Lake Red Rock is the largest lake in Iowa with a surface area of 15,250 acres at conservation pool. The lake lacks adequate littoral structure. The project will increase structural habitat, improve angler opportunities and enhance the quality of the fishery in Lake Red Rock. The project will provide quality structural habitat for natural spawning, nursery locations for young fish, congregation areas for forage fish and feeding opportunities for predator fish. The project will place 42 Mossback Essential Shallow Water Bundles, 20 Mossback Essential Deep Water Bundles, 22 Mossback Basic Shoreline Bundles, 14 Mossback Mega Reef structures. In addition, there will be placement of 30 Cedar Trees Adjacent to the newly treated USACE shoreline riprap stabilization project.
Lake Red Rock is a flood control reservoir on the Des Moines River, operated by the US Army Corp of Engineers (USACE), with initial construction beginning in 1960 and culminating with the completion of the dam in 1969. Located in the north central portion of Marion County Iowa between the towns of Knoxville and Pella with the primary purpose of flood risk management, but also authorized to provide wildlife management, fisheries management and other outdoor recreation opportunities. At elevation 742, normal conservation pool, Lake Red Rock is the largest lake in Iowa with a surface area of 15,250 acres, at full flood pool elevation of 780; the lake surface area exceeds 65,000 acres. The project area around the lake encompasses over 50,000 acres of fee land that consists of various upland terrains and has 25,000 acres of flowage easement, making Red Rock Reservoir the largest public land holder in Iowa; which is utilized by hundreds of thousands of outdoor enthusiast year round. Amenities are diverse and numerous around the lake that include multiple access points to the lake either along shorelines or at boat ramps for fisherman, boaters and other water recreationist. Campgrounds, picnic areas and year round cabins are available for use in public parks surrounding the developed portion of Lake Red Rock, with the upper undeveloped reaches of the project area primarily utilized by hunters and nature seekers. The USACE manages several recreation areas along the lake and below the dam in the tail water area, the Iowa Department of Natural Resources manages Elk Rock State Park (IDNR) on the south side of the lake and the Marion County Conservation Department (MCCD) manages Roberts Creek Park and Cordova Park on the north side of the lake, both the IDNR and MCCB areas are fee agreement contracts with the USACE (Figure 1. Lake Red Rock Area Map). Multi use trails adjacent to the lake are abundant and the trail surfaces vary from earthen to granular to hard surfaced. These trails connect many of the recreation areas to each other, with one hard surfaced trail culminating in the city of Pella.
The recreational fishery at Lake Red Rock is diverse, many fishermen are generalist looking to catch any fish, but many other fishermen are targeting specific species. Crappies, Channel Catfish, White Bass and Largemouth Bass are the most desired species sought after by anglers. Channel Catfish and White Bass are the most consistent for anglers to catch, Crappies are more easily harvested during spawning in April and May, but anglers have fair success all summer “Spider Rigging”. Several fishing clubs will host fishing tournaments at various times of the year for Crappies, Channel Catfish and Largemouth Bass. Very little ice fishing is done on Lake Red Rock, partially due to the difficulty in locating fish, changing water levels and varying ice thickness. In recent years, anglers have hard sporadic success catching crappies through the ice in the Competine Creek arm. The biggest obstacle to angler success is the lack of structure in the lake, making it more difficult for fisherman to locate fish. One of the priorities of this project is to provide more permanent habitat to create better opportunities for the fishery and anglers.
Anglers visiting Lake Red Rock come from neighboring states as well as from local communities. According to the 2019 Iowa Lakes Survey, 78% of visitors to the lake are within 90 miles, with the average visitor traveling 60 miles. Expenditures averaged $32.95/day per Iowa trip takers. Lake Red Rock attracts an estimated 318,000 day trips per year, versus the statewide average of 65,000. This visitation rate generates in excess of 19 million in expenditures and is consistently one of the top seven visited lakes in Iowa (Krogman, IDNR, personal communication). A study by the American Sport Fishing Association in 2020 outlined the economic benefits of the four congressional districts in Iowa. In US Congressional District 1 and District 3, the two congressional districts encompassing the Lake Red Rock area, anglers created $179.9 million in retail sales and 1890 jobs (American Sport Fishing Association 2021). This suggests that Lake Red Rock greatly contributes to local economies and that a quality fishery is worth the expense to enhance and maintain. The Vermeer Foundation, Kuyper Foundation and Rolscreen Foundation, contributing partners, also recognize that quality recreational opportunities assist in recruiting and retaining a dedicated workforce as demonstrated by their financial support to the project.
