China Needs Managed Aquifer Recharge

By Yan Zheng, Peter Dillon, Weiping Wang, Fandong Zheng 16 March, 2016

Wastewater & water consumption are increasing in China, MAR can help. Zheng, Wang, Zheng & Dillon expand

This article benefited from discussions during the 2015 IAH-MAR China Chapter Workshop that took place at the Institute of Water Sciences at Peking University. A China Managed Aquifer Recharge working group has been formed and members of that working group, Dr. Yan Zheng of Peking University, Dr. Weiping Wang of Jinan University, Dr. Fandong Zheng of Beijing Water Science and Technology Institute and Dr. Peter Dillon of IAH-MAR Commission wrote this article assisted by Meng Ma, Linfeng Zhang and Jie Liu of Peking University.

With economic development and improving living standards, water use in China has risen from 557 billion m³ in 1997 to 610 billion m³ in 2014. To match the growing demand in northern cities, China has completed two of the three planned transfer aqueducts of the “South-to-North Water Transfer Project”. Since September 2015, the Central Aqueduct brings about 3 billion m³ per year of water to Beijing.

In 2014 Beijing discharged 1.6bn m³ of wastewater, up from 1.3bn m³ in 2003

More water use means more wastewater discharge. In 2014, Beijing discharged 1.6 billion m³ per year, up from 1.3 billion m³ in 2003. With a further expected rise in the volume of wastewater discharged, increasing efforts are being made to “reclaim” effluents from wastewater treatment plants into valuable resources. In 2015, the use of reclaimed water was 0.95 billion cubic meters in Beijing, accounting for a quarter of the total water used in the city.
The ‘Water Pollution Prevention and Control Action Plan’, released by the Chinese government in 2015, includes reclaimed water utilization as part of a comprehensive water resource management plan.

Managed Aquifer Recharge (MAR) is often overlooked as a method to reclaim treated wastewater

Treated wastewater can be “reclaimed” for a wide range of uses including landscaping and irrigation. An often overlooked method to reclaim the treated wastewater is through Managed Aquifer Recharge (MAR), which stores this water in aquifers for later use. We believe MAR can play an important role as China quickly develops its comprehensive water resource management system. The advantages of MAR including enhanced climate resilience are described below.

What is Managed Aquifer Recharge and how does it enhance resilience in water supply?

Managed Aquifer Recharge (MAR) is the purposeful recharge of water to aquifers for subsequent reuse or for environmental benefit.

MAR is the purposeful recharge of water to aquifers for subsequent reuse
It can enhance water supply by improving groundwater quality, preventing salt water intrusion into aquifers & more

It can be used to store water from various sources, such as storm-water, reclaimed water, desalinated seawater, rainwater or even groundwater from other aquifers, provided it has been previously treated – MAR is not a wastewater disposal method. Later-on, the stored water can be recovered and sometimes after additional treatment, used for different purposes such as drinking water, industrial water, irrigation, toilet flushing, and sustaining ecosystems.
MAR can secure and enhance water supply by improving groundwater quality, preventing salt water from intruding into coastal aquifers and reducing evaporation of stored water. It can also better support ecosystems which improve local amenity, land value and biodiversity. There are additional benefits as well, such as improving coastal water quality by reducing urban discharges, mitigating floods and facilitating urban landscape improvements.

Experience of MAR outside China

MAR has been used in many countries, such as India, the US and Australia. These countries have developed dedicated guidelines and implemented many different types of MAR projects.
In Australia’s Northern Territory, Alice Springs relies on slowly renewed groundwater from deep aquifers for its water supply. To prevent winter overflows of sewage effluent to Ilparpa Swamp and to provide irrigation water supplies for horticultural development, a managed aquifer recharge project was constructed to allow intermittent infiltration of treated reclaimed water. Each year, 600,000 m³ of reclaimed water is stored in a paleochannel aquifer.¹ Later on, this water may be pumped again and used for irrigation purposes.
Because the stored water is percolating through the soil towards the aquifer, the quality of the water is progressively improved thanks to natural physical, chemical and biological processes – the so-called soil-aquifer treatment. At this site, the brackish groundwater is freshened but nitrogen removal is slight.² This is only one of a wide range of MAR techniques involving filtration from ponds, river channel modifications or injecting water into wells.³

