Lab 8 Groundwater - Earth Sciences 1081b 2011 Lab#8...

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Earth Sciences 1081b 2011 Lab #8: Groundwater Lab 8: Groundwater & Groundwater Pollution OVERVIEW (This lab is modified from MacRae and Sell, 2000 and Misra, 1997, with additional explanatory text and figures by Tsujita, 2011) Groundwater is an essential and vital resource for about a quarter of all Canadian, used as a source of water for domestic drinking and washing, as well as for farming and manufacturing. Yet for the majority of Canadians, groundwater is a hidden resource whose value is not well understood or appreciated. Today, even in Canada, under the pressures of human development, many 'fresh' waters are losing their unspoiled quality. We dispose of human wastes, animal wastes and chemical substances into the environment at such a rate that even some of the largest lakes and river systems – the Great Lakes and the St. Lawrence River, for example – are having serious difficulty cleansing themselves and sustaining life. Pollution of groundwater is a particularly significant problem. Groundwater refreshes itself very slowly and as a result, cleaning groundwater is difficult and expensive. In today’s lab, we will examine how groundwater flows and how pollutants are transported through this environment. Today’s Exercises I. Calculations using Darcy’s Law. II. Constructing groundwater flow lines and relating to Darcy’s Law. III. Map groundwater flow lines and comment on possible pollution. IV. Construct contour map, map groundwater flow lines, and comment on possible pollution. What is Groundwater and where is it? A common misconception is that water flows through underground rivers or collects in underground lakes. Groundwater is not confined to only a few channels or depressions in the same way that surface water is concentrated in streams and lakes. Rather, it exists almost everywhere underground. It is found underground in the spaces between particles of rock and soil, or in crevices and cracks in rock. The water filling these openings is usually within 100 metres of the surface. Much of the earth's fresh water is found in these spaces. At greater depths, because of the weight of overlying rock, these openings are much smaller, and therefore hold considerably smaller quantities of water. The ratio of the open spaces in rock or soil relative to the total rock or soil volume is called porosity, and expressed as a percentage. Generally, the higher the porosity of a material, the more groundwater it can hold. Not all of the water stored in pore spaces can be moved, however. The ease or difficulty with which groundwater flows through any geologic material is controlled partly by the size of the pores but particularly by the degree of interconnection among the pores. The rate of flow of water through a material is called its permeability , and is commonly measured in units of metres per day.
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