Joint Simulation And Prediction Of Surface Water - Groundwater In Dagu River Basin Under Changing Environment

In recent years, the impact of climate change on water resources will become the dominant.Because of the problems caused by climate change and water quality change of the temporaland spatial distribution of water resources, it has become the focus of attention of scientists andgovernments in the word, whether it has sufficient available water resources will be anenormous challenge to the people.The change of the environment in this study is mainly reflected in the two main factors ofclimate change and human activities. Along with the change of climate and local environment,the problem of water resources in Dagu river basin is becoming more and more serious, mainlyfor the water resources demand increases sharply,falling water level,seawater intrusion, soilsalinization,different degrees of water pollution, less water, drought drying up, ecologicaldeterioration along the river and so on.Watershed as a human activity unit most closely relatedto the natural water cycle,how to realize the reasonable development of water resources andefficient use, how to better manage the water environment protection and rational allocation ofwater resources has become the major problem to be solved.Study and simulation of moving process of surface water and groundwater has attracted theattention of domestic and foreign literature and hydrological geology experts and scholars.Throughout the researches on surface water and groundwater, scholars focus on the two dividedinto two relatively independent field research for a long time.There is a close relation of surfacewater and groundwater in nature, in order to understand the effects of climate change andhunman activitieson water cycle process, it is necessary to study surface water and groundwateras a whole system.In this study, we take Dagu river comprehensive treatment project that strongly impact ofhuman activities on the evolution of basin water resources as a starting point, based on thestudy of Dagu river basin water resources in time and space variation on the law, study theinteraction and affected relationship of climatic factors-human activity-hydrological factors-surface water–groundwater under the changes of the environment, using a hydrological modelpopular at home and abroad to study basin surface water and groundwater in the mainland jointsimulation,the quantitative method of noparametric statistics analysis influence of environment change on watershed hydrology and water resources, in order to provide a theoretical referencefor the future water resources rational allocation and efficient use of available.The maincontents and conclusions are as follows:1. The trend change of hydrometeorological factors during the past50years in basinBased on nearly50years of meteorological and hydrological data of representativesignificance meteorological station and hydrological station, mainly selected temperature,rainfall, evaporation, runoff and other meteorological factors and hydrological factors as theresearch object, the main use of the Spearman order correlation test method, Daniel test, linearregression, moving average trend test method and other methods analyzes the changing trend ofhydrological and meteorological elements, the main use of Mann-Kendall test, the sliding t-test,YAMAMOTO test signal to noise ratio (SNR) and other analytical methods to identifymutations point, analyzes the hydrological and meteorological elements trends point mutations,using wavelet analysis method rainfall cycle were analyzed. The results show that: the past50years, Dagu river basin warming trend is consistent with the general trend of the nationalclimate change at0.05confidence level, the average temperature was fluctuating over timeupward trend significantly, the average annual temperature mutations mainly after1985year;the annual precipitation in the watershed fluctuate over time downward trend, but the declinewas not significant, and the point mutations of annual precipitation occurs between1975-1985year, precipitation variability occurs relatively large; the annual evaporation fluctuate over timeshowed a downward trend in the basin, and the decline is significant. Runoff overall wasdecreasing trend over time, by sliding the t-test and the SNR that mutation point in the studyarea annual runoff occurs mainly in1965-1968year, between1975-1983year, precipitationmutation lead to annual runoff mutation.2. The surface runoff based on SWAT model simulation analysis in Dagu river basinThe basic data required for the construction of SWAT model of building space and attributedatabase are analyzed and pretreatment.It focus on land use data and soil type data of spatialdatabase pretreatment, the related parameters of meteorological and soil database in attributedatabase are calculated. On the basis of previous studies on the construction of attributedatabase of soil erosion and soil particles conversion methods achieve improved. With the helpof