Reservoir Research Program Science-Based Information for Protecting Our Most Crucial Natural Resource

Reservoir Research Program Science-based information for protecting our most crucial natural resource Kansas Biological Survey Our shrinking water supply For more than a century, the State of Kansas has faced the continual challenge of providing the needed supply of water. Since the mid‐ 1800s, more than 200,000 surface water impoundments have been built, primarily in central and eastern Kansas. They continue to fill with sediment. To the west, thousands of groundwater wells continue to reach less water as more is removed than can naturally recharge. Many miles of perennial streams have been lost due to this lowering of the water table. Just as we continue to draw upon science to care for Kansans’ health and food supply, we must seek science‐based solutions to care for and sustain our water supply. Two research agencies of the State—the Kansas Biological Survey and the Kansas Geological Survey—can help guide the better protection and use of our water supply. Researchers at these centers at the University of Kansas work together and with other university scientists to study both surface and groundwater resources. Research collaborations come from the Kansas Water Office and other agencies, organizations, institutions of higher education and the private sector. To best manage a changing resource, we must recognize the causes of change. To address both quantity and quality of our water supplies, we rely on careful research to better understand our state’s water limitations and what causes them. In addition, we are learning what can be managed and what cannot—and, for the latter, what our options truly are. Kansas is developing a long‐term vision for the future of water Wilson Lake, in Russell County, has lost less than 5 percent of its capacity to sedimentation since operation began in 1963. Wilson Lake map: Kansas supply, and we must all work together, sharing our expertise and Biological Survey. Wilson Lake photo: Harland Schuster. experience, to find sustainable solutions. Understanding the causes Natural lakes in North America are thousands of years old, but reservoirs never will be. Reservoirs constructed where they were not formed naturally are inherently less stable and thus difficult to manage. Natural conditions provide stability to areas where they prevail, but where they do not, management challenges appear. There are few natural lakes in Kansas. Of our 200,000 constructed impoundments, the 24 federal reservoirs contain about three times as much water as all the others combined. By the end of this century, these 24 are expected to lose 44 percent of their capacity to sedimentation. Some of the 24 will have lost more than 50 percent, Toronto Lake, completed in 1959 in Greenwood and Woodson counties, has lost nearly 45 percent of its original capacity to others less than 10 percent. Sedimentation rates are unknown for sedimentation. Toronto Lake map: Kansas Biological Survey. nearly all of the non‐federal impoundments, many of which are in Toronto Lake photo: Harland Schuster. the watersheds of the federal reservoirs. We have not identified all the factors that consistently cause rapid sedimentation. Millions of dollars are being invested to mitigate upland and in‐stream erosion, but it is not certain that this is reducing the rate of reservoir capacity loss, as inflows can acquire sediment from other sources. To achieve the most effective management, a better understanding of the causes of sedimentation will be necessary as the state works toward long‐term sustainability of our reservoir resources. Diminishing capacity through sedimentation The state’s federal reservoirs vary widely in capacity, age and capacity loss. With an average age of more than 50 years, these reservoirs have lost about 17 percent of their collective volume to sedimentation. The largest reservoir, Tuttle Creek, completed in 1962 near Manhattan, has had the greatest capacity loss at 45 percent. Nearby Milford Lake, completed in 1967, has lost 12 percent capacity but has greater reoccurrence of cyanobacterial growth, which affects water quality. Understanding the causes for these differences, in the watersheds and in the reservoirs, will help define strategies for sustainable management. A decade ago, John Redmond Reservoir, in Coffey County, was projected to lose 50 percent of its capacity by 2018. Since then, the lake level was raised 2 feet after considerable interactions with the federal government, and $20 million has been invested by the State to remove sediment through dredging. These actions are valuable, as they extend the date for 50 percent capacity loss by about 15 years. While it is likely that sediment removal from reservoirs must continue, it is clear that this approach Federal reservoir watershed map, capacity chart and Tuttle Creek Lake photo: Kansas Biological Survey. manages a symptom but does not address causes. A dynamic landscape Kansas land cover patterns have been tracked by the Kansas Biological Survey for decades. While sediment and nutrients that end up in Kansas streams can come from cropland, grassland, urban areas or other cover types, contributions and characteristics can differ greatly. With high‐resolution LiDAR elevation data now available statewide, the door is open to high‐detail analysis of runoff and surface flow, which can be used to identify and prioritize sites where landscape preservation or remediation efforts can produce the most benefit. A disproportionate amount of sediment is delivered to reservoirs during high‐water events.This suggests that reducing flood severity could be effective for slowing sedimentation. Over the years, many streams have become disconnected from their floodplain and its wetlands through flood control actions such as levee construction and channel straightening. Many streams have become entrenched through the buildup of legacy soils in their floodplain—a consequence of severe erosion that occurred before conservation‐minded farming practices became widespread. All of these factors intensify downstream flooding. Working with the Kansas Alliance for Wetlands & Streams and other entities, the Biological Survey seeks research and implementation opportunities focused on floodplain and wetland reconnection, in an effort to mitigate flood severity and thereby reduce sedimentation rates. Other benefits include improved wildlife habitat LiDAR shaded relief for a portion of the Fourmile Creek floodplain in Morris County (background image) and 2007 land cover map: Kansas Biological Survey. and water quality. As Kansans have continued to use and manage surface waters to meet human needs, many south of Marysville (inset). Looking downstream, this hotspot has had wing dams installed to natural streams have become or have been intentionally straightened, narrowed and entrenched, slow the current, in addition to a grass buffer that filters overflow and provides resistance to which leads to increased channel erosion. In recent years, the state has invested in bank streambank erosion. Google Earth image. Photo of the Wolf River in Brown County near stabilization efforts to remediate erosion hotspots, such as areas along the Big Blue River Robinson: Harland Schuster. Upstream flow modifications In their historic state, Kansas streams were wider, more sinuous and better connected with With thousands of miles of streams to address, approaches with holistic effects should be their floodplains. Changes over the last 150 years—including cultivation and urbanization, and considered. For example, efforts directed toward floodplain reconnection will reduce flood attempts at engineering water flow across the landscape—have resulted in a Kansas hydrology intensity and thus have positive impacts that extend downstream, mimicking the natural characterized by more rapid, concentrated and turbulent flows. These conditions lead to v approach to flood mitigation that was commonv historically. Coupling such tactics with more increased erosion. While conservation efforts in agriculture such as terracing and reduced tillage direct, localized erosion reduction efforts such as streambank stabilization presents a diverse, have substantially decreased cropland erosion, studies indicate that sedimentation rates of our multi‐pronged approach that could prove effective at addressing both symptoms (erosion federal reservoirs have changed little. Attention is now being directed toward channel and hotspots) and causes (flooding) of sedimentation. streambank erosion as possibly having a greater contribution to reservoir infilling. The Kansas Biological Survey’s long-term study of the Perry Lake watershed in Perry is predicted to be 50 percent infilled by 2088. Perry Lake photo (background): northeastern Kansas serves as a model for other watershed-reservoir systems. With major Harland Schuster. Photos of Delaware sedimentation and field research, and watershed sediment accumulation at the mouth of the Delaware River (below right, top photo), map for Perry Lake: Kansas Biological Survey. A history of stream research at the Biological Survey Since the 1970s, the Kansas Biological Survey has conducted surveys of streams across ● Does streambank erosion or land use Kansas. This research has been wide‐ranging, from updating species lists of aquatic practice have the greater impact on organisms to assessing levels of nutrients and pesticides in the water. Other work has reservoirs? included assessing land‐use practices in the Delaware River watershed, which includes Perry ● How much water flows through small Lake. More recently,

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