears old. Some thousand years are not uncommon and for deep aquifer (that have little hydrostatic pressure reason to flow towards an ocean). It can be millions or even [billion][5] years old. The age of groundwater can be detected by Carbon-14 decay or by measuring known contamination, eg. CFCs, depending on the age range. If you are worried about contamination of you your well, apart from analyse the water, I'd make some sketches of the groundwater flow, e.g. map nearby rivers (river surface = groundwater surface) and the hydrostatic level (well water surface) in your well to find out what direction the water and contamination flow. If the contamination is between you and a river, the best guess would be that the contamination flows away from you, but if you pump up alot of water, the gradient of the groundwater table might change and the contaminations flow toward your well instead of the river. [1]: https://en.wikipedia.org/wiki/Groundwater_flow_equation [2]: https://en.wikipedia.org/wiki/Darcy%27s_law [3]: https://i.stack.imgur.com/eCiHi.png [4]: https://en.wikipedia.org/wiki/Aquifer [5]: http://www.livescience.com/32028-oldest-water-found-underground.html