Invasive Species: sucking our water resources away

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By Mike Sarchet Comparison of managed land after the removal of Russian olive and salt cedar in the Nine Mile watershedTraditionally, Nebraska has had two amazing resources, our people and our surface water. Unfortunately, we are rapidly losing both of these major resources with no noticeable return to benefit the rest of the state. Efforts are being made throughout Nebraska to curb the loss of our young people and to bring their talents back to benefit the state, but an equally important task at hand is to maintain the health of our rivers with adequate stream flows, wildlife habitat and native species of plants. Controlling invasive species that are removing water from these streams is an integral part of that mission. This essay will attempt to tackle why this is so important from a drought-mitigation perspective by using a project in its third year in western Nebraska to illustrate the promising effects of the management of invasive species in riparian areas. Whether it’s phragmites attacking the eastern North Platte River and the Republican River or Russian olive and salt cedar attacking the western North Platte watershed, these three invasive species are responsible for an amazing reduction in surface stream flows in the North Platte and Republican River basins and their associated creeks and streams as they flow west to east across Nebraska. Those who do not live near these rivers may believe that this is an alarmist statement, but for those people who have the privilege of living within the immediate area of either the Platte or Republican River, it is easy to see how these species have invaded the watersheds and are diminishing stream flows, while at the same time creating a massive flood control issue. Studies have suggested an enormous transpiration rate of water into the atmosphere from these plants and have suggested that the water usage can be over 150 gallons of water each day for each plant. This exacerbates the effect of the now eight-year-old drought that many in this state are still experiencing. These species have an incredible ability to consume water and to exist in the most of extreme conditions—these abilities and their invasive nature have created a problem that must be mitigated to ensure that our streams and rivers stay healthy, that there is enough habitat for native deciduous trees and grasses, and to ensure flood control. With the long-lasting effects of the drought evident in both ground and surface water systems, every drop of water that these invasive trees transpire into the atmosphere along these watersheds cannot long be tolerated in these basins. To that end, and thanks to federal and state legislative imperatives, individuals and groups in western and southern Nebraska have embarked on projects to control and eradicate these three species to conserve water in two of the major surface streams here in Nebraska; restore native habitat for wildlife, grazing and carbon sequestration; and to eventually restore native, healthy and natural flood barriers in these riparian areas. The Nine Mile Creek was once recorded as one of the most significant and productive cold-water trout streams in the northern Great Plains. Situated just east of Scottsbluff, this stream runs for about 20 miles until it drains into the North Platte River. Recently, the stream was choking under the pressure of invasive Russian olives and salt cedar trees which had overgrown, causing the stream flow to diminish, the water temperature to rise and the trout to seek spawning grounds elsewhere. This vegetation had also killed off the native grass and invited other invasive forbs into the basin, creating a significant problem for landowners adjacent to the creek. In response to these conditions, a public-private partnership was formed with individuals representing the Natural Resources Conservation Service (NRCS), the North Platte Natural Resources District (NPNRD), Twin Cities Development (TCD), the Nebraska Game and Parks Commission, the Nebraska Department of Environmental Quality and the landowners in the drainage. Through the use of an Environmental Protection Agency (EPA) sponsored and Nebraska Department of Environmental Quality (NDEQ) cosponsored project, with $150,000 in assistance from the Nebraska Environmental Trust, a massive effort was commenced to remove Russian olive and to control other noxious weeds within the Nine Mile Creek watershed. This project has totaled more than $350,000 over the past three years. The results, though they cannot scientifically document all of the benefits for those people associated with this watershed, were immediate in stream-flow improvement, temperature stabilization and habitat improvement. Affiliated landowners have been pleased and somewhat surprised at the results that we saw immediately upon removing Russian olive from this heavily impacted watershed. Our research indicates that there is a quantitative change, and while not scientific, it does show promise. Using the only measurable data that is available—measuring at the drainage of Nine Mile Creek—one notes the significant changes in stream flow throughout an average year, and the difference in flows before this project and after are interesting. In 2004 (prior to the treatment), we have noted that in the spring when the leaves would start gaining foliage and growing rapidly, we would experience a significant decrease in the amount of water reaching the Platte River. We also see an uptick in flows from July to August, representing the recharge from the irrigation canal system in the basin as it recharges the groundwater table and increases flows. This increase in the groundwater table facilitates the flow of springs which provide the water into these small tributary creeks. The flow then peaks in the fall and levels off in the winter months. In 2006, however, a year after the removal of the Russian olives, we note a different cycle. There was no large drop in surface flow as the Russian olive trees would normally go into full foliage, and the amount of recharge was significantly higher once the canal systems started refilling the groundwater table. Though we cannot state scientifically that the only explanation for this rise in flow rate going into the North Platte River is the removal of Russian olive trees, we can, with some certainty, conclude that the removal of these invasive species had an immediate and, one would hope, a lasting impact on the watershed. The lack of scientific data is related to several issues. Unfortunately, no one predicted this drought was going to occur, and no one could have predicted that the upper watershed of Nine Mile Creek would have over 40 residential wells go completely dry between 2002 and 2004. No one was prepared to