Researches On The Effects Of Land Cover Change Of Typical Basin In Sanjiang Plain On Water Resources

As the key composing elements of physical geographical system, water resources and soil resources are interrelated, interpenetrated, and mutually restricted. Whether water resources can be utilized rationally will have a direct effect on the productivity of soil resources while the utilization/cover change of soil resources will have a great impact on each link of hydrological cycle. Sanjiang plain is an important commodity grain production base of our country, a typical representative of Northeast Black Soil, and the key to thousands of tons of grain development strategic target of Heilongjiang Province and food safety of our country. The research region is Hongxinglong reclamation area (the Baoqing River Basin), located in the center of Sanjiang plain with highly developed modernization of agriculture and gradually accelerated speed of urbanization; the research contents involve the effects of human activity and soil utilization/cover on water resources, and land utility models suitable for water requirement of ecological river basin. The contents of this research are helpful for further studies on the variation law of hydrological characteristics in urbanization areas under new circumstances, providing a decision-making basis for regional flood control and disaster mitigation and rational utilization of water and soil resources, offering great supports to the local ecological construction and sustained economic development, and supplying effective references to the rational utilization of water and soil resources in Northeast Black Soil Developing Area and mitigation of flood and drought disasters.To have a better research on hydrological response of different land utilization/cover conditions, this dissertation established grid-based distributed hydrological models suitable for cold regions with the help of programming technologies such as GIS, data base, Matlab, etc. With the support from data of weather, topography, vegetation, soil, etc., using the measured data and its simulation results to verify, using grid-based distribu(?)ted hydrological model of cold regions to simulate the effects of 7 kinds of land utilization/cover circumstances in the Baoqing River Basin on runoff flow, calculating ecological water requirement in research areas, and simulating the land utilization/ cover models suitable for ecological sustainable development, the main results and conclusions are as follows:Establishment of grid-based distributed hydrological models. With the application of data from weather, precipitation, DEM, NDVI, land cover, etc., the S-W model and SAC model is introduced to establish the evapotranspiration module and the runoff module, and the bus module and snow cover and snowmelt module are coupled to construct grid-based distributed hydrological models, making the best use of the present daily precipitation, flow and conventional meteorological data to continuously stimulate daily potential evapotranspiration, actual evapotranspiration, soil moisture and runoff. During the stimulation of daily flow of Baoqing River Basin located in the cold region, the coefficient of determination is high, well reproducing the daily flow process of this basin, and model calculating results can provide data basis for researches on problems such as ecological water requirement. Verification of grid-based distributed hydrological models. Apply 2000-2001 measured data of annual runoff to verify. The simulated and measured values are are in good conformity, respectively 0.7619, 0.6044,0.7027 in the deterministic coefficient of rate of regular 1997-1999 years, and respectively 0.7845,0.5286 in the deterministic coefficient of validation period of 2000-2001 years, and the average deterministic coefficient of the 5 years is 0.7329. According to "the norms of hydrological forecast" promulgated by the Ministry of water resources, except for 2001, the simulation value of this model reached B precision grade in different years and 5 years in a row, and can better reproduce the measured flow process of Baoqing section.Model in flow’s response to land utility change/cover. Considering many factors including spatial distribution of land cover, proportion of various land cover, and the national policy on reforesting the cultivated lands, using Baoqing land cover as control scenario, setting up a variety of land use/cover change scenarios, daily basin flow under different scenarios is simulated based on the established grid-based distributed hydrological model.Calculation of regional ecological water demand. It is recommended that river ecological flow obtained by R2CROSS method is viewed as related river’s ecological water threshold value, for better protecting river ecological system and maintaining the stabilization of river ecological system. By comparing the calculation result of ecological water demand of the 5 rivers within Hongxinglong reclamation area with R2CROSS method and Tennant method (30% flow), it can be concluded that it is reasonable of the Tennant method to choose 30% of the average flow as related river’s ecological flow. With the absence of relevant data by using the improved R2CROSS method for calculating the river ecological flow, Tennant method of 30% of the average history flow can be used as ecological water use threshold values.