You can find the original work that proposed the deuterium-excess here: Dansgaard, W. (1964), Stable isotopes in precipitation, Tellus, 16(4), 436–468, doi:10.1111/j.2153-3490.1964.tb00181.x.

However, it often makes sense to account for the local precipitation, and thus the local meteoric water line, from which the water samples will deviate according to its evaporation fractionation. This is described by the "line-conditioned excess" (short lc-excess) as described by Landwehr, J. M., and T. B. Coplen (2006), Line-conditioned excess: a new method for characterizing stable hydrogen and oxygen isotope ratios in hydrologic systems, in International Conference on Isotopes in Environmental Studies, pp. 132–135, IAEA, Vienna.

Examples are of its application are these

Landwehr et al. (2014, doi: 10.1002/hyp.10004)

Hervé-Fernández et al. (2016, doi: 10.1002/hyp.10984)

McCutcheon et al. (2016, doi: 10.1002/hyp.11052)

Sprenger et al. (2016, doi: 10.1002/2015RG000515)

Sprenger et al. (2017, doi: 10.1002/2016WR019258)

Sprenger et al. (2017, doi: 10.5194/hess-21-3839-2017)

There are many applications of deterium excess in hydrology. They are:

1, It can be use as a tool to isotopic study to assess water (snow) resources.

2. It can help to determine the source of high altitude.

3. The deterium excess of precipitation can be used in the reconstruction of past climate changes from ice cores. Please read the attached pdf for more details.

Dr. J.C. Tarafdar has mentioned valuable points. In addition, the following may also be considered:

1.The slope and d-excess indicate the climatic condition of an area. The low d-excess value (< 10)  indicates evaporated rainfall whereas high d-excess value points towards recycled moisture.

2. If the d-excess values ranges between 8 and 10, it is expected that it may be due to primary precipitation.

You can find the original work that proposed the deuterium-excess here: Dansgaard, W. (1964), Stable isotopes in precipitation, Tellus, 16(4), 436–468, doi:10.1111/j.2153-3490.1964.tb00181.x.

However, it often makes sense to account for the local precipitation, and thus the local meteoric water line, from which the water samples will deviate according to its evaporation fractionation. This is described by the "line-conditioned excess" (short lc-excess) as described by Landwehr, J. M., and T. B. Coplen (2006), Line-conditioned excess: a new method for characterizing stable hydrogen and oxygen isotope ratios in hydrologic systems, in International Conference on Isotopes in Environmental Studies, pp. 132–135, IAEA, Vienna.

Examples are of its application are these

Landwehr et al. (2014, doi: 10.1002/hyp.10004)

Hervé-Fernández et al. (2016, doi: 10.1002/hyp.10984)

McCutcheon et al. (2016, doi: 10.1002/hyp.11052)

Sprenger et al. (2016, doi: 10.1002/2015RG000515)

Sprenger et al. (2017, doi: 10.1002/2016WR019258)

Sprenger et al. (2017, doi: 10.5194/hess-21-3839-2017)

For East Asia, read papers of Kwang-Sik Lee (Korea Basic Science Institute). He uses d-excess values extensively in his studies. I am attaching a paper for your reference for that purpose.  d-excess values is generally regarded as the most useful stable-isotope property for characterizing the vapor origin of water. I also used d-excess values to differentiate rainfall from throughfall in a forested catchment. You can follow that here, 

http://www.tandfonline.com/doi/abs/10.1080/02626667.2017.1358813