Bolster C H, Genereux D P, Saiers J E
School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, USA.
Ground Water. 2001 Sep-Oct;39(5):768-77. doi: 10.1111/j.1745-6584.2001.tb02368.x.
Data from a large-scale canal-drawdown test were used to estimate the specific yield (sy) of the Biscayne Aquifer, an unconfined limestone aquifer in southeast Florida. The drawdown test involved dropping the water level in a canal by about 30 cm and monitoring the response of hydraulic head in the surrounding aquifer. Specific yield was determined by analyzing data from the unsteady portion of the drawdown test using an analytical stream-aquifer interaction model (Zlotnik and Huang 1999). Specific yield values computed from drawdown at individual piezometers ranged from 0.050 to 0.57, most likely indicating heterogeneity of specific yield within the aquifer (small-scale variation in hydraulic conductivity may also have contributed to the differences in sy among piezometers). A value of 0.15 (our best estimate) was computed based on all drawdown data from all piezometers. We incorporated our best estimate of specific yield into a large-scale two-dimensional numerical MODFLOW-based ground water flow model and made predictions of head during a 183-day period at four wells located 337 to 2546 m from the canal. We found good agreement between observed and predicted heads, indicating our estimate of specific yield is representative of the large portion of the Biscayne Aquifer studied here. This work represents a practical and novel approach to the determination of a key hydrogeological parameter (the storage parameter needed for simulation and calculation of transient unconfined ground water flow), at a large spatial scale (a common scale for water resource modeling), for a highly transmissive limestone aquifer (in which execution of a traditional pump test would be impractical and would likely yield ambiguous results). Accurate estimates of specific yield and other hydrogeological parameters are critical for management of water supply, Everglades environmental restoration, flood control, and other issues related to the ground water hydrology of the Biscayne Aquifer.
来自大规模运河水位下降试验的数据被用于估算比斯坎含水层的比出水量（sy），该含水层是佛罗里达州东南部的一个无压石灰岩含水层。水位下降试验包括将运河中的水位降低约30厘米，并监测周围含水层中水头的响应。通过使用解析河流 - 含水层相互作用模型（Zlotnik和Huang，1999年）分析水位下降试验非稳定部分的数据来确定比出水量。根据各个测压管处的水位下降计算出的比出水量值范围为0.050至0.57，这很可能表明含水层内部比出水量存在非均质性（水力传导率的小规模变化也可能导致了各测压管之间比出水量的差异）。基于所有测压管的所有水位下降数据计算得出的值为0.15（我们的最佳估计值）。我们将比出水量的最佳估计值纳入基于MODFLOW的大规模二维数值地下水流模型中，并对距离运河337至2546米处的四口井在183天期间的水头进行了预测。我们发现观测水头与预测水头之间具有良好的一致性，这表明我们对比出水量的估计代表了此处研究的比斯坎含水层的大部分情况。这项工作代表了一种实用且新颖的方法，用于在大空间尺度（水资源建模的常见尺度）上，针对高渗透性石灰岩含水层（在其中进行传统抽水试验不切实际且可能产生模糊结果）确定一个关键的水文地质参数（模拟和计算瞬态无压地下水流所需的储存参数）。准确估计比出水量和其他水文地质参数对于供水管理、大沼泽地环境恢复、防洪以及与比斯坎含水层地下水文相关的其他问题至关重要。
