［Background］ The Loess Plateau，which is characterized by weak ecological environments
and scarce water resources，is located in the Northwest of China． Due to the development of economy and
increment of population，this region has been faced with the increasing pressure of water resources
shortage． In order to achieve the scientific allocation and efficient utilization of water resources in
watershed，it is of great significance to conduct the investigations on characteristics of waters
transformation in the area． ［Methods］As typical case for study，the Jiuyuangou Watershed，which is
located in Suide County，Yulin City of Shaanxi Province，was selected to investigate the characteristics of
waters transformation in the loess hilly and gully regions． Precipitation samples，gully-channel water
samples and well water samples were collected and tested to quantify the compositions of the hydrogen and
oxygen isotopes in each water during Sept． 15 to 19，2014． ［Ｒesults］ By analyzing the relationships
between δD and δ18 O in the gully-channel water and well water of Jiuyuangou，it was found that theevaporation line equation of gully-channel water was EL-1: δD = 5. 40 δ18 O － 20. 34( n = 13，Ｒ2 =
0. 99) ，and the evaporation line equation of the gully-channel water and well water was EL-2: δD =
5. 33δ18O － 20. 89( n = 19，Ｒ2 = 0. 98) ． Additionally，the temporal and spatial variations of δ18O in
gully-channel water and well water were illustrated in the paper． It was visualized that the δ18O in gullychannel
water on Sept． 16 was the lowest during the period of sampling，and the δ18O in gully-channel
water increased progressively from the upper to the lower reaches of Jiuyuangou Watershed． The δ18O of
well water tended to be more positive and more stable than that of gully-channel water． The impacts of
rainfall，air temperature and wind speed on the variation of δ18O in gully-channel water was greater than
that on the variation of δ18O in well water． It was concluded that the surface water and ground water in
Jiuyuangou Watershed were both supplied by atmospheric precipitation． The weighted average value of
hydrogen and oxygen stable isotopes in precipitation which could effectively recharge the ground water was
δ18O = － 11‰ and δD = － 79. 80‰ respectively． Besides，the gully-channel water and well water in the
upper reaches presented a similar evaporation trend with similar slope and intercept，implying that there
was some degree of transformation between them． Furthermore，the main transformation relationship
between the gully-channel water and well water was characterized by unidirectional recharge from the
gully-channel water to the well water with a slow recharge rate，indicating that the retention time of the
water in Jiuyuangou Watershed was longer． ［Conclusions］ Finally，based on the above results，water
loss caused by evaporation in the transformation process between the gully-channel water and well water is
also calculated using Ｒayleigh distillation model and regression equation between absolute temperature T
and fractionation factor 18αw － v and 2αw － v with an assumption that the water vapor exchange is
equilibrated． The estimated result shows that the gully-channel water will lose 7% during the
transformation process．
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