Web-based global inventory of managed aquifer recharge applications

Sources of information

For the compilation of the MAR inventory, a comprehensive survey on MAR case studies was conducted over a period of about 12 months. The data were extracted from freely available publications, including journal articles (22%), reports (31%), conference papers (10%), presentations (5%), books and book sections (9%), academic theses (5%), and partially websites (10%), newspaper articles (1%), and other documents (7%). The first attempts of online search using specific evident keywords gave very discouraging results, indicating that most case studies are not readily available via common search engines. In addition, the search in specialized databases such as Web of Science, Academic Search Complete, ScienceDirect and similar was not giving satisfactory results due to very different terminology used in articles’ metadata. The most efficient search method was proven to be the manual screening of references listed in already available papers. This led to a systematical search with results either geographically localized or grouped by similar technologies and objectives. Once a certain case study was geographically localized, further sources were identified in available databases using the location’s name as keyword. This led to a cross verification and validation of the original paper and often enabled the harvesting of additional information about the site.

Given the international scale of the survey, it was obvious that a search in local languages might reveal supplementary information. Using the same methodology as described above, the screening was thus continued, beside English, in German, Spanish, Portuguese, French, and Chinese by MAR experts fluent in these languages. In addition, the search for European case studies was conducted by DEMEAU project team also in Polish and Dutch.

All the papers collected were stored in Zotero (2016), a reference management software that allows to easily collect, manage, and organize bibliographic information (metadata).

Criteria for site selection

A set of criteria was formulated for the selection of suitable references for the review. The first condition was that the MAR scheme is either in the advanced planning phase with clear perspectives for implementation or at different construction or operational stages. The category included projects that were shut down by the time of publication but operated in the past, as well as pilot projects followed or not by full-scale implementation. Not included were simulation studies conducted for the estimation of feasibility of MAR schemes and optimisation of existing applications. If at one site, more infiltration tests were conducted and at least one parameter was different (MAR type, objectives, influent type or end use of effluent), then multiple entries were assigned to the site following the number of distinct infiltrations. A second criterion was the description of either main or specific MAR types in the paper analyzed, with papers only mentioning aquifer recharge but without description of the method being excluded. Further criteria included public availability of the reference, either as direct web reference or through institutional subscription at local university and state library.

A special situation was created by the identification of very large amounts of case studies concentrated in small regions such as the “Catalog of recharge basins on Long island, New York, in 1969” published by the U.S. Geological Survey in its 70th Bulletin in 1973 (Seaburn and Aronson 1973). The catalog contains descriptions of 2162 recharge basins in Long island, New York, constructed between 1923 and 1969. Another example is the personal communication received from the Brazilian Institute of Geography and Statistics (Instituto Brasileiro de Geografia e Estatística) with technical data and locations of 3914 subsurface dams constructed between 2008 and 2015 in nine federal states of north eastern Brazil. These kinds of bulk data sets were not included in the present edition of the inventory, but they might be included in future updates after a more consistent review.

Database structure

Data collected was structured in four main categories, following the general structure of the DEMEAU catalog with minor modifications and extensions (Table 1): (1) general information (18 parameters); (2) operational parameters (18); (3) hydrogeological properties (9); and (4) water quality parameters (water quality monitoring with 6 fields and hydrochemical data with 106 fields). Mostly, general information about the site was available in the collected references with some relevant aspects remaining unclear. For example, the exact number of MAR schemes in operation is currently unknown, same for the operational capacity of the schemes, existing monitoring programs or pre- and post-treatment measures. Nevertheless, more parameters are planned to be added in the future but these must be extracted from other sources (e.g., national hydrogeological maps, climate databases, etc.).

Due to data inconsistency (values within brackets indicate the number of sites where the parameter was reported, as percent from the total number of sites), the web-based portal contains at this stage mostly general information about the MAR sites (parameters marked with “*” in Table 1), including the original reference. In future updates, additional parameters are planned to be added, including financial and economic data from selected MAR schemes.

