Research On Landscape Pattern And The Responses Of The Runoff Variation In The Upstream Of Manas River Basin During The Last 40 Years

In the recent decades, landscape dynamic change and the runoff change has attracted a wide range of attention. Watershed runoff changes with the change of landscape pattern, making a study of the relationships between the landscape dynamics and the runoff is very important to solve rational use of the water resources, environmental and ecological issues.In this paper, upper Manasi river basin was selected for case study, first of all, based on remote sensing image and DEM data, with the use of remote sensing technology and geographic information system, through the remote sensing image interpretation, the types of landscape dynamic and spatial structure analysis, studies the landscape pattern change of Manasi river basin since 1976; Then, with four phase of the land use chart, DEM, soil, runoff and meteorological data as data sources, constructing the Manasi river basin monthly scale SWAT hydrological models, and simulated 1976, 1989, 2000 and 2014, four kinds of land use situation of hydrological process by using the model; Lastly, based on the changes of landscape structure and the simulation results of the SWAT model, through correlation analysis, to explore the dynamic changes in the watershed landscape pattern and the relationship between surface runoff. The conclusion is as follows:1. From 1976 to 2014, characteristics of watershed landscape pattern change is significant. Grassland has increased persistently, glacier, unused land and forest land’s area showed a trend of volatility decreases. Basin of change magnitude of land use overall present to strengthen the weakened, the characteristics of the conversion process(1989-2000) is the most actively. On the landscape type level, the grassland is given priority to with into the process, the transfer process is slow; Unused land transfer process is active; Glacier into process tend to be more active, its transfer process by active flatten out. Landscape shape is complicated, showed a trend of fragmentation and connectivity has slightly lower, unbalance distribution.2. Build the SWAT model has certain applicability of manasi river valley. This paper established the SWAT hydrological model of the basin, and the monthly runoff is simulated. Then, based on SWAT–CUP’s SUFI-2 calibration algorithm parameters, thus the model calibration and verification. Calibration period of the fit of the simulated values and measured values, R2 is 0.78, NS is 0.69; The validation period, R2 decreased to 0.76, NS dropped to 0.65, but overall the calibration and validation of various assessment indexes meet the evaluation criteria.3. Nearly 50 years, runoff on the whole is a linear trend of slow growth in the basin, the distribution of years is: less in the spring and winter, summer fall more features. From 1976 to 2014, as the change of land use, runoff with different degree of change in the study area. In the Watershed scales, unused land’s area has increased, making increased runoff, and grassland has increased, decrease of the runoff; In addition to Shannon evenness index correlation with water rate is bigger, the rest of the landscape types basically, the absolute value of correlation coefficient is less than 0.5, and only in some periods showed significant, basin shape tend to be more complex and various landscape types distribution in disequilibrium, the basin water cycle is accelerated, can lead to increased runoff, and the basin together degree of various landscape types increases, leads to reduced run-off.