China’s experience with MAR

Wang et al. of Jinan University initiated a MAR project using roof-collected rain water for recharge in the city of Jinan, Shandong Province.⁴ The pilot-scale system consists of a rooftop catchment, a first-flush removal device, a regulating tank, a filtration tank and recharge well. The roof water harvested from rainfall is first treated by flush removal, then filtered and finally recharged into the fracture karst aquifer through a deep well to restore the groundwater reserves. In Jinan, known as the Spring City of China, the karst groundwater plays an important role in maintaining spring flow that has been diminishing. This example demonstrates MAR’s potential to protect both ecosystem services and the cultural identity of a place.

MAR project using roof-collected rain water for recharge in the city of Jinan, Shandong Province

Another experiment was conducted in the Chaobai River. Zheng et al. from the Beijing Water Science and Technology Institute investigated infiltration of reclaimed water discharged into this river to enhance the aesthetic value of an urban park.⁵ Infiltration of this water has prevented the groundwater level from declining further at the shallowest level (<30m). However, there has been increases in total dissolved solids and chloride levels deeper in the aquifer (up to 80m), raising concerns on how the infiltration of reclaimed water may affect the quality of the water supplied by deeper wells.

Reclaiming of water discharged into the Chaobai River prevented the groundwater level from declining further

Challenges to the application of MAR –  shifting perceptions

The foremost challenge for MAR’s application in China is to overcome the perception that there is a risk that is not worth taking. The Chinese translation of managed aquifer recharge is reminiscent of disposing waste through injection into deep wells or irrigation with sewage discharge, adding to the risky perception. There is also a valid concern that even with a guideline with the best intent to manage the environmental risks associated with MAR, it is unclear whether such a guideline can be adhered to in practice.

Need overcome the perception that it is not a risk worth taking & the do-nothing approach

In light of these challenges, it would be prudent to carefully evaluate costs and benefits of MAR in comparison with a range of options including improved water conservation, tapping new surface water supplies or aquifers, rainwater harvesting, and groundwater or sea water desalination. It would also be prudent to consider the risks associated with a do-nothing approach: the increasing volume of treated (and sometimes untreated) wastewater still needs to be dealt with and some of which will likely infiltrate underground unintentionally.
The question then becomes whether it’s better to manage such risks or let the risks manifest by doing nothing. Regardless, establishing MAR standards and guidelines is a necessary first step. It is also necessary to support pilot projects in order to assess the risks associated with MAR to compare with the currently prevailing do-nothing option.

Massive urbanization will bring need and opportunity for MAR to increase climate resilience

With massive urbanization the need and opportunities for MAR are likely to increase in China. MAR increases climate resilience. We believe that MAR is likely to shift from a niche technology to become a key component of a standard water management portfolio, among more traditional techniques available to urban and rural water managers across China.

“We believe that MAR  is likely to shift from a niche technology to become a key component of a standard water management portfolio…”

The quality of the recharging water is crucial for both public health and the environment. Water quality evaluations will require more precise and localized information on aquifer properties and source water quality, some of which is likely to require site-specific investigations, which can be both time- and money- intensive.
Therefore, it is vital to better understand the groundwater recharge, runoff and discharge, as well as the hydrogeological structure of the recharge area and estimate its water storage capacity through implementing pilot MAR projects in China.
Experiments and numerical modelling can help better understand the groundwater flow and the solute transport as well as evaluate the changes of water quality after infiltrating through the unsaturated zone. The water-rock interaction also plays a significant role, and dynamic monitoring is needed to prevent clogging during the MAR operation. Pilot projects will also give water managers the required experience to improve the effectiveness and reliability of their operations, thereby giving greater confidence that all the risks can be managed and covered in the guideline.

¹ Vanderzalm, J.L. et al. (2015) Economics and experiences of managed aquifer recharge (MAR) with recycled water in Australia, Australian Water Recycling Centre of Excellence Report.