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Step by Step Approach to Watershed Assessment and Planning
The incentive for a watershed assessment of Mill Coulee Creek was the TMDL. The Clean Water Act and subsequent associated legislation has had a major impact on our nations's water resources and the way natural resource management agencies and community based citizen action groups use our lakes, streams, and rivers. Probably the most significant event which has impacted the nation's water resources since passage of the Clean Water Act of 1972 is the defining of the TMDL (total maximum daily load) process. TMDL's provide a guideline or target threshold for identified impairments, sources, and causes of impairments to a waterbody. Presumably, identification of the TMDL, determination of cause and effect relationships, assessment of land use practices which impact water resources and implementation of wise management practices will lead to fewer impairments and improvement in the nation's water resources.
In order for the TMDL process to take effect, some key steps need to be taken. Past experience has taught that watershed management, which is a key part of the TMDL process, takes a unanimous effort toward identification of impairment sources and community based watershed planning. We have also learned from past experience that partnershipping can be an important and effective mechanism for achieving locally based natural resource management, particularly watershed management. Approaching a water body with the purpose of undertaking either the TMDL process or developing a watershed management plan is a slow-going process that requires some deliberate thought, serious reconnaissance, and often involves numerous parties. With good communication and careful planning, a well devised watershed plan can work!
The goal of the Montana State University Extension Service assessment of the Mill Coulee Creek watershed was clearly defined by the problem or situation perceived by partners of the watershed committee and public comment: streamflow within Mill Coulee Creek appeared to fluctuate dramatically during the irrigation season, yet appeared to remain relatively stable during the non-irrigation season. This dramatic fluctuation in streamflow, initially attributed to irrigation practices within the Mill Coulee Creek watershed, has been presumed to cause significant bank and channel erosion, overland flow, and impairment of fisheries habitat and spawning potential within Mill Coulee Creek.
Although we have not taken a direct approach to addressing the TMDL issue at Mill Coulee Creek, we have outlined an approach to impairment identification, the cause and effect relationships between land use practices and water resource impairment, community based involvement, landowner education, and partnershipping. Development of a protocol for guidelines and recommendations for watershed management and water quality improvement have also been outlined.
Mill Coulee Creek is a tributary to the Sun River and is located in Cascade County, Montana. The confluence of Mill Coulee and the Sun River is near the community of Sun River, Montana. Two sections of the Sun River, the first from Gibson Dam to Muddy Creek and the second from Muddy Creek to the mouth of the Missouri River, have been categorized as "high" priority for TMDL (total maximum daily load) development by the Montana Department of Environmental Quality. http://www.deq.state.mt.us/ppa/mdm/303_information.asp
Mill Coulee is a relatively small irrigation management unit of the Greenfields Irrigation District (GID), a USDA Bureau of Reclamation project. The basement layer below the Asheulot and Fairfield Benchland is a thick layer of shales that have been interbedded with sandstones. This layer is relatively impermeable and acts as an aquiclude to keep subsurface water in the layer above. The layer above the shales are comprised of coarse grained sediments that range in depth from approximately 10 to 20 feet.
Today Mill Coulee Creek is a perennial tributary to the Sun River. This, however, has not always been the case. Historic records show that at one time Mill Coulee Creek was an ephemeral stream, flowing during spring snowmelt runoff and during high intensity rainfall events. During the remainder of the year, Mill Coulee Creek was probably an intermittent stream, which during extreme precipitation events, frequently incised and cut its banks as it meandered back and forth across the valley floor. The transition from an ephemeral to perennial stream, a consequence of sustained baseflow and drainage from approximately 85,000 acres of annually irrigated land of the Asheulot and Fairfield Benches, has transformed Mill Coulee into a sustainable fishery habitat.
The Greenfields Irrigation District is a publicly owned Bureau of Reclamation project. The GID consists primarily of two geologic landforms, locally referred to as the Asheulot and Fairfield Benches. Mill Coulee is the primary surface rainage system for the Asheulot Bench. Both the Asheulot and Fairfield Bench are areas of broad, nearly level benches of glacial outwash material overlaying shales, sandstones, and consolidated glacial tills of the Wisconsin glaciation era. The surface soils are mixed fine and coarse materials, with good to excellent permeability and water holding capacity. Because of the nearly level surface topography, these areas have been historically developed for irrigated malt barley, wheat, canola, and alfalfa production. Development of this area has provided a reliable source of water to approximately 85,000 acres of irrigated agriculture within the vicinity of Mill Coulee Creek. Presently, the apparent situation is that deep percolation from irrigation return flow and drainage, surface discharges, and spillage all contribute to the perennial baseflow of Mill Coulee Creek. Shallow groundwater, within 20 feet of the land surface, currently provides the primary source of domestic and livestock water within the Mill Coulee Creek watershed. Landowners have reported that water tables typically rise as the irrigation season progresses and the irrigation supply canals are filled. The cessation of irrigation in the fall results in a gradual drop in the water table levels. Without large scale irrigation and subsequent deep percolation contributing to groundwater recharge, Mill Coulee Creek would likely still be an intermittent, ephemeral stream.
Partnershipping has been a key component to the progress made within the Mill Coulee Creek watershed. Since the Mill Coulee Creek watershed lies partially within Cascade and Teton Counties, the Montana State University Extension Service has played an active role in landowner education within Mill Coulee Creek watershed in the past. In December 2000, the Sun River Watershed Committee organized a scoping meeting to which representatives of the Extension Service were requested to attend. At that meeting, the Extension Service indicated a willingness to work cooperatively with the Sun River Watershed Committee, the Bureau of Reclamation, and the Greenfields Irrigation District, to conduct an assessment of Mill Coulee Creek - looking specifically at land use practices, irrigation project management, and factors contributing to widely fluctuating streamflow and associated sediment within Mill Coulee at the point of discharge to the Sun River.
A key resource which has been made available to landowners within the Mill Coulee watershed is a three-year, NRCS administered EQIP (Environmental Quality Incentives Program) grant. The USDA-NRCS utilizes a variety of resource management programs to focus on improving water resource management and EQIP is designed to provide technical and cost share assistance to implement water quality improvement programs. EQIP is designed to carry out conservation programs on private lands with farmers and ranchers, on a voluntary basis, that maximizes environmental benefits per dollar expended.
At the local level, state, tribal, and federal partnerships implement a "customized" EQIP that provides flexible technical, educational, and financial assistance to producers and which encourages environmental enhancement of natural resources while complying with federal, state, and tribal environmental laws, including the highly erodible land (HELC) and wetland conservation (WC) provisions. EQIP provides technical assistance, cost-share payments, incentive payments, and education to producers who enter into 5 to 10 year contracts based on their conservation plan. The NRCS has overall leadership to the program; however, partnering, both in developing on-the-ground practices and working with landowners, is a key component of most EQIP projects.
Partners in the Mill Coulee Creek Project include the following:
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