Feddersen Falk, Boehm Alexandria B, Giddings Sarah N, Wu Xiaodong, Liden Doug
Scripps Institution of Oceanography UCSD La Jolla CA USA.
Dept Civil and Environmental Engineering Stanford University Stanford CA USA.
Geohealth. 2021 Nov 1;5(11):e2021GH000490. doi: 10.1029/2021GH000490. eCollection 2021 Nov.
The popular beaches of the San Diego-Tijuana (US/MX) border region are often impacted by untreated wastewater sourced from Mexico-via the Tijuana River Estuary (TJRE) and San Antonio de los Buenos outfall at the Pt. Bandera (SAB/PTB) shoreline, leading to impacted beaches and human illness. The US-Mexico-Canada trade agreement will fund border infrastructure projects reducing untreated wastewater discharges. However, estimating project benefits such as reduced human illness and beach impacts is challenging. We develop a coupled hydrodynamic, norovirus (NoV) pathogen, and swimmer illness risk model with the wastewater sources for the year 2017. The model is used to evaluate the reduction in human illness and beach impacts under baseline conditions and three infrastructure diversion scenarios which (Scenario A) reduce SAB/PTB discharges and moderately reduce TJRE inflows or (Scenarios B, C) strongly reduce TJRE in inflows only. The model estimates shoreline untreated wastewater and NoV concentrations, and the number of NoV ill swimmers at Imperial Beach CA. In the Baseline, the percentage of swimmers becoming ill is 3.8% over 2017, increasing to 4.5% during the tourist season (Memorial to Labor Day) due to south-swell driven SAB/PTB plumes. Overall, Scenario A provides the largest reduction in ill swimmers and beach impacts for the tourist season and full year. The 2017 tourist season TJRE inflows were not representative of those in 2020, yet, Scenario A likely still provides the greatest benefit in other years. This methodology can be applied to other coastal regions with wastewater inputs.
圣地亚哥 - 蒂华纳（美国/墨西哥）边境地区的热门海滩经常受到来自墨西哥未经处理的废水影响，这些废水通过蒂华纳河河口（TJRE）和班德拉角（SAB/PTB）海岸线的圣安东尼奥德洛斯布埃诺斯排污口流入，导致海滩受污染和人类患病。美墨加贸易协定将为边境基础设施项目提供资金，以减少未经处理的废水排放。然而，估算项目效益，如减少人类患病和海滩受影响程度，具有挑战性。我们开发了一个耦合水动力、诺如病毒（NoV）病原体和游泳者患病风险的模型，该模型考虑了2017年的废水来源。该模型用于评估在基线条件和三种基础设施分流情景下人类患病减少情况和海滩受影响程度，这三种情景分别为：情景A减少SAB/PTB排放并适度减少TJRE流入量；情景B和C仅大幅减少TJRE流入量。该模型估算了加利福尼亚州帝国海滩海岸线未经处理的废水和诺如病毒浓度，以及感染诺如病毒的患病游泳者数量。在基线情况下，2017年游泳者患病百分比为3.8%，在旅游季节（阵亡将士纪念日至劳动节）由于南向涌浪驱动的SAB/PTB羽状水流，这一比例增至4.5%。总体而言，情景A在旅游季节和全年对患病游泳者数量和海滩受影响程度的减少幅度最大。2017年旅游季节TJRE的流入量并不代表2020年的情况，然而，情景A在其他年份可能仍然能带来最大效益。这种方法可应用于其他有废水输入的沿海地区。
