The average pH value of rainwater is 5.7.
The total economic benefit was 1.34 billion RMB in 2009 (RMB: Chinese currency, US$1 = RMB6.83), which is equivalent to three-quarters of the maintenance cost of Beijing's green spaces; the value of rainwater-runoff reduction was 21.77 thousand RMB per hectare.
The spring water chemistry reveals a well-mixed system with minor inter-spring variation; TDS values of spring waters are low (27 72 mg L−1), major ion compositions are homogenous (Na Si DIC Cl) and δ18O and δ2H values are reflective of rainwater origin with little evaporation prior to recharge.
A negative correlation between the δ18O value of modern rainwater and its amount (known as amount-effect) in the study site is used as a framework for interpreting variations in δ18Ocarbonate values.
The slightly depleted values of groundwater besides rainwater can be attributed to a preferential winter/autumn recharge.
Table 4 Mean values of different heavy metals of rainwater samples collected from five zones of Lucknow city (ppm parts per million or mg/l, BDL below detection limit) S. no.
The average values of δ18O and δ2H in rainwater are −1.61 and 1.33 ‰, respectively.
The low values of d-excess in the groundwaters at most parts of the study area suggest that there is significant evaporation of rainwater, leaving the residual groundwater with lower values of d-excess.
A shift towards higher δ18O values in campaign 2 was attributed to a higher contribution of rainwater.
The mean pH value of 7.6 of the studied samples greatly exceeds that of rainwater (pH 6.1, Table 4).
