Managed Aquifer Recharge

Groundwater recharge is part of the water cycle and happens continuously through river and stream losses as well as from rainfall.  Water filters down through the soils into our underlying aquifers.  The tools of Managed Aquifer Recharge mimic nature as closely as possible and are designed to capture available surface water and use this water to enhance the natural groundwater recharge process. 

The aim of MAR is to replenish aquifers during the wetter winter months with excess flows to enable additional water supply in our aquifers in advance of each summer, and drier seasons, while ensuring that water quality in the aquifer is maintained. 

Sites are designed to ensure only high quality water is sourced and then used for recharge. Water filtering methods use first and foremost our natural processes of the subsurface soils and gravels. We then use ‘infiltration galleries’ to capture water that has filtered through the gravels. Water is filtered as much as possible at its source before it is delivered to a MAR recharge site. At the recharge site further filtering occurs using riparian planting and wetlands and for this pilot where we are replenishing the deep aquifer water is filtered a third time through an additional ‘infiltration gallery’. Although MAR aims to replenish the water levels the design of the site is always centred around ensuring high quality water. 

With the rising pressures of extreme droughts, and the uncertainty of climate change, ensuring that groundwater levels and the quality of freshwater stored in aquifers are appropriately managed is increasingly important. 

Water quality is a priority when designing the MAR recharge site and before the project even proceeds it must meet consenting conditions. 

Water being diverted from the Waipawa River is filtered before it moves to the MAR site and is further filtered through a constructed wetland and the gravels as part of nature’s natural filtering processes. 

During operation, a live water-quality monitoring programme will be operating to ensure the filtering processes are working as expected and that only high-quality water is recharging the aquifer. 

A pilot offers the opportunity to trial these tools and learn how they operate in our environment.

This is a small-scale pilot at a single site and the Pilot aims to test and demonstrate how the tools of MAR work here in Central Hawkes Bay. We will be measuring the impacts and benefits so we can determine if MAR offers a viable alternative water storage option.

Alongside testing the effectiveness of MAR we will be learning a lot about the hydrogeological area that will help us determine where and how MAR may be deployed to support other local areas if it performs well. 

Our priority is ensuring the environment has the water it needs to thrive. 

If the MAR pilot performs as expected, it will be an additional and important tool in supporting our goal of ensuring Hawke's Bay has long-term, climate resilient and secure supplies of freshwater, for all. 

If the pilot is successful, a network of MAR sites could be strategically located to operate as a groundwater replenishment scheme, helping us to manage the overall water balance in our catchments - supporting the environment and securing water for other uses in future. 

By piloting MAR, we're not only seeking to hold the line for the environment in the face of climate change but also provide a viable option to store more freshwater to meet the increasing demands of growing populations and thriving industry and agriculture.

While we see the Waipawa and Tukituki rivers running above ground, there is a much larger water system underground – the Ruataniwha Aquifer -  being accessed by homes, industry and for irrigation. 

The Ruataniwha groundwater system is within a large basin (covering nearly 800 km2) bordered by the Ruahine Ranges to the west and limestone hills to the east with relatively distinct layers separating the shallow and deep aquifers . The basin’s gravels act like a reservoir, storing and filtering water from rainfall, rivers and streams, that replenish the aquifers with high-quality water. Due to the groundwater system’s specific characteristics, scientists believe that it is likely to respond well to proactive recharge using MAR.  A Pilot aims to provide us further information and understanding. 

The MAR site is located between Ongaonga and Tikokino on the Ruataniwha Plains. Water being diverted from the Waipawa River is filtered before it is delivered across farmland by an underground pipe to the MAR recharge site approximately 2.5km away. The actual recharge site has a small engineering footprint and fits within approx. 1hectare of land. It has been designed to be integrated into the working farm environment. The concept design has also been adjusted to provide an aesthetically and visually appealing site with the inclusion of a wetland, riparian and native planting. 

Figure X Schematic of the MAR Pilot concept design

The diversion and storage of water using MAR is site specific. In this case, the project is seeking to divert up to approximately 3 million cubic metres of water a year through the natural river bed for use at the MAR trial site, of which most will be diverted during the wetter, winter months.   This will be monitored and tracked throughout the three year trial period. 

The pilot will test how water recharged into the shallow aquifer will improve the environmental and cultural values of the trial area.  In addition to supporting the environment during summer, up to 60% of the water replenishing the deeper aquifer will be recovered for a productive use trial.  The remaining 40% is new stored water for the groundwater system.  Access to this newly stored groundwater is controlled by Regional Council through allocation limits and the water permit process. 

