Study On Ecological Water Use In Qaidam Basin

With the rapid development of social economy,the total water consumption is growing rapidly,which result in the shortage of water resources in Qaidam basin and it is a serious threat to the sustainable development of regional social economy.In this study,datas of water resources,vegetation and soil and water conservation in Qaidam basin were collected as the basis,then the concept and content of ecological water use was defined through analyzing and predicting the situation of water resources in the Qaidam basin,and then the ecological regionalization of Qaidam basin was carried out based on the distribution of river basin and the administrative division.According to the theory of plant evapotranspiration and the equation of water balance,the water consumption of the vegetation in the basin was calculated through datas of vegetation transpiration model and vegetation coefficient achieved from the experiment,then the ecological water consumption in the lake wetland and the river course can be obtained by the method of quota and empirical formula,and then the ecological water consumption in the Qaidam basin can be calculated.The ecological water use coefficient Cu and the ecological water use modulus Mu were used to analyze the present situation of ecological water use in the Qaidam basin,and the demand of ecological water use in the basin was then analyzed and predicted.The results can be summarized as follows:(1)The analysis of water resource situation showed;taking the year of 1994 as the first year in the time sequence,the available surface water(S)in the basin and the year in the sequence(x)are satisfied with the equation of S=0.0 123x2-0.067x+5.4516(R2=0.73),the available ground water(G)and the year in the sequence(x)are satisfied with the equation of G=0.4872x+0.5208(R2=0.82).Then it can be inferred that the available surface water supply will be 12.36 × 108m3 in 2020,19.48 ×108m3 in 2030,and the available ground water supply will be 2.71 × 108m3 in 2020,3.19×108m3 in 2030.And the water supply and consumption projections indicated that the supply and the consumption in Qaidam basin was basically equal at present,while it would experience a negative 0.87 × 108m3 in 20 20,3.05 × 108m3 in 2030.(2)Granier thermal diffusion method was used to observe and calculate the canopy transpiration rate(Ec).Results show that the solar radiation(Rs)and vapor pressure deficit(VPD)is the dominant environmental factors for Ec.The response of Ec to Rs and VPD shows different patterns in morning and the afternoon,and there was a clear hysteresis loop demonstrated in the correlation between Ec and VPD.The dimensionless decoupling coefficient(Ω)showed that the transpiration of main tree species in Qaidam basin was strongly controlled by the canopy conductance,and the canopy conductance was highly coupled to the atmosphere,while was affected more significantly by VPD,Rs and T,the correlation coefficient was VPD>RS>T.(3)Combined the stem sap flow with the meteorological data,and the diurnal variation of canopy transpiration in the Qaidam Basin can be simulated on the basis of the Penman-Monteith equation and Jarvis-type model taking the delay effect into consideration.The results showed that the Jarvis model can obtain good simulation results to Qing Yang and seabuckthorn,the determination coefficient of the model can be more than 0.8,and the relative errors are within 25%(Qing Yang)and 12%(sea buckthorn),the simulated values and measured values are in good consistency.What’s more,the determination coefficient value of the Jarvis model would be higher taking the delay effect into consideration,and the accuracy of the simulation would improve 6%.This method has a higher precision than simulating the process of diurnal variation of transpiration by calculating the stomatal resistance for extending the scale using the Li-1600 steady state stomatal apparatus.(4)The total amount of ecological water use was 111.14×108m3 at present based on the theory and method above,among which the subject is the consumption of vegetation with the value of 63.21%of the total ecological water consumption.The amount of consumptive ecological water use in the basin was 107.97 × 108m3,of which the amount of consumptive ecological water use of rainfall was 70.25 × 108m3 and the amount of runoff consumptive ecological water use was 37.72 × 108m3,and the amount of the non-consumptive ecological water use was 3.17×108m3.(5)In terms of the space distribution of ecological water use,the ecological water consumption of a region depend on the distribution of vegetation and river to a great extent.The amount of ecological water use in Qaidam East(67.95 × 108m3)was significantly higher than that in the west(43.19 × 108m3),and the Mu of the Qaidam West was significantly lower than that of Qaidam East,which indicates that the forest coverage in the Qaidam East is high and the ecological environment is good,while in the West Qaidam,the forest coverage is low to some extent,and the ecological construction needs to be intensified.And it can be seen in the aspect of administrative divisions that the ecological water use coefficient is of the highest value in Golmud in the basin,and the ecological water use modulus is of a relatively less value,which indicates that the vegetation coverage is high but the water consumption for vegetation is relatively less.The ecological water use coefficient and modulus is relatively higher in Wulan and Dulan districts,which indicates that the coverage rate is much higher,and the ecological construction is more advanced.While the Cu and Mu is the lowest in Haixi,Qaidam West,which indicates that the vegetation coverage rate is much lower,and there is great space for ecological development.(6)Take the year 2020 as an example,the demand of ecological water consumption can be predicted and the equation of water balance can be analyzed from the aspects of abundant water year,flat water year and dry year,thus the ecological water use in the wetland of Qaidam basin can be standard quantified,the results show that the ecological water consumption of the lake and wetland in the basin were 41.56 X 108m3,17.50×108m3 and 11.11 × 108m3,respectively in the year of abundant water,flat water year and dry year.That is to say,we must make sure that the basic basin lake wetland ecological water consumption is 11.11 × 108m3.