According to latest survey information provided by IDNR fisheries, abundant numbers of Channel Catfish, Crappies and White Bass were recorded. The amount of preferred sizes for each though was a small percentage of the total; 10% of Channel Catfish – 24-28 inches, 12% of Crappies – 10-12 inches and 16% of White Bass – 12-15 inches (Figure 11.). The IDNR stocked 10 million Walleye fry in 2021 and 1 million Hybrid White Bass in 2022, but by most estimates, survival rate to adults for stocked fry is only 2%.
The Red Rock Lake Association (RRLA) partnered with the ACOE in 2014 to repurpose two unused sewage lagoons into fish rearing ponds. The project entailed refurbishing the lagoons, installing piping and constructing a concrete fish kettle to recapture fingerlings or juvenile fish. The newly reared stock is transferred to Lake Red Rock in an aerated aluminum transport tank that was commissioned and paid for by the Red Rock Lake Association (Figure 12.). In 2022, 10,000 Walleye fingerlings averaging 2.0 inches were stocked into the lake from the rearing ponds, the ponds were then refilled; two gallons of fathead minnows were purchased by the RRLA and released into the ponds, Largemouth Bass fingerlings were then placed in the ponds. After 5 weeks, 1,200 juvenile Largemouth Bass were stocked into the lake; average length for the bass was 4.7 inches. All the stock and data recordings are provided by the IDNR Fisheries Bureau. By most estimates giving fry and fingerlings this protected nursery greatly increases the survivability to adulthood percentage.
As is typical of a large flood control reservoir as described in the RFHP “Reservoir Fish Habitat Management” manual, sedimentation carried into the basin from a vast drainage is a key issue to deal with for fisheries management. "Unlike natural lakes, reservoirs tend to have large watersheds and large tributaries because they were engineered to capture as much water as possible to serve flood control…. Depositional filling effectively results in surface area and volume reductions, habitat fragmentation, loss of depth, and associated changes in water quality. Unnatural water-level fluctuations interact with wave action to degrade shorelines that were once uplands and are unable to withstand continuous flooding, which promotes erosion and ultimately homogenization of once diverse littoral habitats. Lack of woody debris deposition in the littoral zone, limited access to adjacent backwaters, and lack of seed banks and stable water levels to promote native aquatic vegetation characterize barren littoral habitats in many reservoirs" (2017 Dr. Miranda, Reservoir Fish Habitat Management, 1.1 Introduction).
This is the perfect assessment of conditions at Lake Red Rock and describes how the current habitat conditions have been formulated. Once the dam began operations, reservoir inflows and water level fluctuations exceeded expectations. Natural lake bottom structures began to degrade or even disappear and sediments started to accumulate, which created a muck/silt substrate, which over several years has become a predominately featureless stratum and virtually no aquatic macrophyte presence.
The Red Rock Reservoir drainage area is a vast watershed covering over 12,300 square miles in central, north central and northwest Iowa, with a large percentage of that surface area in some form of agriculture production in private ownership. The dam is situated on the Des Moines River, but several tributaries coalesce into one inflow upstream from the confluence with Lake Red Rock. The reservoir is prone to high inflows of water with large amounts of suspended sediment, which adversely affects lake depth. The upper reaches of the reservoir, west of State Highway 14, are mostly less than 4 feet in depth (Figure 2.) with many acres of exposed mud flats where inflows are beginning to slow (Figure 3.), but due to these flash inflows, sediment is dispersed throughout the lake. Littoral zones are also impacted from suspension of shoreline particulate from wave action and fluctuating water conditions (Figure 4.).