collect needed measurements to actually see how much water was being lost to invasive trees. Though these issues are important, it is equally important to note that the Land Owners Council formed in 2003 decided early on that the thick stands of Russian olive trees and the other invasive weeds that came along with them was a reduction force on the creek that needed to be dealt with. That has led to this unique project on Nine Mile Creek, and the council is very pleased with the results. The techniques used in this watershed were laborious and time consuming. The removal and chemical-control methods on the Russian olive trees has had a great effect, but follow-up management treatments will be required, and chemical treatments on salt cedar will also require follow-up. The relative low expense and measurable impacts have awakened other watershed groups throughout the west. Working with the North Platte NRD and landowners, presentations have been made throughout Wyoming, Montana and South Dakota to watershed groups, showing them the potential for invasive control within their watersheds. Using Nine Mile as a model, several notable projects have developed. The State of Wyoming had no plans in 2005 and 2006 for invasive eradication in the Platte Basin, but it embarked on an aggressive effort, through the use of state funding, for the removal of Russian olive and salt cedar in both Platte and Goshen counties. The Nine Mile project has also had an awakening impact in other parts of Nebraska. Landowners along the Platte and Republican River basins had not considered the impact the invasive species have had on stream flows and habitat within their watershed. The nearly decade-old drought and compact requirements have obligated landowners to consider these issues, however, and we now see massive efforts in that basin as well as the Platte River above Lake McConaughy. It is the hope of all involved in this issue that these efforts will serve as a call to action for policy-makers, water managers and landowners to have a proactive stance toward these species. We are certain that this is an important tool for drought mitigation and for preserving the health of the rivers in the northern Great Plains and the American west. Moreover, it is important to note that the management of these species could have a positive impact on the recently signed Platte River Recovery Implementation Program, also known as the Platte River Agreement. This agreement, recently signed by the states of Nebraska, Colorado, Wyoming and the US Fish and Wildlife Service, includes a requirement of roughly 130,000 acre-feet of surface flow be returned to the North Platte River for endangered species on the lower North Platte. To illustrate this promise, it is noted that a recent research project conducted by the University of Nebraska on mapping the North Platte River from Lake McConaughy west to the Nebraska state line for the infestation of salt cedar and Russian olive within a half-mile-wide buffer zone. Conservative estimations on the amount of water that could be consumed by these invasive species compared to the amount we would expect to be consumed by the native grasses and forbs that should be along the river banks are astonishing—to the tune of hundreds of thousands of acre-feet that could be restored to the stream flow. Much of the Republican and eastern North Platte River has a somewhat different problem, as they are highly impacted by phragmites. These plants were brought into the region for their ornamental value. They are a beautiful breed. They can grow up to 12 feet tall with a fluffy, bloomy seed head that is very attractive. Unfortunately, this very attractive ornamental has an astonishing ability to outcompete native vegetation and to take over the islands and the river banks in the Republican River and eastern North Platte River—and again it consumes an amazing volume of water. These reeds grow so rapidly with such thick stems that it is astonishing how quickly they grow. In just two years, these phragmites can grow from just a small patch on a sandbar to where the sandbar has become an island and is providing significant problems for downstream flow. This is not only an issue for the Kansas Nebraska Compact but for flood control. After an amazing spring of precipitation, the Harlan County reservoir once again has water and is to the point of approaching nearly full. There is concern about what would happen if there had to be a quick release of water from the reservoir. A trial release this spring proved the Republican River was so clogged with phragmites that the downstream flow was reduced to 20 percent or less of what used to be normal stream-flow capabilities. This is a serious problem. If that area along the Republican River were to receive heavy additional rain, there would be significant flooding along the Republican River due to the choking effect of phragmites. The funds that were recently appropriated in Legislative Bill 701 for control of invasive species on Nebraska watersheds have provided the opportunity for the Republican River organizations to aggressively work at controlling phragmites. Initially, much of this work will be done by helicopter, spraying phragmites that are immediately located along the banks and on the islands. There will also be several follow-up projects to control other invasive woody trees within the riparian area, and we expect the same promising results that we have seen in the Nine Mile watershed. Sadly, this is a long-term battle, but success is being realized in the Nine Mile watershed. Three years into the project, those that visit the watershed witness the transformation this trout stream has gone through after the removal of Russian olive. But, they will also notice new Russian olive saplings emerging, proving the need for follow-up control of these invasive trees and additional noxious weeds that move into these watersheds. We anticipate that this will take three to five years for effective control. In addition to these removal treatments, we must also be diligent in reestablishing native habitat. In the case of Nine Mile creek, after achieving a state of control, we will embark on replanting native species bushes. The native habitat bushes, such as service berry and buffalo berry, will provide the habitat needs for the wildlife and stabilize banks along the creek. These reestablishments again will require follow-up. The successes in the Nine Mile Creek basin and the promise of projects in other parts of Nebraska and other states show the great potential of the removal of these species from our riparian areas. These projects will ensure maximum stream flows, restoration of habitat and flood control—maximizing the health and vitality of our rivers. All photos are courtesy of the author.

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