Groundwater pumping reduces river flows

Water allocations over done.

In Nevada, as in many other western states, those who first put water to beneficial use (growing a crop or providing drinking water to a town, for example) have a right to use that water over those who come later. Early on most water used in the state came from surface waters such as the Truckee or Humboldt Rivers or smaller streams which flowed from the state’s numerous mountain ranges or from local or large regional springs. Most of the surface waters in Nevada were already claimed before the 1930s. The beneficial uses claimed became water rights. Water rights can be bought and sold.

Native Americans were already here.

Sketch of the Pyramid from Fremont's Report on surveys in Nevada and California (1844)
Sketch of the Pyramid from Fremont’s Report on surveys in Nevada and California (1844)

Ignored in the claiming of water rights beginning in the late 1850s was the cyclic nature of water availability in the dry Great Basin and Mojave Deserts. Water that is present in a sagebrush covered valley one year may be absent the next one or longer. And while the newcomers claimed the water for themselves, none appeared to notice that the Paiute, Shoshone, and Washoe Peoples already occupied the land and were prior users of the rivers and springs that nourished many wetlands, lakes, and meadows with the wildlife and plants the People depended on for survival. The Indigenous population found that the water that supported their way-of-life for thousands of years was used somewhere else by someone else. The water supplied by the natural world that had sustained them disappeared.

Newcomers claim the water.

Native American Petroglyph

Over the decades more and more water claims depleted rivers, lakes, springs, and wetlands throughout the state. Lakes such as Pyramid fed by the Truckee River and Walker fed by its namesake shrank as their river’s flows diminished – or disappeared altogether. And large wetlands on the Humboldt and Carson Rivers shrank as water went to farms and industry.

Demands on the Truckee River exceed the rivers ability to keep up. The river is particularly stressed during droughts which could become more common.
Long stretches of dry winters result in only a trickle in the Truckee River through Reno. Water rights diversion remove most of the small flow that remains.

Taking water flowing in a river, stream, or spring has an immediate effect. For example, consider a small stream that has a flow of 10 cubic-feet per second (CFS) with two users who each claim 5 CFS. If water user number 1 diverts half of the flow of the stream to an irrigation ditch, then the flow downstream of the diversion is immediately reduced to 5 CFS. The remaining water in the stream continues downstream to water user number 2. When water user number 2 diverts his share, then downstream of the diversion, the stream is dry. In a different year or later in the season, when the stream’s flow is 5 CFS, then water user number 1 diverts all flow and nothing remains for water user number 2. When the stream has 1 CFS, water user number 1 still diverts all the flow, but is unable to get her full water right and water user number 2 again has no water to divert.†† From the environmental perspective, the stream no longer has flow to support riparian trees or meadows below the diversions and eventually, they disappear. Essentially, every year becomes a drought year downstream of the diversion.

1.0 cubic-foot per second is approximately 7.481gallons per second. Early miners were among the first to appropriate water in Nevada using “miner’s inch“. Today, Nevada has a legal definition that a “miner’s inch” is equal to 0.025 cubic-feet per second.
†† Certain surface water allocations depend on “return flow” when not all the water is consumed irrigating a crop or water is returned to a stream from a sewage treatment facility. “Return flow” can then be diverted by another appropriator.

Water already claimed in rivers and springs.

The appropriation of surface water had negative effects on the rivers and streams and springs, because the original benefits of flow through the river’s environment were reduced. But the cyclic nature of water in the desert continued and when rivers and springs couldn’t keep up with the water users demand and reservoirs shrank, a new group of folks wanted water that they could depend on whether it rained or not. Groundwater pumping was a promise of unlimited supply – that unseen resource just beneath your feet. The promise was a false one and today we face a reckoning of over spending our water bank account on both fronts.

The “new” water: Groundwater.

(Illustration: USGS)
Pumping from an aquifer can draw water from nearby streams and lakes. (Illustration: USGS)

Pumping significant amounts of groundwater from aquifers was really not possible during the time when most of the state’s surface water was allocated between the various industrial and agricultural users. Beginning in the mid-20th century, however, groundwater extraction with powerful pumps became more and more common. The Nevada State Engineer (NSE) allowed groundwater wells to be drilled for agriculture or other uses even in basins with fully appropriated rivers and streams and springs such as the Humboldt River and the Walker River and around Moapa’s springs. The NSE now admits, in many cases, the overallocation was known at the time, but the NSE didn’t expect that the people getting the permits would be economically successful (an erroneous assumption as it turned out!) or that they didn’t consider the negative effect groundwater pumping would have on rivers and springs. The damage to rivers and springs due to over pumping, however, is a matter of hydrology. The excuses for why it was allowed to continue for decades doesn’t change the negative outcome for river and spring flows and the consequences for the people dependent on them and to the fish and wildlife that can’t survive without them.

