典型喀斯特峰丛洼地降雨特性及浅层地下水埋深变化特征

以桂西北典型喀斯特峰丛洼地连续6年(2006-2011年)的降雨资料和浅层地下水埋深的实测数据为基础,分析研究区降雨特性和浅层地下水的变化特征。结果表明:研究区虽然降雨丰富,但年际变化大且季节分布不均。除2008年为丰水年(1 979.8mm)、2011年为欠水年(1 127.3mm)外,其余年份均为平水年(1 302.7～1 510.1mm);降雨主要集中在4-9月(雨季),其占全年降雨量的比例表现为平水年(82.4%～85.1%)>丰水年(74.7%)>欠水年(65.9%);有效降雨次数、累计有效降雨量和最大日降雨量有随年降雨量增加而增加的趋势;60min雨强大于16mm/h的降雨和最大日降雨量的最大值分别为67.4mm/h和152.9mm,主要集中在5-8月;年内50%以上为无雨天气,其中,平均出现26次连续3d以上,5次连续10d以上的无雨天气,不同水文年差异不大,且多发生在旱季,年降雨量并未因无雨天数的增加而降低。雨季地下水埋深约为2m,旱季大于3m,呈中等变异,且雨季大于旱季;地下水埋深年内随降雨呈单峰型分布,但峰值维持时间短,前期降雨对地下水位的涨落有重要影响。

Variation of Precipitation Characteristics and Shallow Groundwater Depth in the Typical Karst Peak-cluster Depression Areas

Based on the measured data of precipitation and shallow groundwater depth during 2006-2011,precipitation characteristics and the variation of shallow groundwater depth were analyzed in the typical Karst peak-cluster depression areas of northwest Guangxi of China.The results showed that though rainfall was abundant,it distributed unevenly within and among years,and ranged from 1 127.3 mm in 2011 to 1 979.8 mm in 2008.The precipitation mainly concentrated in rainy season from April and September,which occupied 82.4%~85.1%,74.7% and 65.9% of the total annual precipitation for normal year,rainy years and dry year respectively.The frequency and accumulation of effective precipitation and the maximum of daily precipitation tended to increase with the increase in annual precipitation.The precipitation with rainfall intensity higher than 16 mm/h and the maximum of daily rainfall mainly concentrated between May and August,and they were 67.4 mm/h and 152.9 mm,respectively.More than half a year did not have rain,and the weather without rainfall happened frequently.On average,the weather without rainfall for more than 3 days and 10 days took place 26 times and 5 times each year,and it mainly occurred in dry season.However,the annual precipitation didn’t decrease with the increase of rainless days and it mainly depended on the frequency of different magnitude of precipitation.The groundwater depth was shallower with higher variation in wet season than in dry season,and it varied moderately and was 2 m and 3 m on average,respectively.The dynamic change of shallow groundwater depth with rainfall was single-peak type and the peak value lasted for a short time,and the antecedent precipitation had an important influence on its fluctuation.