Critical streamflow for water supply safety based on the withdrawal avoiding saltwater model in coastal areas-taking the water supply for Zhuhai and Macao in the Guangdong-Hong Kong-Macao Greater Bay Area as a case

Abstract

枯水期咸潮入侵已经严重威胁到了感潮河流区域供水安全.本文通过构建避咸蓄淡供水模型，耦合了咸度预测、河库联合供水调度和供水安全分析模块，为依赖感潮河流为水源地的区域供水安全管理提供了一种整体思路和决策方法.以面向粤港澳大湾区珠海东部及澳门的珠江三角洲磨刀门水道取供水为例，基于潮汐、径流和风等因子及咸度实测数据，较好地拟合了基于BP神经网络的咸度预测模型，及含氯度与超标时间的曲线函数，建立了上游来水和咸度超标时间之间的联系，得到了避咸蓄淡取水时机.咸度预测与当地河库联合供水调度相结合，得到了上游枯水期来水过程的当地区域供需平衡状况.枯水期不考虑水库调蓄的资源性缺水临界需水量为3.22亿m³，水库参与调蓄的工程性缺水临界需水量为3.75亿m³.通过供水安全分析模块，基于设定的风险阈值和临界阈值识别出了不同需水规模的上游来水临界流量特征.对于当地规划的需水规模4.23亿m³，期望上游枯水期临界流量均值约为3372 m³/s.整体上来说，需水规模越大，对上游来水期望的临界流量越大，但同时还与枯水期流量分布有关.;Salt-tide invasion in the dry season seriously threatens regional water supply in a tidal river area. In this paper, a new model, the withdrawal avoiding saltwater model (WASM), which combines salinity prediction, joint water supply of rivers and reservoirs, and security of water supply analysis, was developed. The model provides an overall idea and decision-making method for security analysis of regional water supply, depending on the withdrawal from tidal river. The water supply for Zhuhai and Macao of the Guangdong-Hong Kong-Macao Greater Bay Area from the Modaomen waterway in the Pearl River Delta was considered as an example. Data of tide, streamflow, and wind factors as well as those of salinity were used. The BP-ANN model for salinity prediction and the function between daily average chlorine and the time exceeding its standard value were well fitted. Upstream streamflow and the time of excessive salinity in the waterway were connected, and the time of withdrawal avoiding saltwater for the streamflow was obtained. The joint water supply of rivers and reservoirs associated with salinity prediction, regional water supply, and demand facing any upstream streamflow during the dry season was analyzed. If only the capacity of withdrawal from the river was considered, the critical demand for the resource supply accounted for 322 million m³ in the dry season. When the regulation of reservoirs was also taken into consideration, the critical demand for the engineering supply accounted for 375 million m³ in the dry season. Then, water supply security was further analyzed, and critical upstream streamflow for various scenarios of water demand in the dry season was identified for given thresholds of risk and critical. The critical streamflow in the dry season accounted for 3372 m³/s when the demand increased to 423 million m³ of local planning water demand. Overall, the larger the demand was, the greater the expected critical streamflow in upstream was. However, the security of water supply is associated with the distribution of upstream streamflow in the dry season.