An outlook on Managed Aquifer Recharge projects in the world

This section describes the outlook of the managed aquifer recharge projects in different continents in the world. A total of 93 case studies were analysed that include regional examples, site-specific examples, and pilot projects. Some of the

projects have been incorporated to the overall water resources management of the respective area. Some of the projects are focused to solve local water resources problem and some projects aim for scientific understanding of certain issues relevant to the local problems. In order to assess the large amount of information on MAR, published research reports and guideline reports were taken in consideration. Figure

2.6 shows the distribution of the projects analysed in the study. Although MAR is practiced throughout the world, much of the information is sourced in USA, Europe, Australia, Israel, and India.

Information regarding MAR implementation in South Africa and Latin America is scant and the description of MAR projects is not well documented in most of the cases. The following section Figure 2.6: Continental and regional distribution of MAR projects analysed in this study

briefly describes worldwide practice of MAR projects in terms of water source, water use, MAR techniques, and aquifer type.

Water source

The source of water varies across the projects and includes surface water (43%), treated effluent (22%), storm water (17%), and mixed type water (18%). From the analysis (Figure 2.7a), it can be concluded that in most cases the water source is surface water because of the availability and the lower pre-treatment requirement. Advanced treatment of wastewater and subsequent injection of treated effluent into the aquifer is now being increasingly practiced. This type of water is mainly used in developed countries. In the United States, most of the current ASR schemes involve potable water (AWWA, 2002). The Dan Region project, the largest artificial recharge project in Israel, uses the treated effluent from Tel Aviv and reuses the stored water for unrestricted irrigation. The use of storm runoff is widely practiced in the countries, which have heavy rainwater during the wet season such as in India. Some MAR projects function by mixing treated effluent with storm water (IGRAC, 2010).

However, the quality of source water is now the main determining factor for MAR implementation worldwide.

Use of water / Objective of the project

MAR now plays an important role for the improvement of water supply conditions. In this study, 39%

of the projects reviewed aim at improving water supply at the localities. In Germany, 54% of the applications are mostly for drinking water supply (Water & Forestry, 2007). Seasonal storage of water is another main objective of MAR where enough rainfall is available during the wet season.

Reclaimed water can be reused for agricultural use after water quality improvement in the aquifer (Figure 2.7b).

Figure 2.7: (a) Water source for MAR projects and (b) uses of MAR projects

Very few projects are working on the aim of protecting salinity intrusion in the coastal aquifer. In china, most MAR projects are aimed at the enhancement of groundwater resources (Han, 2003). Many

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projects have been implemented to achieve two or three of the objectives mentioned above. The Burdekin Delta scheme, the oldest and largest infiltration scheme in Australia, provides water for sugarcane areas using surface infiltration techniques. It is also used to prevent salt water intrusion into the aquifer (Narayan et al., 2007).

Aquifer types

In this study, the hydrogeological environments (aquifer type) are grouped into four general categories, namely alluvium, fractured hard

rock, consolidated sandstone and carbonate aquifers, according to the description given earlier in section 2.2. In the USA, a number of MAR schemes are using the alluvium aquifer. In most cases, the confined aquifers are being used for water storage. The majority of successful MAR schemes within Australia operate in deep, confined, tertiary limestone (calcarenite) aquifers, whereas

limited success has occurred in sandy aquifers (DWLBC, 2002). Of the bedrock types, the predominant rock type is sedimentary. MAR projects in fractured rock aquifers exist in India (CGWB, 2000) for transferring the captured storm/surface water over large distances.

MAR techniques

The spreading basin is the most popular MAR technique all over the world. The spreading basin offers the most benefit of SAT and it is economical. A number of pilot ponds have been constructed in order to develop site-specific information

on the hydrogeology and water quality of the aquifer. Considerable innovative implementation of the ASR scheme and research into ASR has recently been

undertaken in Australia and the USA. Bank infiltration is well practiced in Germany (Balke and Zhu, 2008) along the Rhine, Main, Elbe and Ruhr rivers. Approximately 15% of Germany‘s drinking water is produced through MAR (Water & Forestry, 2007). In-channel modification and rainwater

Figure 2.9: Worldwide practiced MAR Techniques in different hydrogeological conditions

Figure 2.8: Predominant aquifer types for MAR projects in the world.

harvesting are a commonly practiced technique in the various provinces of India, Pakistan, and Australia. Mostly roof-top harvesting is done in India (CGWB, 2000; UNESCO-IHE, 2005). Roof-top rainwater harvesting is being made mandatory, by amending the building by-laws, in urban areas of India where ground water levels are more than 8 meters below the ground surface or the roof area is more than 100 m² (UN-Habitat, 2006; CGWA, 2001).

Lesson learned from the analysis

A number of lessons learned can be drawn from the analysis of the 93 projects. First of all, it can be concluded from the review that MAR can significantly contribute to the water resources problem solution. The main benefits of MAR are: water storage and supply for domestic consumption and irrigation, enhancement of groundwater resources, and the prevention of salinity intrusion and the minimization of environmental damages. Besides the advantages, MAR schemes face a number of problems that should be considered during planning. First of all, well clogging is a problem that many MAR projects in the world have faced. Back flushing of recharge wells and wetting/drying cycles of the infiltrations basin are the main technique to manage clogging problem (Maliva and Missimer, 2010). Depending on the aquifer type, the frequency of back flushing and wetting/drying are set.

Little information is available about the GW quality monitoring network. Many documents reviewed suggested implementing a good monitoring network to understand the geochemical processes, well hydraulics, and the degree of water quality improvement. Economics of MAR is another prime issue for MAR implementation. Very few documents reported on the cost-benefit analysis of the MAR projects. Brown et al., (2005) reported that the cost of a cubic meter of recovered water is $1.54 for non-brackish sites while it is $3.56 for the brackish water. The issue of regulation and permit is also a great concern and sometimes frustrating to the ASR operators. One Californian ASR facility requires permits from 14 separate agencies for that facility (Water and Forestry, 2007). The main conclusion drawn from this literature review is that the study of and application of decision support systems for planning and management of MAR projects has been lacking. AWWA, 2002 reported that 89% of the ASR operators were satisfied with their projects. Due to the lack of proper decision and good understanding of the system, a number of projects became unsuccessful in some other countries. The future challenge of MAR is the proper planning and management of projects.

2.1.4 Managed Aquifer Recharge project planning, impact assessment, and Decision