  |
Wells, shafts and boreholes
Case-study
General information
1. Name technique: ASR (Aquifer Storage and Recovery) wetlands (Australia)
2. Pictures
Figure 1: ASR well at Parafield ASR project site, Australia (Source: Dillon P. 2005)
Figure 2: Schematic drawing of ASR system. (Source: Gale I. 2005).
3. Brief description of the situation:
South Australia is the driest state in Australia, which in turn is the driest inhabited continent on earth. Access to cheap, good quality water is one of the critical issues facing the development of the State. In the past, storm water and sewerage effluent has always been channeled to the coast, where it has degraded the marine environment. Water for utilization has always been pumped from River Murray, a river that is undergoing an ecological crisis through over use and mismanagement.
The city of Salisbury, located 25km north of Adelaide in South Australia, is nowadays an international leader in the use of wetlands and ASR technology for stormwater management and utilization. Stormwater, traditionally regarded as a problem, and in some cases a threat, is now harnessed and utilized by Salisbury in a series of wetlands, enhancing the landscape and creating habitat diversity.
The Parafield stormwater treatment and reuse project is one of the most recent and most challenging of the Salisbury wetlands projects. Urban stormwater is harvested at Parafield airport, treated, and injected into a formerly brackish limestone aquifer to provide low salinity water supplies for industrial use and irrigation in Salisbury (Figure 1). This project is described in more detail here.
Technical information
4. Brief description of the technique:
Aquifer storage and recovery (ASR) may be defined as the storage of water in a suitable aquifer through a well during times when water is available, and recovery of the water from the same well during times when it is needed (Figure 2). Design of structures can vary considerably and includes the construction of boreholes in the base of wells and backfilling the well with graded filter material to restrict ingress of suspended solids that would rapidly clog the system, and restrict inflow of contaminants.
5. Attributes overview:
| Attribute | Description |
| Use | Industry, ecology and environment, and to a lesser degree agriculture |
| Management purpose | Quality improvement |
| Scale | Large |
| Source of water | Urban storm water |
| Geology | Limestone |
6. Construction:
Urban stormwater is guided through several components. First the stormwater is harvested and diverted from existing drains to a constantly flowing system of, bird-proofed reed bed ponds. Then the water is stored in a capture basin. From there it is pumped to a similar capacity holding basin, from where it is gravitated to a two hectare cleansing reed bed. Water will then flow continuously through the densely planted reed bed to biologically cleanse the water. After cleansing and filtering, the water is supplied directly to users. Surplus water is injected into a formerly brackish limestone aquifer via ASR-wells, to provide low salinity water for extraction during dry periods. The ASR wells are drilled to depths between 160 to 180 m.
7. Capacity:
- The scheme capacity for both the direct supply to users and the ASR extraction is 1.1 Mm3/year in the first stage. A proposed second stage of the Parafield scheme will expand minimum yield to 2.1 Mm3/year by adding other catchments. Use of the water will be facilitated by the development of an ASR borefield.
- Injection rate is 35 l/s
- The total catchment area from which stormwater is harvested is 1600 ha.
- The system is designed to provide an average of 10 days of residence time for the stormwater in order to ensure optimal treatment efficiency.
- The flood protection ratio is 1 in every 10 years.
8. Experiences with Operation and Maintenance:
In general, design of ASR-structures can vary considerably and include the construction of boreholes in the base of wells and backfilling the well with graded filter material to restrict ingress of suspended solids that would rapidly clog the system, and restrict inflow of contaminants. Clogging of aquifer material or the borehole screen can be managed by:
- Mechanical and/or chemical treatment of recharge water
- Introduction of water through a valve to ensure a continuous column to the surface
- Regular recovery using surging and pumping
9. Experiences with Monitoring and Evaluation:
At Parafield, flow rates, pressures and water quality are automatically monitored and linked to a programmed control system with telemetry to council offices. Online monitoring is performed on pH, TDS, and SS.
10. Experiences with related subjects (e.a. erosion prevention, quality of drinking water, ..):
Water quality: At the Parafield site, nutrient and pollutant loads will be reduced by up to 90% and the treated water has a salinity of <250 mg/L.
Financial information
11. Experiences with management:
Over the last 20 years, the Salisbury Council has constructed more than 30 wetlands covering an area of 260 hectares and costing in excess of US$ 14 million. The Parafield site is one of the most recent of these wetland areas.
12. Benefits:
The costs of the first stage of the Parafield project are US$ 2.9 million. Benefits include the harnessing and utilization of stormwater (traditionally regarded as a problem), enhancing the landscape and creating habitat diversity. The ASR system provides low salinity water supplies for industrial use and irrigation in Salisbury.
General conclusions
13. Generic factors of success and traps ('do's and don'ts'): To successfully apply ASR, extensive research and ASR pilot testing is needed, to evaluate permeability of aquifers, chemical changes in aquifer, the quality of recovered water, the efficiency of schemes and environmental impact. 14. What can be used elsewhere, under which conditions:
ASR is used where thick, low permeability strata overlie target aquifers. Recharge wells are also advantageous when land is scarce. Ideally, ASR sites should be located in a confined, single porosity aquifer at sufficient distance from the outcrop to have an acceptable impact on flows in streams. A readily accessible source of water for injection is needed and access to an existing treatment works could be important if the recovered water is not wholly potable. ASR can be applied to saline or brackish aquifers. This is possible when the potable injection water displaces, rather than mixes with, the natural water. Some mixing on the fringes of the stored water does take place and reduces the quality of some of the recovered water.
15. Advantages and disadvantages:
| Advantages | Disadvantages |
|
|
16. Links to detailed information of this project / technique:
Paul Pavelic
CSIRO land and water, Adelaide, Australia
Peter Dillon
CSIRO land and water, Adelaide, Australia
17. References
- Chaudhary H., Pitman C. 2002. Implemnting large scale stormwater recycling schemes -meeting economic, environmental and community objectives. Management of Aquifer Recharge for Sustainability. Proceedings of ISAR-4, Adelaide, South Australia.
- Gale I. 2005. Strategies for Managed Aquifer Recharge (MAR) in semi-arid areas. IAH - MAR, UNESCO IHP. Paris, France.
- Pyne, R. D. G. (1995). Groundwater recharge and wells: A guide to Aquifer Storage Recovery. Florida, USA., CRC Press.