“The Disappearing West”, a report produced by Conservation Science Partners based in nearby Truckee, documents the dramatic degradation of rivers in an interactive series of maps and animated illustrations. The report appears online at the Center for American Progress website.

The report attempts to map 300,000 miles of rivers and streams in the 11 western states and show the human impacts made to their flows and floodplains. The interactive map allows anyone to zoom in on any western state location and identify the extent of damage to large rivers and small rivers and headwater streams in mountain ranges from the Rockies across the Great Basin to the Sierra and Cascades. The map colors range from deep blue to fire red depicting a range from near natural condition to extremely altered or unnatural condition for either stream flow restriction or floodplain modification. Some states have far more severely modified streams and rivers than others. Overall, however, the west appears more red-colored than blue-colored with surprisingly small streams high in mountains suffering from flow reduction and floodplain modification. While the report offers a valuable tool to look at how our rivers and streams are suffering, we’ve discovered that reporting on the Truckee River flows below Reno-Sparks underestimates the severe dewatering of the river at Derby Dam.

A cautionary note: It could be that the report underestimates damage from flow reductions in other states if the Truckee River flow diversions were missed.

The report shows Nevada ranked 2nd in the major rivers and 3rd in the smaller rivers categories that suffer from flow restrictions, 94% and 31% respectively. Utah ranks first in reduced flows in major rivers at 96%. I used the “Disappearing Rivers” information to develop the bar graphs, presented below, ranking states by flow restrictions and floodplain alterations for major rivers.

Likewise, the report also shows Nevada 2nd in modification to major river floodplains at 73% and smaller river floodplains at 51%. Colorado ranks first in major river floodplain modification at 77%.

Reducing river flows and developing river floodplains can eventually kill riverine ecosystems by eliminating the riparian forest that grows along the stream, warming the stream from reduced flows, eliminating cold water fish and invertebrates that live in the stream as well as increasing pollution and reducing recreation.

The report separates the rivers and streams into categories: headwater streams with less than 6 cubic-feet-per-second (CFS), smaller rivers and streams between 6 CFS and 163 CFS, and major rivers with more than 163 CFS.² In Nevada, the Truckee, Carson, and Walker Rivers that originate in California’s Sierra Nevada all had historical average flows greater than 163 CFS. The Humboldt River which is entirely within Nevada also had historical average flows greater than 163 CFS. Today, the Truckee River is a mere trickle at Pyramid Lake when US Bureau of Reclamation diversions at Derby Dam take as much as three-fourths of its flow to farms in Lahontan Valley; the Carson River is essentially dry during many summer and autumn seasons before it reaches Lahontan Reservoir due to upstream diversions; and the Walker is often completely dry – sometimes for years – before it reaches Walker Lake. The Humboldt River, likewise, is more frequently dried out before it reaches Rye Patch Reservoir upstream of Lovelock.

Any measure of flowing water can take a little getting used to, but remember, the flow in a river or stream is measured by how much water (volume) is moving downstream over a period of time. It can be in gallons-per-minute or cubic-feet-per-second or acre-feet per year. The US standard way to measure flowing water in a river is CFS or cubic-feet-per-second.¹

Lower Truckee River flow restriction much worse than shown in “Disappearing Rivers” Interactive Map

The Disappearing Rivers analysis shows the lower portion of the Truckee River as having only 8% flow restriction in the lower River between Derby Dam and Pyramid Lake. Unfortunately, this is not accurate. The screen capture from the interactive tool shows the diversion at Derby Dam, but inaccurately says it is only 2,500 acre-feet. It isn’t clear where that number comes from.

In fact, tens of thousands of acre-feet of water are diverted from the Truckee River most years and hundreds of thousands have been diverted in the 21st century alone. So, the representation in the online tool for the Truckee River flow restriction downstream of Derby Dam³ isn’t correct. The problem appears to be that the data used to model the restricted flow caused by Derby Dam doesn’t accurately reflect how much water is diverted on average over an entire year. Derby Dam itself, doesn’t store much water, but the effect of its diversion is the most significant loss on the entire Truckee River below Lake Tahoe.

