The El Qaa Plain, Sinai South, Egypt faced frequent droughts in recent decades, which increased stress on aquifers and severely impacted the groundwater resources of the region.
A new study highlighted that using storage dams and recharge wells effectively captures rainfall and prevents loss of evaporation or runoff into the sea. This approach enhances aquifer recharge and improves groundwater sustainability, especially during drought periods.
Integrated Water Resource Management, combined with techniques like rainwater harvesting and managed aquifer recharge, collectively known as RWH-MAR, becomes a sustainable and reliable solution for arid and semi-arid regions, according to the report published in Springer Nature journal.
The study was carried out in the desert of El Qaa Plain, which is the largest groundwater aquifer in Sinai, Egypt. The area is suitable for carrying out the RWH-MAR techniques.
It demonstrated the potential benefits of the RWH-MAR system for the El Qaa Plain by modelling groundwater using technologies such as the Watershed Modeling System and the SEAWAT software. The former mainly carries out the hydrologic and hydraulic modelling of a watershed and the latter helps to simulate how harvested rainwater can flow into the groundwater and improve aquifer recharge.
In the coastal areas of Sinai, the hydraulic aquifer recharge method was used to supplement the groundwater, which is exploited due to over-pumping. In this method, harvested rainwater is recharged in the ground, creating a hydrostatic pressure of freshwater column that prevents sea water intrusion. This method is adopted to control flash flood risks, increase groundwater recharge and ensure water security.
Harvesting rainfall in different areas of Saudi Arabia through this method will control the runoff during heavy rains due to climate change and help mitigate the risks of flooding on one hand, while providing freshwater recovery through groundwater recharge on the other hand.
To understand the role and impact of rainfall, runoff, terrain, drainage and soil characteristics in the study area, watershed modelling was done using the El-Quad watershed modelling system. The terrain was studied by processing the Digital Elevation Model (DEM) data in the system. A watershed model was developed using this DEM, dividing the entire watershed into sub-watersheds.
The modelling also created drainages using the DEM data, to study the streams and their characteristics in the study area. Using the hydrologic modelling module software, a relationship between rainfall and runoff was observed. The advanced modelling method Hydrologic Engineering Center–River Analysis System (HEC-RAS) was used to design the streams and detention structures like dams and study their impact on recharging groundwater. This included analysis of rainfall data for different return periods.
Using these parameters, software and methods, surface runoff for different values of rainfall was estimated. This could be harvested by the detention structures for groundwater recharge.
The impact of rainwater harvesting on groundwater through these detention structures was studied using a groundwater conceptual model, developed using DEM data and other required parameters.
Different aquifer systems were simulated as per the real situation. The entire model has a rectangular dimension of 65,380 x 60,324 square metres, representing an active aquifer spread in the area of 1,584 square kilometres (66 km in length and 24 km in width).
“In the El Qaa Plain study, this method utilised recharge wells and storage dams to intercept runoff and infiltrate water into the aquifer. The results show a substantial increase in aquifer potentiality, with water storage improving by 11.8-127.4 per cent under varying scenarios of return periods (10-100 years) compared to the base year of 2014.
RWH-MAR system not only augments groundwater supplies but also mitigates the risks of flash floods and reduces water loss through evaporation. “This dual benefit underscores its importance in addressing water scarcity and promoting sustainable development in arid and semi-arid regions,” Alban Kuriqi, research scientist, department of civil engineering, architecture and georesources, Universidade de Lisboa, Lisbon, Portugal, author of the study added.
“In India also the RWH-MAR system is applicable in arid and semi-arid regions. Techniques like storage dams (check dams) and recharge wells help increase groundwater availability and mitigate the impacts of water scarcity in such regions,” said Durjoy Chakarborthy, retired scientist, Central Groundwater Board.
In Rajasthan, the use of traditional water harvesting systems like johads / talabs and check dams demonstrates the feasibility of such techniques in arid and semi-arid areas, he added.
Managed aquifer recharge using percolation tanks / ponds has proven successful in replenishing groundwater in semi-arid zones of Gujarat region. In Tamil Nadu, recharge wells and rainwater harvesting systems have been mandated to augment groundwater resources.
The RWH-MAR system maximises the use of flash flood waters and prevents runoff losses, making it highly relevant for Indian arid and semi-arid regions facing similar challenges.
In the era of rainfall variability, RWH-MAR system plays a significant role and has become a valuable tool. Successful implementation of such a technique requires a better understanding of the hydrological conditions in the region, careful planning and proper implementation. This kind of approach will help practitioners and policymakers to address the issues such as groundwater depletion and drought.
Combining rainwater harvesting and managed aquifer recharge provides a sustainable solution to improve water availability, especially in areas that are facing water crisis. This technique is essential for managing water resources effectively and ensuring resilience against climate change impacts, making it a crucial strategy for tackling water scarcity and supporting long-term water security.