This work focuses on the modeling and evaluation of water resources in complex aquifer systems and the use of scarce data. The modeling work is developed based on the GLUE (Generalized Likelihood Uncertainty Estimatio...This work focuses on the modeling and evaluation of water resources in complex aquifer systems and the use of scarce data. The modeling work is developed based on the GLUE (Generalized Likelihood Uncertainty Estimation) method. This method is still little used in hydrogeology, although its applications in other disciplines such as hydrology proved quite efficient. The study site, located in the Republic of Djibouti (Horn of Africa), is represented by the volcanic massif of Goda. The hydraulic properties of this massif are highly heterogeneous since they are associated with fracturing and weathering of the geological formations. The data are too few to enable a conventional modeling approach of this volcanic system. The implementation of the GLUE method in a numerical groundwater flow model allowed developing a stochastic analysis of the spatial distribution of the hydraulic conductivity and the recharge modalities of this complex volcanic system. The hydraulic conductivities range from 10-6 to 10-8 m·s-1 for the basalt and the rhyolite formations (values are yet generally lower for rhyolites) and are higher than 5 × 10-7 for the sedimentary formations. In addition, considering diffuse recharge as the main mechanism by which the precipitation reaches the aquifer results in more consistent groundwater head simulations than considering only indirect recharge. The average recharge amount estimated for the Goda aquifer system is 28 mm·yr-1. The results led to a numerical representation of this system, with the least uncertainty. This model was able to estimate the available water resources of this system. This result is important because the Goda system supplies water to the city of Tadjourah. Assessment of available resources is vital for the future development of this city. From a methodological point of view, the GLUE method proved very promising for water resources assessment in complex hydrogeological systems for which little data are available.展开更多
恒河是印度最长的河流,目前正遭受人类活动和气候变化的影响,其中瓦拉纳西区域所受的影响尤为严重。预计气候变化和不断扩张的人口会进一步影响水资源的有效利用。本研究利用水土评价工具(soil and water assessment tool,SWAT)模型进...恒河是印度最长的河流,目前正遭受人类活动和气候变化的影响,其中瓦拉纳西区域所受的影响尤为严重。预计气候变化和不断扩张的人口会进一步影响水资源的有效利用。本研究利用水土评价工具(soil and water assessment tool,SWAT)模型进行水文模拟,研究区选择恒河流经的印度北方邦南部地区,覆盖面积达15 621.612 km^2。本研究主要目标如下:(1)检验SWAT模型在径流和产沙量预测方面的可行性和适用性,(2)对序贯不确定性分析(SUFI-2)、普适似然不确定性估计(GLUE)和并行求解(ParaSol)这3种常规校准算法进行对比分析,并确定出最佳校准算法。SWAT模型中输入数据的来源为航天飞机雷达地形测绘任务(SRTM)获取的数字高程模型(DEM)、Landsat-8卫星图像、土壤数据和逐日气象数据。首先,本研究将研究流域划分为46个子流域,使用土地利用/土地覆被(LULC)图和土壤图创建了水文响应单元(HRU)。然后,构建了基于SUFI-2、GLUE和ParaSol算法的模型,并基于5类标准对这些校准算法进行了比较,标准包括目标函数、使用概念、性能、P因子和R因子值。研究结果表明:(1) SUFI-2算法需要的运行时间较少,同时校准结果最好,ParaSol算法最差;(2)使用SUFI-2算法对模型进行校准后,获得对模拟结果影响最显著的5个敏感参数——主河道水力传导率(CH_K2)、USLE方程水土保持因子(USLE_P)、主河道曼宁系数值(CH_N2)、地表径流滞后时间(SURLAG)以及土壤有效含水量(SOL_AWC);(3) 40号子流域(SW#40)产生的径流量最大,土地利用类型为荒地的36号子流域(SW#36)的产沙量最大,达到50 t·a^(–1)。研究区的平均蒸散量为411.55 mm·a^(–1)。校准后的模型可以用于探究未来LULC的变化、气候变化和土壤侵蚀的影响。展开更多
文摘This work focuses on the modeling and evaluation of water resources in complex aquifer systems and the use of scarce data. The modeling work is developed based on the GLUE (Generalized Likelihood Uncertainty Estimation) method. This method is still little used in hydrogeology, although its applications in other disciplines such as hydrology proved quite efficient. The study site, located in the Republic of Djibouti (Horn of Africa), is represented by the volcanic massif of Goda. The hydraulic properties of this massif are highly heterogeneous since they are associated with fracturing and weathering of the geological formations. The data are too few to enable a conventional modeling approach of this volcanic system. The implementation of the GLUE method in a numerical groundwater flow model allowed developing a stochastic analysis of the spatial distribution of the hydraulic conductivity and the recharge modalities of this complex volcanic system. The hydraulic conductivities range from 10-6 to 10-8 m·s-1 for the basalt and the rhyolite formations (values are yet generally lower for rhyolites) and are higher than 5 × 10-7 for the sedimentary formations. In addition, considering diffuse recharge as the main mechanism by which the precipitation reaches the aquifer results in more consistent groundwater head simulations than considering only indirect recharge. The average recharge amount estimated for the Goda aquifer system is 28 mm·yr-1. The results led to a numerical representation of this system, with the least uncertainty. This model was able to estimate the available water resources of this system. This result is important because the Goda system supplies water to the city of Tadjourah. Assessment of available resources is vital for the future development of this city. From a methodological point of view, the GLUE method proved very promising for water resources assessment in complex hydrogeological systems for which little data are available.
