The study has led to a debate in the scientific community over the utilisation of these groundwater resources in the drought-hit state
As California endures the fifth year of a record-breaking drought, researchers from Stanford University have revealed that there is a vast amount of unrecognised and untapped deep groundwater resource in the state.
The study, published in Proceedings of the National Academy of Sciences in June 2016, has claimed that the groundwater resides at depths between 300 and 900 metres below the ground in Central Valley. Mary Kang, an environmental engineer, and Robert Jackson, an earth scientist, from Stanford University in Palo Alto, California, conducted the study. They said that with the findings, they have been able to extrapolate the size, volume and water quality of the aquifers beneath eight California counties.
Previous California groundwater estimates were based on data which was decades old and the groundwater extended only up to a maximum depth of 300 m. Using a public database, the researchers were able to examine underground water at levels more than five times deeper than had been studied before. Little was known about the amount and quality of water in deeper aquifers.
The study has, however, led to a debate in the scientific community over the utilisation of these groundwater resources. Few have said the study is naïve and misleading, while others consider it as an important step. Overall, the extraction of this deep groundwater could be extremely expensive and would run the risk of causing considerable land subsidence. Sustainability issues related to management of the resource in the long run is another unresolved concern. Economically, technologically and environmentally feasible extraction methods are needed.
Groundwater status in California
There are about 515 groundwater basins and sub-basins in California that contribute around 38 to 46 per cent of the total water supply. Over the last decade (2005-2015), the groundwater level has fallen up to 3 m in 50.2 per cent of groundwater basin areas. The groundwater level decrease is between 3 m and 0.7 in 27.1 per cent of the groundwater basin area. Groundwater extraction in excess of natural and managed recharge has caused historically low groundwater elevations in many regions of California.
The projections made after this study may offer little hope in tackling the groundwater crisis, but in the long run, a more detailed study is needed to mainstream the applicability of these scientific findings. Complications in terms of water quality and pumping of groundwater also need to be considered. The quality of groundwater has been questioned as it is located in regions vulnerable to contamination from oil and gas drilling, wastewater injections and hydraulic fracturing. If considered as a source of water, these deep aquifers should be extracted and treated with minimal environmental consequences.