WATER DISTRICT PLACES CAP ON MESQUITE GROWTH

By Mark Hill

Mesquite’s Growth will end in 2035, according to the Virgin Valley Water District’s (VVWD) revised water Conservation plan.

Based on an annual growth rate of 3.5%, VVWD estimates that underground water pumped from local Basin 222, the principal water source for the city, which crosses Arizona and Utah boundaries, will not sustain a population greater than 40,000.

Growth higher than that will result in the gradual draining of the aquifer. The city government will have no feasible alternative but to halt issuing residential, commercial, and industrial building permits.

Municipalities throughout the lower Colorado River watershed are grappling with increasing growth and population as water sources decline. Cedar City, Hurricane, St. George, Ivans, Santa Clara, Henderson, to Las Vegas have implemented water conservation measures to forestall a catastrophe while searching for new water sources. Some communities are already restricting growth by slowing the building permit process or placing moratoriums on new permits.

The 12-year horizon in the VVWD water plan is based on escalating water consumption and pumping, even while introducing iterative conservation actions. Unfortunately, from now until 2027, the plan calls for a minimal direct effort to reduce water consumption but continued planning and public outreach. From 2028 to 2034, the plan anticipates more stringent interventions and controls will be necessary. And beyond 2035 Water Board plans to notify developers, city officials, and others when they have developed 90% of VVWD groundwater rights (11,044 acre-feet) and suggest the city put a stop-building permit moratorium in place.

The latest population figures for Mesquite are 23,968 people. VVWD assumes a growth rate of 3.5%, equating to a population of around 40,000 by 2035. VVWD cites a water usage rate of 120 gallons per person per day (shorthand of gpcpd) for residential use. This number does not include commercial or industrial use.

For planning and modeling purposes, the VVWD’s Master Plan uses an estimate of 270 gpcpd, which would make Mesquite the highest water user municipality in
The Lower Colorado watershed. Las Vegas and other cities use 200 gpcpd or less. VVWD’s goal by 2035 is to reduce water usage to 85 gpcpd. This goal is ambitious but in line with other municipality goals.

VVWD’s water conservation plan estimates water savings efforts from now until 2027 of 4 gpcpd Per year or 20 gpcpd over that period. From 2028 to 2034, the estimated water savings will be five gpcpd to attain the 85 gpcpd goals. VVWD cautions that the approved 12,271 acre-feet of groundwater will be in full beneficial use by 2034, assuming the annual growth rate of 3.5% is static and that the city does not approve any new large water-consuming businesses.

Many assumptions are inherent in VVWD’s water conservation plan – growth rate, the effectiveness of water savings efforts, public acceptance, reduction in development, and building permits – but the VVWD is also unsure of what increasing pumping is doing to the aquifer.

VVWD does not get any water from the main flow of the Colorado River. However, The Virgin River, mountain springs, and the associated Basin 222 aquifer are tributaries to the Colorado River flowing into Lake Mead. And several state and federal collaborative agreements and laws govern these hydrological interactions. 

In 1980 the Nevada State Engineer William J. Newman “designated” Basin 222 as one where permitted groundwater rights exceed the estimated average annual recharge requiring additional administration by the Nevada State Engineer.

In Basin 222, permits equal 12,547 acre-feet annually. That is 8,947 acre-feet over the Nevada State Engineers’ established recharge (perennial yield) rate of 3,600 acre-feet annually (AFA). The Perennial yield is the amount of water that can be pumped from an aquifer without steadily lowering the water table year after year. The average annual pumping has steadily increased, and today VVWD pumps over 7,000 acre-feet per year. This rate is well below the 12,271 acre-feet VVWD allocated, but it is twice the perennial yield of Basin 222.

Nevada law requires the management of the aquifer, the springs, and the river conjunctively, not separately. Other statutes require the Nevada State Engineer to manage the conjunctively and set a water budget accordingly. 

The State Engineer’s designation of Basin 222 as a designated management area reflects the overallocation of permits beyond the perennial yield.

That yield came from a 1968 conjunctive study of the Virgin River Valley by The US Geological Survey. The USGS performed that study 55 years ago, before the 25-year drought, climate change, less precipitation, and ever-increasing pumping to match population growth.

Currently, VVWD relies on nine production wells, with two additional wells drilled but not online.

While hydrologists rely on simple precipitation patterns to provide insights into recharge levels, the VVWD  relies on a long-term water sustainability study measuring the changes in Basin 222 from pumping. The study’s results indicate the aquifer’s static water level has declined by 10 to 20 feet. According to that method, the recovery of the water table from deep pumping is slow, taking three to nine months to recover to the static level. While VVWD believes this is a sign of recharge over time, the district is unsure of the current perennial yield from the aquifer, which can be projected from precipitation analysis.

The Nevada State Engineer sets the water budget for the basins, which they are required by law to manage conjunctively. And while the Nevada State Engineer has a conjunctive analysis model, the VVWD has funded an out-of-state firm to complete a perennial yield (underground only) study by 2024.

The Virgin Valley Water Districts assume they can continue to pump enough underground water to equal their over-appropriated permits of 12,065 without concern for the 3,600 AFA underground limitations imposed by the water engineer nor the need for a conjunctive analysis.

Without a conjunctive approved water budget assigned by the Nevada water engineer, any attempt at conservation is virtually useless.

While the VVWD is limited to taking underground water from the Basin, they have acquired about 500 AFA of Virgin River surface water which they someday plan to clean and deliver to their customers.

Unfortunately for the public, the river has extremely high levels of Total Dissolved Solids (TDS) and other constituents that would require significant treatment to meet drinking water standards. Thus for every gallon of river water cleaned, only about one-half will be available for domestic use. Therefore the cost of producing domestic water from river water is very high.

Also, developing VVWD water rights on mountain springs and creeks requires habitat surveys and wetland mapping to determine compliance with the Clark County Multispecies Habitat Conservation Plan and the Federal Clean Water Act and limit water diversion to less than their “paper” water right.

Mesquite’s mayor and city council members were asked to comment on VVWD’s 2023 water conservation plan. Mayor Al Litman responded that he had not read the plan, and Council Member Wes Boger deferred to some time in the future when VVWD would make an oral presentation to the city council. Council Members Karen Fielding, Pattie Gallo, Paul Wanlass, and Brian Wursten did not respond to the request for comment.