US Army Corps of Engineers
Memphis District

Environmental Impact Summary

Purpose - Provide a brief summary of environmental coordination, impacts, and benefits

Existing Conditions - The project area was historically tall-grass prairie but was uniquely suited for rice production because of its clay cap. Only about 650 acres of native prairie remain of the original 500,000. A genetic study conducted by Southern Illinois University at Carbondale indicates that native prairie grasses are genetically different that commercially available cultivars. Approximately 17,400 acres of harvested crop fields are flooded each winter to provide a high quality food source for waterfowl. Stuttgart has become know as the rice and duck capitol of the world. The project area is underlain by a shallow (alluvial) aquifer and a deep (Sparta) aquifer.

Both aquifers in the entire project area have been declared a critical groundwater area by the state of Arkansas because of the severe groundwater depletion. A large cone of depression in the alluvial aquifer is located under the Stuttgart area. The aquifers historically interacted with streams and wetlands in the area. Farmers are switching to surface water and have installed dams and pit reservoirs to irrigate from natural streams. Water levels in many streams are severely depleted during the irrigation season.

Future Without-Project Conditions - The alluvial aquifer will no longer be able to sustain irrigated agriculture by 2015. Rice production will drop to 23% of current levels and agriculture will switch to soybean production. The aquifer as a resource could sustain damage, a high quality food source (rice) for waterfowl will be lost, and the natural streams will continue to be depleted during the irrigation season. The aquifer's natural interaction with the wetlands and streams will be lost.

Environmental Coordination - A project team was established that included the U.S. Fish and Wildlife Service (USFWS), Natural Resources Conservation Service (NRCS), Arkansas Game and Fish Commission (AGFC), Arkansas Natural Heritage Commission (ANHC), and Arkansas Soil and Water Conservation Commission. This team participated in all aspects of project planning and was provided project data. All study proposals were coordinated with these agencies, and study results were provided to them. A multi-agency team led by the ANHC and NRCS, with participation by the AGFC, USFWS, Corps, and Arkansas Highway and Transportation Department (AHTD), conducted a study that assessed potential impacts to White River floodplain wetlands. The USFWS conducted a mussel survey on tributary streams within the project area. A nationally recognized fisheries biologist from the U.S Army Waterways Experiment Station (WES) led the fisheries investigations. 

 

Project environmental features

  • No land will be converted to cropland
  • Roll (to increase macroinvertebrate production and accelerate stubble decay) and flood 38,529 acres of harvested rice fields for waterfowl
  • Provide fisheries in canals
  • Provide an additional 8,000 surface acres of reservoirs (these reservoirs will provide habitat for fish, shorebirds, and waterfowl)
  • Construct weirs to maintain minimum water levels in tributary streams and prevent desiccation during the summer months.
  • Plant prairie grasses on as much as 3,000 acres of canal right-of-way (seeds from native prairie grasses will be use to preserve genetic integrity)
  • Preserve and sustain the aquifer

Additional Environmental Features - A study to examine additional environmental features has been initiated. This study is focusing on additional measures for aquifer protection, waterfowl conservation, and wetland restoration (including wetland prairie restoration). The study is scheduled for completion in March 2001.

Potential Project Impacts - Scientific investigations were conducted on White River floodplain wetlands and on fisheries in the river as well as tributary streams. Potential impacts associated with withdrawals from the White River will occur downstream of DeVall's Bluff. The maximum impacts of the pumping station on White River stages will be about one foot at the lowest river stages before pump cutoff in the lowest possible pumping conditions. The impacts decrease at higher flows and cutoff levels and are essentially immeasurable at stages above bankfull. The impacts of these changes on both fish and wetlands were found to be minimal.

The operation of the pump station will be governed by the operations plan that will be referenced in the project cooperation agreement (PCA). The withdrawals must be limited to the withdrawals specified in the general reevaluation report. The withdrawals were based on the draft Arkansas State Water Management Plan for the White River, with varying withdrawals in different months. Environmental criteria were considered by the state, and the state will issue a permit for water withdrawal to the sponsor. Any change in the operation would require a supplement to the EIS.

Fisheries Impacts - Dr. K. Jack Killgore (WES) led the fisheries studies. It was concluded that larval fish entrainment at the pump station should not negatively affect the White River fishery; however, larval fish entrainment will be monitored following project construction. It was also determined that withdrawals from the river will not significantly impact littoral area habitat of fish and invertebrates. Four oxbow lakes were identified that could possibly have changes in connectivity with the river. The duration of the changes will be minor and were not considered significant, but a post-construction monitoring program for the lakes will be established.