Yes, and very successfully in places such as Spain, India, the United Kingdom, and Africa and throughout the United States.  

While a new method for New Zealand, MAR has been used extensively overseas for over 60 years in various capacities, developing over time with new techniques to improve water quality. 

Here is a map of the various groundwater replenishment schemes established throughout the world;

MAR has been proven internationally to be an effective and sustainable water management tool, and both Canterbury and Gisborne have successfully trialled and implemented MAR in priority catchments to support localised groundwater management. 

After the success of Canterbury's Hinds MAR, the community is now rolling out a further 16 MAR sites to ensure they have plenty of quality freshwater throughout the year. 

Climate change is projected to affect our groundwater levels. Less rain, longer, hotter summers and drought means less natural recharge of the aquifers. This, paired with a growing demand for water at the point of time in the water cycle when supply is least available, means at times we are consuming more freshwater than the environment naturally recharges. 

Much of the worlds’ freshwater is found in groundwater aquifers.  Groundwater moves slowly through aquifers, at a snail’s pace compared to rivers and streams above.  Therefore, groundwater held in aquifers is termed as ‘storage’. 

Of the approximate 3 million cubic metres a year available for recharge, more than 60% is targeted for the shallow aquifer system. This is for the sole purpose of increasing baseflows that support springs, wetlands and down-gradient tributary streams feeding the lower Waipawa River trial area. 

Approximately 40% of the recharge is targeted on the deeper system, for replenishing groundwater storage. This deeper aquifer provides groundwater supplies for a vast majority of the water users in this sub-catchment area.  

The key challenge to developing water security is the timing of water availability - relative to demands and/or needs. The MAR project diverts most of its water during the wetter, higher flow periods.  

Additional water recharge into aquifers during those periods helps to slow water down, utilising the natural storage features of the catchment.  This stored groundwater releases to spring-fed streams and rivers as baseflow through the drier, hotter summer months when ecological habitats and cultural values are under pressure.  

Climate change is impacting both ends of the hydrological processes in the catchment with higher, short duration winter peak flows coupled with more prolonged, lower summer flows which makes this kind of project important for our future water security. 

Regional Council has put a number of interventions in place to control water usage, including capping the number of groundwater allocations and raising the river level flows for when takes cease. Based on our projections that still won’t be enough in decades to come, as the gap between demand and supply grows due to climate change. 

Regional Council also works with city and district councils to encourage efficient water use. Alongside the objectives to supplement depleted waterways, the Regional Council continues to investigate ways to further reduce demand for water and as part of the Regional Planning Processes will be reviewing current freshwater limits and how water is allocated to implement central governments revised Freshwater Management 2020 regulations.

MAR is just one solution the Regional Water Security Programme is investigating for water storage. The feasibility of above-ground storage for the Heretaunga Plains is also being investigated, as well as considering water conservation, alternative farming systems and land-use changes to increase supply and manage demand. Regional Council has investigated above ground water storage options extensively in Central Hawke’s Bay and this continues to be an option explored within the community. 

In Hawke's Bay, most of the water we consume is from groundwater. MAR offers a way to give back to the system we take from and provides a means to manage the overall water balance. 

MAR offers a low-energy water storage option, mimicking natural recharge processes to replenish our aquifers. Proactive groundwater replenishment helps to increase water levels and sustain baseflows to surrounding spring-fed streams, wetlands, and rivers. 

The MAR trial is one of the Hawke's Bay Regional Council's Water Security projects, co-funded in partnership with Kānoa - Regional Economic Development & Investment Unit (formerly Provincial Development Unit). 

We are running a three-year trial to test the effectiveness and concepts of MAR in Central Hawke’s Bay to determine whether it’s a viable storage option under the Regional Water Security Programme. 

This project offers a wonderful opportunity to partner with mana whenua and incorporate into the learnings a Te Aō Māori (Māori world) view of the project.  As part of the consenting process, the project engaged with mana whenua and a Cultural Impact Assessment (CIA) was produced documenting cultural values, interests and associations mana whenua have in the area where the trial will occur. It also identifies any potential impacts the project may have and how mana whenua would like to see these managed.   As the project progresses our aim is to deepen and enhance the partnershiop with mana whenua putting in place a  Cultural Health Monitoring programme to operate alongside the surface and groundwater monitoring. This is to be developed and led by mana whenua and offers an evolved approach for projects like this to integrate Matauranga science.