Rationale

Managed Aquifer Recharge (MAR) is used worldwide in different applications to replenish overexploited aquifers and to improve water quality, although details of the functioning and role of relevant hydrological and biogeochemical processes and pathways still need to be better understood. In a broad sense, MAR is a low-energy and low-cost water recycling technology and in practice the only technology available to restore depleted aquifers. The water is purified during passage through the soil and aquifer sediment, and ultimately increases the groundwater recharge.

The major concerns with MAR still arise from the potential contamination of the aquifer with trace concentrations of organic chemicals, nutrients and pathogens not removed during infiltration. To minimize the pollution risks, specific reactive barriers placed in the infiltration basins have been suggested. Further, combinations of engineered and natural treatments may be used to achieve safe use.

Another issue hampering the MAR technology in general is the potential clogging of the subsurface. Despite these challenges, many large scale MAR projects have succeeded in both restoring aquifers and improving water quality because careful research took place to fully address real and perceived risks. A key challenge associated with infiltration of river and reclaimed waste water, is the presence of numerous trace organic contaminants and micro-pollutants that can be harmful to ecosystem and human health. For successful MAR application the concentrations of organic pollutants such as pharmaceuticals, hormones, and personal care products must be reduced to certain levels depending on the purpose of the water use.

Although MAR is a well-known technology, tools for proper management of degradation processes securing safe water for multiple purposes are still lacking. In this project we will develop a dual-stage MAR (DUST-MAR) concept with two treatment steps. Initially, river water (or reclaimed waste water) is infiltrated to shallow aquifers for removal of pathogens and easily degradable organic compounds; secondly this purified water will be infiltrated or injected to deeper aquifers for storage and further degradation of more recalcitrant pollutants. Water from the shallow aquifer may be used immediately for purposes where water quality demands are lower e.g. irrigation, while the stored water may be used for drinking either directly or following further treatment at the waterworks.

While it is recognized that MAR is important for replenishment of overexploited and depleted aquifers, and may improve water quality following proper management, it is unknown to which extent MAR will be able to significantly alleviate the water scarcity in the North China Plain (NCP). The potential impact of large scale MAR schemes can only be studied by scenario analysis, which requires an integrated surface water groundwater model to provide reliable distributed estimates and accounting for all major water fluxes.

An appropriate regional scale model should be able to quantify the major boundary fluxes and internal water flows for the NCP. These include the surface and groundwater inflow from the upstream mountains in the Haihe basin, the extensive irrigation throughout the NCP and groundwater pumping for human and industrial consumption. In addition, the anthropogenic water transfers related to the SNWT and the discharges of treated wastewater should be quantified. There is a need to gather existing hydrological data, new satellite based information and previous modelling efforts on the NCP in an updated regional scale integrated surface water groundwater model tailored to address the questions related to the potential for large-scale MAR implementation.

Objectives

The long term objective of the project is to prepare experts and water managers in China with the best possible knowledge base in order to make informed decisions on large scale MAR implementation in the NCP as a tool for alleviating water scarcity.

The immediate objective of the project is to examine the potential of large scale MAR implementation in NCP through both a quantitative and qualitative assessment. This is achieved through three work packages dealing with 1) Regional scale and site specific integrated surface water -groundwater modelling as a tool for scenario testing and examination of upscaling potentials of MAR, 2) Research in laboratories and at selected MAR installations targeting degradation and treatment processes related to trace organic contaminants and pathogens, and 3) Communication of knowledge through stakeholder involvement, policy briefs and preparing a MAR technical guideline for the NCP.

The project will contribute to the state-of-the-art by developing a regional scale coupled groundwater-surface water model with improved boundary conditions and spatial representation by combining previous modelling efforts with flux and state estimates from satellite data. At the field sites degradation processes will be monitored along groundwater flow paths in a dual-stage framework by evaluating the water quality improvements of reclaimed water in shallow aquifers after river bank filtration (stage I) and after prolonged groundwater storage in confined aquifers (stage II), where push-pull or forced gradient tests will be utilized. Laboratory experiments simulating the MAR environment will be conducted for specific contaminants. Finally, stakeholder involvement will ensure knowledge sharing and development of MAR application strategies to be tested through scenario modelling. Throughout the project, joint research will be carried out on both modelling and field/laboratory work, which will result in both research publications, policy briefs and a MAR technical guideline for China.

WP1: Integrated hydrological modelling of coupled surface-water and groundwater systems.

The key question to address in WP1 is: How much can MAR contribute towards solving the water scarcity problem in NCP? This question will be pursued through a modelling framework that integrates groundwater and surface water resources. The modelling studies will be carried out at the regional scale to evaluate the overall potential of MAR for restoring groundwater resources and at the field site scale to assess the potential of specific MAR installations within the NCP.

WP2: Water quality improvements through managed aquifer recharge in the North China Plain.

WP2 will assess the potential of managed aquifer recharge for turning treated waste water or polluted river water into valuable water resource. A dual-stage MAR approach (DUST-MAR) will be developed where, at stage I, shallow aquifers are replenished by river bank infiltration providing groundwater of a quality allowing it to be used for e.g. irrigation. Water from stage I will then in stage II be injected or allowed to infiltrate to deeper confined aquifers for storage and further degradation of more recalcitrant contaminants (stage II). This water may be used for purposes where higher quality standards are required preferably for drinking after a simple treatment at the waterworks.

WP3: Dissemination of results.

WP3 will disseminate the results to a wide audience through an active stakeholder involvement. Relevant stakeholders will be identified among the existing academic and professional network of the project team, from the SSC Network and from the stakeholders involved in the China Europe Water Platform and other relevant projects, such as the PIANO Project.
The research within WP1 and WP2 will be compiled in the form of a technical guideline for MAR; a document that will assist a science based development of MAR in NCP by combining research and experience within the project group.

WP3 includes an economic and socio-economic assessment of the potential of MAR as a tool to alleviate water scarcity. The analysis will identify economic drivers and barriers for a wider implementation of MAR in Northern China.

Outcome 1: WP1: Development of a knowledge base to access the quantitative aspects of the large scale potential of MAR as a tool for water scarcity alleviation

Outputs to outcome 1

1.1 Regional scale hydrological modelling
1.2 Field site groundwater modelling
1.3 Modelling of MAR implementation scenarios developed in WP3

Outcome 2: WP2: Development of a knowledge base to access the water qualitative aspects of MAR in NCP

Outputs to outcome 2

2.1 Evaluate the water quality effects of river bank infiltration to shallow aquifers
2.2 Evaluate the water quality effects of prolonged aquifer storage in deeper aquifers
2.3 Laboratory experiments in Denmark to evaluate degradation processes and build capacity in laboratory work

Outcome 3: WP3: Increase the knowledge on MAR among stakeholders, practitioners and policy makers

Outputs to outcome 3 3.1 Communicate research findings and develop MAR implementation scenarios in collaboration with stakeholders and policy makers 3.2 Collecting knowledge and experience on MAR in China for writing guideline 3.3 Quantify the economic and socio-economic potential of extended MAR on the NCP