渭河平原地下水分布特征与环境同位素研究──以白杨水源地为例

A STUDY ON THE DISTRIBUTION AND ENVIROUNMENT ISOTOPEOF UNDERGROUND WATER IN THE WEIHE PLAIN ENVIDENCE FROM BAIYANG SOURCE REGION OF WATER

白杨水源地座落在渭河下游重镇——渭南市西北约５ｋｍ处，为谓河冲积平原的一部分。区内第四纪松散堆积物巨厚，地形平坦，降水充沛，地表水丰富，为地下水储存提供了良好的空间。按含水介质的埋藏条件可划分为潜水、浅层承压水、中层承压水和深层承压水４个含水岩组。为了进一步研究地下水的补给形成机制、储存运移过程、排泄开采条件，本文结合环境同位素（包括￣（１４）Ｃ、￣（１３）Ｃ、￣３Ｈ、Ｄ和￣（１８）Ｏ）对水源地地下水年龄、地下水运动速率以及一些水文地质参数进行研究和探讨。而同位素测定表明：水源地潜水为现代水，￣３Ｈ含量较高，河水补给量占１／２左右；中、深层承压水补给途径较远，￣（１４）Ｃ年龄分别在距今０．４－０．５Ｍａ和０．８－０．９Ｍａ左右；δＤ和δ￣（１８）Ｏ值变化不大，说明它们主要来源于大气降水补给。

Weihe river,the largest tributary of Yellow river,is the main trunk river of river system in thecentral Shaanxi Plain.Weihe river plain is situated in the middle sector , Shaanxi province.It was resulting from longevolution of Weihe river system. It is a Cenozoic graben basic with considerable thich Cenozoicdeposits. The south and north borders are respectively bounded by Qinling Mountains and NorthMountains,Which extends about 300km in length from Baoji on the west to Tongguan on east,Shaanxi province where it meet Yellow river.Weihe river has an asymmetric drainage.Its north bank tributaries present a dendritic drainage,whereas south tributaries a featherllke drainage.Baiyang source region of water is located at the flood plain-terrace I on the south bank of Weiheriver, near the Linghe- Weihe rivers junction at Baiyang country in Weinan county , covering an areaabout 10km￣2. It is a source region of water of polylaminate texture consisting of quaternary alluvionsand lake deposits, containg a phreatic water,a shallow,a middle and a deep confined water four aquifers。Phreatic water is maily supplied by lateral influent seepage of river,and infiltration ofprecipitated water.Being exploited,it is mainly supplied by lateral influent seepage of river and run-off.Confined water is mainly supplied by underground water flow from west side of explorationregion,As phreatic table is a little higher than shallow confined water, and middle confined waterhigner than deep confined water, there is an overwash relationship between them,Shallow confinedwater and phreatic water in some section of seurce region of water turn into saline water.It resultfrom gelolgical environment and hydrogeochemical environment characters of the storage andmigration of underground water at the source region of water。Feeding water from Weihe river makes up abeut 1/2 of feeding phreatic water at the Baiyangseurce region of water,Water-bearing strata have a better pormeabiling,and water exchange is bettertoo,The water preduction of a single well is more than 5 0 00m￣3/d.Middle and deep confined waterwas buried at a deeper depth,with feeder channel being longer,and the age of underground waterbeing more than 4 000-8000 years.B.P.