Study On Water Cycle Mechanism And Synergetic Evolution Between Water Cycle And Oasis In Heihe River Basin

Based on the data of river flow monitoring of the G312 Heihe Bridge and each hydrological station and the groundwater high frequency monitoring, this paper studied the infiltration mechanism of river and spring overflow in binary mode by using various methods, River infiltration and spring overflow over the years. The cross-wavelet method was used to reveal the interaction between river and groundwater level, groundwater level and overflow. The experimental field of unsaturated zone tracer was established in the middle reaches of the Heihe River, and the infiltration coefficient of precipitation and the infiltration coefficient of irrigation water were obtained quantitatively. The spatial distribution characteristics of artificial oasis and natural oasis in Heihe River mainstream was interpreted by remote sensing technology. The evolvement process of Oasis in Heihe River Basin since the Quaternary and the Han Dynasty and the past 60 years has been explored. The exponential weighting method was used to quantitatively express the intensity of human activities in the Heihe River basin since the Han Dynasty and to explore the driving mechanism of the evolution of the Heihe oasis since the Han Dynasty. Based on the water resources system structure of the Middle Reaches of the Heihe River, the goal planning model is constructed and the main control factors of the main channel discharge in the Heihe River are obtained. The objective programming prediction and analysis are carried out with two schemes of different water quantity and different irrigation quota. And the following understanding:1) The main stream of the Heihe River infiltration occurred in the middle reaches of the Ying River Gap-G312 Heihe River Bridge section (conversion section) and just below the river gorge. The relationship between water infiltration quantity and river seepage is a clear function. The annual water infiltration of Yingluowa-G312 Heihe Bridge is 5.4×108m3, and the annual average amount of water inflow from 2001 to 2013 is 6.60×108m3, which is 2.08 ×108m3 higher than that of 1981-1999. The annual average of river seepage is 3.485×108m3 from the Zhengyixia Gorge to the Langxinshan Gorge, and the average annual of river seepage from 2001 to 2013 is 3.51×108m3, which is 0.54×108m3 higher than that from 1990 to 1999.2) The tracer experiment of artificial had been established in the Pingyuanbao of Zhangye, by using NaBr as tracer and taking the hydrology year as the step length. Through dosing, sampling, testing and data analysis, the results showed that the recharge coefficient of infiltration is 0.09, and 0.23 for recharge coefficient of dripirrigation, and 0.18 for recharge coefficient of flood irrigation, the recharge coefficient in dripirrigation areas is greater than flood irrigation areas, and greater than infiltration areas.3) The spring overflows in Heihe main stream occurs from the G312 Heihe Bridge(the Conversion Section) to the Zhengyixia Gorge. The spring overflow is very uneven along the river, and the spring overflow from the conversion section to Tangwan reach is the most abundant. The average of the spring overflow calculated is 12.60×108m3. from 1956 to 2013, which is the alternation of abundance, flatness and dryness.4) The cross-wavelet analysis was used to analyze the correlation and time-delay characteristics of river infiltration, spring overflow and groundwater level, and groundwater level between aquifers. The results show that the longer the distance from the Heihe River, the longer the water table lags behind the river infiltration. The greater the distance from the Heihe River, the longer the lag time of the overflow relative to the water level. The spring overflow lagged behind the river infiltration of 3.54-4.46 years.5) From a spatial point of view, the Heihe oasis is mainly located on both sides of the tributary of the Heihe River and spreads along the rivers and channels. From the point of view of the time domain, the evolution of the Heihe artificial oasis shows a decreasing trend-a slow increase-a sharp increase. From the Han Dynasty to the mid Qing Dynasty, the intensity of human activities is weak, natural condition is the main driving force of oasis, since the mid Qing Dynasty, the intensity of human activities is increasing, especially in the past 60 years, the intensity of human activities is increasing rapidly, has become the main driving force of the evolution of oasis.6) Based on the structure of water resources system, this paper constructs the target programming model of middle reaches Zhanglingao irrigation areas, and concludes that the change of river flow in Heihe main stream is mainly influenced by Yingluoxia Gorge water quantity, channel diversion amount and spring overflow of the G312 Heihe Bridge-Tangwan reach. Through the simulation analysis of the two schemes of different water quantity and different irrigation quota, it is concluded that the water saving technology in the middle reaches irrigation area is one of the important and effective ways to protect the middle reaches of artificial oasis and Zhengyixia discharge amount.