黄土高原丘陵区小流域地下水补给特征

地下水补给量反映了含水层的可更新能力，是地下水资源管理与合理开发利用的关键参数之一。为定量研究黄土高原丘陵沟壑区小流域地下水的补给特征，基于岔巴沟流域上游、中游、下游3个水文站1959-1969年降水与日径流观测资料，通过退水分析法估算了流域地下水补给量，并分析了与降水量和基流量的关系及其在年内的补给变化过程。结果表明：岔巴沟流域年平均基流量为13.09 mm·a^-1，更新时间为124 d，补给量为11.46 mm·a^-1，降水入渗补给率为0.025，基流补给率为0.89。从上游到下游地下水补给量与入渗补给率逐渐增大，且上游与下游之间有显著差异（P<0.05）；基流补给率逐渐减小，各集水区之间差异均显著。地下水补给量与降水量呈线性正相关（R²>0.40），在下游集水区内随降水量变化的增幅较大。基流量与降水量也呈正相关关系（R²>0.77），干流基流80%以上源于降水补给转化。以5月份为节点可将地下水补给过程分为"一次补给"和"二次补给"2个主要阶段，其分别占全年总补给量约30%和70%，并且"二次补给"是造成岔巴沟流域不同集水区地下水补给量差异的主要阶段，并且为无资料地区小流域地下水资源的评价提供借鉴。

Characteristics of groundwater recharge of small watershed in hilly and gully region of the Loess Plateau

It has serious water resources shortage and soil erosion in hilly and gully region of the Loess Plateau,China.The groundwater has become an important water source for vegetation breeding and human life as well as the production in the arid and semi-arid areas.Groundwater recharge refers to the process that the aquifers obtain water from the outside,reflecting the renewable capacity of aquifers.It is one of the key parameters in groundwater resource management,development and utilization.It is of significance to study quantitatively the correlation between groundwater recharge and precipitation,recharge and base flow,and explore the characteristics of temporal and spatial variation of groundwater recharge in small watershed of the loess hilly region.This paper was based on the observation data of daily precipitation and runoff from three hydrologic stations in the period from 1959 to 1969.These stations are located in the upper,mid and downstream of the Chabagou Watershed,respectively.The groundwater recharge was estimated by the method of recession curve method.The results showed that the average annual precipitation and runoff were 489.00 mm and 75.17 m³·s^-1,respectively.The base flow and base flow recharging index were 13.09 mm and 0.89,respectively.The groundwater recharge and recharging index were 11.45 mm and 0.03,respectively,and the residence time was 124 d.The groundwater recharge had been gradually and significantly increased from upstream to downstream (P<0.05).But there weren't significant difference between the upstream and the midstream,the midstream and downstream (P>0.05).The base flow recharging index has been decreased gradually from upstream to downstream,which has significant difference between different catchments.There was linearly positive correlation between groundwater recharge and precipitation (R²>0.40),and the Pearson correlation coefficient was 0.69.And the amplitude of increase of groundwater recharge with precipitation in downstream catchment was the largest.The base flow and precipitation were also positively correlated (R²>0.77),and the Pearson coefficient was above 0.80.More than 80% of the base flow in main stream is derived from the transformation of precipitation.The groundwater recharge process can be divided into two main stages in May,namely the "first recharge" and the "second recharge".The supplementary amount of the "first recharge" and the "second recharge" of each catchment in the Chabagou Watershed were as follows:upstream (3.02,5.58 mm) < midstream (3.76,8.84 mm) < downstream (4.75,11.54 mm).They accounted for about 30% and 70% of the annual total recharge,respectively.And the "second recharge" is the main stage of the groundwater recharge causing difference in each catchment.This study could provide reference for the groundwater resources evaluation in the small watershed without recorded data.