Hydrological impacts of recharge dams on Aflaj systems in Oman: A long-term analysis

Abstract

• Recharge dams increased annual Aflaj discharge volume by about 65 % compared to pre-dam flow. • Groundwater levels downstream of dams became more stable, reducing long-term depletion trends. • Flow duration and discharge sustainability increased by 25 %, even during periods of limited rainfall. • Event-based analysis showed that dam operations and temperature changes directly affected Aflaj discharge. The Aflaj system, a traditional subterranean irrigation network, represents one of the most enduring examples of indigenous water engineering in arid regions. These systems channel groundwater by gravity to sustain agricultural and domestic water needs without requiring external energy input. However, increasing drought frequency, groundwater depletion, and climate variability have significantly reduced flow rates in many Aflaj networks. To mitigate these challenges, recharge dams have been introduced as integrated solutions to enhance groundwater storage and sustain the functionality of Aflaj systems. This study presents a comprehensive long-term and event-based assessment of the impacts of recharge dams on Aflaj systems, focusing on a case study in the North Sharqiyah Governorate, Oman. The analysis integrates 24 years of hydrological data from two comparable catchments, one with a recharge dam and one without, to evaluate changes in groundwater levels, discharge flow, and seasonal variability. Results reveal that the construction of recharge dams increased annual Aflaj discharge volumes by approximately 65 % compared to pre-dam conditions, while improving flow duration and discharge stability by about 25 %, even during low rainfall events. Groundwater levels downstream of the dam also showed higher stability and reduced depletion trends. Event-based observation further indicates that dam operations and fluctuations in climate temperature directly influence short-term Aflaj discharge behavior. The findings show that recharge dams positively support the sustainability of traditional Aflaj systems by enhancing water availability and groundwater resilience in arid regions. The study provides quantitative evidence to support the integration of modern recharge structures with traditional water management for long-term hydrological stability.