| Honghe Hani Rice Terraces is a healthy ecosystem with unique natural and cultural landscape. Water is the most active and the most critical element in the landscape. In this unique landscape, mutual relationships with a variety of water bodies and hydraulic connection of which the precipitation is the most important are very complex. Studying on hydrogen and oxygen stable isotopes of precipitation deeply and its supply relationship with other water bodies will provide a strong basis on making a good understanding of the hydrological cycle law and the optimal allocation of water resources of Honghe Hani Rice Terraces. Based on this, select the Core Area of Honghe Hani Rice Terraces landscape, the typical watershed- Ma Li Zhai River as the research object, using the tracer method of hydrogen and oxygen stable isotopes to explore the spatial and temporal characteristics, sources of water vapor and its influencing factors of hydrogen and oxygen stable isotopes of precipitation in the basin, and analysis comparatively a different body of water isotopic characteristics and discuss the transformation of the relationship between them. The main conclusions are as follows:(1) Hydrogen and oxygen stable isotopes characteristics of precipitation(1) δ value of instantaneous water samples in the main rainy season had a large amplitude, with the overall bias negative.The reasons were: there was a big difference between rainfalls and therefore a large amplitude mainly due to scale precipitation events screenings; water vapor marine in rainy season were from the air masses of warm and humid in the sea, affected by the "dilution" effect,thus with a biased negative δ. The changes on δ of precipitation month mixed water sample was much smaller, with the mean more negative, indicating that the source of moisture had experienced a considerable degree of dilution process. The characteristics of composition of it was close to Kunming and Guiyang, indicating that the source of water vapor was similar.(2) In terms of time distribution characteristic, precipitation δ value in the study area as a whole was a seasonal variation with "high in summer and low in winter", but a lower δ value also appeared in November, differing from other regions, which was related to the unique clouds appearing in winter. In terms of spatial distribution characteristic, terraces in the middle reaches of the river basin were affected by two evaporation overall with a higher δ18O than the upstream region.(3) Analyzing the relationship between δ18O and δD, propose precipitation line equation of study area: δD = 8.31δ18O + 16.98, which reflected the climate characteristics that the study area is in the rainy and wet and precipitation process was impacted on the secondary evaporation with a smaller δ in the whole; compared with the dry and the rain, the rainy season was more intense evaporation; on the one hand, it was related to rain and heat in the same period of subtropical mountainous monsoon climate;on the other hand, more clouds weather during the dry season in the study area.(4) The time changing characterizes of deuterium surplus were: low in the rainy season, high in the dry season; in the terms of the spatial distribution, the elevation got higher with no monotonically increasing relationship, but a weakly bimodal distribution in the middle terraced valley, which was related to the intense cloud secondary evaporation and water vapor in the terraced area. Using the backward trajectory model to seek moisture source of precipitation, the results showed monsoon rains doubly influenced by the southwest monsoon and the southeast monsoon from the ocean, and dry season mainly influenced by continental air mass and westerly control, but there were also added from the low-latitude oceans and excursions moisture.(5) In terms of factors, there were significant rainfall effect and humidity effect in the study area and the temperature effect were only in transient samples, and monthly mixed samples were with even a slight "anti-temperature effect" that was because the significant precipitation effect may influence and obscure the temperature effect. There was a significant altitude effect with more significant in the rainy season than the dry season. The factors of affecting hydrogen and oxygen stable isotopes characteristics and spatial and temporal distribution of precipitation with the comprehensive factors and multiple regression analysis in the study area were a diversified multi-factor interaction.(2) Compared with hydrogen and oxygen stable isotopes characteristics of different waters,it found that time change of precipitation isotopes was greater than the space; and space changes of spring was greater than time, mainly reduced the unevenness of precipitation isotopes caused by infiltration in time, but did not weaken unevenness of infiltration isotopes caused in space. The study also found that the supply sources of field water were complex, with the biggest change; the river with the smallest change due to the effect of the mixing average, because it was always in the slope of the valley area, receiving multi-slope water supply; spring with the more change due to human disturbance and perturbations of field water. The average of field water and spring water was too large affected by "active evaporation" and "passive evaporation", the average smaller compared to river water and precipitation.(3) Based on the analysis of δ18O and δD relationship in different water bodies, first proposed the water line of the study area, the spring line and the field water line; found that precipitation was the most initial supply sources of other water bodies, supply relations of rivers and springs were the most frequent and close, precipitation and spring water were the main source of water supply; the field water was deviated from precipitation line to the farthest by multiple factors, with supply sources very complex; spring update was the slowest, with the residence time of the "old water" longer by evaporation violently.(4) Using the isotopic mixing ratio formula to estimate recharge rate of the different waters in the study area, the results showed that: The river with precipitation and spring water as the main supply source, spring accounted for 59.18%; the spring with field water and river water as the main supply source, river water accounted for 57.96%; precipitation with field water and river water, the field water accounted for 60.96%. On the seasonal differences, the changing difference of the water supply of river was the biggest, precipitation was the biggest source of river during the rainy season and water supply in the dry season was spring. On account of the contribution of local water vapor to precipitation, the water field was the largest contributor, accounting for 60.13 in the dry season, accounting for 68.21 in the rainy season. Thus, evaporation with an irreplaceable role of a large area of field water contributed to the local loop of water vapor and precipitation. Using IsoSource to calculate the contribution rate, the results showed that: the whole year, the field water was the largest contributor to spring water, and the river in the dry season; in the contrary, the spring in the rainy season was the biggest contributor to the field water, precipitation was the biggest contributor to the river all over the year; the interconversion of the field water and springs into each other made the precipitation keep the maximum after falling to the ground. |
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