| Baseflow is the main source of water supply in dry season,and is the main way of groundwater discharge.Baseflow separation is always the key and difficult point in the study of hydrology and ecological hydrology.However,there is not yet a universally recognized rational segmentation method because of regional difference.Compared with traditional methods,digital filtering method can be rapid and effective to segment baseflow from streamflow,which overcomes the defects of complex,low efficiency and strong subjectivity.What's more,the selection of data will directly affect the accuracy and reliability of the results,especially for the Huai River Basin(HRB),which is unable to get full data due to usually controlled by gate-dam.Therefore,it is of great importance to study the influence of the results of the baseflow separation in different dates and the influence of the dam on the data selection in the Huaihe basin.It also provides the key technical support for the rational allocation of water resources in HRB.The article used the Kalinin and digital filter method to segment baseflow from streamflow with the daily runoff series and monthly runoff from 2001 to 2014 in 9 key sections in the HRB,and compare differences.In this base,the 34 important control section long time runoff dates are used to calculate the baseflow in the whole HRB.Based on the study of the temporal and spatial distribution characteristics of the basic flow in the HRB,this paper makes a quantitative assessment of the contribution of surface groundwater recharge and discharge to surface water nitrogen pollution load in the HRB.The main research results are as follows:(1)Spatial distribution characteristics of base flow index based on Kalinin base flow estimationThe baseflow index of the site in Jialu River and the Ying River decreased from the north to the south,while which increased in Huaihe River from the west to the east.Compared with the results of digital filtering based flow segmentation,the results show that the error of the base flow index is less than 3%in the no controlled sites,and the error of base flow index is about 5%in the controlled sites.(2)The influence of different time precision runoff series on the result of baseflow segmentationThe daily runoff series and monthly runoff series can both be used in digital filtering method for base flow separation,when the daily runoff series used,it needs three or two times filtering to get better fitting results,which is better than the results when the monthly runoff series used with only one filter.But the segmentation results can be better characterize the actual hydrological process in some extent(3)Optimize the selection of datasIf datas permits:We prefer the daily runoff series than the the monthly runoff series in no controlled sites.In controlled sites,however,hydrological data of flood discharge process is firstly chosen for hydrology method,followed by digital base flow separation with the monthly runoff series.If the data is not allowed,it is necessary to collect more complete monthly runoff series data for digital filtering based on the flow segmentation.(4)Characteristics of temporal and spatial distribution of base flow in Huaihe River BasinIn space,the basic flow model of the Huaihe river system shows the characteristics of the south of the main stream of Huaihe River,which is higher than that of the north of Huaihe River,the lower reaches of the upper reaches to the middle reaches of the river,and the hilly area is generally higher than the plain area.In time,the department of Surabaya Yishu river base annual distribution inhomogeneity is higher than that of the Huaihe river.The uneven distribution of the internal temporal distribution of the river system in the Huaihe river system shows an upward trend from the upper reaches to the middle reaches.The base flow of each control section is mainly concentrated in the flood season(4-9 months),and the base flow rate exceeds the annual base flow rate of 50%.(5)Quantitative assessment of surface groundwater recharge and discharge and the contribution of groundwater to surface water nitrogen pollution load in Huaihe BasinIn the 91.5%area of Huaihe River Basin,in the dry season and low water year,the river base flow can reach more than 40%of the total runoff,with an average annual contribution of about 26.5%.The total nitrogen load of surface water recharge is about 46 thousand and 500 t/a,which accounts for about 40%of the nitrogen flux.In the north and south ends of the supply of nitrogen pollutants load is small,the basin above of the Bengbu gate area and Yishuhe River supply large amount of nitrogen pollutants load. |
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