The El Niño event of 2015–16: Climate anomalies and their impact on groundwater resources in East and Southern Africa
The El Niño event of 2015–16: Climate anomalies and their impact on groundwater resources in East and Southern Africa
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2015-16年厄尔尼诺事件：气候异常及其对东部和南部非洲地下水资源的影响
DOI：
10.5194/hess-2018-516
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发表时间：
2018
影响因子：
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通讯作者：
D. MacLeod
中科院分区：
文献类型：
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作者：
S. Kolusu;M. Shamsudduha;M. Todd;R. Taylor;D. Seddon;J. Kashaigili;G. Ebrahim;M. Cuthbert;J. Sorensen;K. Villholth;A. MacDonald;D. MacLeod
抽象的。尽管饮用水、农业和工业广泛依赖地下水作为资源，但气候变化对地下水储存的影响受到的关注有限。在这里，我们通过对原位地下水测压和 GRACE 卫星数据的分析，评估了 2015-16 年重大厄尔尼诺事件期间南部非洲 (SA) 和东非赤道以南 (EASE) 发生的气候异常，及其对跨尺度地下水储存的相关影响。在大陆尺度上，2015-16 年的厄尔尼诺现象与 EASE 和南部非洲（约 12°S 南北方向）上空的明显反向降雨异常偶极子有关，这是 ENSO 的一种特征模式。根据对地表水平衡异常跨尺度区域强度（以标准化降水-蒸散指数，SPEI为代表）的分析，南部非洲发生了历史记录中最严重的干旱事件，估计重现期至少为200年，最佳估计为260年。气候风险正在发生变化，我们估计仅人为变暖（忽略其他气候变量的变化，例如降水量）就使此类极端 SPEI 干旱事件的风险增加了大约一倍。 GRACE 卫星和林波波盆地测压数据表明，这些地表水平衡赤字抑制了地下水补给，导致地下水储量大幅下降。相反，在 2015-16 年厄尔尼诺事件期间的 EASE 上，观察到异常潮湿的条件，预计重现期约为 10 年，可能由于缺乏强烈的印度洋纬向模阶段而有所缓和。卫星 GRACE 数据显示，强雨季但并非极端雨季增加了地下水储存量，并且坦桑尼亚中部某个地点观测到的地下水位不断上升。我们注意到 GRACE 数据中将地下水与总储水量分开存在很大的不确定性，并表明当空间平均尺度具有可比性时，GRACE 和地下水储量的测压估计之间的一致性是显而易见的。这些结果对可持续和气候适应型地下水资源管理具有影响，包括采取适应性战略的潜力，例如在间歇性补给事件期间管理含水层补给。
Abstract. The impact of climate variability on groundwater storage has received limited attention despite widespread dependence on groundwater as a resource for drinking water, agriculture and industry. Here, we assess the climate anomalies that occurred over Southern Africa (SA) and East Africa, south of the equator (EASE), during the major El Niño event of 2015–16, and their associated impacts on groundwater storage, across scales, through analysis of in situ groundwater piezometry and GRACE satellite data. At the continental scale, the El Niño of 2015–16 was associated with a pronounced dipole of opposing rainfall anomalies over EASE and Southern Africa, north/south of ~12° S, a characteristic pattern of ENSO. Over Southern Africa the most intense drought event in the historical record occurred, based on an analysis of the cross-scale areal intensity of surface water balance anomalies (as represented by the Standardised Precipitation-Evapotranspiration Index, SPEI), with an estimated return period of at least 200 years and a best estimate of 260 years. Climate risks are changing and we estimate that anthropogenic warming only (ignoring changes to other climate variables e.g. precipitation) has approximately doubled the risk of such an extreme SPEI drought event. These surface water balance deficits suppressed groundwater recharge, leading to a substantial groundwater storage decline indicated by both GRACE satellite and piezometric data in the Limpopo basin. Conversely, over EASE during the 2015–16 El Niño event, anomalously wet conditions were observed with an estimated return period of ~10 years, likely moderated by the absence of a strongly positive Indian Ocean Zonal Mode phase. The strong but not extreme rainy season increased groundwater storage as shown by satellite GRACE data and rising groundwater levels observed at a site in central Tanzania. We note substantial uncertainties in separating groundwater from total water storage in GRACE data and show that consistency between GRACE and piezometric estimates of groundwater storage is apparent when spatial averaging scales are comparable. These results have implications for sustainable and climate-resilient groundwater resource management, including the potential for adaptive strategies, such as managed aquifer recharge during episodic recharge events.