Fully understanding the management strategies of Lake Red Rock is not possible without knowing about the reservoirs involvement in the Sustainable Rivers Program (SRP). SRP is a nationwide partnership, initially organized by the Corps of Engineers and The Nature Conservancy, to find ways to operate dams and other Corps owned and operated infrastructure in more environmentally friendly ways. In 2016 Red Rock hosted a two-day environmental flow and pool management workshop with biologists, stakeholders and other scientific experts to learn what primary ecological concerns they had with the Des Moines River. Eight recommendations were realized from the workshop: Reduce nitrate levels, mussel mortality, sturgeon mortality (downstream), gas bubble trauma, downstream bank erosion; and improve conditions for migrating water birds, conditions for reptiles and amphibians, and conditions for downstream river recreation. These recommendations were influential in a revised lake regulation manual.
To accommodate the above-mentioned recommendations and other environmental conditions, a conservation band was incorporated into the regulation manual to enable the Corps to adjust pool levels to benefit a biological purpose either in the lake or for downstream conditions. The Corps developed an Adaptive Management and Monitoring Plan (AMMP), along with assistance from partners and stakeholders. In-lake water level management strategies and environmental flows downstream of the dam are specific elements of the AMMP that seek to support fish and mussel life histories. Many successful environmental flows and research studies have sprung from that plan and it is regarded as a model for dams and reservoirs across the country. Currently, Lake Red Rock is one of four designated SRP Science project sites. SRP is funding the Iowa State University Cooperative Research Unit to conduct a 2-year research program associated with the fisheries, mussels, and their habitat in the Des Moines River, with the goal of evaluating how fisheries and mussel resources respond to the operations of Red Rock Dam. This data will be utilized in the adaptive management of dam operations and continued refinement of the Des Moines River Adaptive Management and Monitoring Plan.
Ongoing SRP efforts also work to find solutions that address nitrification and other water quality concerns within the Des Moines River. Early research on the denitrification ability of Lake Red Rock from 1974-2019 has concluded that the reservoir has reduced nitrates 12% from incoming flow to its release through the dam. Through a contract with the University of Iowa, Hydroscience & Engineering, the Corp hopes to further understand this process and how pool management may influence denitrification. In a complimentary effort, the USACE has partnered with the Natural Resources Conservation Service (NRCS) to find ways to reduce nutrient inputs into the lake. Thirty-three watersheds encompassing Red Rock and Saylorville Lake, another USACE flood control reservoir situated on the Des Moines River, just upstream of the city of Des Moines, have been assessed to determine locations where soil conservation structures could exist, and opportunities for modifications to land use practices or soil conservation structures to reduce the nutrient and sediment input to the reservoirs. Two websites have been developed that utilize arc gis mapping to evaluate watershed features and assist landowners to implement the Best Management Practices (BMP) for soil and water conservation measures and improve the Lake Red Rock watershed via a Watershed Resilience Tool.
Other statewide programs, targeted initiatives and watershed associations are also attempting to address water quality issues and reduce sedimentation. Saylorville Lake tends to trap sediments from the upper portions of the Des Moines River, preventing those sediments from reaching Lake Red Rock. The North and South Raccoon Rivers merge northwest of the city of Des Moines and empty into the Des Moines River on the south side of the city. Several Watershed Management Authorities (WMA) are active in the upper reaches of the Red Rock Lake drainage (Figure 5.), providing resources to improve water quality (Figure 6.).
Two tributaries, Whitebreast Creek and Competine Creek flow into Lake Red Rock from the southwest, creating two separate arms adjacent to the main lake (Figure 7.). The conditions exhibited in the main lake are mirrored in these two separate arms, but not to the extent as seen in the larger portion of the reservoir. The combined watershed for these two tributaries is just over 275,000 acres versus several million acres for the Des Moines River (Figure 8. Blue highlighted Red Rock Watershed is 1.55 million acres, but does not include the Raccoon River watershed). The Iowa Department of Agriculture and Land Stewardship (IDALS) provides cost share money to landowners in the Lake Red Rock watershed for Best Management Practices (BMP) that curb run-off and soil loss, which directly impact the water quality and sediment load flowing into the lake (Figure 9. K. Ament IDNR). As illustrated on the IDALS spreadsheet (Figure 9. K. Ament IDNR), the number of implemented practices and total dollars spent in the Whitebreast and Competine Creek watersheds is practically equal to the practices and monies spent in the larger Red Rock watershed. This demonstrated level of support for water quality measures is part of the reason for primarily targeting the Whitebreast Creek and Competine Creek arms for fish habitat enhancement.
