GMWLGlobal Meteoric Water Line
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Caption: Figure 6: [delta][sup.2]H and [delta][sup.18]O are plotted with reference to the global meteoric water line (GMWL).
The underlying assumption [23] is that water with an isotopic composition that falls along the GMWL originates from the atmosphere and is relatively unaffected by isotopic processes.
The guaranteed minimum withdrawal benefit for life (GMWBL or GMWL), also referred to as a Lifetime Income Benefit (LIB) or Guaranteed Lifetime Withdrawal Benefit (GLWB), guarantees a minimum percentage of premium withdrawal amounts for life.
This relationship was developed as an average of many local meteoric water lines that, because of climatic and geographic factors, differ from the GMWL. Differential fractionation of [[delta].sup.2]H and [[delta].sup.18]O occurs as a function of humidity during primary evaporation of water vapor from the ocean, and as a function of temperature during secondary evaporation as rain falls from a cloud (figure 1).
We also compare several reported LMWLs to the GMWL (Craig, 1961) and to the LMWL calculated for this report.
In the remainder of this report, we compare this new LMWL with the GMWL.
The winter precipitation signal tends to have the more negative delta values, with [[delta].sup.18]O less than or equal to about -16 permil, and the data plot close to the GMWL (figure 4).
Deuterium-excess, defined by d (in permil) = [[delta].sup.2]H - 8 [[delta].sup.18]O (Dansgaard, 1964), can be thought of as an index of deviation from the GMWL that has a d-excess value of 10 permil.
Caption: Figure 7: (a) Relationship of [delta][sup.18]O and [[delta].sup.2]H in groundwater with the GMWL and LMWL at Xinzhou and Shenzao; (b) [[delta].sup.2]H-Cl diagram; and (c) [delta][sup.18]O-Cl diagram.
The stable isotopic composition of water relative to the GMWL revealed important information on groundwater recharge patterns, the origin of waters in hydrologic systems, and mixing of groundwater and surface water [30, 31].
The [sup.18]O and D isotope data show that the springs in Kangding geothermal field are close to the GMWL, indicating that they are mainly deriving from the precipitation.
The samples collected in the mainland area (i.e., Zhanjiang city area) are mainly located along the GMWL and LMWL, indicating that the confined groundwater in the mainland area is of meteoric origin.