How rivers (and the Netherlands) recharge Beijing’s groundwater
Beijing is well known for its variations in precipitation and it’s severe water shortages. Adequate groundwater levels are key to securing urban water supply for households, but also for industrial and agricultural needs. However, Beijing’s groundwater has been overexploited for decades. The well-known South-North Water Transfer Project transfers the hard-needed water towards the north, but how to actually use this water to recharge the groundwater? The past two years, together with the Beijing Water Authority and funded by ADB, the Dutch World Waternet, Royal Haskoning-DHV and IHE-Delft have been looking into it. And not without success.
One of the most common causes of low groundwater levels is simply the high volume pumped to the surface. The so called aquifers, underground water reserves, cannot replenish fast enough. Luckily, we can influence this process and recharge these aquifers. For Beijing, the Dutch consortium looked into managed aquifer recharge, which means that this process is actively managed and expedited.
To explain the concept of managed aquifer recharge we can take a look at the Dutch ‘dune water system’ [waterleidingduinen] in Amsterdam. The system has been operational for over 60 years. In five steps water from the river first recharges the groundwater and then continues its journey to become tapwater, a process which takes about three months:
- First, the river water goes through pretreatment by a surface water treatment plan;
- Through pipelines, the treated water is transported to the infiltration area;
- In special infiltration ponds the water slowly recharges the groundwater. Through gravity, the water is naturally pulled into the dunes, where the sand automatically and naturally filters the water.
- Most of the water automatically comes back to the surface in lower-laying areas and drains also help in reclaiming the rest.
- After further treatment the water can be transported and used as tap water.
Such a managed aquifer recharge project has more advantages than just recharging the groundwater levels. It can help increase the water supply security and quality, as soil infiltration helps remove harmful substances. Also, the water storage in the aquifer can provide a strategic supply during calamities. In addition it will contribute to the reduction of operational costs, as this form of water storage does nog occupy any land area.
The Dutch World Waternet, engineering firm Royal Haskoning-DHV and educational institute IHE-Delft produced guidelines for Managed Aquifer Recharge and carried out a feasibility study to create an aquifer recharge project in the Chaobai River near Beijing. The study was presented at the Beijing Ground Water Recharge and Management Seminar. Anne te Velde, Counsellor Infrastructure and Environment at the Netherlands Embassy in Beijing explains: “Although there are many differences between the cities of Amsterdam and Beijing, the good practice of Amsterdam’s dune water system sets an example for the Beijing Water Authority. The feasibility study shows a large potential for the Chaobai River channel for managed aquifer recharge.” The consortium delivered a conceptual design, with the aim to realize the project in the upcoming years.