Despite the problem I’ve identified where the Disappearing Rivers Map underestimates restricted flows for the lower Truckee River below Derby Dam, the tool remains valuable to show how our rivers have suffered from loss of flows and modification to the floodplains in Nevada and throughout the 11 western states. The tool affords even the casual user a stark window into the damage inflicted on our rivers from continually taking too much floodplain land for development and too much water from river flow.

In broad terms, the summary provided for the state of Nevada is sobering:

“In Nevada, 53 percent of all rivers are altered. That’s equal to 3,593 unnatural river miles— enough to cross the state more than 11 times. Of the 11 Western states in the Disappearing Rivers analysis, Nevada had the 5th most altered rivers in the West. When broken down by size, 96 percent of all major rivers, 64 percent of all smaller streams and rivers, and 36 percent of all headwaters are altered.”

How can we reverse continual losses of river flows and floodplain lands? Can society embrace increasing natural river flows and restoration of floodplain lands? Increasing population and climate change is making the job of fixing what ails our rivers harder. This report makes clear that in a little over a century, we’ve diverted at least 61% of the flow of our western rivers and negatively modified 63% of river floodplains. And, additional impacts to river flows and floodplains occur daily from the direct effect of development but also from climate change which is making the west warmer – and possibly drier as well. Few people want to have a dry Truckee River surrounded by parking lots and warehouses, but our representatives in federal, state and local governments seem to be taking us to just such a future. It is time to ask politicians to find ways to reduce the amount of water we take from our rivers and aquifers, protect our remaining floodplains, and restore our overdeveloped floodplains.

There have been some restoration successes on the Truckee River over the past couple of decades. We have seen the restoration of several floodplain reaches of the Truckee River below Reno from Lockwood to the McCarran Ranch. The Nature Conservancy’s McCarran Ranch represents one of the earliest successful efforts to show how a degraded river can be transformed with a vibrant riparian corridor of wetlands and forest that can support spawning trout and a valuable recreational fishery and recreation. The Truckee River Water Quality Agreement between the Cities of Reno and Sparks and the Pyramid lake Tribe called for the cities to purchase water rights for the Truckee River to increase river flows during low flow. The Cities have purchased more than 11,000 acre-feet of water which can mean the difference between having a dry river and a wet one. The water purchased stays in the river all the way to Pyramid Lake.

Flows in the Truckee River can be greatly improved by reducing diversions from the river, improving farm practices, and increasing water conservation in cities and towns along the river.

Now is the time to make sure our rivers will not continue to disappear.

---

¹   [For people who like to think in gallons, there are 7.48 gallons in a cubic foot. For example, during February 2018, the Truckee River has been running between 350 and 450 CFS through downtown Reno or between 2,618  and 3,366 gallons per second.  You can check out the flow of the Truckee River every day in the RGJ newspaper on the weather page or look on the TROA website under daily report] 

²   6 CFS for one year is 11.9 acre-feet or 3.88 million gallons; 163 CFS over a year is 188 thousand acre-feet or 38.5 billion gallons. To offset the effect of evaporation from Lake Tahoe requires about 350,000 acre-feet of water each year above what flows out into the Truckee River; likewise, it takes more than 400,000 acre-feet of water each year to maintain Pyramid Lake’s water level.

³    Derby Dam on the Truckee River is the largest diversion on the Truckee River. The dam, completed in 1905, was the first project of the US Bureau of Reclamation called the Newlands Reclamation Project. While most people in Reno and Sparks have never heard of the project, it is responsible for the greatly reduced flows of the lower Truckee River downstream of the cities. The dam allows Truckee River water to be put into a 112 year-old canal, permanently removed from the Truckee River basin, and sent to farms on the lower Carson River’s Lahontan Valley. Once diversions began, Pyramid Lake and the lower Truckee River were sent into a steep decline. Flows in the Pyramid Lake Paiute Tribe Reservation‘s portion of the Truckee River were reduced to just a trickle. Any time during many years (flood years being the exception), a substantial portion of the water in the Truckee River as it flows through Reno-Sparks will end up in Lahontan Valley and not Pyramid Lake due to the diversions at Derby Dam. The dam at Lake Tahoe is also part of the Newlands Reclamation Project and the water stored in Lake Tahoe by the dam benefits farmers in Lahontan Valley. The Lake Tahoe dam can store over 700,000 acre-feet of water by raising Tahoe’s water elevation by up to 6.1 feet.