Study of the mechanism that increases the hardness of groundwater: A case study from Beijing urban area

The rapid development of construction and the increase of population water demand were increased rapidly in Beijing, China’s capital city, yet one of its fastest-growing municipalities is running out of water. Today, more than 70% of the municipality’s total water supply comes from groundwater. Therefore groundwater has been over-exploited a long time which led to regional water level down and more and more groundwater is becoming polluted, which has disadvantage on drinking water. As a consequence of a series of physico-chemical and biochemical reactions, including dissolution, ionexchange and reactions involving organic compounds, the calcium and magnesium in the infiltrating solutions have increased. The solutions have infiltrated into aquifers and increased the hardness of the groundwater; over-abstraction of groundwater has accelerated the process. The ISD = f (ISC) diagram indicates that central part of Beijing's groundwater is relatively recent with a speed of mean circulation.