Setup of a web-based portal for data visualization

To increase the availability and facilitate continuous update of the MAR inventory, an MAR web-based portal was developed and integrated into IGRAC’s Global Groundwater Information System (GGIS). The GGIS is an interactive, web-GIS portal to groundwater-related information and knowledge. The main purpose of the GGIS is to assist in collection and analysis of information on groundwater resources and its sharing among water experts, decision makers and public. The GGIS consists of several modules structured around six themes, including a theme on Managed Aquifer Recharge. The MAR theme has its own portal (http://marportal.un-igrac.org) with underlying database to allow storing and visualizing the global MAR data in a systematic way. By facilitating access and promoting international sharing of information and knowledge on MAR, the web-based MAR portal aims to increase awareness of MAR as a viable solution for sustainable groundwater resources development and management, and to provide a new tool for better planning of MAR at regional and global scale.

The system was developed based on cloud solutions to enable processing of large data sets, including excel files, raster and shapefiles. The IT architecture of the system consists of a PostGIS database, a map server (GeoServer) and the user interface (Fig. 1). The mapserver follows the international standards for geospatial data of the Open Geospatial Consortium (OGC). Information in the MAR Portal can therefore be shared and easily integrated with external Geographic Information Systems (GIS) using web map services (WMS).

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Implementation of web-based MAR portal

The MAR portal consists of a data layer catalog, a map viewer to visualize the selected data on a geographic location and a features panel to provide tabular output of the selected data. Additional information for each (point) location, such as references, can be displayed in the feature info. The portal can be used to generate new pieces of information by creating overlays of map layers (MAR suitability maps, or other overlays) and to build queries on the data. Users can export the global MAR inventory data in excel format via download functionalities in the system or by making use of the web services. Users can provide new data via an online submission form. Data is reviewed before including it into the web-based MAR portal. The MAR portal is available online and can be accessed without the prerequisites of any GIS knowledge or software licenses.

MAR sites

Among the four categories described in Table 1, almost 100% data coverage was found only in the first category (general information) while information about water quality was extremely scarce (either no water quality monitoring program was available or this kind of data was simply not published). For this reason, only the following parameters were selected for the web-based MAR portal: site name, country, location (latitude/longitude), MAR type, year of scheme deployment, the source of infiltration water, the final use of abstracted water, as well as the main objectives of the project (Fig. 2):

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Due to the high diversity of data sources, the terminology used in various papers was highly heterogeneous, which led to the creation of very long lists of thematic layers. For simplicity, a standardized classification system was needed so that data could be easily visualized and understood. The classification system selected was based on the methodology created within the DEMEAU project, which includes 15 MAR subtypes (Table 2), 7 project objectives, 8 types of infiltration water and 4 final uses of abstracted water (Table 3). The detailed description of the respective categories is very well documented elsewhere (Hannappel et al. 2014) and was therefore not included in this paper.

Table 2

Classification of specific MAR types

	Main MAR type	Specific MAR type
Techniques referring primarily to getting water infiltrated	Spreading methods	Infiltration ponds and basins
		Flooding
		Ditch and furrow
		Excess irrigation
		Reverse drainage method
	Induced bank infiltration
	Well, shaft and borehole recharge	Deep well injection	ASTR
			ASR
		Dug well/shaft/pit injection
Techniques referring primarily to intercepting the water	In-channel modifications	Recharge dams
		Subsurface dams
		Sand dams
		Channel spreading
	Runoff and rainwater harvesting	Barriers and bunds
		Trenches
		Rooftop rainwater harvesting

Table 3

Classification of other MAR parameters used in the web-GIS portal

Primary objective	Type of infiltration water	Final use of abstracted water
Ecological benefits Management of water distribution systems Maximize natural storage Physical aquifer management Water quality management Other benefits	Brackish water Distilled water Groundwater Lake water River water Storm water Tap water Wastewater	Agricultural Domestic Ecological Industrial

ASTR aquifer storage, transfer and recovery, ASR aquifer storage and recovery

MAR suitability maps

The identification of suitable locations for the implementation of MAR interventions is another tool to improve planning of MAR at regional scale (Bonilla et al. 2016). Existing regional MAR suitability maps are collected and made available within the portal to improve accessibility to this information and provide guidance for MAR suitability (Fig. 3). References and reports of MAR suitability mapping are available via the portal.

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