Eastoe Christopher J, Hess Greg, Mahieux Susana
Clear Creek Associates, 221 N Court Ave., Tucson, AZ, 85701.
Ground Water. 2015 Apr;53 Suppl 1:133-8. doi: 10.1111/gwat.12183. Epub 2014 Mar 17.
Groundwater in the Todos Santos watershed in southern Baja California, and throughout the peninsula south of latitude 28°N, has values of (δ18 O‰, δD‰) ranging between (-8.3, -57) and (-10.9, -78). Such negative values are uncharacteristic of the site latitude near the sea level. Altitude effects do not explain the isotope data. Tropical depressions originating along the Pacific coast of North America yield rain with isotopic depletion; rain from these weather systems in southern Arizona commonly has δ18O values<-10‰ in comparison with amount-weighted mean summer and fall rain at -6‰. Isotope data indicate hurricane rain as the predominant source of recharge in southern Baja California, where named tropical depressions bring large rains (>50 mm) at least once every 2 to 3 years, and along the Pacific coast between Jalisco and Oaxaca.
下加利福尼亚州南部托多斯桑托斯流域以及北纬28°以南整个半岛的地下水，其（δ18O‰，δD‰）值介于（-8.3，-57）和（-10.9，-78）之间。如此负值在海平面附近的该地点纬度并不常见。海拔效应无法解释同位素数据。源自北美太平洋沿岸的热带低气压带来同位素贫化的降雨；与亚利桑那州南部夏季和秋季降雨的量加权平均值-6‰相比，这些天气系统带来的降雨通常δ18O值＜-10‰。同位素数据表明，飓风降雨是下加利福尼亚州南部主要的补给水源，在那里，被命名的热带低气压至少每2至3年带来一次大雨（＞50毫米），在哈利斯科州和瓦哈卡州之间的太平洋沿岸亦是如此。
