| Effect of Climate Change and Human Activities on groundwater recharge is one of the important scientific issues for sustainable development and management of water resources. As a vital part of evaluation of groundwater resources, groundwater recharge has a direct influence on the extent of development and utilization of groundwater resources in an area, so its estimation has both important theoretical and realistic significances.Generally, groundwater recharge rate is not constant, it is affected by many factors, mainly natural and human factors. Because of large spatial and temporal variation, the direct measurement of groundwater recharge rate is hardly possible, so it is very difficult to reconstruct the groundwater recharge history and estimate the changes of recharge rate. Three methods, physical methods,tracer approaches and numerical modeling, are usually used to estimate groundwater recharge: These methods provide different limitations,applicability(range of spatial and temporal scales) and ratings. This paper discussed the changes of the groundwater recharge rate by using environmental tracers, and compared the results with those obtained from multiple tracers.The purpose of this paper is to estimate groundwater recharge rate,reconstruct the groundwater recharge rate,identify the different sources of recharge and recharge mechanisms,discuss the changes of natural recharge rate and distinguish the amount of natural and artificial recharge, which can provide a theoretical basis for the estimation of recharge rate and rational development and utilization of groundwater resources.This paper mainly focuses on research in the following aspects: (1) the distribution character of environmental tracers in aquifer; (2) the structure of groundwater age and total groundwater recharge rate in the aquifer; (3) the natural groundwater recharge history and average natural groundwater recharge rate; (4) distinguish the different component of groundwater recharge and the influence of human activity. The key scientific problems of these are reconstruction of groundwater recharge in unsaturated zone and distinguish for the groundwater mechanisms.Choosing ShiJiazhuang area which located in the upper part of Hutuo River alluvial-proluvial fan as a typical region, this paper discussed the changes of groundwater recharge rate in the Hutuo river alluvial-proluvial fan by environmental tracers, isotope hydrological method and conventional hydrogeological methods, on the basis of the hydrochemical and isotopic information that conserved in the unsaturated zone and aquifer. Through research, the following conclusion can be suggested:(1) In this area, the main source of groundwater recharge is vertical infiltration, and there is a certain degree of lateral flow. The average lateral recharge rate in the depression cone near ShiJiazhuang is different from the piedmont plain.(2)The average natural groundwater recharge rate calculated by environmental tracers in unsaturated zone is 0.089m/a from 1971 to 1998. The natural recharge rate shows a fluctuant trend of ups and downs in the past 27a, it tends to decrease during 1974-1977, 1985-1988, 1990-1997, while during 1971-1974, 1977-1985, 1988-1990, it has a little increase. The changes of groundwater recharge rate is mainly influenced by the changes of precipitation, and lags behind it by comparing the changes of groundwater recharge rate with precipitation and groundwater level.(3)The range of groundwater age in shallow groundwater is 0～36a. The average total groundwater recharge rate is 0.228～0.304m/a calculated by ~3H-~3He method. The average lateral Darcy velocity in the depression cone near ShiJiazhuang is 0.349～0.465m/d, and in the piedmont plain is 0.204～0.272m/d, these results are similar with the results that calculated by water balance method.
|
PDF Full Text Request