| Human activity becomes one of the major driving forces of the global environmental changes.There are significant differences in response to global climate change in different regions.The response of hydrologic cycle to climate change is the most direct.The research on evolution regulation of hydrologic cycle under the influences of both climate change and human activity becomes the most important in the field of hydrologic cycle.Human activity has an effect on naturalrunoff mechanism through altering underlying surface factor,as well as on spatial and temporal distribution of water resources through directly getting water for inderstrial and agricultural use,constructing reservoirs and interregional water transfer.Human activity is one of the main driving forces for the evolution of hydrological cycle in the basin.Southwest China has the most karst area in the world among which the exposed area of karst surface reaches is up to 51×104km2.The broken terrain strong development of karst caused it to be the typical ecologically fragile region in China.Meanwhile,the social and economy is undeveloped.The rural population is large,so the contradiction between people and land is serious.As a typical ecologically fragile region,there is a significant difference of hydro-geological environment and hydrologic cycle contrary to non-karst area.Karst dynamic system is sensitive to external environmental changes.High-intensive human activity changes the hydrologic process in karst areas at different levels,which leads to the serious ecological environment problems such as water and soil loss and rocky desertification.Therefore,analyzing the influences of human activity on watershed hydrologic cycle in karst areas in Southwest China and knowing the influence mechanism of human activities on karst hydrologic cycle and water resources evolution are really important and meaningful to develop water resources,restore ecology and promote regional sustainable development.Based on the above,the paper selected the typical karst area--Houzhaihe Watershed,in Puding County,Guizhou Province as the study area.There are the most karst river observation data in Houzhaihe Watershed.The paper analyzed the major environmental changes and the characteristics of human activities in the watershed.The farmland area declined,and the forest and construction area increased from 1992 to 2004 in the watershed.There is a trend that the paddy field turned into the dry land and then the dry land turned into forest.The human activity mainly refers to large-scale migrants.The analysis sampling data of village in watershed showed that the total number of migrant workers is 11527 in 2014,which is about 29.5%of the total population of the watershed.Among the migrant workers,most of them are young adults;labor-force-transfer is affected by "push" factors and "pull" factors."Push" factors includes insufficient agricultural income,surplus labor force,children's education,and house building due to getting married."Pull" factors includes high income outside of the countryside and enough job opportunities.Natural disasters and ecology restoration have small effect on labor force transfer relatively.During agricultural production,there is a trend that labor-intensive paddy cultivation started to turn into low labor-intensive dry farming.Moreover,a large number of migrant workers caused arable abandonment.Using cumulative departure,sliding t test and MK non-parametric test,the paper discussed whether there is a abrupt change of climate from 1961 to 2014.The results showed that the changes of precipitation,temperature and ET0 are not abrupt change of climate but the climate remains the state of natural fluctuation.The paper analysed the variation of precipitation and runoff from 1987 to 2002 by using precipitation-runoff cumulative curve,which showed that there is a good correlation between runoff and precipitation in the study period without slope deviation.The analysis of possible driving forces that caused variation runoff in natural is mainly affected by climate-change;in terms of the human-activity,the variation is possibly affected by land use change,large-scale migrant workers.The paper analysed the characteristics of runoff yield and the leakage recharge relationship of some sites in basin.A flow calculation was built that applied for paddy fields,forest,dry land and constructive land based on the theory of stored-full runoff.In the paper,the confluence effect of non-covered sinkhole and covered sinkhole is simulated by using the water tank with single layer.The runoff yield is divided into overland flow,fast fractured flow and slow fractured flow.The concentration action of river channel and underground pipeline is simulated by GIUH,and each unit basin in watershed is simulated by the double water tank.In the end of the study,a semi-distributed hydrological model that applied for calculating precipitation runoff is established.The results of model calibration and verification show that the average deterministic coefficients of the model is 0.76,0.79 in the calibration period and teste period respectively,and the average relative error of total annual flow rate is 7.4%and 9.9%,respectively.It shows that the model simulates the daily rainfall runoff process of the watershed well.The research period is divided into non-migration human activity period and migration human activity period based on time point that mass migrants started in watershed.With model parameters and meteorological input conditions remaining the same,selecting different land use data under non-migration human activity period and migration human activity period as inputs,the model simulates the effects of different kinds of land use change to watershed runoff.The result shows that although the land-use change increases the total watershed runoff,it only has a small effect on it,the land use change under different human activity period has an increasing impact on runoff change.Meanwhile,the highly increased forest area has a redistributive and adjustive effect on seasonal distribution of watershed runoff.Forest weakens the flood peak in rainy seasons and increases runoff in non-rainy seasons.Moreover,the land use change has more effects on daily runoff change in rainy seasons than that in non-rainy seasons.Additionally,in 2014,the water footprint and daily water consumption of migrants in the watershed are accounted for 16.9%and 1.1%of the total average groundwater runoff from 1987 to 2002.The proportion about migrants daily water consumption of total underground runoff and the effect of land use change to runoff are of the same order of magnitude.The land use change,meteorological factor and potential evapotranspiration being the model input,the climate and the amount of water resource under land use condition of 2032 are calculated respectively,and the effect of the land use within the same term and migrants change to water resource is analyzed by using CA-Makov model,NCC/GU-WG 2.0 and Thornthwaite formula.The result shows that the change of future land use in watershed has a small impact on the total runoff,and the land use plays a role in flood dispelling and scanty compensation.In addition,the prediction shows that in 2034,the migrants' water footprint and the amount of daily-use water will be accounted for 17.9%and 1.42%of total runoff within the same period.Moreover,based on the specialties of ecology and socio-economy,the paper comes up with strategies of development of water-saving agriculture,increase of the livelihood diversification,and the perfection of basic water conservancy facilities in farmland.The paper builds the semi-distributed hydrological model that is used to calculate precipitation runoff in watershed during the analysis of the effects of human activity to water resources in watershed;in addition,the paper also considers the confluence effect of sinkholes in different landform types to the runoff.In the sight of migration-worker population changes in basin,the paper analyzes the labor migrants in watershed and the effect of the caused environmental changes on water resources.In the past,regarding to research of the effect of human-activity on hydrology and water resources in karst area,it mainly used land use changes as the research subject,the paper enriches this research field and it has certain innovations. |
PDF Full Text Request