Analysing the origin of rain- and subsurface water in seasonal wetlands of north-central Namibia.
Analysing the origin of rain- and subsurface water in seasonal wetlands of north-central Namibia.
复制标题
分析纳米比亚中北部季节性湿地雨水和地下水的来源。
DOI：
10.1088/1748-9326/aa5bc8
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发表时间：
2017
影响因子：
6.7
通讯作者：
M.
中科院分区：
文献类型：
--
作者：
Hiyama;T.;Kanamori;H.;Kambatuku;J.;Kotani;A.;Asai;K.;Mizuochi;H.;Fujioka;Y.;Iijima;M.
我们调查了纳米比亚中北部季节性湿地的雨水和地下沃茨的来源，这对该地区的水和粮食安全至关重要。该区域包括Cuvelai盆地的Cuvelai系统季节性湿地的南部，Cuvelai盆地是一个跨界河流流域，覆盖安哥拉南部和纳米比亚北方。分析了雨水、地表水和浅层地下水中氢（HDO）和氧（H2 18 O）的稳定水同位素。在2013年10月至2014年4月的雨季每次降雨期间收集雨水样本。分析了每个雨水样品中的HDO（δD）和氧H2 18 O（δ 18 O）同位素比值，然后用每个降水量加权，得出降水中（δD，δ 18 O）的年平均值。利用三角洲图（绘制δD与δ 18 O），我们表明，年平均值是确定CSSW地下沃茨来源的良好指标。为了确认雨水的来源并解释同位素比值的变化，我们使用热带降雨测量使命（TRMM）多卫星降水分析（TMPA）数据和ERA-Interim大气再分析数据进行了大气水收支分析。结果表明，在地方区域尺度上，大约四分之三的雨水来自循环水。卫星观测到的向外长波辐射（OLR）以及来自中分辨率成像分光辐射计（MODIS）和高级微波扫描辐射计（AMSR）系列的补充卫星数据表明，雨水中的同位素比率受到从对流云中落下的雨滴蒸发的影响。因此，综合SWI分析的雨水，地表水和地下沃茨，再加上大气水收支分析，揭示了浅层地下水的小湿地在这一地区很可能是从地表沃茨，这是暂时汇集在小湿地。这也支持了氚（3 H）计数目前的雨水和地下沃茨在该地区。我们强烈建议不要大量抽取浅层地下水，以保护地表水和地下沃茨水，这两者都是该地区的重要水资源。
We investigated the origins of rain-and subsurface waters of north-central Namibia's seasonal wetlands, which are critical to the region's water and food security. The region includes the southern part of the Cuvelai system seasonal wetlands (CSSWs) of the Cuvelai Basin, a transboundary river basin covering southern Angola and northern Namibia. We analysed stable water isotopes (SWIs) of hydrogen (HDO) and oxygen (H 2 18 O) in rainwater, surface water and shallow groundwater. Rainwater samples were collected during every rainfall event of the rainy season from October 2013 to April 2014. The isotopic ratios of HDO (δD) and oxygen H 2 18 O (δ 18 O) were analysed in each rainwater sample and then used to derive the annual mean value of (δD, δ 18 O) in precipitation weighted by each rainfall volume. Using delta diagrams (plotting δD vs. δ 18 O), we showed that the annual mean value was a good indicator for determining the origins of subsurface waters in the CSSWs. To confirm the origins of rainwater and to explain the variations in isotopic ratios, we conducted atmospheric water budget analysis using Tropical Rainfall Measuring Mission (TRMM) multi-satellite precipitation analysis (TMPA) data and ERA-Interim atmospheric reanalysis data. The results showed that around three-fourths of rainwater was derived from recycled water at local–regional scales. Satellite-observed outgoing longwave radiation (OLR) and complementary satellite data from MODerate-resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer (AMSR) series implied that the isotopic ratios in rainwater were affected by evaporation of raindrops falling from convective clouds. Consequently, integrated SWI analysis of rain-, surface and subsurface waters, together with the atmospheric water budget analysis, revealed that shallow groundwater of small wetlands in this region was very likely to be recharged from surface waters originating from local rainfall, which was temporarily pooled in small wetlands. This was also supported by tritium (3 H) counting of the current rain-and subsurface waters in the region. We highly recommend that shallow groundwater not be pumped intensively to conserve surface and subsurface waters, both of which are important water resources in the region.