Editor’s Note: The City Council sets the demand for water through zoning and licensing. Once approved, the Water District Board tells the city council that they can deliver water to meet that demand, with the proviso in small print: “if available.” Both groups of elected officials know that the local Basin remains over appropriated. The Water District pumps over 8,684 Acre Feet Yearly (AFY) (2020 amount), 5,084 AFA over the 3,600 AFA underground perennial yield. At a minimum, the City Council should publish the water demand over the perennial yield and the consumptive (gallons per day) per person rate each time they decide to increase the water demand in the community.
by Mark Hill, Watershed Scientist
The point at which there will be insufficient water in Mesquite to sustain growth beyond a given population is called the “build out”. That point may be closer than the Virgin Valley Water District and Mesquite city council assume.
The May 31,2022, issue of the Desert Valley Times carried an article by the Associated Press describing how western cities are responding to the drought. In the article, it was noted that while Las Vegas and the Southern Nevada Water District have set a goal to reduce consumptive water use from about 200 gallons per day per person to 105-gal per person per day, other municipalities like Mesquite have set no goals to reduce its consumption from 270 gallons per day per person. The consumption value for Mesquite is extraordinary when compared to other cites with high consumption. For example, the Central Iron County Water Conservation District in Utah delivers 262 gallons per capita per day, exceeding Utah’s average by nine percent.
Consumption is the amount of water that is removed from aquifers, rivers and springs and not returned. The amount of water consumed can be reported as gal/capita/day or as acre-feet per year (ac-ft/yr). Water districts like Virgin Valley (VVWD) prefer to describe water volume consumption as acre-feet per year.
Using population growth predications for Mesquite and the 270 gal/capita/day rate of consumption, the annual water demand can be calculated.
2020: 6,808,464 gal/day for 25,214 people = 7,626 ac-ft/yr
2030: 9,465,670 gal/day for 35,055 people = 10,602 ac-ft/yr
2035: 11,161,020 gal/day for 41,333 people = 12,502ac-ft/yr
2040: 12,751,410 gal/day for 47,223 people = 14,283 ac-ft/yr
Currently, VVWD supplies Mesquite and Bunkerville by pumping the aquifer Basin 222 via nine wells. In 1968, the US Geologic Survey performed a conjunctive study on Basin 222 to determine how much water goes in and how much goes out of the aquifer. The USGS concluded that Basin 222 has a sustainable perennial yield of 3,200 ac-ft. When the volume of water pumped out of an aquifer exceeds the aquifer’s perineal yield, it is called “mining” the aquifer. Overtime, mining can totally deplete an aquifer, or lower the water table to such a degree that either the water is too deep to economically pump, or, in the worst case, water quality at great depths is so contaminated with arsenic and fluoride and metals that pumping is prohibited.
VVWD pumps over 7,000 ac-ft annually. This is from a basin which has been shown to have a sustainable annual yield of 3,200 ac-ft. Of course, this raises the question is Basin 222 being mined? The VVWD and the Nevada water engineer have consistently ignored this likelihood even granting VVWD additional water rights to Basin 222 to the tune of 12,271 ac-ft. VVWD has “paper” water rights to 12,271 ac-ft. Nobody knows if there is that much water in the aquifer.
In the absence of a conjunctive study that quantifies the current sustainable yield, it can be concluded that Basin 222 is already over drafted. Two years ago, VVWD was pumping 7,626 ac-ft, today that figure is probably closer to 8,000+ ac-ft.
But the real story is Mesquite runs out of water from Basin 222 between 2030 and 2035 – maybe eight years from now when VVWD hits its theoretical apportionment ceiling. Then, according to VVWD, they will have to exercise their “paper” water rights on springs and the Virgin River. Again, paper water rights are not the same as “wet” water rights.
In their 2020 Master Plan VVWD recognizes the differences between wet and dry water rights “…the District holds a total of 11,321 AF of surface water rights, for a total combined water right (groundwater and surface water) of 23,592 AF…. This value represents the legal annual water use limit for the District, sometimes referred to as “paper water”. In reality, the actual amount of water present in aquifers, springs, and rivers (referred to as “wet water”) may vary from what is designated in the “paper” water right…. What is specified as “legally” available in a water right may or may not actually be available to the District for use”.
Not withstanding the difference between paper and wet water rights, VVWD simply assumes there will be sufficient groundwater and surface water to accommodate a build out in Mesquite of 72,900 people. An assumption not grounded in data.
At 270 gal/day per capita, this equates to a consumption of 22,048 ac-ft/yr; about twice VVWD’s 12,271 “paper” water right from Basin 222 and will require tapping the river and springs in the hope that will be adequate flows to exercise their “paper” water rights.
The water situation throughout the Lower Colorado is so dire that Mesquite may be gambling with the cities’ future by relying upon assumptions about Basin 222’s sustainable yield and the hope that “paper” water rights can magically transform into “wet” water rights.
There are several pro-active steps the Mesquite City Council and VVWD along with the state water engineer can take now to avoid a serious water shortage in the near future.
First, a conjunctive study is needed to determine just what the current perennial yield is from Basin 222, so that water managers and political leaders can make sound decisions based upon reliable data.
Second, until a conjunctive study is completed the Mesquite City Council should impose a temporary moratorium on building permits, residential and commercial. More pumping from the aquifer at this point may only exacerbate the mining of groundwater.
Third, the state water engineer should also call a halt to any additional well drilling until a conjunctive study is completed. As in Utah, the Nevada water engineer should adopt a groundwater management plan that slowly rescinds water rights until the Basin is back within safe yield estimates.
Fourth, the city council needs to set a goal for reducing water consumption. For example, from 270 gal/capita/day to at least 150 gal/capita/day by 2030. Methods being employed in Las Vegas, St. George, Ivins, Santa Clara, and other area municipalities can be adopted along with a campaign to inform and educate the citizens of Mesquite.