Concentration of nitrates in groundwater at the Nitrate Vulnerable zone of Faro, south Portugal, reaches values as high as 300 mg/l; therefore, according to the EU Water Framework Directive, mitigation measures need to be implemented. A Managed Aquifer Recharge scheme is proposed to accelerate the dilution and natural discharge of nitrates from the system. Source water availability is estimated from rainfall intercepted at existing greenhouses. Within the highest nitrate concentration area, estimated water availability for injection in existing wells is 1.50 hm³/year, a significant volume which represents approximately 15% of the aquifer direct recharge. It is proposed this is recharged to the aquifer through existing large-diameter traditional wells that are no longer used for abstraction. Injection test results suggest that the likely infiltration capacity of such wells is more than sufficient to allow collection of 95% of daily rainfall events. The effect of injecting this volume in the aquifer was estimated with the support of a 3D numerical groundwater flow and transport model. Results show considerable improvement in nitrate concentrations in the study area, in certain locations decreasing up to 70 mg/l by 2027. The model results predict a decrease in the number of nitrate threshold exceedances in observation points, from 33 to 30 by 2027 and 14 to 9 by 2040. It is likely that this measure may have a positive effect on other issues identified in the area, mostly related with quantity problems and seawater intrusion. Notwithstanding, issues including landowner support, clogging, conditions of greenhouses and wells, water quality, and climate change impacts will require further consideration to develop a successful and beneficial MAR scheme.

中文翻译：

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评估利用收获的温室径流进行有管理的含水层补给，以改善葡萄牙南部的地下水状况

葡萄牙南部法鲁的硝酸盐脆弱地区地下水中硝酸盐的浓度高达300毫克/升。因此，根据欧盟水框架指令，需要采取缓解措施。提出了管理含水层补给方案，以加快系统中硝酸盐的稀释和自然排放。根据现有温室截获的降雨来估算水源可用性。在最高硝酸盐浓度区域内，估计现有井中的注水量为1.50 hm ³/年，这意味着大约占含水层直接补给量的15％。建议将其通过不再用于提取的现有大口径传统井补给含水层。注入测试结果表明，此类井的可能的渗透能力足以收集每天95％的降雨事件。在3D数值地下水流和运移模型的支持下，估算了将这一体积注入含水层的效果。结果表明，研究区域的硝酸盐浓度有了显着改善，某些地方的硝酸盐浓度到2027年将降低至70 mg / l。模型结果预测，观察点硝酸盐超标的数量将从2027和33的33减少到30到2040年达到9。该措施可能会对该地区发现的其他问题产生积极影响，主要与数量问题和海水入侵有关。尽管如此，包括土地所有者的支持，堵塞，温室和水井的状况，水质以及气候变化影响在内的问题仍需要进一步考虑，以制定成功且有益的MAR计划。