Abstract Water repellency makes soils capable of resisting to the penetration of water applied on the surface and inflict various influences on groundwater. The objectives of the present study were to identify the water repellency under pine and eucalyptus plantations, to determine social impacts of water level changes, to find possible changes in groundwater levels in the surrounding areas during the past four decades, and to relate water repellent characteristics of soils with the groundwater level changes. The study was conducted in eucalyptus (Eucalyptus grandis) and pine (Pinus caribaea) plantation forests located in Upcountry intermediate zone, Sri Lanka. Each land was separated into three blocks (B1, B2, B3) based on the slope. Water repellency was measured with water drop penetration time (WDPT) and contact angle. The water entry value was estimated with the pressure head method. Interconnected social impacts was examined using a questionnaire based survey. Groundwater levels from 1980 to present were modeled with remotely sensed information. Both eucalyptus and pine forest soils showed water repellency, which decreased with increasing soil depth. Eucalyptus soils showed highly hydrophobic conditions on the surface (WDPT>7200 s). Ponding depths required for entry of water into the soil in eucalyptus soils was 4.6–5.3 cm, whereas that of pine soils was 1.5–4.0 cm, although achieving these levels would be difficult considering the steep slopes. Contact angle showed positive logarithmic correlation with water entry value. The people living in the surrounding areas expressed less water availability for their domestic purposes, decreased water level in household wells, and drying up of natural water resources at present compared with 1980s. Modelling with remotely sensed thematic maps confirmed that the groundwater levels in both areas has decreased over the time. It indicated that the eucalyptus and pine vegetation have created unfavorable conditions in regard with water entry and groundwater recharge. Proper attention from the responsible authorities will be essential to prevent the adverse impacts of on groundwater resources.

中文翻译：

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桉树和松林森林土壤的拒水性及其与地下水位的关系，用多时相模型估算

摘要 拒水性使土壤能够抵抗施加在地表的水的渗透，并对地下水产生各种影响。本研究的目的是确定松树和桉树人工林下的防水性，确定水位变化的社会影响，找出过去 40 年周边地区地下水位可能发生的变化，并关联防水特性随地下水位变化的土壤。该研究在位于斯里兰卡内陆中间带的桉树 (Eucalyptus grandis) 和松树 (Pinus caribaea) 人工林中进行。每块土地根据坡度分为三个区块（B1、B2、B3）。防水性通过水滴渗透时间（WDPT）和接触角来测量。进水值采用压头法估算。使用基于问卷的调查研究了相互关联的社会影响。从 1980 年到现在的地下水位是用遥感信息建模的。桉树和松林土壤都表现出拒水性，随着土壤深度的增加而降低。桉树土壤在表面表现出高度疏水条件（WDPT>7200 s）。桉树土壤中水进入土壤所需的积水深度为 4.6-5.3 厘米，而松树土壤的积水深度为 1.5-4.0 厘米，尽管考虑到陡峭的斜坡，要达到这些水平是很困难的。接触角与水进入值呈正对数相关。居住在周边地区的人们表示家庭用水较少，与 19 世纪 80 年代相比，家庭井水位下降，目前天然水资源枯竭。使用遥感专题图进行建模证实，这两个地区的地下水位随着时间的推移而下降。这表明桉树和松树植被在取水和地下水补给方面创造了不利条件。主管当局的适当关注对于防止对地下水资源的不利影响至关重要。这表明桉树和松树植被在取水和地下水补给方面创造了不利条件。主管当局的适当关注对于防止对地下水资源的不利影响至关重要。这表明桉树和松树植被在取水和地下水补给方面创造了不利条件。主管当局的适当关注对于防止对地下水资源的不利影响至关重要。