Modeling The Impact Of Forest Pattern Management On Water Resources Considering Climate Change:Urumqi River Basin

Water resource is the key factor for maintenance and development of arid and semi-arid ecological environment.In addition,the forest ecosystem has drawn increase attention for its ecological service function in water resources conservation.So,it is an effective measure to maintain the sustainable development of Urumqi River basin,where belongs to oasis eco-environment,by using forest ecosystems to protect and optimize local water resources.In this paper,the forest management patters of the Tianshan spruce forest(Picea schrenkiana var.tianschanica)in the Urumqi River Basin were studied in order to obtain forest patterns for optimizing and conserving the water resources of the Urumqi River Basin under different future climate scenarios.The content of this paper is as follows: In the future climate scenarios,taking the middle and lower reaches of the Urumqi River in the northern slope of the Tianshan Mountains as the research area,the SWAT model is used as a research tool to simulate the hydrological process for the watershed.The obtained forest conditions in the basin are regard as the variables for forest management patterns simulations in the calibrated and validated SWAT model.And the water resources of Urumqi River basin under different forest patterns were quantified.Finally,the Picea schrenkiana var.tianschanica forest patterns that can increase the runoff adjust the water resources in the Urumqi River Basin are selected by analysis of the basin water resources quantification results.Base on the above research content,the results and possible innovations of this paper are as follows:(1)This paper models the middle and lower reaches of the Urumqi River based on the SWAT model,which simulated discharge process for 30 years(1983-2012).The applicability and model uncertainty of the SWAT model in Urumqi River basin were evaluated and quantified.SWAT model of the basin was constructed using the digital elevation model data,meteorology observation data,land cover data,and soil type data of the area.The model simulated monthly and daily steps discharge of Urumqi River.At monthly steps,both the NS and R2 of the SWAT model during the simulation period were 0.93,and the NS and R2 during the validation period were both greater than 0.88;at the daily steps,both the NS and R2 of the SWAT model during the simulation period were greater than 0.73.Both NS and R2 were above 0.65.For model uncertainty: SWAT model fitted more than 77% of observation data,and the uncertainty amount was about 0.82 at monthly steps during both calibration and validation periods.The SWAT model fitted more than 73% of observed data,and the uncertainty amount was about 1.23.(2)Calculate and determine the CN values of 11 runoff plots of the forest based on the SCS method.Using the slope-scale precipitation-runoff observation data,the runoff characteristics of the forest runoff plots under 11 stand conditions were quantified,and the factors that affected the CN values were analyzed.The CN values of the runoff plots with 11 stand conditions were all greater than 74.Through correlation analysis,the CN value of stand had a significantly correlation with its canopy density.(3)Based on parameterization of the runoff plots' runoff characteristics,the SWAT model and the 11 stand conditions of forest are coupled with to conduct the forest management pattern simulation.The CN values of the runoff plots of the Picea schrenkiana var.tianschanica forest with average antecedent soil moisture condition(AMC II)were used as the simulation parameters(CN2)in the SWAT model,and the water resources of the Urumqi River Basin for different forest management patterns were evaluated under future climate scenarios.The forest management patterns that optimized the water resources of the basin were inversed.The final forest management patterns optimized water resources in the Urumqi River Basin were constituted by artificial plantations.