Pumping from two wells extends the cones of depression.
Pumping from two wells quickens the drawdown of groundwater. Many of Nevada’s desert valleys have dozens of approved pumping wells. In too many cases, there are also surface water users dependent on flows from rivers or streams or springs now seeing affects due to groundwater drawdown. (USGS Illustration)

In all groundwater pumping, groundwater levels decline by the very action of extracting water and bringing it to the surface. Essentially, a cone-shaped hole develops around the well. If pumping ceases soon after the pumping begins, the cone-shaped hole or depression slowly fills in and after a long enough period of time, it may get close to the original groundwater level, but that generally takes far longer to happen than the length of time the groundwater pumping occurred.

Over appropriating the groundwater.

Overallocated basins shown in green, yellow, and red. Note: “PY” is perennial yield, an estimate of the amount of water consumed by plants and surface water discharges (springs, creeks, and rivers) before the proposed development of groundwater.[ NSE office graphic]

Over the decades the Nevada State Engineer (NSE) has permitted groundwater users to over-appropriate as many as half of Nevada’s hydrographic basins in the state with the least amount of water. Theoretically, pumping is supposed to be “balanced” by drying out the surface and eliminating plants and water “discharges” (like springs) that use groundwater through evapotranspiration. (Eliminating all evapotranspiration to achieve this “balance” with groundwater pumping can result in a barren landscape increasing dust as well as damaging seeps, springs, and meadows dependent on groundwater.)

Pumping groundwater appears, at first, to be benign. When groundwater pumping begins, it removes water that may be a source of supply to rivers or springs, but the effect of pumping takes time to deplete the flow of a river or spring (see illustration above). The further away the river or spring is from the pumping, the longer it takes. Effects of the State’s overallocation of groundwater and the near complete allocation of surface water are now being felt with continually declining groundwater levels in as many as 50% of Nevada’s basins, but it is also affecting iconic rivers like the Humboldt – the largest river completely contained within the state’s borders. However, no river or stream is immune to the damage caused from pumping of groundwater (or the over allocation of surface water, for that matter). The extent of the pumping, leading to over pumping and continually dropping groundwater levels, harms the environment and leads to conflicts between water rights holders and to discord between and among rural and urban Nevadans.

Nevada water law is clear.

Before approving any water applications, Nevada water law (Title 48, NV Revised Statutes) requires the NSE to find that water is available at the source and it will not conflict with existing water rights. This requirement applies to both the allocation of surface water or groundwater. Nevertheless, the NSE has, in fact, allocated water far beyond the available supply. In the graphic above, those areas shown in “red” are 300% or greater over the available supply and the “yellow” and “green” areas are more than 200% or more than 110% over the available supply, respectively. It is easy to see why conflicts are escalating between and among users and why the environment in many areas suffers from a lack of water.

Nevada State Engineer now wants changes to the law.

The NSE now wants the legislature to change the law to allow the NSE to “deal with” the conflicts his water office has created over many decades (and in contradiction to the law’s provisions.) These changes are embodied in two pieces of legislation the NSE has brought to the 2019 Nevada Legislature – AB30 and AB51. Check out our next blog to see how these could affect our critically important rivers and streams and springs throughout Nevada.

Derby Dam (1905) diverts Truckee River Water away from Pyramid Lake. The project was the first of the new Bureau of Reclamation which was created by the Federal Government. The project still operates today and has shrunk Pyramid Lake by 80 feet and dried up Winnemucca Lake. (Historic photograph of the project’s completion: UNR Library Collection)
This entry was posted in Keep it flowing, Science on by .

About Dennis Ghiglieri

My concern for the Truckee River grew over the years. It started with picking up trash and supporting better water quality. I helped create the "living river"plan with other citizens on the Community Flood Coalition; a plan to reduce flood impacts to infrastructure through river restoration and protection of the floodplain. I understand how critical the Truckee River is to the environment – and economy – of our entire region. I'm hoping that through these pages we can all understand our connection to the Truckee River and why we need to protect it.

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