Arc SWAT by Arc GIS10.1the entire study area divided into37sub-basins,445hydrological response units.Using of canzhi hydrological station and nancun hydrological station measured annualrunoff data calibration and validation the model, we selected2000-2007year as the calibrationperiod of the model;2008-2010year is verify period of the model. The simulation value andmeasured value of the relative error Re were0.4%and0.25%, the coefficient of determinationR2were0.998and0.945; Nash-Suttcliffe (Ens) coefficients were0.982and0.927. Use of2003-2010year measured month runoff data calibration and validation the model, selected2003-2005year as the calibration period of the model;2008-2010year as the verification stageof the model, the relative error of calibration model were5.64%and9.8%, the Ens coefficientswere0.98and0.91, the coefficient of determination R2were0.98and0.94.After the calibration of the model, the four land use/cover data into SWAT model, thesimulation analysis the change of runoff under different land use types, the results show thatsurface runoff in2010year increased by26.1m3/s constract of runoff in1990year, the rate ofincrease is relatively large.The effects of environment change on runoff is more obvious.3. Numerical simulation of groundwater based on Visual MODFLOW in Dagu river basinThrough the analysis of spatial and temporal dynamic changes of groundwater level and therecharge, runoff and discharge patterns of groundwater, and grasp the distribution ofgroundwater flow field of Dagu river basin.According to the hydrogeological conditions in thestudy area, determine the composition of the regional aquifer system, the establishment of ahydrogeological conceptual model of the study area. Selected the first day of January in2000year to the thirty-one day of December in2007year for the recognition stage of the model; thefirst day of January in2008year to the thirty-one day of December in2010year for therecognition validation phase of the model. The water level fit by measured and calculating inmodel identification and validation stage, the water level observations values and modelcalculations values fitting error is smaller than the observed value of the number of wells0.5mmore than75%of the total number of wells; and the number of observation wells less than1mmore than93%of the total number of wells. After the parameters of the model identificationand verification, show that numerical groundwater model built to be reliable, laid thefoundation for the joint simulation of surface water and groundwater.4. The surface water and groundwater joint simulation based on SWAT and Visual MOFLOW With the help of Arc GIS, realizing the conversion of the whole basin between HRUwhich isSWAT output and CELLwhich is in Visual MODFLOW.The groundwater recharge and phreaticwater evaporation of the result of the SWAT model introduce into the correspondinggroundwater recharge module RCH and diving evaporation sub-module EVT of VisualMODFLOW, realizing joint simulation of surface water and groundwater.On this basis, throughtwo ways to quantitiative explore the effect of joint simulation, the results show that:the surfacewater and groundwater amount of joint simulation respective contrast with the surface wateramountof SWAT simulation and groundwater amount of Visual MODFLOW simulation,throughthe error analysis,the quantitative analyzed effects of combined simulation of surface andgroundwater,the error is small between the surface and groundwater single simulation and thecombined simulation,the effect of joint simulation is good;the groundwater level by means ofsurface water and groundwater of joint simulation,selected representive wells measured waterlevel in the study areas,carries on the contrast analysis,the results show that the simulationresults and the measured value of the correlation coefficient R2is0.898,the fitting effect isgood.5. The prediction of surface runoff and groundwater based on SRES modelBased on SRES model and Dagu watershed years of meteorological data, using land use/cover data in2010year and meteorological data in2013year, different combinations ofprecipitation and temperature prediction, the results show: there was a positive correlationbetween the rainfall and runoff, runoff was negatively correlated with air temperature, thefuture of precipitation is the main factor affecting runoff, temperature effect is relatively small.The study assumes that all climate scenarios, so that the largest increase in runoff is P increasedby20%, T reduce4oC, which is the future of Dagu runoff increased the most favorablecombination of scenarios.Lead to runoff decreased most scenarios is P reduce by20%, Tincreased4oC, which is the future runoff most unfavorable combination in Dagu basin.Theevaporation is not change, the precipitation increase,the level of groundwater is rising, Theprecipitation is not change, the evaporation increase,the level of groundwater is decreasing,theeffect of precipitation on changing the level of groundwater is stronger than the evaporation.