Introduction
There has been much discussion in the media and among policymakers regarding the conflict between the Southern Nevada Water Authority (SNWA) and a group of Utah farmers and ranchers. This conflict centers on a plan by SNWA to pump and transport 810,000 acre-feet of groundwater annually from eastern Nevada into Las Vegas. SNWA says the water is needed to meet current and future growth in the Las Vegas area. Utah ranchers say the groundwater, held in a natural aquifer that straddles state lines, is inadequate to meet the demands of the proposed pipeline. Withdrawing that much water every year would lead to environmental degradation of the local ecosystem and ultimately ruin the ranchers’ livelihood.

The major hurdle in resolving this dispute is the lack of hard scientific data regarding exactly how much water is contained within the aquifer and the recharge rate—the rate at which the aquifer can replenish water withdrawn. Each side disputes the other’s measurements in regard to these two phenomena.

In situations such as these, since each state can grant water rights independently of the other, the resolution would simply come when the Nevada state engineer’s office granted SNWA rights to the water in the aquifers and construction on the wells and pipeline began. It would be up to the Nevada state engineer to determine the amount of water SNWA could claim and use. However, in this case, the pipeline will be built on federal land and the Bureau of Land Management (BLM) has stepped in to determine the environmental impacts of the project on those federal lands. By so doing, BLM is also trying to determine the depth and recharge rate of the aquifers themselves. If they find that either is inadequate to the demands of the SNWA project, BLM can refuse to grant permission for construction of the pipeline. If BLM permission is denied, SNWA’s project would essentially be dead since there is not a route that would not cross federal lands. Alternatively, BLM could grant permission but limit the amount of water withdrawn from the aquifers or grant permission for the project as proposed. A draft environmental impact statement from BLM is due out in 2008 and should provide an opinion on the project and BLM’s recommended course of action.

In the meantime, the dispute provides an opportunity to examine water usage, especially of groundwater, by both states. The remainder of the article focuses on this topic.

Publicly Supplied Water Use in Utah and Nevada
Every five years, the US Geological Survey provides summary data on water usage in the US by state and county. The last census of water was done in 2000 and the data released in 2004. These data show some interesting contrasts between Utah and Nevada, especially in the amount of groundwater within the publicly supplied system.

First, the populations of both states are primarily supplied water through public water systems. Utah ranks number one in the country with 97% of the population accessing their water through a municipal or other public supplier. Only 3% of the population relies on personal wells or private companies for water. Nevada ranks 3^rd in the nation, with 94% of their population also using supplied water. Figure 1 below shows the percentages and ranks for all the Intermountain States.

Figure 1

Source: US Geological Survey

The differences in the percentages can be attributed to agriculture and urbanization. In those states—Arizona, Utah, Nevada and Colorado—with most of the population concentrated in an urban core, the rate of publicly supplied water is going to be much higher than in the more rural, farming and ranching states. Arid Western states, for the most part, are going to have a higher rate of public systems as the legacy of federal subsidization programs. States in the East with a high percentage of private water companies and private wells are also those with a more abundant natural water supply.

The one advantage to having most of the population receiving water through a public system is that water use can be more closely monitored and in the end, controlled, to meet conservation goals. Las Vegas, for example, has a very aggressive program to save water. All new residential construction must meet strict xeric landscaping guidelines. Additionally, residents can be ticketed and fined for violations, such as running sprinklers during undesignated times of day. Finally, all the large hotels have some type of gray water reuse system.

Despite these measures, Nevada has the highest per capita water use of any state. In 2000, residents use 315 gallons daily, much of it outside the home. Utah ranked second with 286 gallons per day, as shown in Figure 2.

Figure 2

Source: US Geological Survey

What is concerning about these data is the trend when comparing 2000 data to 1995. In 1995, water withdrawals in Utah were 269 gallons per day per capita while in Nevada they were 325. The increase in Utah withdrawals can be accounted for by the drought in the state during the late 1990s through the early part of this decade. This, plus a rapid increase in population, can be blamed for most of the increase in water demand. However, Nevada was suffering through the same drought and had an even more rapid increase in population, yet managed to reduce water withdrawals by 10 gallons a day per capita—a significant decrease. If reducing water demand is a concern of Utah policymakers, they may want to consider some of the conservation measures discussed above since they appear to have helped Nevada reduce consumption.

Groundwater Consumption and the Proposed Project
The addition of 810,000 acre-feet of groundwater to the Nevada water supply is significant. According to the 2000 USGS data, Nevada currently uses approximately 169,000 acre-feet of ground water annually. This, plus the state’s 500,000 acre-feet allotment of Colorado River water, is almost the entire fresh water supply for the state’s public system. In contrast, Utah’s municipal systems are more reliant on groundwater sources—408,000 acre-feet compared to 307,000 acre-feet of surface water. Utah’s consumption of groundwater, in percentage terms, ranks the state 10^th in the nation for reliance on this resource. Figure 3 compares the Intermountain States.

Figure 3

Source: US Geological Survey

If the proposed pipeline is completed and all the groundwater added to the public system, Nevada’s groundwater consumption will increase dramatically—to 979,000 acre-feet annually. This would shift the composition of the water supply to 64.6% groundwater. Finally, it would boost overall water consumption to 1,515 acre-feet annually. This is roughly the same amount as Georgia, Ohio and Pennsylvania—states with larger populations and greater water resources.

Conclusion
The focus of this article has been water supplied by the public system or water that is used in homes and businesses. However, it is important to keep in mind that in both states, municipal water is only a fraction of total water consumption. For both states, agricultural irrigation comprises the largest percentage of water used—75% in Nevada and 77.7% in Utah. The reason that municipal water is such a concern is the fact that populations in both states are growing rapidly and the water to meet the needs of this growth must come from somewhere. While a portion of agricultural water is being converted to municipal use, there is much that is unusable. Thus, these states turn to other sources, such as the pipeline. These sources are more difficult and costly to obtain. The capacity of these sources is also largely unknown and we could be faced with serious environmental consequences in the future.