Tributary Stream Impacts - The project does not include any channel enlargements of tributary streams. The project does use tributary streams to transport irrigation water and will place weirs in these streams. The location of the weirs will be determined with consideration given for sensitive environmental areas and plant communities. Currently, most tributary streams in the project area are used for irrigation; and water levels are greatly reduced during the summer months. The project will maintain water in the tributary streams to the level of weirs. This will provide a significant increase in fish habitat.

Water Quality Impacts - The increased farm efficiencies include tailwater recovery to capture and reuse irrigation water. The farm runoff will decrease with the project.

Mussels - Malacologists, Dr. John Harris (AHTD), Dr. Paul Heartfield (USFWS), and Dr. Andrew Miller (WES) were consulted regarding potential impacts to mussels within the White River and the need for a quantitative impact study. It was concluded that the minor reductions in surface water elevations of the White River should not cause significant impacts to mussels and that no quantitative impact assessment was necessary.

A major concern raised by natural resource agencies was the potential impact that zebra mussels (introduced from the White River) could have on native mussels in the tributary streams. A reconnaissance mussel survey of LaGrue Bayou was conducted by the USFWS in order to determine the need for more intensive surveys. The USFWS, led by Dr. Heartfield, conducted the reconnaissance survey on LaGrue Bayou because it was thought to be the stream most likely to contain at least a moderate mussel population. However, the survey revealed only low-density mussel populations. The USFWS attributed the scarcity of mussels to channel modification, agricultural runoff, and irrigation withdrawals. Based on the reconnaissance survey, the USFWS informed the Corps that more intensive surveys were not needed. Moreover, if zebra mussels proliferate in the White River, their introduction into the smaller tributary streams is likely inevitable, with or without the project.

Wetland Impacts - A scientific investigation, led by the ANHC and NRCS, was conducted to determine the impacts on White River wetlands. The White River is controlled by a series of reservoirs. The reservoirs provide more stable flow conditions and much higher than natural or pre-dam flows in the summer months. The investigations concluded that the project would move the river conditions to slightly more natural or historical conditions.

Waterfowl Impacts - Since the effect of the pumping station would be essentially immeasurable during flooding conditions on the White River, the project would have no impacts on the area or duration of the floods used by waterfowl. The project would provide significantly more waterfowl habitat in the Grand Prairie and reliably provide this habitat sooner in the waterfowl season. Without the project, much of the flooded rice fields currently used by waterfowl in the Grand Prairie would be lost.

Cumulative Impacts - The final environmental impact statement assesses the cumulative impacts of other potential projects in the White River basin. The other irrigation projects that would rely on the White River are neither authorized nor funded for study. The Grand Prairie Project has minimal impacts and significant environmental benefits, and it is needed now to save the aquifer. Waiting to initiate construction would place the start of project operation dangerously close to the predicted depletion of the aquifer in 2015.

Mitigation - Canal and pipeline alignments were determined considering environmental impacts. Unavoidable impacts will be fully mitigated. The mitigation includes not only wetlands mitigation but also mitigation for upland hardwoods. The mitigation necessary for on-farm features was also estimated and will be included with project mitigation in manageable blocks.

Benefits
Aquifer Protection Benefits - The project will provide the water necessary to save the aquifers (both alluvial and Sparta). Without the project, the aquifers will be depleted.

Fishery Benefits - The new irrigation canals and reservoirs will provide additional fisheries to the project area. The pooling effect of weirs and maintenance of year-round minimum water levels will improve the quality of habitat in tributary streams.

Waterfowl Flooding in the Grand Prairie - The goals of the waterfowl plan were established with assistance from waterfowl biologists with the AGFC and the USFWS. The flooding will be part of the operation plan for the PCA and the on-farm plans for the individuals. The White River Irrigation District requested that waterfowl conservation be made part of the authorized project.

Prairie Grass Restoration - The prairie grasses will not be planted in a large contiguous block. However, the native genotypes will be preserved and expanded to up to five times their current area. Much publicity has been given to the railroad prairie, a strip of prairie along an abandoned railroad. Like the railroad prairie, prairie restoration areas will be linearly configured. These strips of prairie should still restore much-needed habitat for certain prairie wildlife species. Additionally, the on-going prairie grass research should enhance the chances for successful establishment of prairie grasses; this could, in turn, encourage the planting of native prairie grasses by others in similar situations.