SHERIDAN COUNTY CONSERVATION DISTRICT

SHERIDAN COUNTY GROUND-WATER MANAGEMENT PROGRAM

MANAGING A WATER RESERVATION FROM THE CLEAR LAKE AQUIFER

BY MONITORING IMPACTS OF IRRIGATION

A very significant water resource in eastern Montana occupies a broad valley formed by the ancestral Missouri River. The Clear Lake aquifer contains sand and gravel deposited by the ancestral Missouri River and by later glacial meltwater streams. These deposits form a complex aquifer system with some areas capable of supporting high yield irrigation wells. 

Lakes and wetlands cover thousands of acres overlying the Clear Lake aquifer. These lakes are important habitat for migratory birds and other wildlife. The U.S. Fish and Wildlife Service (USFWS) Medicine Lake Wildlife Refuge manages many of these lakes and wetlands. At the beginning of this project the USFWS was concerned that irrigation withdrawals would deplete water from the wetlands and lakes thereby diminishing the value of the habitat. Although the concern remains, proper management and monitoring has shown that the anticipated depletion has not taken place.  USFWS historically objects to any major water development in the area.

The Sheridan County Conservation District (SCCD) was authorized to manage 15,479-acre-feet of water from the Clear Lake aquifer as part of a water reservation in 1994. DNRC stipulated that the SCCD could begin permitting for the use of up to 5809 acre-feet of the water. Applications permitted and pending reached 5,170 acre-feet in 2004 and the SCCD requested an increase in the amount authorized for permitting to 15,497 acre-feet. The result of this request was an authorization for the SCCD to permit up to 10,000 acre-feet annually. Once this cap is reached, permitting will be suspended until it is shown that allocating additional water will not adversely impact other water resources. The SCCD continues to evaluate and carefully address potential concerns related to further ground­water development through their permitting system. It will be necessary to continue to collect and interpret ground­water and surface-water data to determine if the additional 5,479 acre-feet of water can be developed.

The SCCD, through its’ Technical Advisory Committee, has developed an effective water management and monitoring program that provides data, interpretations, and recommendations to allocate water from the Clear Lake aquifer. Maintaining this monitoring program is critical for evaluating existing and future applications, determining multi-aquifer layers (both quality and quantity), and evaluating impacts on other water uses. Members of the Technical Advisory Committee include representatives from USFWS, Ft. Peck Tribes, DNRC, MBMG, and NRCS

Funding to support this program has come from the Montana Legislature through the DNRC and the SCCD. USFWS contributes substantial in-kind assistance, as does the Ft. Peck Tribes.

With the state of Montana water such that it is, this project is a crucial piece of the overall water management in Northeast Montana. With costs, especially transportation, increasing annually, it will soon be necessary to secure additional funding if this project is to continue at an effective level. 

GROUND-WATER MANAGEMENT PLAN

The SCCD, with assistance from DNRC and the MBMG, has developed an effective water management plan for the Sheridan County Water Reservation that has been successfully used for the last thirteen years. Water management includes evaluating irrigation impacts of the 15 permits currently authorized, 3 pending applications, other new applications, and 26 provisional permits previously granted by the MT DNRC. The management system has dictated the denial of 14 applications. The main components of the plan are summarized below.

• Monitoring and compiling water-resource data.

• Measuring water levels from over 150 wells, wetlands, and lakes.

• Analyzing water quality from many of these sources.

• Compiling climatic data from Medicine Lake, Westby, and other climatic stations.

• Calculating water use from both State and SCCD water rights.

Aquifer delineation

• Mapping hydrogeologic features.

• Defining aquifer extent, characteristics, and volume.

• Defining important areas of recharge and discharge.

• Estimating volume of recharge and discharge.

Interpreting water resource data.

• Evaluating potential impacts to existing water rights.

• Evaluating potential impacts to wetlands and lakes.

• Assessing potential undeveloped areas for irrigation potential.

Water management

• Using all of the information listed above to evaluate new applications to divert ground water for irrigation.

• Assist applicants in determining the project feasibility, adequate water quantities and water quality, and water rights for their selected project.

• Provide and explain data, interpretations, and recommendations to the Technical Advisory Committee in charge of authorizing water permits.

• Testify and provide expert witness testimony to water right hearings when requested.

Funding

• The SCCD receives $30,000 per year to cover some of the expenses required to adequately manage this aquifer.

• The funding ($30,000/yr.) is inadequate to meet the requirements of the tasks involved in managing the aquifer. Realistic funding should be at least $100,000 per biennium.

• Additional funding sources have been acquired for test well drilling and other activities that have enhanced our knowledge of this aquifer and consequently have improved our ability to manage the water resources of Northeast Montana.