How much groundwater exists in Moab and Spanish Valley?
That’s what a proposed study spearheaded by the Utah Division of Water Rights (DWRI), and undertaken by the United States Geological Survey (USGS), hopes to determine in order to guide future development within Moab-Spanish Valley in Grand and San Juan counties.
On Tuesday, July 29 area stakeholders, including representatives from Grand and San Juan counties and the City of Moab, attended a public presentation and discussion about the proposed study at the Grand Water and Sewer Service Agency (GWSSA) office. David Susong, from the USGS Utah Water Science Center outlined the proposed three-year study that will attempt to calculate how much water exists in the Glen Canyon Aquifer (GCA), the sole source of culinary water for Moab-Spanish Valley.
“The fundamental question for future growth in Moab-Spanish Valley is what water resources are available for that growth,” Susong said. “The proposed study will provide new estimates of a “water budget” for the long-term management of water resources in the area.”
The idea for a comprehensive groundwater study for Moab-Spanish Valley isn’t new. The Nature Conservancy (TNC) and the City of Moab have been involved in the process for over 10 years.
“This is extremely exciting,” said Sue Bellagamba, Canyonlands regional director for TNC in Utah. “We don’t understand our system well enough.”
Grand County Council chairman Lynn Jackson said that he supports Grand County’s participation in the study.
“I think any community should be aware of, and have data regarding, the functioning of an aquifer system relied on for culinary and other needs,” Jackson said. “Our needs seem to be expanding and we have been in a sustained period of drought. It would seem to be relevant for all of us to have a better understanding of our system to allow informed decisions for the future.”
Interest in the study has been renewed in part because of recent large applications for water rights. In 2007, San Juan County applied for 5,000 acre feet of water to develop a portion of Spanish Valley. One acre foot of water equals 326,000 gallons of water. The average home in Moab-Spanish Valley uses approximately 185,000 gallons of water per year.
The DWRI issued a decision that granted San Juan county only a portion of the water rights it applied for until it could better determine how much water existed.
“We need to know how much water is available for appropriation so we aren’t pulling out more than is being recharged,” DWRI representative Marc Stilson said.
Stilson cited two groundwater basins in southwestern Utah that he said were “heavily overdrawn.”
“We don’t want to get there in Grand and San Juan counties” he said.
In his presentation, Susong showed aerial photographs of the Matheson Wetlands taken in 2004
and in 2013. The 2004 photo shows a much larger area of greenery than the one taken in 2013.
The wetlands are thought to be the main discharge area for the GCA, but a University of Utah study published in 2004 found that most of the groundwater in the wetlands didn’t share the same geochemical signature as water in the GCA.
This information suggests that water from the GCA is exiting the system somewhere other than the wetlands, either upstream or downstream, or that groundwater from the aquifer is being “mined.”
Mining groundwater refers to the process of taking more out than is being put in.
Bellagamba, whose organization owns the Matheson Wetlands along with the Utah Division of Wildlife Resources, said that though this may be cause for concern, TNC bases its work on the best science available.
“I would say that this points to the need for further studies such as the one currently being proposed,” she said. “We want to know how much water we are using to make sure there is enough left in the system for non-consumptive uses such as wetlands, creeks, riparian areas, and other things that we as a society value.”
Living Rivers executive director John Weisheit said that groundwater yields have been dropping throughout the 15 year drought that has affected the Colorado River Basin.
“Moab is just like the rest of the Colorado River Basin,” Weisheit said. “Supply is down, consumption is up.”
Weisheit is worried about what increased development in Spanish Valley will do to the area groundwater supply.
“We need to respect our carrying capacity or we’ll be drinking Colorado River water which is already over-allocated,” he said.
The Colorado River, one of the most over-allocated rivers in the world, is currently strained to meet the needs of downstream users, with both Lake Powell and Lake Meade currently at below 50 percent of capacity.
Moab-Spanish Valley doesn’t currently rely on water from the Colorado River, and instead relies solely on the GCA, which has often been thought of as a hedge against Colorado River shortages. But an article soon to be published by Geophysical Research Letters reporting on satellite data from NASA’s GRACE mission shows that groundwater is being depleted much faster than previously thought, far exceeding the depletion of Lakes Powell and Meade, particularly during the timetable of 2004-2013.
“Up to this point it seems, the Grand County community has assumed that we haven’t yet come to the point that we are using more water than is being recharged,” Canyonlands Watershed Council executive director Chris Baird said. “If this study is accurate, we have been depleting our groundwater at alarming rates. This turns my concept of our groundwater health on its head.”
Jackson said that before hitting the “panic button,” people must go back and look at how the aquifer has responded to several extended droughts during the last century. He said that by studying groundwater measurements in wells that have existed for decades, it will be possible to tell if the aquifer is responding similarly, and that it is possible that the aquifer has very rapid recharge and discharge rates.
“If those studies show that it’s never been this low, then we would likely have a serious situation,” he said.
Susong said the study has two main objectives. The first is to evaluate the components of the “water budget” which consists of aquifer recharge, or amount of water coming into the system through precipitation, and aquifer discharge which is the amount of water going out through irrigation, culinary withdrawal, and natural seepage. The second objective is to improve understanding of groundwater flow, flow paths, and connectivity between aquifers and the Colorado River.
Susong said that water levels in existing wells will be measured and that data will be collected on water use, gains and losses from streams, as well as other factors including evaporation, precipitation, aquifer
geology and groundwater flow paths. In addition, monitoring wells will be drilled, both in areas of discharge, near the wetlands preserve, and in areas of recharge in the Navajo Sandstone on the eastern edge of the valley.
The proposed study is expected to cost $530,000 over the next three years with USGS offering to pay 40 percent, or $212,000. The Utah State Engineers Office will pay $120,000 toward the project. This leaves $198,000 to be divided between stakeholder cities, counties, and water providers in Moab-Spanish Valley. If divided evenly, this amount would total $16,500 a year for each entity.
“It’s so important that all the entities buy into this together,” Moab City manager Donna Metzler said. “Now, with the cooperation of the State and the USGS, we have a real opportunity.”
Weisheit said that it is important to get started, but that data from wells and test drills will only tell part of the story.
“Forecasting and modeling will tell us more about the future,” he said. “A good leadership call would be to put a moratorium on development until a study is completed with the goal of providing a guaranteed 100-year water supply for the people that live here.”
“We need to know how much water is available for appropriation so we aren’t pulling out more than is being recharged.”
Study seeks to find out how quickly Glen Canyon Aquifer is being depleted
