JOSHUA TREE - Think Joshua Tree's got plentiful groundwater? Think again.
By Sara Munro
Mojave Water Agency
Water Delivery Facilities
The results of a five-year study completed by the United States Geological Survey and released to the public Wednesday set the record straight on groundwater recharge, dashing any lingering hopes perpetrated by a fraudulent study portraying copious water stored in underground rivers and lakes.
"You are de-watering your aquifer," said USGS hydrologist Tracy Nishikawa. "You are extracting water faster than it's being recharged."
USGS hydrologists employed three methods of study showing that natural recharge is taking place at 71, 158 and 200 acre feet per year, significantly below the 1,800 acre feet the district extracts each year.
Tests indicate the Joshua sub-basin level has dropped 35 feet between 1958 and 2001.
Those seeking hope for rising aquifer levels due to recent rainfall will also be disappointed. Contrary to commonly held beliefs, rainfall has little to no impact on groundwater recharge.
"Summer storms do nothing for groundwater recharge," said Nishikawa, who used a Power Point presentation to show that winter precipitation is the source of natural recharge. He also explained that most of the water dropped in storm events like the most recent rainfall, runs off. What doesn't won't percolate into the aquifer for several hundred years.
The study indicates that the youngest water coming out of the taps of Joshua Tree is 2,400 years old, and the oldest is 32,000.
The good news is the water quality remains high, and there's no septic material in the groundwater.
Showing their concern over groundwater contamination due to nitrates from septic tanks, the board asked a slew of questions on the matter.
"At present, you are not seeing it in the groundwater supply," said Nishikawa. "It doesn't mean it's not saturating."
Nishikawa said the issue "may need to be considered in future scenarios."
General manager Joe Guzetta pointed out the business of the district is to take this information and use it to ask some pertinent questions, to predict future water levels and budgets, to investigate recharging alternatives and to consider "what if" pumping scenarios.
It is estimated that probably only 10 to 20 percent of the groundwater can be extracted cost-effectively.
"We're working with our geologist to determine what percentage is reasonable to extract," said Guzetta.
District policy sets how much of the extractable water can be removed.
The question on everyone's mind is: How much time can the district maintain pumping at current levels?
Director Rick Beatty said, "We know the problem is important, we don't know how urgent it is."