The habitat project is being implemented to improve degraded or nonexistent littoral structure in Lake Red Rock to bolster the fishery and increase angler success. The objectives of the project are to provide quality fish habitat in Lake Red Rock that will promote natural spawning, provide nursery habitat for fry and fingerlings, allow for congregation of forage fish and opportunities for predatory fish.
To accomplish the goals of the plan, artificial fabricated fish structures (Mossback) in conjunction with natural materials, where feasible, will be placed in areas that will best promote the objectives of the project. Depth, shoreline composition, susceptibility to shoreline erosion from wave action and safety for other water recreationist will be scrutinized prior to placement of new habitat structures. The enhancement project will benefit any fish species that utilize physical structure, which include Largemouth Bass, Crappie and Bluegill. All three of these species are sought after by Lake Red Rock anglers. Channel Catfish will also benefit from the new structures, as will Walleye and White Bass to a lesser degree, primarily as nursery cover to facilitate growth until migrating to more open water areas.
As an additional benefit to the project, the ACOE will be completing an already scheduled riprap project, doing two sections of shoreline stabilization with riprap in spring of 2023. One of the shoreline areas will be within the targeted area of the fish habitat enhancement project on an area referred to as Whitebreast Point and the other will be the T’Lam section (Figure 10.). 5400 tons of shot rock base and 10,500 tons of riprap will be used to stabilize a length of 1046 feet by 60 feet of shoreline in the T’Lam section; 3220 tons of shot rock base and 2200 tons of riprap will be used to stabilize a length of 350 feet by 60 feet of shoreline in the Whitebreast Point section, total combined cost for both sections will be $1,956,000.
Red Rock Lake Association members and USACE personnel will conduct angler interviews in 2023 and prior to deployment of new fish habitat structures in 2024, with technical advice from Iowa DNR Fisheries Bureau. Data from these interviews will be compared to data from subsequent surveys after the introduction of new habitat. This data will allow for comparison of angler catch success, locations of success and satisfaction of success and see if these align with the placement of new fish structures. This information combined with the Iowa Lakes Survey, which is conducted every five years, should enable a better calculation of visitation and economic impact. IDNR staff will utilize sonar mapping to assist in providing accurate descriptions of new habitat locations and monitor any changes in habitat quality. IDNR staff will provide comprehensive fish sampling using electrofishing and hoop nets to survey all species present for two years, plus data analysis.
The Corp of Engineers (USACE) will continue to analyze data from the Adaptive Management and Monitoring Plan (AMMP) that evaluates the response of fisheries and mussel resources to the operation of the Lake Red Rock dam. Current and new Sustainable Rivers Program initiatives will be evaluated to gauge the state of the reservoir water quality, denitrification and recreational use.
The Red Rock Lake Association membership will enlist and coordinate volunteers in conjunction with an already established USACE volunteer program. Companies associated with the foundation partners will be encouraged to provide teams of employees to assist with components of the project. The opportunities to be involved will be primarily with the assembly and deployment of the fish habitat structures for which the requested funding is being utilized. Awareness of, and recruitment of volunteers for the Lake Red Rock Fish Habitat Enhancement Project will be shared by in person contacts, on the RRLA website and Facebook page, on the Lake Red Rock USACE Facebook page and displays at the Visitor Center, on the Marion County Conservation Facebook page and through informational packets created for local media sources (Figure 15. Illustration of a display for a previous small grant project). Progress throughout the course of implementing the project will be updated on RRLA, USACE and MCCB social media outlets. The RRLA firmly believes that involving community members in the success of this project will lead to more engagement and ownership of recreational needs and improvements in and adjacent to Lake Red Rock.
Once implemented, narratives and detailed maps (Figure 15.) regarding the project will be uploaded to the RRLA and Lake Red Rock USACE websites. Signage and/or displays of the project will be posted at boat ramps, recreation area bulletin boards and at the Lake Red Rock Visitor Center. The Red Rock Lake Association will continue to locate suitable sites for more fish habitat enhancement and continue to also seek additional partners and funding for future projects.
- Iowa Department of Natural Resources
- Marion County Conservation
- Central College Angling Club
- U.S. Army Corps of Engineers