Interpretation of hydrologic trends from a water balance perspective: The role of groundwater storage in the Budyko hypothesis
Interpretation of hydrologic trends from a water balance perspective: The role of groundwater storage in the Budyko hypothesis
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DOI：
10.1029/2010wr010100
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发表时间：
2012-03
影响因子：
5.4
通讯作者：
E. Istanbulluoglu;Tiejun Wang;Olivia M. Wright;J. Lenters
中科院分区：
文献类型：
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作者：
E. Istanbulluoglu;Tiejun Wang;Olivia M. Wright;J. Lenters
我们使用布迪科假说作为诊断工具，调查了内布拉斯加州中部几个流域观测到的年径流正趋势。在径流以基流为主的流域，估算的年蒸散量(ETA)与降水量(P)之比(ETA/P)与干旱指数(ETP/P)呈负相关，其中ETP是潜在的年蒸散量。这一观察结果与布迪科假说不一致。我们假设，所观察到的负趋势是由于流域蓄水量的显著年际变化造成的。这一假设是使用内布拉斯加州沙山地区地下水监测井的数据进行验证的。地下水蓄积量与年干旱度指数的年变化曲线图显示，年平均干旱度指数是控制盆地蓄水量损益动态的关键气候变量。在与平均气候绝对偏差相同的情况下，我们发现多雨的年份地下水储量的增加大于干旱年份的净损失。我们认为，这种蓄水损益行为在水文系统中建立了气候记忆，导致了年径流的持久性和统计上的显著趋势。建立了一个简约的模型，该模型将Budyko假设与基流的线性水库方程相结合，并用来检验观测到的年径流正趋势的可能原因。我们发现，细微的、在统计上不显著的年P增加导致了正的、统计上不显著的趋势，在年度Eta和P−Eta。另一方面，年径流预测具有很高的持续性和统计意义，与观测结果一致。进一步的模型敏感性分析表明，增加地下水库的规模与增加年径流的长期(数十年)持续性有关，并将气候的高频、高幅度变化转化为低频、低幅度的径流响应。我们的结果强调了在完整的水预算背景下评估任何系统变量的明显趋势的重要性。
We investigate the observed positive trends in annual runoff in several basins in central Nebraska using the Budyko hypothesis as a diagnostic tool. In basins where runoff is dominated by base flow we found that the estimated annual evapotranspiration (ETa) to precipitation (P) ratio (ETa/P) from data is negatively related to the aridity index (ETp/P, where ETp is potential annual evapotranspiration). This observation is inconsistent with the Budyko hypothesis. We hypothesized that the observed negative trend results from significant interannual changes in basin water storage. This hypothesis is tested using data from groundwater monitoring wells in the Sand Hills region of Nebraska. Plots of the yearly changes in groundwater storage versus the annual aridity index revealed the mean annual aridity index as a critical climatological variable that controls basin storage gain‐loss dynamics. For the same absolute deviation from the mean climate, we found that a wetter year leads to a larger gain in groundwater storage than the net loss in a drier year. We argue that this storage gain‐loss behavior builds a climate memory in the hydrologic system, causing persistence and statistically significant trends in annual runoff. A parsimonious model was developed that couples the Budyko hypothesis with a linear reservoir equation for base flow and was used to examine the possible causes of observed positive trends of annual runoff. We found that subtle, statistically insignificant, increases in annual P have led to positive and statistically insignificant trends in annual ETa and P − ETa. Annual runoff, on the other hand, was predicted to have high persistence and statistical significance, consistent with observations. Further model sensitivity analyses showed that increasing the size of the groundwater reservoir is associated with increased long‐term (multidecadal) persistence in annual runoff and translates high‐frequency, high‐amplitude variation in climate to low‐frequency, low‐amplitude runoff response. Our results underscore the importance of evaluating apparent trends in any system variable in a complete water budget context.