An error was made in the definition of the density parameter ρ in Equations 7, 8 and 9 of the original article. It was defined as the bulk density of the aquifer, whereas it should have been the density of pore water. Additionally the density of the aquifer solid matrix ρ_s, used in equation 11 to compute the retardation factor, was not defined in the original article. The misuse of the bulk density instead of water density resulted in incorrect values of the computed thermal distribution coefficient, i.e. the bulk thermal diffusivity, and the retardation factor in Table 5. Some of the units were also incorrect. The corrected table is given here.

As a result, the sub-section ‘Temperature variations in the recovered water in wells’ should be corrected through stating the following: With a corrected retardation factor of 2.85, the average residence time of sources of water contributing to the wells is 74 days, which is sufficiently long to improve the water quality.

Managed aquifer recharge (MAR) is increasingly used to secure drinking water supply worldwide. The city of Amsterdam (The Netherlands) depends largely on the MAR in coastal dunes for water supply. A new MAR scheme is proposed for the production of 10 × 10⁶ m³/year, as required in the next decade. The designed MAR system consists of 10 infiltration ponds in an artificially created sandbank, and 25 recovery wells placed beneath the ponds in a productive aquifer. Several criteria were met for the design, such as a minimum residence time of 60 days and maximum drawdown of 5 cm. Steady-state and transient flow models were calibrated. The flow model computed the infiltration capacity of the ponds and drawdowns caused by the MAR. A hypothetical tracer transport model was used to compute the travel times from the ponds to the wells and recovery efficiency of the wells. The results demonstrated that 98% of the infiltrated water was captured by the recovery wells which accounted for 65.3% of the total abstraction. Other sources include recharge from precipitation (6.7%), leakages from surface water (13.1%), and natural groundwater reserve (14.9%). Sensitivity analysis indicated that the pond conductance and hydraulic conductivity of the sand aquifer in between the ponds and wells are important for the infiltration capacity. The temperature simulation showed that the recovered water in the wells has a stable temperature of 9.8–12.5 °C which is beneficial for post-treatment processes. The numerical modelling approach is useful and helps to gain insights for implementation of the MAR.

An approach is presented to determine groundwater flow in unconsolidated aquifers with a heat pulse response test using a heating cable and a fiber-optic cable. The cables are installed together using direct push so that the cables are in direct contact with the aquifer. The temperature response is measured for multiple days along the fiber-optic cable with Distributed Temperature Sensing (DTS). The new approach fits a two-dimensional analytical solution to the temperature measurements, so that the specific discharge can be estimated without knowledge of the position of the fiber-optic cable relative to the heating cable. Two case studies are presented. The first case study is at a managed aquifer recharge system where fiber-optic cables are inserted 15 m deep at various locations to test the fitting procedure. Similar and relatively large specific discharges are found at the different locations with little vertical variation (0.4–0.6 m/day). The second case study is at a polder, where the water level is maintained 2 m below the surrounding lakes, resulting in significant groundwater flow. The heating and fiber-optic cables are inserted to a depth of 45 m. The specific discharge varies 0.07–0.1 m/day and is significantly larger in a thin layer at 30-m depth. It is shown with numerical experiments that the estimated specific discharge is smoother than in reality due to vertical conduction, but the peak specific discharge is estimated correctly for layers thicker than ∼1.5 m.

Soil passage of (pretreated) surface water to remove pathogenic microorganisms is a highly efficient process under oxic conditions, reducing microorganism concentrations about 8 log¹⁰ within tens of meters. However, under anoxic conditions, it has been shown that removal of microorganisms can be limited very much. Setback distances for adequate protection of natural groundwater may, therefore, be too short if anoxic conditions apply. Because removal of microorganisms under suboxic conditions is unknown, this research investigated removal of bacteriophage MS2 and PRD1 by soil passage under suboxic conditions at field scale. At the field location (dune area), one injection well and six monitoring wells were installed at different depths along three suboxic flow lines, where oxygen concentrations ranged from 0.4 to 1.7 mg/l and nitrate concentrations ranged from 13 to 16 mg/L. PRD1 and MS2 were injected directly at the corresponding depths and their removal in each flow line was determined. The highest bacteriophage removal was observed in the top layer, with about 9 log removal of MS2, and 7 log removal of PRD1 after 16 meters of aquifer transport. Less removal was observed at 12 m below surface, probably due to a higher groundwater velocity in this coarser grained layer. MS2 was removed more effectively than PRD1 under all conditions. Due to short travel times, inactivation of the phages was limited and the reported log removal was mainly associated with attachment of phages to the aquifer matrix. This study shows that attachment of MS2 and PRD1 is similar for oxic and suboxic sandy aquifers, and, therefore, setback distances used for sandy aquifers under oxic and suboxic conditions provide a similar level of safety. Sticking efficiency and the attachment rate coefficient, as measures for virus attachment, were evaluated as a function of the physico-chemical conditions.

Artificial recharge of aquifers can be performed for various purposes and under varying hydrogeological conditions. We present an overview of deep-well recharge applications which have taken place in the Netherlands over the last two decades. We present the purpose of each application, the issues which had to be resolved, the preventive measures which were taken to improve performance and the lessons learned from each experience. Examples are given of applications which aimed at the storage of water for drinking and other purposes such as irrigation, achieving environmental goals and disposal of wastewater. Applications aiming at drinking water production usually faced issues related to the quality of the abstracted water not meeting drinking water standards with respect to various elements, such as iron, manganese and arsenic. Storage of water in brackish aquifers was complicated by buoyancy effects making part of the recharged water irrecoverable. Recharge of water with the purpose of recovering declined groundwater tables and fighting seawater intrusion was hindered by clogging of the injection well while the disposal of wastewater was limited to aquifers of lower groundwater quality.